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Ion thruster

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ion_thruster

The 2.3 kW NSTAR ion thruster of the NASA for the Deep Space 1 spacecraft during a hot fire test at the Jet Propulsion Laboratory.

NEXIS ion engine test (2005)

A prototype of a xenon ion engine being tested at NASA's Jet Propulsion Laboratory

An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.

An ion thruster ionizes a neutral gas by extracting some electrons out of atoms, creating a cloud of positive ions. These ion thrusters rely mainly on electrostatics as ions are accelerated by the Coulomb force along an electric field. Temporarily stored electrons are finally reinjected by a neutralizer in the cloud of ions after it has passed through the electrostatic grid, so the gas becomes neutral again and can freely disperse in space without any further electrical interaction with the thruster. By contrast, electromagnetic thrusters use the Lorentz force to accelerate all species (free electrons as well as positive and negative ions) in the same direction whatever their electric charge, and are specifically referred to as plasma propulsion engines, where the electric field is not in the direction of the acceleration.

Ion thrusters in operation typically consume 1–7 kW of power, have exhaust velocities around 20–50 km/s (I_sp 2000–5000 s), and possess thrusts of 25–250 mN and a propulsive efficiency 65–80% though experimental versions have achieved 100 kW (130 hp), 5 N (1.1 lb_f).

The Deep Space 1 spacecraft, powered by an ion thruster, changed velocity by 4.3 km/s (2.7 mi/s) while consuming less than 74 kg (163 lb) of xenon. The Dawn spacecraft broke the record, with a velocity change of 11.5 km/s (41,000 km/h), though it was only half as efficient, requiring 425 kg (937 lb) of xenon.

Applications include control of the orientation and position of orbiting satellites (some satellites have dozens of low-power ion thrusters) and use as a main propulsion engine for low-mass robotic space vehicles (such as Deep Space 1 and Dawn).

Ion thrust engines are practical only in the vacuum of space and cannot take vehicles through the atmosphere because ion engines do not work in the presence of ions outside the engine; additionally, the engine's minuscule thrust cannot overcome any significant air resistance. Moreover, notwithstanding the presence of an atmosphere (or lack thereof) an ion engine cannot generate sufficient thrust to achieve initial liftoff from any celestial body with significant surface gravity. For these reasons, spacecraft must rely on other methods such as conventional chemical rockets or non-rocket launch technologies to reach their initial orbit.

Origins

SERT-1 spacecraft

The first person who wrote a paper introducing the idea publicly was Konstantin Tsiolkovsky in 1911. The technique was recommended for near-vacuum conditions at high altitude, but thrust was demonstrated with ionized air streams at atmospheric pressure. The idea appeared again in Hermann Oberth's "Wege zur Raumschiffahrt" (Ways to Spaceflight), published in 1923, where he explained his thoughts on the mass savings of electric propulsion, predicted its use in spacecraft propulsion and attitude control, and advocated electrostatic acceleration of charged gasses.

A working ion thruster was built by Harold R. Kaufman in 1959 at the NASA Glenn Research Center facilities. It was similar to a gridded electrostatic ion thruster and used mercury for propellant. Suborbital tests were conducted during the 1960s and in 1964, the engine was sent into a suborbital flight aboard the Space Electric Rocket Test-1 (SERT-1). It successfully operated for the planned 31 minutes before falling to Earth. This test was followed by an orbital test, SERT-2, in 1970.

An alternate form of electric propulsion, the Hall effect thruster, was studied independently in the United States and the Soviet Union in the 1950s and 1960s. Hall effect thrusters operated on Soviet satellites from 1972 until the late 1990s, mainly used for satellite stabilization in north–south and in east–west directions. Some 100–200 engines completed missions on Soviet and Russian satellites. Soviet thruster design was introduced to the West in 1992 after a team of electric propulsion specialists, under the support of the Ballistic Missile Defense Organization, visited Soviet laboratories.

General working principle

Ion thrusters use beams of ions (electrically charged atoms or molecules) to create thrust in accordance with momentum conservation. The method of accelerating the ions varies, but all designs take advantage of the charge/mass ratio of the ions. This ratio means that relatively small potential differences can create high exhaust velocities. This reduces the amount of reaction mass or propellant required, but increases the amount of specific power required compared to chemical rockets. Ion thrusters are therefore able to achieve high specific impulses. The drawback of the low thrust is low acceleration because the mass of the electric power unit directly correlates with the amount of power. This low thrust makes ion thrusters unsuited for launching spacecraft into orbit, but effective for in-space propulsion over longer periods of time.

Ion thrusters are categorized as either electrostatic or electromagnetic. The main difference is the method for accelerating the ions.

Electrostatic ion thrusters use the Coulomb force and accelerate the ions in the direction of the electric field.
Electromagnetic ion thrusters use the Lorentz force to move the ions.

Electric power for ion thrusters is usually provided by solar panels. However, for sufficiently large distances from the sun, nuclear power may be used. In each case, the power supply mass is proportional to the peak power that can be supplied, and both provide, for this application, almost no limit to the energy.

Electric thrusters tend to produce low thrust, which results in low acceleration. Defining $1g=9.81\;\mathrm {m/s^{2}}$ , the standard gravitational acceleration of Earth, and noting that $F=ma\implies a=F/m$ , this can be analyzed. An NSTAR thruster producing a thrust force of 92 mN will accelerate a satellite with a mass of 1 Mg by 0.092 N / 1000 kg = 9.2×10⁻⁵ m/s² (or 9.38×10⁻⁶ g). However, this acceleration can be sustained for months or years at a time, in contrast to the very short burns of chemical rockets.

F=2{\frac {\eta P}{gI_{\text{sp}}}}

Where:

F is the thrust force in N,
η is the efficiency
P is the electrical power used by the thruster in W, and
I_sp is the specific impulse in seconds.

The ion thruster is not the most promising type of electrically powered spacecraft propulsion, but it is the most successful in practice to date. An ion drive would require two days to accelerate a car to highway speed in vacuum. The technical characteristics, especially thrust, are considerably inferior to the prototypes described in literature, technical capabilities are limited by the space charge created by ions. This limits the thrust density (force per cross-sectional area of the engine). Ion thrusters create small thrust levels (the thrust of Deep Space 1 is approximately equal to the weight of one sheet of paper) compared to conventional chemical rockets, but achieve high specific impulse, or propellant mass efficiency, by accelerating the exhaust to high speed. The power imparted to the exhaust increases with the square of exhaust velocity while thrust increase is linear. Conversely, chemical rockets provide high thrust, but are limited in total impulse by the small amount of energy that can be stored chemically in the propellants. Given the practical weight of suitable power sources, the acceleration from an ion thruster is frequently less than one-thousandth of standard gravity. However, since they operate as electric (or electrostatic) motors, they convert a greater fraction of input power into kinetic exhaust power. Chemical rockets operate as heat engines, and Carnot's theorem limits the exhaust velocity.

Electrostatic thrusters

Gridded electrostatic ion thrusters

A diagram of how a gridded electrostatic ion engine (multipole magnetic cusp type) works

Gridded electrostatic ion thrusters development started in the 1960s and, since then, it has been used for commercial satellite propulsion and scientific missions. Their main feature is that the propellant ionization process is physically separated from the ion acceleration process.

The ionization process takes place in the discharge chamber, where by bombarding the propellant with energetic electrons, as the energy transferred ejects valence electrons from the propellant gas's atoms. These electrons can be provided by a hot cathode filament and accelerated through the potential difference towards an anode. Alternatively, the electrons can be accelerated by an oscillating induced electric field created by an alternating electromagnet, which results in a self-sustaining discharge without a cathode (radio frequency ion thruster).

The positively charged ions are extracted by a system consisting of 2 or 3 multi-aperture grids. After entering the grid system near the plasma sheath, the ions are accelerated by the potential difference between the first grid and second grid (called the screen grid and the accelerator grid, respectively) to the final ion energy of (typically) 1–2 keV, which generates thrust.

Ion thrusters emit a beam of positively charged ions. To keep the spacecraft from accumulating a charge, another cathode is placed near the engine to emit electrons into the ion beam, leaving the propellant electrically neutral. This prevents the beam of ions from being attracted (and returning) to the spacecraft, which would cancel the thrust.

Gridded electrostatic ion thruster research (past/present):

NASA Solar Technology Application Readiness (NSTAR), 2.3 kW, used on two successful missions
NASA's Evolutionary Xenon Thruster (NEXT), 6.9 kW, flight qualification hardware built
Nuclear Electric Xenon Ion System (NEXIS)
High Power Electric Propulsion (HiPEP), 25 kW, test example built and run briefly on the ground
EADS Radio-frequency Ion Thruster (RIT)
Dual-Stage 4-Grid (DS4G)

Hall effect thrusters

Schematic of a Hall effect thruster

Hall effect thrusters accelerate ions by means of an electric potential between a cylindrical anode and a negatively charged plasma that forms the cathode. The bulk of the propellant (typically xenon) is introduced near the anode, where it ionizes and flows toward the cathode; ions accelerate towards and through it, picking up electrons as they leave to neutralize the beam and leave the thruster at high velocity.

The anode is at one end of a cylindrical tube. In the center is a spike that is wound to produce a radial magnetic field between it and the surrounding tube. The ions are largely unaffected by the magnetic field, since they are too massive. However, the electrons produced near the end of the spike to create the cathode are trapped by the magnetic field and held in place by their attraction to the anode. Some of the electrons spiral down towards the anode, circulating around the spike in a Hall current. When they reach the anode they impact the uncharged propellant and cause it to be ionized, before finally reaching the anode and completing the circuit.

