Mars sample return missions have been proposed that would return material from the surface of Mars back to Earth
The study of surface characteristics (or surface properties and processes) is a broad category of Mars science that examines the nature of the materials making up the Martian surface.
The study evolved from telescopic and remote-sensing techniques
developed by astronomers to study planetary surfaces. However, it has
increasingly become a subdiscipline of geology as automated spacecraft
bring ever-improving resolution and instrument capabilities. By using
characteristics such as color, albedo, and thermal inertia and analytical tools such as reflectance spectroscopy and radar,
scientists are able to study the chemistry and physical makeup (e.g.,
grain sizes, surface roughness, and rock abundances) of the Martian
surface. The resulting data help scientists understand the planet's
mineral composition and the nature of geological processes operating on
the surface. Mars’ surface layer represents a tiny fraction of the total
volume of the planet, yet plays a significant role in the planet's
geologic history. Understanding physical surface properties is also very important in determining safe landing sites for spacecraft.
Albedo and Color
Like
all planets, Mars reflects a portion of the light it receives from the
sun. The fraction of sunlight reflected is a quantity called albedo,
which ranges from 0 for a body that reflects no sunlight to 1.0 for a
body that reflects all sunlight. Different parts of a planet's surface
(and atmosphere) have different albedo values depending on the chemical
and physical nature of the surface.
Mollweide
projection of albedo features on Mars from Hubble Space Telescope.
Bright ochre areas in left, center, and right are Tharsis, Arabia, and
Elysium, respectively. The dark region at top center left is Acidalium
Planitia. Syrtis Major is the dark area projecting upward in the center
right. Note orographic clouds over Olympus and Elysium Montes (left and
right, respectively).
No topography is visible on Mars from Earth-based telescopes. The
bright areas and dark markings on pre-spaceflight-era maps of Mars are
all albedo features. (See Classical albedo features on Mars.)
They have little relation to topography. Dark markings are most
distinct in a broad belt from 0° to 40° S latitude. However, the most
prominent dark marking, Syrtis Major Planum, is in the northern hemisphere, outside this belt. The classical albedo feature Mare Acidalium (Acidalia Planitia)
is another prominent dark area that lies north of the main belt. Bright
areas, excluding the polar caps and transient clouds, include Hellas, Tharsis, and Arabia Terra.
The bright areas are now known to be locations where fine dust covers
the surface. The dark markings represent areas that the wind has swept
clean of dust, leaving behind a lag of dark, rocky material. The dark
color is consistent with the presence of mafic rocks, such as basalt.
The albedo of a surface usually varies with the wavelength of light hitting it. Mars reflects little light at the blue end of the spectrum
but much at red and higher wavelengths. This is why Mars has the
familiar reddish-orange color to the naked eye. But detailed
observations reveal a subtle range of colors on Mars' surface. Color
variations provide clues to the composition of surface materials. The
bright areas are reddish-ochre
in color, and the dark areas appear dark gray. A third type of area,
intermediate in color and albedo, is also present and thought to
represent regions containing a mixture of the material from the bright
and dark areas. The dark gray areas can be further subdivided into those that are more reddish and those less reddish in hue.
Reflectance Spectroscopy
Reflectance spectroscopy
is a technique that measures the amount of sunlight absorbed or
reflected by the Martian surface at specific wavelengths. The spectra
represent mixtures of spectra from individual minerals on the surface
along with contributions from absorption lines in the solar spectrum
and the Martian atmosphere. By separating out (“deconvolving”) each of
these contributions, scientists can compare the resulting spectra to
laboratory spectra of known minerals to determine the probable identity
and abundance of individual minerals on the surface.
Using this technique, scientists have long known that the bright ochre areas probably contain abundant ferric iron (Fe3+) oxides typical of weathered iron-bearing materials (e.g., rust). Spectra of the dark areas are consistent with the presence of ferrous iron (Fe2+) in mafic minerals and show absorption bands suggestive of pyroxene,
a group of minerals that is very common in basalt. Spectra of the
redder dark areas are consistent with mafic materials covered with thin
alteration coatings.
Thermal inertia
measurement is a remote-sensing technique that allows scientists to
distinguish fine-grained from coarse-grained areas on the Martian
surface.
Thermal inertia is a measure of how fast or slow something heats up or
cools off. For example, metals have very low thermal inertia. An
aluminum cookie sheet taken out of an oven is cool to the touch in less
than a minute; while a ceramic plate (high thermal inertia) taken from
the same oven takes much longer to cool off.
Scientists can estimate the thermal inertia on the Martian
surface by measuring variations in surface temperature with respect to
time of day and fitting this data to numerical temperature models. The thermal inertia of a material is directly related to its thermal conductivity, density, and specific heat capacity.
Rocky materials do not vary much in density and specific heat, so
variations in thermal inertia are mainly due to variations in thermal
conductivity. Solid rock surfaces, such as outcroppings, have high
thermal conductivities and inertias. Dust and small granular material in
the regolith have low thermal inertias because the void spaces between
grains restrict thermal conductivity to the contact point between
grains.
Thermal inertia values for most of the Martian surface are
inversely related to albedo. Thus, high albedo areas have low thermal
inertias indicating surfaces that are covered with dust and other fine
granular material. The dark gray, low albedo surfaces have high thermal
inertias more typical of consolidated rock. However, thermal inertia
values are not high enough to indicate widespread outcroppings are
common on Mars. Even the rockier areas appear to be mixed with a
significant amount of loose material.
Data from the Infrared Thermal Mapping (IRTM) experiment on the Viking
orbiters identified areas of high thermal inertia throughout the
interior of Valles Marineris and the chaotic terrain, suggesting that
these areas contain a relatively large number of blocks and boulders.
Radar Investigations
Radar studies provide a wealth of data on elevations, slopes, textures, and material properties of the Martian surface.
Mars is an inviting target for Earth-based radar investigations because
of its relative proximity to Earth and its favorable orbital and
rotational characteristics that allow good coverage over wide areas of
the planet's surface.
Radar echoes from Mars were first obtained in the early 1960s, and the
technique has been vital in finding safe terrain for Mars landers.
Radargram of north pole layered deposits from SHARAD shallow ground-penetrating radar on Mars Reconnaissance Orbiter.
Dispersion of the returned radar echoes from Mars shows that a lot of
variation exists in surface roughness and slope across the planet's
surface. Wide areas of the planet, particularly in Syria and Sinai Plana, are relatively smooth and flat. Meridiani Planum, the landing site of the Mars Exploration RoverOpportunity,
is one of the flattest and smoothest (at decimeter-scale) locations
ever investigated by radar—a fact borne out by surface images at the
landing site.
Other areas show high levels of roughness in radar that are not
discernible in images taken from orbit. The average surface abundance of
centimeter- to meter-scale rocks is much greater on Mars than the other
terrestrial planets. Tharsis and Elysium, in particular, show a high
degree of small-scale surface roughness associated with volcanoes. This
extremely rough terrain is suggestive of young, ʻaʻā
lava flows. A 200-km-long band of low to zero radar albedo ("stealth"
region) cuts across the southwest Tharsis. The region corresponds to the
location of the Medusa Fossae Formation, which consists of thick layers of unconsolidated materials, perhaps volcanic ash or loess.
Ground-penetrating radar instruments on the Mars Express orbiter (MARSIS) and the Mars Reconnaissance Orbiter (SHARAD)
are currently providing stunning echo-return data on subsurface
materials and structures to depths of up to 5 km. Results have shown
that the polar layered deposits are composed of almost pure ice, with no
more than 10% dust by volume and that fretted valleys in Deuteronilus Mensae contain thick glaciers covered by a mantle of rocky debris.
The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its official name, Space Transportation System (STS), was taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. It flew 135 missions and carried 355 astronauts from 16 countries, many on multiple trips.
The Shuttle is the only winged crewed spacecraft to have achieved
orbit and landing, and the first reusable crewed space vehicle that
made multiple flights into orbit.[a]Its missions involved carrying large payloads to various orbits including the International Space Station (ISS), providing crew rotation for the space station, and performing service missions on the Hubble Space Telescope. The orbiter also recovered satellites
and other payloads (e.g., from the ISS) from orbit and returned them to
Earth, though its use in this capacity was rare. Each vehicle was
designed with a projected lifespan of 100 launches, or 10 years'
operational life. Original selling points on the shuttles were over 150
launches over a 15-year operational span with a 'launch per month'
expected at the peak of the program, but extensive delays in the
development of the International Space Station never created such a peak demand for frequent flights.