Field-emission electric propulsion

Field-emission electric propulsion (FEEP) thrusters may use caesium or indium propellants. The design comprises a small propellant reservoir that stores the liquid metal, a narrow tube or a system of parallel plates that the liquid flows through and an accelerator (a ring or an elongated aperture in a metallic plate) about a millimeter past the tube end. Caesium and indium are used due to their high atomic weights, low ionization potentials and low melting points. Once the liquid metal reaches the end of the tube, an electric field applied between the emitter and the accelerator causes the liquid surface to deform into a series of protruding cusps, or Taylor cones. At a sufficiently high applied voltage, positive ions are extracted from the tips of the cones. The electric field created by the emitter and the accelerator then accelerates the ions. An external source of electrons neutralizes the positively charged ion stream to prevent charging of the spacecraft.

Electromagnetic thrusters

Pulsed inductive thrusters

Pulsed inductive thrusters (PIT) use pulses instead of continuous thrust and have the ability to run on power levels on the order of megawatts (MW). PITs consist of a large coil encircling a cone shaped tube that emits the propellant gas. Ammonia is the gas most commonly used. For each pulse, a large charge builds up in a group of capacitors behind the coil and is then released. This creates a current that moves circularly in the direction of jθ. The current then creates a magnetic field in the outward radial direction (Br), which then creates a current in the gas that has just been released in the opposite direction of the original current. This opposite current ionizes the ammonia. The positively charged ions are accelerated away from the engine due to the electric field jθ crossing the magnetic field Br, due to the Lorentz Force.

Magnetoplasmadynamic thruster

Magnetoplasmadynamic (MPD) thrusters and lithium Lorentz force accelerator (LiLFA) thrusters use roughly the same idea. The LiLFA thruster builds on the MPD thruster. Hydrogen, argon, ammonia and nitrogen can be used as propellant. In a certain configuration, the ambient gas in low Earth orbit (LEO) can be used as a propellant. The gas enters the main chamber where it is ionized into plasma by the electric field between the anode and the cathode. This plasma then conducts electricity between the anode and the cathode, closing the circuit. This new current creates a magnetic field around the cathode, which crosses with the electric field, thereby accelerating the plasma due to the Lorentz force.

The LiLFA thruster uses the same general idea as the MPD thruster, with two main differences. First, the LiLFA uses lithium vapor, which can be stored as a solid. The other difference is that the single cathode is replaced by multiple, smaller cathode rods packed into a hollow cathode tube. MPD cathodes are easily corroded due to constant contact with the plasma. In the LiLFA thruster, the lithium vapor is injected into the hollow cathode and is not ionized to its plasma form/corrode the cathode rods until it exits the tube. The plasma is then accelerated using the same Lorentz force.

In 2013, Russian company the Chemical Automatics Design Bureau successfully conducted a bench test of their MPD engine for long-distance space travel.

Electrodeless plasma thrusters

Electrodeless plasma thrusters have two unique features: the removal of the anode and cathode electrodes and the ability to throttle the engine. The removal of the electrodes eliminates erosion, which limits lifetime on other ion engines. Neutral gas is first ionized by electromagnetic waves and then transferred to another chamber where it is accelerated by an oscillating electric and magnetic field, also known as the ponderomotive force. This separation of the ionization and acceleration stages allows throttling of propellant flow, which then changes the thrust magnitude and specific impulse values.

Helicon double layer thrusters

A helicon double layer thruster is a type of plasma thruster that ejects high velocity ionized gas to provide thrust. In this design, gas is injected into a tubular chamber (the source tube) with one open end. Radio frequency AC power (at 13.56 MHz in the prototype design) is coupled into a specially shaped antenna wrapped around the chamber. The electromagnetic wave emitted by the antenna causes the gas to break down and form a plasma. The antenna then excites a helicon wave in the plasma, which further heats it. The device has a roughly constant magnetic field in the source tube (supplied by solenoids in the prototype), but the magnetic field diverges and rapidly decreases in magnitude away from the source region and might be thought of as a kind of magnetic nozzle. In operation, a sharp boundary separates the high density plasma inside the source region and the low density plasma in the exhaust, which is associated with a sharp change in electrical potential. Plasma properties change rapidly across this boundary, which is known as a current-free electric double layer. The electrical potential is much higher inside the source region than in the exhaust and this serves both to confine most of the electrons and to accelerate the ions away from the source region. Enough electrons escape the source region to ensure that the plasma in the exhaust is neutral overall.

Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

The proposed Variable Specific Impulse Magnetoplasma Rocket (VASIMR) functions by using radio waves to ionize a propellant into a plasma, and then using a magnetic field to accelerate the plasma out of the back of the rocket engine to generate thrust. The VASIMR is currently being developed by Ad Astra Rocket Company, headquartered in Houston, Texas, with help from Canada-based Nautel, producing the 200 kW RF generators for ionizing propellant. Some of the components and "plasma shoots" experiments are tested in a laboratory settled in Liberia, Costa Rica. This project is led by former NASA astronaut Dr. Franklin Chang-Díaz (CRC-USA). A 200 kW VASIMR test engine was in discussion to be fitted in the exterior of the International Space Station, as part of the plan to test the VASIMR in space – however plans for this test onboard ISS were canceled in 2015 by NASA, with a free flying VASIMR test being discussed by Ad Astra instead. An envisioned 200 megawatt engine could reduce the duration of flight from Earth to Jupiter or Saturn from six years to fourteen months, and Mars from 7 months to 39 days.

Microwave electrothermal thrusters

Microwave electrothermal thruster

Thruster components

Discharge chamber

Under a research grant from the NASA Lewis Research Center during the 1980s and 1990s, Martin C. Hawley and Jes Asmussen led a team of engineers in developing a Microwave Electrothermal Thruster (MET).

In the discharge chamber, microwave (MW) energy flows into the center containing a high level of ions (I), causing neutral species in the gaseous propellant to ionize. Excited species flow out (FES) through the low ion region (II) to a neutral region (III) where the ions complete their recombination, replaced with the flow of neutral species (FNS) towards the center. Meanwhile, energy is lost to the chamber walls through heat conduction and convection (HCC), along with radiation (Rad). The remaining energy absorbed into the gaseous propellant is converted into thrust.

Radioisotope thruster

A theoretical propulsion system has been proposed, based on alpha particles (He²⁺
or ⁴
₂He²⁺
indicating a helium ion with a +2 charge) emitted from a radioisotope uni-directionally through a hole in its chamber. A neutralising electron gun would produce a tiny amount of thrust with high specific impulse in the order of millions of seconds due to the high relativistic speed of alpha particles.

A variant of this uses a graphite-based grid with a static DC high voltage to increase thrust as graphite has high transparency to alpha particles if it is also irradiated with short wave UV light at the correct wavelength from a solid state emitter. It also permits lower energy and longer half life sources which would be advantageous for a space application. Helium backfill has also been suggested as a way to increase electron mean free path.

Comparisons

Test data of some ion thrusters
Thruster	Propellant	Input power (kW)	Specific impulse (s)	Thrust (mN)	Thruster mass (kg)	Notes
NSTAR	Xenon	2.3	1700–3300	92 max.	8.33	Used on the Deep Space 1 and Dawn space probes
PPS-1350 Hall effect	Xenon	1.5	1660	90	5.3
NEXT	Xenon	6.9	4190	236 max.	<13.5	To be used in DART mission
X3	Xenon or Krypton	102	1800–2650	5400	230
NEXIS	Xenon	20.5
RIT 22	Xenon	5
BHT8000	Xenon	8	2210	449	25
Hall effect	Xenon	75
FEEP	Liquid caesium	6×10⁻⁵–0.06	6000–10000	0.001–1
NPT30-I2	Iodine	0.034–0.066	1000–2500	0.5–1.5	1.2
AEPS	Xenon	13.3	2900	600	25	To be used in Lunar Gateway PPE module.

Experimental thrusters (no mission to date)
Thruster	Propellant	Input power (kW)	Specific impulse (s)	Thrust (mN)	Thruster mass (kg)	Notes
Hall effect	Bismuth	1.9	1520 (anode)	143 (discharge)
Hall effect	Bismuth	25
Hall effect	Bismuth	140
Hall effect	Iodine	0.2	1510 (anode)	12.1 (discharge)
Hall effect	Iodine	7	1950	413
HiPEP	Xenon	20–50	6000–9000	460–670
MPDT	Hydrogen	1500	4900	26300
MPDT	Hydrogen	3750	3500	88500
MPDT	Hydrogen	7500	6000	60000
LiLFA	Lithium vapor	500	4077	12000
FEEP	Liquid caesium	6×10⁻⁵–0.06	6000–10000	0.001–1
VASIMR	Argon	200	3000–12000	Approximately 5000	620
CAT	Xenon, iodine, water	0.01	690	1.1–2 (73 mN/kW)	<1
DS4G	Xenon	250	19300	2500 max.	5
KLIMT	Krypton	0.5			4
ID-500	Xenon	32–35	7140	375–750	34.8	To be used in TEM

Lifetime

Ion thrusters' low thrust requires continuous operation for a long time to achieve the necessary change in velocity (delta-v) for a particular mission. Ion thrusters are designed to provide continuous operation for intervals of weeks to years.

The lifetime of electrostatic ion thrusters is limited by several processes.

Gridded thruster life

In electrostatic gridded designs, charge-exchange ions produced by the beam ions with the neutral gas flow can be accelerated towards the negatively biased accelerator grid and cause grid erosion. End-of-life is reached when either the grid structure fails or the holes in the grid become large enough that ion extraction is substantially affected; e.g., by the occurrence of electron backstreaming. Grid erosion cannot be avoided and is the major lifetime-limiting factor. Thorough grid design and material selection enable lifetimes of 20,000 hours or more.

A test of the NASA Solar Technology Application Readiness (NSTAR) electrostatic ion thruster resulted in 30,472 hours (roughly 3.5 years) of continuous thrust at maximum power. Post-test examination indicated the engine was not approaching failure. NSTAR operated for years on Dawn.

The NASA Evolutionary Xenon Thruster (NEXT) project operated continuously for more than 48,000 hours. The test was conducted in a high vacuum test chamber. Over the course of the 5.5+ year test, the engine consumed approximately 870 kilograms of xenon propellant. The total impulse generated would require over 10,000 kilograms of conventional rocket propellant for a similar application.

Hall-effect thruster life

Hall-effect thrusters suffer from strong erosion of the ceramic discharge chamber by impact of energetic ions: a test reported in 2010 showed erosion of around 1 mm per hundred hours of operation, though this is inconsistent with observed on-orbit lifetimes of a few thousand hours.

The Advanced Electric Propulsion System (AEPS) is expected to accumulate about 5,000 hours and the design aims to achieve a flight model that offers a half-life of at least 23,000 hours and a full life of about 50,000 hours.

Propellants

Ionization energy represents a large percentage of the energy needed to run ion drives. The ideal propellant is thus easy to ionize and has a high mass/ionization energy ratio. In addition, the propellant should not erode the thruster to any great degree to permit long life; and should not contaminate the vehicle.

Many current designs use xenon gas, as it is easy to ionize, has a reasonably high atomic number, is inert and causes low erosion. However, xenon is globally in short supply and expensive. (~$3,000/kg in 2021)

Some older ion thruster designs used mercury propellant. However, mercury is toxic, tended to contaminate spacecraft, and was difficult to feed accurately. A modern commercial prototype may be using mercury successfully. Mercury was formally banned as a propellant in 2022 by the Minamata Convention on Mercury.

Since 2018, krypton is used to fuel the Hall effect thrusters aboard Starlink internet satellites, in part due to its lower cost than conventional xenon propellant.

Other propellants, such as bismuth and iodine, show promise both for gridless designs such as Hall effect thrusters, and gridded ion thrusters.

Iodine: For the first time in space, Iodine was used as a propellant for electric propulsion on the NPT30-I2 gridded ion thruster by ThrustMe, on board the Beihangkongshi-1 mission launched in November 2020, with an extensive report published a year later in the journal Nature. The CubeSat Ambipolar Thruster (CAT) used on the Mars Array of Ionospheric Research Satellites Using the CubeSat Ambipolar Thruster (MARS-CAT) mission also proposes to use solid iodine as the propellant to minimize storage volume.

VASIMR design (and other plasma-based engines) are theoretically able to use practically any material for propellant. However, in current tests the most practical propellant is argon, which is relatively abundant and inexpensive.

Energy efficiency

Plot of instantaneous propulsive efficiency and overall efficiency for a vehicle accelerating from rest as percentages of the engine efficiency. Note that peak vehicle efficiency occurs at about 1.6 times exhaust velocity.

Ion thruster efficiency is the kinetic energy of the exhaust jet emitted per second divided by the electrical power into the device.

Overall system energy efficiency is determined by the propulsive efficiency, which depends on vehicle speed and exhaust speed. Some thrusters can vary exhaust speed in operation, but all can be designed with different exhaust speeds. At the lower end of specific impulse, I_sp, the overall efficiency drops, because ionization takes up a larger percentage energy and at the high end propulsive efficiency is reduced.

Optimal efficiencies and exhaust velocities for any given mission can be calculated to give minimum overall cost.

Missions

Ion thrusters have many in-space propulsion applications. The best applications make use of the long mission interval when significant thrust is not needed. Examples of this include orbit transfers, attitude adjustments, drag compensation for low Earth orbits, fine adjustments for scientific missions and cargo transport between propellant depots, e.g., for chemical fuels. Ion thrusters can also be used for interplanetary and deep-space missions where acceleration rates are not crucial. Ion thrusters are seen as the best solution for these missions, as they require high change in velocity but do not require rapid acceleration. Continuous thrust over long durations can reach high velocities while consuming far less propellant than traditional chemical rockets.

Demonstration vehicles

SERT

Ion propulsion systems were first demonstrated in space by the NASA Lewis (now Glenn Research Center) missions Space Electric Rocket Test (SERT)-1 and SERT-2A. A SERT-1 suborbital flight was launched on 20 July 1964, and successfully proved that the technology operated as predicted in space. These were electrostatic ion thrusters using mercury and caesium as the reaction mass. SERT-2A, launched on 4 February 1970, verified the operation of two mercury ion engines for thousands of running hours.

Operational missions

Ion thrusters are routinely used for station-keeping on commercial and military communication satellites in geosynchronous orbit. The Soviet Union pioneered this field, using Stationary Plasma Thrusters (SPTs) on satellites starting in the early 1970s.

Two geostationary satellites (ESA's Artemis in 2001–2003 and the United States military's AEHF-1 in 2010–2012) used the ion thruster to change orbit after the chemical-propellant engine failed. Boeing began using ion thrusters for station-keeping in 1997 and planned in 2013–2014 to offer a variant on their 702 platform, with no chemical engine and ion thrusters for orbit raising; this permits a significantly lower launch mass for a given satellite capability. AEHF-2 used a chemical engine to raise perigee to 16,330 km (10,150 mi) and proceeded to geosynchronous orbit using electric propulsion.

In Earth orbit

Tiangong space station

China's Tiangong space station is fitted with ion thrusters. Tianhe core module is propelled by both chemical thrusters and four Hall-effect thrusters, which are used to adjust and maintain the station's orbit. The development of the Hall-effect thrusters is considered a sensitive topic in China, with scientists "working to improve the technology without attracting attention". Hall-effect thrusters are created with crewed mission safety in mind with effort to prevent erosion and damage caused by the accelerated ion particles. A magnetic field and specially designed ceramic shield was created to repel damaging particles and maintain integrity of the thrusters. According to the Chinese Academy of Sciences, the ion drive used on Tiangong has burned continuously for 8,240 hours without a glitch, indicating their suitability for Chinese space station's designated 15-year lifespan.

Starlink

SpaceX's Starlink satellite constellation uses Hall-effect thrusters powered by krypton to raise orbit, perform maneuvers, and de-orbit at the end of their use.

GOCE

ESA's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was launched on 16 March 2009. It used ion propulsion throughout its twenty-month mission to combat the air-drag it experienced in its low orbit (altitude of 255 kilometres) before intentionally deorbiting on 11 November 2013.

In deep space

Deep Space 1

NASA developed the NSTAR ion engine for use in interplanetary science missions beginning in the late-1990s. It was space-tested in the highly successful space probe Deep Space 1, launched in 1998. This was the first use of electric propulsion as the interplanetary propulsion system on a science mission. Based on the NASA design criteria, Hughes Research Labs, developed the Xenon Ion Propulsion System (XIPS) for performing station keeping on geosynchronous satellites. Hughes (EDD) manufactured the NSTAR thruster used on the spacecraft.

Hayabusa and Hayabusa2

The Japanese Aerospace Exploration Agency's Hayabusa space probe was launched in 2003 and successfully rendezvoused with the asteroid 25143 Itokawa. It was powered by four xenon ion engines, which used microwave electron cyclotron resonance to ionize the propellant and an erosion-resistant carbon/carbon-composite material for its acceleration grid. Although the ion engines on Hayabusa experienced technical difficulties, in-flight reconfiguration allowed one of the four engines to be repaired and allowed the mission to successfully return to Earth.

Hayabusa2, launched in 2014, was based on Hayabusa. It also used ion thrusters.

Smart 1

The European Space Agency's satellite SMART-1 launched in 2003 using a Snecma PPS-1350-G Hall thruster to get from GTO to lunar orbit. This satellite completed its mission on 3 September 2006, in a controlled collision on the Moon's surface, after a trajectory deviation so scientists could see the 3 meter crater the impact created on the visible side of the Moon.

Dawn

Dawn launched on 27 September 2007, to explore the asteroid Vesta and the dwarf planet Ceres. It used three Deep Space 1 heritage xenon ion thrusters (firing one at a time). Dawn's ion drive is capable of accelerating from 0 to 97 km/h (60 mph) in 4 days of continuous firing. The mission ended on 1 November 2018, when the spacecraft ran out of hydrazine chemical propellant for its attitude thrusters.

LISA Pathfinder

LISA Pathfinder is an ESA spacecraft launched in 2015 to orbit the sun-Earth L1 point. It does not use ion thrusters as its primary propulsion system, but uses both colloid thrusters and FEEP for precise attitude control – the low thrusts of these propulsion devices make it possible to move the spacecraft incremental distances accurately. It is a test for the LISA mission. The mission ended on 30 December 2017.

BepiColombo

ESA's BepiColombo mission was launched to Mercury on 20 October 2018. It uses ion thrusters in combination with swing-bys to get to Mercury, where a chemical rocket will complete orbit insertion.

Double Asteroid Redirection Test

NASA's Double Asteroid Redirection Test (DART) launched in 2021 and will operate its NEXT-C xenon ion thruster for about 1,000 hours to reach the target asteroid in 2022.

Proposed missions

International Space Station

As of March 2011, a future launch of an Ad Astra VF-200 200 kW VASIMR electromagnetic thruster was under consideration for testing on the International Space Station (ISS). However, in 2015, NASA ended plans for flying the VF-200 to the ISS. A NASA spokesperson stated that the ISS "was not an ideal demonstration platform for the desired performance level of the engines". Ad Astra stated that tests of a VASIMR thruster on the ISS would remain an option after a future in-space demonstration.