Background
Various
shuttle concepts had been explored since the late 1960s. The program
formally commenced in 1972, becoming the sole focus of NASA's human spaceflight operations after the Apollo, Skylab, and Apollo–Soyuz
programs in 1975. The Shuttle was originally conceived of and presented
to the public in 1972 as a 'Space Truck' which would, among other
things, be used to build a United States space station in low Earth orbit
during the 1980s and then be replaced by a new vehicle by the early
1990s. The stalled plans for a U.S. space station evolved into the International Space Station and were formally initiated in 1983 by President Ronald Reagan, but the ISS suffered from long delays, design changes and cost over-runs
and forced the service life of the Space Shuttle to be extended several
times until 2011 when it was finally retired—serving twice as long as
it was originally designed to do. In 2004, according to President George W. Bush's Vision for Space Exploration,
use of the Space Shuttle was to be focused almost exclusively on
completing assembly of the ISS, which was far behind schedule at that
point.
The first experimental orbiter Enterprise was a high-altitude glider, launched from the back of a specially modified Boeing 747, only for initial atmospheric landing tests (ALT). Enterprise's
first test flight was on February 18, 1977, only five years after the
Shuttle program was formally initiated; leading to the launch of the
first space-worthy shuttle Columbia on April 12, 1981, on STS-1. The Space Shuttle program finished with its last mission, STS-135 flown by Atlantis, in July 2011, retiring the final Shuttle in the fleet. The Space Shuttle program formally ended on August 31, 2011.
Conception and development
Early U.S. space shuttle concepts
Before the Apollo 11Moon landing in 1969, NASA began studies of Space Shuttle
designs as early as October 1968. The early studies were denoted "Phase
A", and in June 1970, "Phase B", which were more detailed and specific.
The primary intended use of the Space Shuttle was supporting the future
space station,
ferrying a minimum crew of four and about 20,000 pounds (9,100 kg) of
cargo, and being able to be rapidly turned around for future flights.
Two designs emerged as front-runners. One was designed by engineers at the Manned Spaceflight Center, and championed especially by George Mueller.
This was a two-stage system with delta-winged spacecraft, and generally
complex. An attempt to re-simplify was made in the form of the DC-3, designed by Maxime Faget,
who had designed the Mercury capsule among other vehicles. Numerous
offerings from a variety of commercial companies were also offered but
generally fell by the wayside as each NASA lab pushed for its own
version.
All of this was taking place in the midst of other NASA teams
proposing a wide variety of post-Apollo missions, a number of which
would cost as much as Apollo or more.
As each of these projects fought for funding, the NASA budget was at
the same time being severely constrained. Three were eventually
presented to Vice President Agnew in 1969. The shuttle project rose to the top, largely due to tireless campaigning by its supporters. By 1970 the shuttle had been selected as the one major project for the short-term post-Apollo time frame.
When funding for the program came into question, there were concerns
that the project might be canceled. This led to an effort to interest
the US Air Force
in using the shuttle for their missions as well. The Air Force was
mildly interested but demanded a much larger vehicle, far larger than
the original concepts, which NASA accepted since it was also beneficial
to their own plans. To lower the development costs of the resulting
designs, boosters were added, a throw-away fuel tank was adopted, and
many other changes were made that greatly lowered the reusability and
greatly added to the vehicle and operational costs. With the Air Force's
assistance, the system emerged in its operational form.
President Richard Nixon (right) with NASA AdministratorJames Fletcher in January 1972, three months before Congress approved funding for the Shuttle programShuttle approach and landing test crews, 1976
All Space Shuttle missions were launched from the Kennedy Space Center (KSC) in Florida. Some civilian and military circumpolar space shuttle missions were planned for Vandenberg AFB in California. However, the use of Vandenberg AFB for space shuttle missions was canceled after the Challenger disaster in 1986. The weather criteria used for launch included, but were not limited to: precipitation, temperatures, cloud cover, lightning forecast, wind, and humidity. The Shuttle was not launched under conditions where it could have been struck by lightning.
Challenger (OV-099) was delivered to KSC in July 1982, Discovery (OV-103) in November 1983, Atlantis (OV-104) in April 1985 and Endeavour in May 1991. Challenger
was originally built and used as a Structural Test Article (STA-099),
but was converted to a complete orbiter when this was found to be less
expensive than converting Enterprise from its Approach and Landing Test configuration into a spaceworthy vehicle.
In the course of 135 missions flown, two orbiters (Columbia and Challenger) suffered catastrophic accidents, with the loss of all crew members, totaling 14 astronauts.
The accidents led to national level inquiries and detailed analysis of why the accidents occurred. There was a significant pause where changes were made before the Shuttles returned to flight. The Columbia disaster occurred in 2003, but STS took more than a year off before returning to flight in June 2005 with the STS-114 mission. The previously mentioned break was between January 1986 (when the Challenger disaster occurred) and 32 months later when STS-26 was launched on September 29, 1988.