The VF-200 would have been a flight version of the VX-200. Since the available power from the ISS is less than 200 kW, the ISS VASIMR would have included a trickle-charged battery system allowing for 15 minutes pulses of thrust. The ISS orbits at a relatively low altitude and experiences fairly high levels of atmospheric drag, requiring periodic altitude boosts – a high efficiency engine (high specific impulse) for station-keeping would be valuable, theoretically VASIMR reboosting could cut fuel cost from the current US$210 million annually to one-twentieth. VASIMR could in theory use as little as 300 kg of argon gas for ISS station-keeping instead of 7500 kg of chemical fuel – the high exhaust velocity (high specific impulse) would achieve the same acceleration with a smaller amount of propellant, compared to chemical propulsion with its lower exhaust velocity needing more fuel. Hydrogen is generated by the ISS as a by-product and is vented into space.

NASA previously worked on a 50 kW Hall-effect thruster for the ISS, but work was stopped in 2005.

Lunar Gateway

The Power and Propulsion Element (PPE) is a module on the Lunar Gateway that provides power generation and propulsion capabilities. It is targeting launch on a commercial vehicle in January 2024. It would probably use the 50 kW Advanced Electric Propulsion System (AEPS) under development at NASA Glenn Research Center and Aerojet Rocketdyne.

MARS-CAT

The MARS-CAT (Mars Array of ionospheric Research Satellites using the CubeSat Ambipolar Thruster) mission is a two 6U CubeSat concept mission to study Mars' ionosphere. The mission would investigate its plasma and magnetic structure, including transient plasma structures, magnetic field structure, magnetic activity and correlation with solar wind drivers. The CAT thruster is now called the RF thruster and manufactured by Phase Four.

Interstellar missions

Geoffrey A. Landis proposed using an ion thruster powered by a space-based laser, in conjunction with a lightsail, to propel an interstellar probe.

Popular culture

The idea of an ion engine first appeared in Donald W Horner's By Aeroplane to the Sun: Being the Adventures of a Daring Aviator and his Friends (1910).
Ion propulsion is the main thrust source of the spaceship Kosmokrator in the Eastern German/Polish science fiction movie Der Schweigende Stern (1960). Minute 28:10.
In the 1968 episode of Star Trek, "Spock's Brain", Scotty is repeatedly impressed by a civilization's use of ion power.
Ion thrusters repeatedly appear in the Star Wars franchise, most notably in the Twin Ion Engine (TIE) fighter.
Ion thrusters appear as the primary form of propulsion in vacuum for the spacecraft in the game Space Engineers.
Ion thrusters are referenced as a method of space propulsion in The Martian, where they are used to propel the Hermes crewed spacecraft between Earth and Mars.
Ion drive is a primary means of propulsion for spacecraft and aircraft in the sci-fi series Worlds Spinning Round by T. E. Greene (2005, 2012, 2017)
A pseudo-realistic form of ion thrusters appear in the game Kerbal Space Program, notable for their low thrust and high efficiency much like their real life counterpart.

Sex education

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Sex_education

Sex education
Barbara Hastings-Asatourian of the University of Salford demonstrates "Contraception", a sex education board game played in UK schools

Sex education, also known as sexual education, sexuality education or sex ed, is the instruction of issues relating to human sexuality, including emotional relations and responsibilities, human sexual anatomy, sexual activity, sexual reproduction, age of consent, reproductive health, reproductive rights, sexual health, safe sex and birth control. Sex education which includes all of these issues is known as comprehensive sex education, and is often opposed to abstinence-only sex education, which only focuses on sexual abstinence. Sex education may be provided by parents or caregivers or as part at school programs and public health campaigns. In some countries it is known as Relationships and Sexual health education.

History

In many cultures, the discussion of all sexual issues has traditionally been considered taboo, and adolescents were not given any information on sexual matters. Such instruction, as was given, was traditionally left to a child's parents, and often this was put off until just before their marriage. However, in the late 19th century, the progressive education movement led to the introduction of sex education as "social hygiene" in North American school curricula and the introduction of school-based sex education.

Despite early inroads of school-based sex education, most of the information on sexual matters in the mid-20th century was obtained informally from friends and the media, and much of this information was deficient or of dubious value, especially during the period following puberty, when curiosity about sexual matters was the most acute. This deficiency was heightened by the increasing incidence of teenage pregnancies, particularly in Western countries after the 1960s. As part of each country's efforts to reduce such pregnancies, programs of sex education were introduced, initially over strong opposition from parent and religious groups. Societies where culture and religion inform the actions of their legal institutions, sex education is seriously under contention.

The outbreak of AIDS has given a new sense of urgency to sex education. In many African countries, where AIDS is at epidemic levels (see HIV/AIDS in Africa), sex education is seen by most scientists as a vital public health strategy. Some international organizations such as Planned Parenthood consider that broad sex education programs have global benefits, such as controlling the risk of overpopulation and the advancement of women's rights (see also reproductive rights). The use of mass media campaigns has sometimes resulted in high levels of "awareness" coupled with essentially superficial knowledge of HIV transmission.

According to SIECUS, the Sexuality Information and Education Council of the United States, 93% of adults they surveyed support sexuality education in high school and 84% support it in junior high school. In fact, 88% of the parents of junior high school students and 80% of parents of secondary school students believe that sex education in school makes it easier for them to talk to their adolescents about sex. Also, 92% of adolescents report that they want both to talk to their parents about sex and to have comprehensive in-school sex education. Furthermore, a "study, conducted by Mathematica Policy Research on behalf of the US Department of Health and Human Services, found that abstinence-only-until-marriage programs are ineffective."

Definitions

Leepson sees sex education as instruction in various physiological, psychological and sociological aspects of sexual response and reproduction. Kearney (2008) also defined sex education as "involving a comprehensive course of action by the school, calculated to bring about the socially desirable attitudes, practices and personal conduct on the part of children and adults, that will best protect the individual as a human and the family as a social institution." Thus, sex education may also be described as "sexuality education", which means that it encompasses education about all aspects of sexuality, including information about family planning, reproduction (fertilization, conception and development of the embryo and fetus, through to childbirth), plus information about all aspects of one's sexuality including: body image, sexual orientation, sexual pleasure, values, decision making, communication, dating, relationships, sexually transmitted infections (STIs) and how to avoid them, and birth control methods. Various aspects of sex education are considered appropriate in school depending on the age of the students or what the children can comprehend at a particular point in time. Rubin and Kindendall expressed that sex education is not merely the topics of reproduction and teaching how babies are conceived and born. Instead, it has a far richer scope and goal of helping children incorporate sex more meaningfully into their present and future life and to provide them with some basic understanding of virtually every aspect of sex by the time they reach full maturity.

Evidence

Evidence shows that a combination of comprehensive sex education and access to birth control appears to decrease the rates of unintended pregnancies among teenagers. A meta-analysis that compared comprehensive sex education programs with abstinence-only programs found that abstinence-only programs did not reduce the likelihood of pregnancy, but rather may have increased it. Numerous studies show that curricula providing accurate information about condoms and contraception can lead to reductions in the risky behaviors reported by young people as well as reductions in unintended pregnancies and STIs. Programs that teach only abstinence have not been shown to be effective.

According to UNFPA, "A 2010 review found that 'gender-focused' curricula – meaning curricula that integrate gender equality into the learning material – were substantially more effective in reducing risky behaviors than programmes that did not consider gender." Research has also shown that delay in sexual initiation, use of condoms and practice contraception has been a result of young people adopting egalitarian attitudes about gender roles. These individuals were also found to be less likely engaged in violent relationships and have a lower rate of STIs including HIV and unintended pregnancy.

By emphasizing rights and gender issues, these programs help reduce gender-based violence and bullying, promote safe schools, empower young people to advocate for their own rights, and advance gender equality.

"Few sexual health interventions are designed with input from adolescents. Adolescents have suggested that sex education should be more positive with less emphasis on anatomy and scare tactics; it should focus on negotiation skills in sexual relationships and communication; and details of sexual health clinics should be advertised in areas that adolescents frequent (for example, school toilets, shopping centres)."

Also, a U.S. review concludes that "the overwhelming weight of evidence shows that sex education that discusses contraception does not increase sexual activity". The 2007 study found that "No comprehensive program hastened the initiation of sex or increased the frequency of sex, results that many people fear." Further, the report showed "Comprehensive programs worked for both genders, for all major ethnic groups, for sexually inexperienced and experienced teens, in different settings, and in different communities."

The United Nations Population Fund (UNFPA) recommends comprehensive sexuality education, as it enables young people to make informed decisions about their sexuality. According to UNFPA,

It is taught over several years, introducing age-appropriate information consistent with the evolving capacities of young people. It includes scientifically accurate, curriculum-based information about human development, anatomy and pregnancy. It also includes information about contraception and sexually transmitted infections (STIs), including HIV. And it goes beyond information, to encourage confidence and improved communication skills. Curricula should also address the social issues surrounding sexuality and reproduction, including cultural norms, family life and interpersonal relationships.

When places have more comprehensive sex education STI and pregnancy rates drop. The attitudes of children have also been found to differ depending on the content of their sex education. One comparison of results can be made between the sex education curriculum in the Netherlands and that in the US. On average teens in Europe and the Netherlands (which have more comprehensive sex ed) do not have sex at a younger age than teens in the US (with less comprehensive sex ed); however teens in the Netherlands report having a positive and consensual first sexual experience while 66% of sexually active US teens report that they wished they waited longer for their first sexual experience.

Nine out of ten teens in the Netherlands use contraception during their first sexual experience, which contributes to the lower pregnancy and STI rates. More comprehensive sex ed starting at the elementary level resulted in appreciation of sexual diversity, dating and intimate partner violence prevention, development of healthy relationships, prevention of child sex abuse, improved social/emotional learning, and increased media literacy.

Human rights issues, gender equality and gender roles should be integrated into every aspect of these discussions. This includes human rights protection, fulfilment and empowerment; the impact of gender discrimination; the importance of equality and gender-sensitivity; and the ideas underlying gender roles. Sexual abuse, gender-based violence and harmful practices should also be discussed. Taken together, all this information teaches young people the life skills necessary to assume responsibility for their own behavior and to respect the rights of others."

Comprehensive sex education "enables young people to make informed decisions about their sexuality and health. These programmes build life skills and increase responsible behaviors, and because they are based on human rights principles, they help advance human rights, gender equality and the empowerment of young people."

Sources

A 67 m (220 ft) long "condom" on the Obelisk of Buenos Aires, Argentina, part of an awareness campaign for the 2005 World AIDS Day

Sex education may be taught informally, such as when someone receives information from a conversation with a parent, friend, religious leader, or through the media. It may also be delivered through sex self-help authors, magazine advice columnists, sex columnists, or sexual education discussion board web sites. Training can also be provided through multimedia resources. Adolescents spend a lot of their time on social media, or watching television. Those same adolescents may also have a hard time talking to their families about sexual matters. A study has shown that mass media interventions; for example, use of teaching sexual education through commercials shown on television, or ads on social media, have proven effective and decreased the amount of unprotected sex. Formal sex education occurs when schools or health care providers offer sex education. Slyer stated that sex education teaches the young person what he or she should know for his or her personal conduct and relationship with others. Gruenberg also stated that sex education is necessary to prepare the young for the task ahead. According to him, officials generally agree that some kind of planned sex education is necessary.

Sometimes formal sex education is taught as a full course as part of the curriculum in junior high school or high school. Other times it is only one unit within a more broad biology, health, home economics, or physical education class. Some schools offer no sex education, since it remains a controversial issue in several countries, particularly the United States (especially with regard to the age at which children should start receiving such education, the amount of detail that is revealed, including LGBT sex education, and topics dealing with human sexual behavior, e.g. safe sex practices, masturbation, premarital sex, and sexual ethics).

Wilhelm Reich commented that sex education of his time was a work of deception, focusing on biology while concealing excitement-arousal, which is what a pubescent individual is mostly interested in. Reich added that this emphasis obscures what he believed to be a basic psychological principle: that all worries and difficulties originate from unsatisfied sexual impulses. Leepson asserted that the majority of people favor some sort of sex instruction in public schools, and this has become an intensely controversial issue because, unlike most subjects, sex education is concerned with an especially sensitive and highly personal part of human life. He suggested that sex education should be taught in the classroom. The problem of pregnancy in adolescents is delicate and difficult to assess using sex education. But Calderone believed otherwise, stating that the answer to adolescents' sexual woes and pregnancy can not lie primarily in school programmes which at best can only be remedial; what is needed is prevention education and as such parents should be involved.

When sex education is contentiously debated, the chief controversial points are whether covering child sexuality is valuable or detrimental; whether LGBT sex education should be integrated into the curriculum; the use of birth control such as condoms and hormonal contraception; and the impact of such use on pregnancy outside marriage, teenage pregnancy, and the transmission of STIs. Increasing support for abstinence-only sex education by conservative groups has been one of the primary causes of this controversy. Countries with conservative attitudes towards sex education (including the UK and the U.S.) have a higher incidence of STIs and teenage pregnancy. On the other hand, it seems that in countries where sex education is not part of the curriculum, students show limited knowledge even in basic reproductive issues. For example, in a 2019 study with Greek students, it is reported that about two-thirds of the students failed to name external female genitals, such as the clitoris and labia, even after detailed pictures were provided to them.

Public opinion

A survey conducted in Britain, Canada and the United States by Angus Reid Public Opinion in November 2011 asked adult respondents to look back to the time when they were teenagers, and describe how useful several sources were in enabling them to learn more about sex. By far, the largest proportion of respondents in the three countries (74% in Canada, 67% in Britain and 63% in the United States) said that conversations with friends were "very useful" or "moderately useful." The next reputable source was the media (television, books, movies, magazines), mentioned by three-in-five British (65%) and Canadians (62%) and more than half of Americans (54%) as useful.

In 2011, Angus Reid Public Opinion said that half of Canadians (54%) and Americans (52%) found their sex education courses at school to be useful, only 43% of Britons share the same view. And while more than half of Americans (57%) say conversations with family were useful, only 49% of Canadians and 35% of Britons said so.

By area

Africa

Sex education in Africa has focused on stemming the growing AIDS epidemic. Most governments in the region have established AIDS education programs in partnership with the World Health Organization and international NGOs. These programs were undercut significantly by the Mexico City policy, an initiative put in place by President Ronald Reagan, suspended by President Bill Clinton, and re-instated by President George W. Bush. The Global Gag Rule "required nongovernmental organizations to agree as a condition of their receipt of Federal funds that such organizations would neither perform nor actively promote abortion as a method of family planning in other nations...." The policy was again suspended as one of the first official acts by United States President Barack Obama. The incidences of new HIV transmissions in Uganda decreased dramatically when Clinton supported a comprehensive sex education approach (including information about contraception and abortion). According to Ugandan AIDS activists, the policy undermined community efforts to reduce HIV prevalence and HIV transmission.

Egypt teaches knowledge about male and female reproductive systems, sexual organs, contraception and STDs in public schools at the second and third years of the middle-preparatory phase (when students are aged 12–14). A coordinated program between UNDP, UNICEF, and the ministries of health and education promotes sexual education at a larger scale in rural areas and spreads awareness of the dangers of female genital mutilation.

Asia

The state of sex education programs in Asia is at various stages of development, like in the country Philippines where the topic sex education is considered to be very controversial because it deals with different topics which are sometimes too vague and too broad to be implemented largely in the society.

Thailand

In Thailand there has been progress on sex education, with the boundaries being pushed forward with each revision of the curriculum. The first national policy on sexuality education in schools was announced in 1938, but sex education was not taught in schools until 1978. It was then called "Life and Family Studies", and its content consisted of issues related to the reproductive system and personal hygiene. The education curriculum has been revised several times, involving efforts from both government and non-government sectors, and sex education has been accepted as a problem solving tool for adolescent sexual reproduction and health issues. This has been a consequence of educational reform following the National Education Act B.E. 2542, increasing awareness of problems related to adolescents' sexual practices, and the emergence of women's sexuality and queer movements. Another new approach in sexuality education curricula in Thailand has been the Teenpath Project developed by PATH, Thailand. PATH has also succeeded in institutionalizing sexuality education curricula in schools since 2003.

India

In India, there are many programs promoting sex education including information on AIDS, sex and sexuality in schools as well public education and advertising. AIDS clinics however are not universally available.

India has a strong prevention program which goes hand in hand with care, support and treatment. We have been able to contain the epidemic with a prevalence of just 0.31%. We have also brought about a decline of 50% in new infections annually.
— Shri Gulam Nabi Azad, Hon’ble Minister of Health and Family Welfare, 2011.

UnTaboo, a company dedicated to sex education, however, has age appropriate programs on sex, sexuality and safety awareness education which are conducted in schools and in small private groups outside of schools. Sexual reproduction and different contraceptive methods are taught in grades 8 and 10 (age 14 and 16) compulsorily.

China

In 2000, a new five-year project was introduced by the China Family Planning Association to "promote reproductive health education among Chinese teenagers and unmarried youth" in twelve urban districts and three counties. This included discussion about sex within human relationships as well as pregnancy and HIV prevention. Since the 2010s there has been a great increase in books about sex education for children and young adults.

The state of sex education programs in China barely meets the international standards. China’s sex education is absent, although there have been proposals made to include comprehensive sex education in the curriculum. Although such proposals have been made, there has not been any solid actions to implement such programs in school, mainly due to the conservative and traditional mindsets. The topic of sex is not talked about enough in public, and even shunned in private. Teachers and parents alike are embarrassed to talk about sex-related topics that such education is often skipped, making this topic extremely sensitive. There is demand for sex education that is concentrated on social media platforms such as Weibo, citing the need to have sex education in order for its people to learn how to protect themselves against sexual related abuse and harassments. China currently still experiences sexual illiteracy. China’s government has passed a law that mandates “age-appropriate sex education” in October, 2020, but no outlines have been created yet to clarify how the mandate would be implemented in school.

Most recently, China has introduced a new sexual education for students named the 'Healthy China Initiatives (2019-2030)'. The initiative came after a 2015 study by the China Family Planning Association conducted a study that showed only 10% of approximately 20,000 universities reported that they were not content with their sexual education in grade school and were unknowledgeable to violence, gender, contraceptives, sexually transmitted diseases, and pregnancy among other topics. The initiative is said to help provide students with knowledge of gender, sexuality, equality, consent, and rights.

Other countries

Indonesia, Mongolia, and South Korea have a systematic policy framework for teaching about sex within schools. Malaysia and Thailand have assessed adolescent reproductive health needs with a view to developing adolescent-specific training, messages and materials.

Bangladesh, Myanmar, and Pakistan have no coordinated sex education programs.

In Nepal, sex education is mandatory in school.