The longest Shuttle mission was STS-80 lasting 17 days, 15 hours. The final flight of the Space Shuttle program was STS-135 on July 8, 2011.
NASA
Administrator address the crowd at the Spacelab arrival ceremony in
February 1982. On the podium with him is then-Vice President George
Bush, the director general of European Space Agency (ESA), Eric
Quistgaard, and director of Kennedy Space Center Richard G. Smith
"President Ronald Reagan chats with NASA astronauts Henry Hartsfield and Ken Mattingly on the runway as first lady Nancy Reagan inspects the nose of Space Shuttle Columbia following its Independence Day landing at Edwards Air Force Base on July 4, 1982."[9]
STS-3 lands in March 1982
Accomplishments
Galileo floating free in space after release from Space Shuttle Atlantis, 1989Space Shuttle Endeavour docked with the International Space Station (ISS), 2011
Carried satellites with a booster, such as the Payload Assist Module (PAM-D) or the Inertial Upper Stage (IUS), to the point where the booster sends the satellite to:
U.S. Shuttle Columbia landing at the end of STS-73, 1995
Space art for the Spacelab 2
mission, showing some of the various experiments in the payload bay.
Spacelab was a major European contribution to the Space Shuttle program
European astronauts prepare for their Spacelab mission, 1984.
SpaceLab hardware included a pressurized lab, but also other
equipment allowing the Orbiter to serve as a crewed space observatory (Astro-2 mission, 1995, shown)
Space Shuttle Atlantis
takes flight on the STS-27 mission on December 2, 1988. The Shuttle
took about 8.5 minutes to accelerate to a speed of over 27,000 km/h
(17000 mph) and achieve orbit.A drag chute is deployed by Endeavour as it completes a mission of almost 17 days in space on Runway 22 at Edwards Air Force Base in southern California. Landing occurred at 1:46 pm (EST), March 18, 1995.
Early during development of the Space Shuttle, NASA had estimated
that the program would cost $7.45 billion ($43 billion in 2011 dollars,
adjusting for inflation) in development/non-recurring costs, and $9.3M
($54M in 2011 dollars) per flight.
Early estimates for the cost to deliver payload to low-Earth orbit were
as low as $118 per pound ($260/kg) of payload ($635/lb or $1,400/kg in
2011 dollars), based on marginal or incremental launch costs, and
assuming a 65,000 pound (30 000 kg) payload capacity and 50 launches per
year.
A more realistic projection of 12 flights per year for the 15-year
service life combined with the initial development costs would have
resulted in a total cost projection for the program of roughly
$54 billion (in 2011 dollars).
The total cost of the actual 30-year service life of the Shuttle program through 2011, adjusted for inflation, was $196 billion.
The exact breakdown into non-recurring and recurring costs is not
available, but, according to NASA, the average cost to launch a Space
Shuttle as of 2011 was about $450 million per mission.
NASA's budget for 2005 allocated 30%, or $5 billion, to space shuttle operations; this was decreased in 2006 to a request of $4.3 billion.
Non-launch costs account for a significant part of the program budget:
for example, during fiscal years 2004 to 2006, NASA spent around $13
billion on the Space Shuttle program, even though the fleet was grounded in the aftermath of the Columbia
disaster and there were a total of three launches during this period of
time. In fiscal year 2009, NASA budget allocated $2.98 billion for 5
launches to the program, including $490 million for "program
integration", $1.03 billion for "flight and ground operations", and
$1.46 billion for "flight hardware" (which includes maintenance of
orbiters, engines, and the external tank between flights.)
Per-launch costs can be measured by dividing the total cost over
the life of the program (including buildings, facilities, training,
salaries, etc.) by the number of launches. With 135 missions, and the
total cost of US$192 billion (in 2010 dollars), this gives approximately
$1.5 billion per launch over the life of the Shuttle program.
A 2017 study found that carrying one kilogram of cargo to the ISS on
the Shuttle cost $272,000 in 2017 dollars, twice the cost of Cygnus and
three times that of Dragon.
NASA used a management philosophy
known as success-oriented management during the Space Shuttle program
which was described by historian Alex Roland in the aftermath of the Columbia disaster as "hoping for the best". Success-oriented management has since been studied by several analysts in the area.
Accidents
In the course of 135 missions flown, two orbiters were destroyed, with loss of crew totalling 14 astronauts:
In 1986, Challenger disintegrated one minute and 13 seconds after liftoff.
Close-up video footage of Challenger during its final launch on January 28, 1986, clearly shows that the problems began due to an O-ring failure
on the right solid rocket booster (SRB). The hot plume of gas leaking
from the failed joint caused the collapse of the external tank, which
then resulted in the orbiter's disintegration due to high aerodynamic
stress. The accident resulted in the loss of all seven astronauts on
board. Endeavour (OV-105) was built to replace Challenger
(using structural spare parts originally intended for the other
orbiters) and delivered in May 1991; it was first launched a year later.
After the loss of Challenger, NASA grounded the Space Shuttle program for over two years, making numerous safety changes recommended by the Rogers Commission Report, which included a redesign of the SRB joint that failed in the Challenger
accident. Other safety changes included a new escape system for use
when the orbiter was in controlled flight, improved landing gear tires
and brakes, and the reintroduction of pressure suits for Shuttle
astronauts (these had been discontinued after STS-4; astronauts wore only coveralls and oxygen helmets from that point on until the Challenger accident). The Shuttle program continued in September 1988 with the launch of Discovery on STS-26.
The accidents did not just affect the technical design of the orbiter, but also NASA.
Quoting some recommendations made by the post-Challenger Rogers commission:
Recommendation I – The faulty Solid Rocket Motor joint and
seal must be changed. This could be a new design eliminating the joint
or a redesign of the current joint and seal. ... the Administrator of
NASA should request the National Research Council to form an independent
Solid Rocket Motor design oversight committee to implement the
Commission's design recommendations and oversee the design effort. Recommendation II – The Shuttle Program Structure should be
reviewed. ... NASA should encourage the transition of qualified
astronauts into agency management Positions. Recommendation III – NASA and the primary shuttle contractors should review all Criticality 1, 1R, 2, and 2R items and hazard analyses. Recommendation IV – NASA should establish an Office of Safety,
Reliability and Quality Assurance to be headed by an Associate
Administrator, reporting directly to the NASA Administrator. Recommendation VI – NASA must take actions to improve landing safety. The tire, brake and nosewheel system must be improved. Recommendation VII – Make all efforts to provide a crew escape system for use during controlled gliding flight. Recommendation VIII – The nation's reliance on the shuttle as its
principal space launch capability created a relentless pressure on NASA
to increase the flight rate ... NASA must establish a flight rate that
is consistent with its resources.
Space Shuttle Discovery as it approaches the International Space Station during STS-114 on July 28, 2005. This was the Shuttle's "return to flight" mission after the Columbia disaster
The Shuttle program operated accident-free for seventeen years and 88 missions after the Challenger disaster, until Columbia broke up on reentry, killing all seven crew members, on February 1, 2003. The ultimate cause
of the accident was a piece of foam separating from the external tank
moments after liftoff and striking the leading edge of the orbiter's
left wing, puncturing one of the reinforced carbon-carbon (RCC) panels
that covered the wing edge and protected it during reentry. As Columbia
reentered the atmosphere at the end of an otherwise normal mission, hot
gas penetrated the wing and destroyed it from the inside out, causing
the orbiter to lose control and disintegrate.
After the Columbia disaster, the International Space
Station operated on a skeleton crew of two for more than two years and
was serviced primarily by Russian spacecraft. While the "Return to
Flight" mission STS-114
in 2005 was successful, a similar piece of foam from a different
portion of the tank was shed. Although the debris did not strike Discovery, the program was grounded once again for this reason.
The second "Return to Flight" mission, STS-121
launched on July 4, 2006, at 14:37 (EDT). Two previous launches were
scrubbed because of lingering thunderstorms and high winds around the
launch pad, and the launch took place despite objections from its chief
engineer and safety head. A five-inch (13 cm) crack in the foam
insulation of the external tank gave cause for concern; however, the
Mission Management Team gave the go for launch. This mission increased the ISS crew to three. Discovery touched down successfully on July 17, 2006, at 09:14 (EDT) on Runway 15 at Kennedy Space Center.
Following the success of STS-121, all subsequent missions were completed without major foam problems, and the construction of the ISS was completed (during the STS-118
mission in August 2007, the orbiter was again struck by a foam fragment
on liftoff, but this damage was minimal compared to the damage
sustained by Columbia).
The Columbia Accident Investigation Board, in its report,
noted the reduced risk to the crew when a Shuttle flew to the
International Space Station (ISS), as the station could be used as a
safe haven for the crew awaiting rescue in the event that damage to the
orbiter on ascent made it unsafe for reentry. The board recommended that
for the remaining flights, the Shuttle always orbit with the station.