In Japan, sex education is mandatory from age 10 or 11, mainly covering biological topics such as menstruation and ejaculation.

In Sri Lanka, sex education traditionally consisted of reading the reproduction section of biology textbooks. Young people are taught when they are 12 years old.

The International Planned Parenthood Federation and the BBC World Service ran a 12-part series known as Sexwise, which discussed sex education, family life education, contraception and parenting. It was first launched in South Asia and then extended worldwide.

In Taiwan, compared to China’s progress, has been a lot more progressive in implementing sex education. However, the controversy lies more in anti-gay groups who argue that including same-sex relationships in sex education is morally controversial, despite being the first Asian country to legalize same-sex marriage. Therefore, while sex education is required in school, LGBTQ topics have been rejected by many parents in the society, which potentially violates gender equity education in school. From the Journal of Modern Education Review, Taiwan has committed to achieving gender equity since 2004 with its Gender Equity Education Act (Taiwan) (GEEA), which includes curriculum, material, and activities to be practiced and taught in elementary and middle school. But also as a relatively conservative Asian country and culture, Taiwan has not yet been up to par with international standards, but seemingly on its way towards more progressive sex education.

Singapore

The Singapore Family Planning Association has developed a series of sex education programs for young people, focusing on strict control of sexual behavior and age. The Singapore government attaches great importance to the moral education of young people, and the sentencing of sexual offenses is very strict.

Europe

The World Health Organization and the German Federal Office of Health Education recommend sex education for children of all ages.

Finland

In Finland, sexual education is usually incorporated into various compulsory courses, mainly as part of biology lessons (in lower grades) and later in a course related to general health issues.

France

In France, sex education has been part of school curricula since 1973. Schools are expected to provide 30 to 40 hours of sex education, and pass out condoms, to students in grades 8 and 9 (aged 15–16). In January 2000, the French government launched an information campaign on contraception with TV and radio spots and the distribution of five million leaflets on contraception to high school students. In September 2013, the government launched a new program called les ABCD de l’égalité ('the ABCD of equality') whose main aim is to "fight gender stereotypes at school". The ultimate goal is to foster mutual respect between boys and girls early on so that it impacts their conception of the world later on.

Germany

The first state-sponsored courses on sex education were introduced in Breslau, Prussia, c. 1900 by Dr. Martin Chotzen.

In Germany, sex education has been part of school curricula since 1970. Since 1992 sex education is a governmental duty by law.

It normally covers all subjects concerning the process of growing up, bodily changes during puberty, emotions involved, the biological process of reproduction, sexual activity, partnership, homosexuality, unwanted pregnancies and the complications of abortion, the dangers of sexual violence, child abuse, and sex-transmitted diseases. It is comprehensive enough that it sometimes also includes things in its curricula such as sex positions. Most schools offer courses on the correct usage of contraception.

A sex survey by the World Health Organization concerning the habits of European teenagers in 2006 revealed that German teenagers care about contraception. The birth rate among 15- to 19-year-olds was very low—only 11.7 per 1000 people, compared to 27.8 births per 1,000 people in the UK, and 39.0 births per 1,000 people in Bulgaria (which, incidentally, has the highest birth rate in Europe).

German Constitutional Court and later, in 2011, the European Court of Human Rights, rejected complaints from several Baptists against Germany concerning mandatory sex education.

Greece

A 2022 analysis reported that human reproduction is mentioned in six out of 113 Greek secondary education textbooks used in biology classes from 1870s to present.

Poland

At the time of the People's Republic of Poland, since 1973, sex education was one of the school subjects; however, it was relatively poor and did not achieve any actual success. After 1989, it practically vanished from the school life—it is currently a subject called "family life education" (wychowanie do życia w rodzinie) rather than "sex education" (edukacja seksualna)—and schools explicitly require parental consent for their children to attend sex education classes. This policy is largely due to the strong objection against sex education raised by the Catholic Church.

Portugal

Some sex education is taught as part of biology-related curricula. There is also an official program intended to provide sex education for students.

Netherlands

Subsidized by the Dutch government, the "Long Live Love" package (Lang leve de liefde), developed in the late 1980s, aims to give teenagers the skills to make their own decisions regarding health and sexuality. Nearly all secondary schools provide sex education, as part of biology classes and over half of primary schools discuss sexuality and contraception. Starting the 2012 school year, age-appropriate sex education—including education about sexual diversity —will be compulsory in all secondary and primary schools. The curriculum focuses on biological aspects of reproduction as well as on values, attitudes, communication and negotiation skills. Dutch sex education encourages the idea that topics like masturbation, homosexuality, and sexual pleasure are normal or natural and that there are larger emotional, relational, and societal forces that shape the experiences of sexuality. This type of curriculum can begin for students as young as at age four. The curriculum for children focuses on topics like love, self-image, and gender stereotypes. All elementary level students in the Netherlands are required by law to receive some level of sex education. There is some flexibility in how the subject is taught however there are some required principles such as sexual diversity and sexual assertiveness. Moreover, according to Amy Schalet, Dutch parents tend to form close relationships with their children, openly discussing teen sexuality. Dutch parents try to accept their children's romantic relationships and even allow sleepovers, expecting them to have sex. The media has encouraged open dialogue and the health-care system guarantees confidentiality and a non-judgmental approach. The Netherlands has one of the lowest teenage pregnancy rates in the world, and the Dutch approach is often seen as a model for other countries.

Slovakia

In Slovakia the content of sex education varies from school to school, most frequently as a segment of a larger lesson plan of a subject akin to nature science in English (this course covers both biology and petrology). Generally the sex ed content taught in Slovakia is quite basic, sometimes lacking, though exactly what any given lesson contains varies among schools and is dependent on the teacher's knowledge of the subject. It is not uncommon for teachers to rely on students asking questions (as opposed to documentaries, discussions, textbooks and in-class debates). Classes are usually divided into boys and girls. Boys are taught the basics of sex, usually limited to dialogue between student and teacher of annotated diagrams of genitalia; while girls are additionally taught about menstruation and pregnancy.

Sweden

In Sweden, sex education was established in 1921 for secondary education and in 1942 for all grades. The subject is usually started in kindergarten and continues cumulatively throughout the student's entire schooling. This sexual education is incorporated into different subjects such as biology and history. The Swedish Association for Sexuality Education (RFSU) has a sex education that emphasizes "sexual diversity, freedom and enjoyment", and the RFSU collaborate frequently with government organizations such as the National Institute of Public Health. Alongside this emphasis of sexual diversity, Swedish sex education has equal incorporations of lesbian and gay sexuality as well as heterosexual sexuality. They provide knowledge about masturbation, oral and anal sex as well as heterosexual, genital intercourse.

Switzerland

In Switzerland, the content and amount of sex education is decided at the cantonal level. In Geneva, courses have been given at the secondary level first for girls since 1926 and compulsory programs have been implemented at secondary level for all classes since the 1950s. In most French-speaking cantons since the 1970s, generalized courses have been implemented by states with duly formed and trained specialists working within school health services at the secondary level.

Interventions in primary schools were started during the 1980s, with the basic objective of empowering children, strengthening their resources, and giving the capacity to discriminate what is right or wrong based upon what is and is not allowed by law and society. They are also given knowledge of their own rights, told that they can have their own feelings about themselves, and informed on whom to talk to in case they feel uncomfortable about a private matter and wish to talk about it.

Finally, the objectives include an enforcement of their capacity to decide for themselves and their ability to express their feelings about a situation and say "no". In secondary schools, there are programs at ages 13–14 and 16–17 with the basic objective to give students a secure moment with caring, well-informed adults. With confidentiality and mutual respect, students can talk to an adult who understands youth needs and what they should know about sexual life in conformity with age and maturity.

In the German part of the country, the situation is somewhat different. Sex education as a school implemented program is a fairly recent subject, the responsibility given to school teachers. Though federal structures give authority to each state to decide, there are efforts, notably under the auspices of Santé sexuelle Suisse – the Swiss branch of IPPF (International Planned Parenthood Federation) – to look for and propose possible models of application which take into account all factors of sex education according to their different levels of concern, parents, teachers, and external experts.

United Kingdom

England and Wales

Cecil Reddie ran the first sex education course at a British school in October 1889 at Abbotsholme School but the lessons were only for sex between married couples.

In England and Wales, Sex and relationship education (SRE) is compulsory since 1976, in part, from age 11 onwards. It involves teaching children about reproduction, sexuality and sexual health. It does not promote early sexual activity or any particular sexual orientation. The compulsory parts of sex and relationship education are the elements contained within the national curriculum for science. Parents can currently withdraw their children from all other parts of sex and relationship education if they want.

The compulsory curriculum focuses on the reproductive system, foetal development, and the physical and emotional changes of adolescence, while information about contraception and safe sex is discretionary and discussion about relationships is often neglected. Britain has one of the highest teenage pregnancy rates in Europe However, these have halved across England and Wales in recent years and continue to fall.

Some schools actively choose to deliver age appropriate relationship and sex education from Early Years Foundation Stage, which include the differences between boys and girls, naming body parts, what areas of the body are private and should not be touched unless the child is happy and gives consent.

Following sustained political pressure, in March 2017 it was announced by the Department for Education (DofE) that from September 2019, Relationship Education (RE) in primary schools and Relationship and Sex Education (RSE) in secondary schools will be made mandatory in England by the UK government. The existing category of SRE (Sex and Relationship Education) is now referred to as RSE (Relationship and Sex Education) by the British government.

A consultation was held by the DofE from 19 December 2017 to 12 February 2018 to inform the updated guidelines that will be released before the new mandatory subject being added to the curriculum in England in 2019.