Prior to STS-114, NASA Administrator Sean O'Keefe declared that all
future flights of the Space Shuttle would go to the ISS, precluding the
possibility of executing the final Hubble Space Telescope servicing mission which had been scheduled before the Columbia
accident, despite the fact that millions of dollars worth of upgrade
equipment for Hubble were ready and waiting in NASA warehouses. Many
dissenters, including astronauts[who?], asked NASA management to reconsider allowing the mission, but initially the director stood firm. On October 31, 2006, NASA announced approval of the launch of Atlantis for the fifth and final shuttle servicing mission to the Hubble Space Telescope, scheduled for August 28, 2008. However SM4/STS-125 eventually launched in May 2009.
One impact of Columbia was that future crewed launch vehicles, namely the Ares I, had a special emphasis on crew safety compared to other considerations.
The Space Shuttle retirement was announced in January 2004. President George W. Bush announced his Vision for Space Exploration, which called for the retirement of the Space Shuttle once it completed construction of the ISS.
To ensure the ISS was properly assembled, the contributing partners
determined the need for 16 remaining assembly missions in March 2006. One additional Hubble Space Telescope servicing mission was approved in October 2006. Originally, STS-134 was to be the final Space Shuttle mission. However, the Columbia disaster resulted in additional orbiters being prepared for launch on need in the event of a rescue mission. As Atlantis was prepared for the final launch-on-need mission, the decision was made in September 2010 that it would fly as STS-135 with a four-person crew that could remain at the ISS in the event of an emergency. STS-135 launched on July 8, 2011, and landed at the KSC on July 21, 2011, at 5:57 a.m. EDT (09:57 UTC). From then until the launch of Crew Dragon Demo-2 on May 30, 2020, the US launched its astronauts aboard Russian Soyuz spacecraft.
Following each orbiter's final flight, it was processed to make
it safe for display. The OMS and RCS systems used presented the primary
dangers due to their toxic hypergolic propellant, and most of their components were permanently removed to prevent any dangerous outgassing.Atlantis is on display at the Kennedy Space Center Visitor Complex, Florida, Discovery is at the Udvar-Hazy Center, Virginia,Endeavour is on display at the California Science Center in Los Angeles, and Enterprise is displayed at the Intrepid Sea-Air-Space Museum in New York.
Components from the orbiters were transferred to the US Air Force, ISS
program, and Russian and Canadian governments. The engines were removed
to be used on the Space Launch System, and spare RS-25 nozzles were attached for display purposes.
Atlantis after its final landing, marking the end of the Space Shuttle Program
Preservation
Space Shuttle Discovery at the Udvar Hazy museum
Out of the five fully functional shuttle orbiters built, three remain. Enterprise,
which was used for atmospheric test flights but not for orbital flight,
had many parts taken out for use on the other orbiters. It was later
visually restored and was on display at the National Air and Space Museum's Steven F. Udvar-Hazy Center until April 19, 2012. Enterprise was moved to New York City in April 2012 to be displayed at the Intrepid Sea, Air & Space Museum, whose Space Shuttle Pavilion opened on July 19, 2012. Discovery replaced Enterprise at the National Air and Space Museum's Steven F. Udvar-Hazy Center. Atlantis formed part of the Space Shuttle Exhibit at the Kennedy Space Center visitor complex and has been on display there since June 29, 2013, following its refurbishment.
On October 14, 2012, Endeavour completed an unprecedented 12 mi (19 km) drive on city streets from Los Angeles International Airport to the California Science Center,
where it has been on display in a temporary hangar since late 2012. The
transport from the airport took two days and required major street
closures, the removal of over 400 city trees, and extensive work to
raise power lines, level the street, and temporarily remove street
signs, lamp posts, and other obstacles. Hundreds of volunteers, and
fire and police personnel, helped with the transport. Large crowds of
spectators waited on the streets to see the shuttle as it passed through
the city. Endeavour, along with the last flight-qualified external tank (ET-94), is currently on display at the California Science Center's Samuel Oschin
Pavilion (in a horizontal orientation) until the completion of the
Samuel Oschin Air and Space Center (a planned addition to the California
Science Center). Once moved, it will be permanently displayed in launch
configuration, complete with genuine solid rocket boosters and external
tank.
Crew modules
Spacehab moduleTen people inside Spacelab Module in the Shuttle bay in June 1995, celebrating the docking of the Space Shuttle and Mir.
One area of Space Shuttle applications is an expanded crew. Crews of up to eight have been flown in the Orbiter, but it could have held at least a crew of ten. Various proposals for filling the payload bay with additional passengers were also made as early as 1979. One proposal by Rockwell provided seating for 74 passengers in the Orbiter payload bay, with support for three days in Earth orbit. With a smaller 64 seat orbiter, costs for the late 1980s would be around US$1.5 million per seat per launch.
The Rockwell passenger module had two decks, four seats across on top
and two on the bottom, including a 25-inch (63.5 cm) wide aisle and
extra storage space.
Another design was Space Habitation Design Associates 1983 proposal for 72 passengers in the Space Shuttle Payload bay.
Passengers were located in 6 sections, each with windows and its own
loading ramp at launch, and with seats in different configurations for
launch and landing.
Another proposal was based on the Spacelab habitation modules, which
provided 32 seats in the payload bay in addition to those in the cockpit
area.
There were some efforts to analyze commercial operation of STS. Using the NASA figure for average cost to launch a Space Shuttle as of 2011 at about $450 million per mission, a cost per seat for a 74
seat module envisioned by Rockwell came to less than $6 million, not
including the regular crew. Some passenger modules used hardware similar
to existing equipment, such as the tunnel, which was also needed for Spacehab and Spacelab.
One effort in the direction of space transportation was the Reusable Launch Vehicle (RLV) program, initiated in 1994 by NASA. This led to work on the X-33 and X-34 vehicles. NASA spent about US$1 billion on developing the X-33 hoping for it be in operation by 2005. Another program around the turn of the millennium was the Space Launch Initiative, which was a next generation launch initiative.
The Space Launch Initiative program was started in 2001, and in late 2002 it was evolved into two programs, the Orbital Space Plane Program and the Next Generation Launch Technology program. OSP was oriented towards provided access to the International Space Station.
Other vehicles that would have taken over some of the Shuttles responsibilities were the HL-20 Personnel Launch System or the NASA X-38 of the Crew Return Vehicle program, which were primarily for getting people down from ISS. The X-38 was cancelled in 2002, and the HL-20 was cancelled in 1993.
Several other programs in this existed such as the Station Crew Return
Alternative Module (SCRAM) and Assured Crew Return Vehicle (ACRV).
According to the 2004 Vision for Space Exploration, the next human NASA program was to be Constellation program with its Ares I and Ares V launch vehicles and the Orion spacecraft;
however, the Constellation program was never fully funded, and in early
2010 the Obama administration asked Congress to instead endorse a plan
with heavy reliance on the private sector for delivering cargo and crew
to LEO.
The Commercial Crew Development
(CCDev) program was initiated in 2010 with the purpose of creating
commercially operated crewed spacecraft capable of delivering at least
four crew members to the ISS, staying docked for 180 days and then
returning them back to Earth. These spacecraft, like SpaceX's Dragon 2 and Boeing CST-100 Starliner were expected to become operational around 2020. On the Crew Dragon Demo-2 mission, SpaceX's Dragon 2 sent astronauts to the ISS, restoring America's human launch capability. The first operational SpaceX mission launched on November 15, 2020, at 7:27:17 p.m. ET, carrying four astronauts to the ISS.
Although the Constellation program was canceled, it has been replaced with a very similar Artemis program. The Orion spacecraft has been left virtually unchanged from its previous design. The planned Ares V rocket has been replaced with the smaller Space Launch System (SLS), which is planned to launch both Orion and other necessary hardware. Exploration Flight Test-1 (EFT-1), an uncrewed test flight of the Orion spacecraft, launched on December 5, 2014, on a Delta IV Heavy rocket.
Artemis 1 is the first flight of the SLS and was launched as a test of the completed Orion and SLS system. During the mission, an uncrewed Orion capsule spent 10 days in a 57,000-kilometer (31,000-nautical-mile) distant retrograde orbit around the Moon before returning to Earth. Artemis 2, the first crewed mission of the program, will launch four astronauts in 2024 on a free-return flyby of the Moon at a distance of 8,520 kilometers (4,600 nautical miles).After Artemis 2, the Power and Propulsion Element of the Lunar Gateway and three components of an expendable lunar lander are planned to be delivered on multiple launches from commercial launch service providers. Artemis 3
is planned to launch in 2025 aboard a SLS Block 1 rocket and will use
the minimalist Gateway and expendable lander to achieve the first crewed
lunar landing of the program. The flight is planned to touch down on
the lunar south pole region, with two astronauts staying there for about one week.