Scotland

The main sex education programme in Scotland is Healthy Respect, which focuses not only on the biological aspects of reproduction but also on relationships and emotions. Education about contraception and sexually transmitted diseases are included in the programme as a way of encouraging good sexual health. In response to a refusal by Catholic schools to commit to the programme, however, a separate sex education programme has been developed for use in those schools. Funded by the Scottish Government, the programme Called to Love focuses on encouraging children to delay sex until marriage, and does not cover contraception, and as such is a form of abstinence-only sex education.

North America

Canada

As education is a provincial concern, sex education varies across Canada. Ontario has a provincial curriculum created in 1998. Attempting to update it has proven controversial: a first reform was shelved in 2010 and a new curriculum introduced in 2015 by the Liberal government under Kathleen Wynne was reversed three years later by the Conservatives under Doug Ford, inviting parents to file complaints against teachers who will not comply with the change. Mandatory sex education was removed from the Quebec provincial curriculum in 2005, leaving it at the discretion of each teacher. With rates of syphilis and gonorrhea rising in the province since this change, several researchers and sex educators are criticizing the current policy, most notably Lisa Trimble and Stephanie Mitelman. It was brought back as a facultative subject in 2016–2017, then mandatory for the 2017–2018 school year.

United States

Almost all U.S. students receive some form of sex education at least once between grades 7 and 12; many schools begin addressing some topics in grades 5 or 6. However, what students learn varies widely, because curriculum decisions are decentralized. Many states have laws governing what is taught in sex education classes and contain provisions to allow parents to opt out. Some state laws leave curriculum decisions to individual school districts.

Sex education is required in 30 states, 28 of which also require HIV education. 9 more states require just HIV education. Only 18 states require the information taught to be medically accurate by law. 37 states allow parents to opt their kids out of their Sex Ed. 19 states require instruction that sexual activity should only occur in marriage and 28 states require that abstinence be stressed. Contextually, 11 states must inclusively discuss sexual orientation and 5 legally must emphasize heterosexuality or provide negative information about homosexuality. Only 9 states require the importance of consent in a sexual situation.

For example, a 1999 study by the Guttmacher Institute found that most U.S. sex education courses in grades 7 through 12 cover puberty, HIV, STIs, abstinence, implications of teenage pregnancy, and how to resist peer pressure. Other studied topics, such as methods of birth control and infection prevention, sexual orientation, sexual abuse, and factual and ethical information about abortion, varied more widely.

Abstinence-only sex education tells teenagers that they should be sexually abstinent until marriage and does not provide information about contraception. In the Kaiser study, 34% of high-school principals said their school's main message was abstinence-only.

The difference between these two approaches, and their impact on teen behavior, remains a controversial subject. In the U.S., teenage birth rates had been dropping since 1991. However, a 2007 Centers for Disease Control and Prevention report showed a 3% increase from 2005 to 2006, to nearly 42 births per 1,000. From 1991 to 2005, the percentage of teens reporting that they had ever had sex or were currently sexually active showed small declines. Still , the U.S. has the highest teen birth rate and one of the highest rates of STIs among teens in the industrialized world. Public opinion polls conducted over the years have found that the vast majority of Americans favor broader sex education programs over those that teach only abstinence, although abstinence educators recently published poll data with the opposite conclusion.

Proponents of comprehensive sex education, which include the American Psychological Association, the American Medical Association, the National Association of School Psychologists, the American Academy of Pediatrics, the American Public Health Association, the Society for Adolescent Medicine and the American College Health Association, argue that sexual behavior after puberty is a given, and it is therefore crucial to provide information about the risks and how they can be minimized; they also claim that denying teens such factual information leads to unwanted pregnancies and STIs.

On the other hand, proponents of abstinence-only sex education object to curricula that fail to teach a standard of moral behavior; they maintain that a morality which is based on sex only within the bounds of marriage is "healthy and constructive" and that value-free knowledge of the body may lead to immoral, unhealthy, and harmful practices. Within the last decade, the federal government has encouraged abstinence-only education by steering over a billion dollars to such programs. Some 25 states now decline the funding so that they can continue to teach comprehensive sex education. Funding for one of the federal government's two main abstinence-only funding programs, Title V, was extended only until December 31, 2007; Congress is debating whether to continue it past that date.

The impact of the rise in abstinence-only education remains a question. To date, no published studies of abstinence-only programs have found consistent and significant program effects on delaying the onset of intercourse. In 2007, a study ordered by the U.S. Congress found that middle school students who took part in abstinence-only sex education programs were just as likely to have sex (and use contraception) in their teenage years as those who did not. Abstinence-only advocates claimed that the study was flawed because it was too narrow and began when abstinence-only curricula were in their infancy, and that other studies have demonstrated positive effects.

According to Anna Mulrine of U.S. News & World Report, records show that professionals still do not know which method of sex education works best to keep teens from engaging in sexual activity, but they are still working to find out.

A recent study in January 2022 found that a majority of US teens lack quality sexual education, a trend that has been worsening over years. Instruction on waiting until marriage to have sex declined from 73% to 67% among females (P = 0.005) and from 70% to 58% in males (P < 0.001).

Virginia

Virginia uses the sex education program called the National Campaign to prevent teen and unplanned pregnancy. The National Campaign was created in 1996 and focuses on preventing teen and unplanned pregnancies of young adults. The National Campaign set a goal to reduce the teen pregnancy rate by 1⁄3 in ten years. The Virginia Department of Health ranked Virginia 19th in teen pregnancy birth rates in 1996. Virginia was also rated 35.2 teen births per 1,000 girls aged 15–19 in 2006. The Healthy people 2010 goal is a teen pregnancy rate at or below 43 pregnancies per 1,000 females age 15–17.

Mississippi

Sex education in Mississippi public schools was first introduced in 2011, with the requirement that schools teach “abstinence-only” or “abstinence-plus” curriculum. This law had additional requirements, such as the separation of boys and girls for instruction and not allowing instructors to physically demonstrate contraceptive use, such as condoms. This law was updated as of July 1, 2021. The state’s Department of Education announced they would now mandate curricula to be “culturally proficient, evidence-based, medically accurate, and age-appropriate for middle and high school students”. This was the first time such inclusive measures would be included. However, sex education is still not compulsory, both due to district decisions and individual parents through an “opt-in policy”.

Mississippi, tied with Alabama, is the most highly religious state based on a number of indicators, such as 82% of adults believing in God with absolute certainty. Due to how religious and conservative the state is, advocates for comprehensive sex education often use the state of Mississippi as an example of the negative consequences and failures of abstinence-only education. The World Population Review reports Mississippi as the second-highest teen birth rate in the country, with 29.1 births per 1,000 women between the ages of 15 and 19. This number is up from 27.8 in 2018.

Tennessee

Tennessee has no mandatory sexual education curriculum in place, leaving individual school districts to oversee their own sex ed curricula if it is chosen to be taught. Many of those school districts have relied heavily on abstinence-led curricula. Tennessee schools have created a mandatory family life education program if females ages 15–17 have pregnancy rates higher than 19.5 per every 1000 depending on the county. In 2012, state legislature advanced Senate Bill 3310, otherwise known as the "Gateway Law," to enforce abstinence only sexual education and limit the information given to students by educators that encourage sexual activities with penalties of $500 if done. More recently, in 2017, state legislature passed Senate Bill 1510 to provide intervention, treatment, and prevention of child sex abuse. Though Senate Bill 1510 was implemented, it continued to forbid promoting sexual activities and dispense contraception on school property. Currently pending is Senate Bill 646 where curriculum for students includes "medically accurate and age appropriate" sex education. In doing so, students are able to obtain information about consent, abstinence, sexually transmitted diseases, pregnancy, and communication skills among other things.

Florida

Sex education is not mandatory in Florida, but the state has implemented a comprehensive health education curriculum that teaches pregnancy and considers abstinence to be the "expected social standard". In such courses, students learn about monogamy, heterosexual marriages, and abstinence until marriage. Though courses are taught, parents and guardians are able to opt-out of allowing students to learn with written communication and consent given to their school. Several house bills were proposed to onset the Florida Healthy Adolescent Act where schools were required to introduce students to comprehensive and medically accurate health information that was age appropriate about sexuality, healthy relationships, and contraception. The Senate vetoed the bills to pass the act.

Texas

Sex education in Texas has recently become a policy of much focus in the state. With the rise of recent protests and proposed bills in the Texas House, the current policy has been the focus of much scrutiny. As of 1997, when Senate Bill 1 was enacted, Texas has left the decision of inclusion of sex education classes within schools up to the individual districts. The school board members are entitled to approve all curricula that are taught; however the bill has certain criteria that a school must abide by when choosing to teach sex ed. These include:

present abstinence from sexual activity as the preferred choice of behavior in relationship to all sexual activity for unmarried persons of school age;
devote more attention to abstinence from sexual activity than to any other behavior;
emphasize that abstinence from sexual activity, if used consistently and correctly, is the only method that is 100 percent effective in preventing pregnancy, sexually transmitted diseases, infection with Human Immunodeficiency Virus (HIV) or Acquired Immune Deficiency Syndrome (AIDS), and the emotional trauma associated with adolescent sexual activity;
direct adolescents to a standard of behavior in which abstinence from sexual activity before marriage is the most effective way to prevent pregnancy, sexually transmitted diseases, and infection with HIV or AIDS; and
teach contraception and condom use in terms of real-world failure rates, not statistics based on laboratory rates, if instruction on contraception and condoms is included in curriculum content.

Additionally, school districts are not authorized to distribute condoms in connection with instruction relating to human sexuality.

Since the enactment of this policy, several research studies have been done to evaluate the Sex Ed Policy, namely the abstinence-only aspect of the teaching. Drs. David Wiley and Kelly Wilson published the Just Say Don't Know: Sexuality Education in Texas Public Schools report where they found that:

Shaming and fear-based instruction are commonly used for teaching sex ed
Gender stereotypes are promoted
A majority of students receive no information about human sexuality except abstinence
The materials used regularly contain factual errors and distort the truth about condoms and STDs

According to Texas State Representative Mike Villarreal, "We have a responsibility to ensure that our children receive accurate information in the classroom, particularly when students' health is at stake," Villarreal said. "We're dealing with a myriad of problems in Texas as a result of our sky high teen pregnancy rates. We cannot allow our schools to provide erroneous information—the stakes are far too high." With this in mind, many state legislators have proposed bills to improve sex education in Texas Schools.

SB 852/HB 1624 – In Feb 2011, Senator Ellis proposed The Education Works bill. This bill would require schools that teach sex education to provide evidence-based, age-appropriate information that emphasizes the importance of abstinence as the only 100% effective method of avoiding sexually transmitted infections (STIs) and pregnancy, while also teaching about contraceptive methods to avoid STIs and pregnancy.
HB 741/SB 515 – In 2011, Representatives Joaquin Castro and Mike Villarreal introduced a bill calling for abstinence-plus sexual health education bill. The bill would have medically accurate information, including: abstinence, contraception, and what it really takes to be a parent. The bill received a hearing but was left in committee.
HB 1567/ SB 1076 – Introduced in 2009 by Villarreal, this bill would have required instruction on contraceptive use to be scientifically accurate when it is taught as part of a school's sexual health curriculum. It did not receive a hearing.

Scientific evidence accumulated over many decades demonstrates that the abstinence-only-until-married (AOUM) curriculum taught in Texas schools is harmful and ineffective in reducing the adolescent pregnancy rate in Texas. Despite these facts, recently published in the Journal of Adolescent Health, AOUM programs continue to be funded by the U.S. government. In fact, the U.S. government has spent more than $2 billion over the last 20 years to prohibit comprehensive sex education in public schools, choosing instead to fund the AOUM curriculum while the adolescent pregnancy rates continue to rise.

Catholic schools in Texas follow Catholic Church teachings in regard to sex education. Some opponents of sex education in Catholic schools believe sex ed programs are doing more harm to the young than good. Opponents of sex education contend that children are not mentally and emotionally ready for this type of instruction, and believe that exposing the young to sex ed programs may foster the students with the preoccupation of sex.

The Catholic Church believes that parents are the first educators and should rightfully fight for their duty as such in regard to sex education:

Humanae Vitae teaches that the faithful must form their 'consciences' as a guide to Christ-like decision making in regard to sex education.
the young should not engage in premarital sex, adultery, fornication or other acts of impurity or scandals to others
Pope John Paul II says that sex education is "a basic right and duty of parents."

Oceania

Australia

The Government of Victoria (Australia) developed a policy for the promotion of Health and Human Relations Education in schools in 1980 that was introduced into the State's primary and secondary schools during 1981. The initiative was developed and implemented by the Honorable Norman Lacy MP, Minister for Educational Services from 1979 to 1982.

A Consultative Council for Health and Human Relations Education was established in December 1980 under the chairmanship of Dame Margaret Blackwood; its members possessed considerable expertise in the area.

The council had three major functions:

to advise and to be consulted on all aspects of Health and Human Relations' Education in schools;
to develop, for consideration of the Government, appropriate curriculum for schools;
to advise and recommend the standards for in-service courses for teachers and relevant members of the school community.

Support services for the Consultative Council were provided by a new Health and Human Relations Unit within the Special Services Division of the Education Department of Victoria and was responsible for the implementation of the Government's policy and guidelines in this area. The Unit advised principals, school councils, teachers, parents, tertiary institutions and others in all aspects of Health and Human Relations Education.

In 1981 the Consultative Council recommended the adoption of a set of guidelines for the provision of Health and Human Relations Education in schools as well as a Curriculum Statement to assist schools in the development of their programs. These were presented to the Victorian Cabinet in December 1981 and adopted as government policy.

As of March 2021, respectful relationships education was a core part of Victoria's curriculum, and was to become mandatory in all state schools. Students will also be specifically taught about consent.

New Zealand

In New Zealand, sexuality education is part of the Health and Physical Education curriculum, which is compulsory for the first ten years of schooling (Years 1 to 10) but optional beyond that. Sexual and reproductive health education begins at Year 7 (approximately age 11), although broader issues such as physical, emotional and social development, personal and interpersonal skills, and (non-sexual) relationships begin as early as Year 1 (approximately age 5).

The Health/Hauora curriculum, including the sexuality education component, is the only part of the New Zealand Curriculum/Te Matauranga o Aotearoa (the former for English-medium schools, the latter for Māori-medium schools) in which state and state-integrated schools must legally consult with the school community regarding its delivery, and the consultations must occur at least once every two years. Parents can ask for their children to be removed from the sexuality education component of the health curriculum for any reason, provided they apply in writing to the school principal, and do so at least 24 hours beforehand so alternative arrangements can be made. However, this does not prevent a teacher answering sexuality education questions if a student, excluded or not, asks them.

Morality

There are two opposing sides of the sex education argument amongst parents. Sexual liberals see knowledge on sex as equipping individuals to make informed decisions about their personal sexuality, and they are in favor of comprehensive sexual education all throughout schooling, not just in high school. Sexual conservatives see knowledge on sex as encouraging adolescents to have sex, and they believe that sex should be taught inside the family in order for their morals to be included in the conversation. Sexual conservatives see the importance of teaching sex education, but only through abstinence-only programs.

Another viewpoint on sex education, historically inspired by sexologists such as Wilhelm Reich and psychologists such as Sigmund Freud and James W. Prescott, holds that what is at stake in sex education is control over the body and liberation from social control. Proponents of this view tend to see the political question as whether society or the individual should teach sexual mores. Sexual education may thus be seen as providing individuals with the knowledge necessary to liberate themselves from socially organized sexual oppression and to make up their own minds. In addition, sexual oppression may be viewed as socially harmful. Sex and relationship experts like Reid Mihalko of "Reid About Sex" suggest that open dialogue about physical intimacy and health education can generate more self-esteem, self-confidence, humor, and general health.

Some claim that certain sex education curricula break down pre-existing notions of modesty or encourage acceptance of what they consider immoral practices, such as homosexuality or premarital sex. Naturally, those that believe that homosexuality and premarital sex are a normal part of the range of human sexuality disagree with them.

Many religions teach that sexual behavior outside of marriage is immoral and/or psychologically damaging, and many adherents desire this morality to be taught as a part of sex education. They may believe that sexual knowledge is necessary, or simply unavoidable, hence their preference for curricula based on abstinence.

LGBT sex education

One major source of controversy in the realm of sex education is whether LGBT sex education should be integrated into school curricula. LGBT sex education includes inclusive teaching of safe sex practices for lesbian, gay, bisexual, and transgender individuals and general instruction in topics related to sexual orientation and gender identity. Studies have shown that many schools do not offer such education today. Five states (Alabama, Louisiana, Mississippi, Oklahoma, and Texas) have laws in place that ban teaching LGBT sex education. Only 20% of LGBT students have heard anything positive about their community and they reported in a 2011 Gay, Lesbian and Straight Education Network (GLSEN) report that they were more likely to hear positive information about LGBT people from a history or social studies class rather than a health class. Six states (California, Colorado, New Jersey, Oregon, Rhode Island, and Washington) enforce sex education curricula that includes LGBT information beginning 2020. Beyond states, the District of Columbia has also moved to offer curricula that supports the involvement of LGBT sexual education. Beneficial factors have shown to include lowered rates of depression and suicide, tentative approaches to sexual behaviors, and intimidation from peers.

Pro-LGBT

Proponents of LGBT sex education argue that encompassing homosexuality into the curricula would provide LGBT students with the sexual health information they need, and help to ameliorate problems such as low self-esteem and depression that research has shown can be present in LGBT individuals. They also claim that it could reduce homophobic bullying.

An example of LGBT-inclusive curriculum is introduced by the National Sexuality Education Standards set forth by the Future of Sex Education Initiative. These education standards outline seven core topics that must be addressed in sex education; one of those core topics is identity. The identity topic presents lesbian, gay, bisexual and transgender identities as possibilities for students as they progress through life and come to understand who they are. These standards, the Future of Sex Education argues, will start in kindergarten and will evolve into more complex topics throughout schooling as the students mature and age. In the UK, BigTalk Education's Growing Up Safe programme, which includes LGBT relationship education from Primary School age, was awarded the 2017 Pamela Sheridan award for innovation and good practice in relationships and sex education (RSE), services and projects for young people.

Anti-LGBT

Opponents often argue that teaching LGBT sex education would be disrespectful to some religions and expose students to inappropriate topics. They say that including homosexuality in the curriculum would violate parents' rights to control what their children are exposed to and that schools should not inflict a particular political view on students. Currently, many sex education curricula do not include LGBT topics, and research has reported that students often feel that they do not receive adequate instruction in LGBT sex topics.

Parental rights in education

Recently, some states have opted to restrict topics about LGBT matter and people. One of the most controversial laws passed has been labeled the "Don't Say Gay" law that has most recently been passed in Florida. The bill seeks to ban gender and sexuality issues being presented to students while in lower grade school in efforts to allow parents to make the decision as to when or if they will introduce their child to Gender and Sexuality subject matter.

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