Gallery
Linear aerospike engine for the cancelled X-33
The Dragon spacecraft, one of the Space Shuttle's several successors, is seen here on its way to deliver cargo to the ISS
NASA's Orion Spacecraft for the Artemis 1 mission seen in Plum Brook On December 1, 2019
The Core Stage for the Space Launch System rocket for Artemis I
The Space Launch System Core Stage rolling out of the Michoud Facility for shipping to Stennis
The Boeing CST-100 Starliner spacecraft in the process of docking to the International Space Station
The SpaceX Crew Dragon in the process of docking to the International Space Station
Assets and transition plan
Atlantis about 30 minutes after final touchdown
The Space Shuttle program occupied over 654 facilities, used over
1.2 million line items of equipment, and employed over 5,000 people. The
total value of equipment was over $12 billion. Shuttle-related
facilities represented over a quarter of NASA's inventory. There were
over 1,200 active suppliers to the program throughout the United States.
NASA's transition plan had the program operating through 2010 with a
transition and retirement phase lasting through 2015. During this time,
the Ares I and Orion as well as the Altair Lunar Lander were to be under development, although these programs have since been canceled.
The partial reusability of the Space Shuttle was one of the primary design requirements during its initial development.
The technical decisions that dictated the orbiter's return and re-use
reduced the per-launch payload capabilities. The original intention was
to compensate for this lower payload by lowering the per-launch costs
and a high launch frequency. However, the actual costs of a Space
Shuttle launch were higher than initially predicted, and the Space
Shuttle did not fly the intended 24 missions per year as initially
predicted by NASA.
The Space Shuttle was originally intended as a launch vehicle to
deploy satellites, which it was primarily used for on the missions prior
to the Challenger disaster. NASA's pricing, which was below
cost, was lower than expendable launch vehicles; the intention was that
the high volume of Space Shuttle missions would compensate for early
financial losses. The improvement of expendable launch vehicles and the
transition away from commercial payloads on the Space Shuttle resulted
in expendable launch vehicles becoming the primary deployment option for
satellites. A key customer for the Space Shuttle was the National Reconnaissance Office
(NRO) responsible for spy satellites. The existence of NRO's connection
was classified through 1993, and secret considerations of NRO payload
requirements led to lack of transparency in the program. The proposed Shuttle-Centaur program, cancelled in the wake of the Challenger disaster, would have pushed the spacecraft beyond its operational capacity.
The fatal Challenger and Columbia disasters demonstrated
the safety risks of the Space Shuttle that could result in the loss of
the crew. The spaceplane design of the orbiter limited the abort
options, as the abort scenarios required the controlled flight of the
orbiter to a runway or to allow the crew to egress individually, rather
than the abort escape options on the Apollo and Soyuz space capsules.
Early safety analyses advertised by NASA engineers and management
predicted the chance of a catastrophic failure resulting in the death of
the crew as ranging from 1 in 100 launches to as rare as 1 in 100,000.Following the loss of two Space Shuttle missions, the risks for the
initial missions were reevaluated, and the chance of a catastrophic loss
of the vehicle and crew was found to be as high as 1 in 9.
NASA management was criticized afterwards for accepting increased risk
to the crew in exchange for higher mission rates. Both the Challenger and Columbia
reports explained that NASA culture had failed to keep the crew safe by
not objectively evaluating the potential risks of the missions.
Support vehicles
Many other vehicles were used in support of the Space Shuttle program, mainly terrestrial transportation vehicles.
A 36-wheeled transport trailer, the Orbiter Transfer System, originally built for the U.S. Air Force's launch facility at Vandenberg Air Force Base in California (since then converted for Delta IV rockets)
would transport the orbiter from the landing facility to the launch
pad, which allowed both "stacking" and launch without utilizing a
separate VAB-style building and crawler-transporter roadway. Prior to
the closing of the Vandenberg facility, orbiters were transported from
the OPF
to the VAB on their undercarriages, only to be raised when the orbiter
was being lifted for attachment to the SRB/ET stack. The trailer allowed
the transportation of the orbiter from the OPF to either the SCA "Mate-Demate" stand or the VAB without placing any additional stress on the undercarriage.
The Crew Transport Vehicle (CTV), a modified airport jet bridge,
was used to assist astronauts to egress from the orbiter after landing.
Upon entering the CTV, astronauts could take off their launch and
reentry suits then proceed to chairs and beds for medical checks before
being transported back to the crew quarters in the Operations and Checkout Building. Originally built for Project Apollo.
The Astrovan
was used to transport astronauts from the crew quarters in the
Operations and Checkout Building to the launch pad on launch day. It was
also used to transport astronauts back again from the Crew Transport
Vehicle at the Shuttle Landing Facility.
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