Terminal illness

From Wikipedia, the free encyclopedia

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

Terminal illness or end-stage disease is a disease that cannot be cured or adequately treated and is expected to result in the death of the patient. This term is more commonly used for progressive diseases such as cancer, dementia or advanced heart disease than for injury. In popular use, it indicates a disease that will progress until death with near absolute certainty, regardless of treatment. A patient who has such an illness may be referred to as a terminal patient, terminally ill or simply as being terminal. There is no standardized life expectancy for a patient to be considered terminal, although it is generally months or less. Life expectancy for terminal patients is a rough estimate given by the physician based on previous data and does not always reflect true longevity. An illness which is lifelong but not fatal is a chronic condition.

Terminal patients have options for disease management after diagnosis. Examples include caregiving, continued treatment, palliative and hospice care, and physician-assisted suicide. Decisions regarding management are made by the patient and their family, although medical professionals may offer recommendations of services available to terminal patients.

Lifestyle after diagnosis varies depending on management decisions and the nature of the disease, and there may be restrictions depending on the condition of the patient. Terminal patients may experience depression or anxiety associated with impending death, and family and caregivers may struggle with psychological burdens. Psychotherapeutic interventions may alleviate some of these burdens, and is often incorporated into palliative care.

Because terminal patients are aware of their impending deaths, they have time to prepare for care, such as advance directives and living wills, which have been shown to improve end-of-life care. While death cannot be avoided, patients can strive to die a death seen as good.

Management

Main article: End-of-life care

By definition, there is not a cure or adequate treatment for terminal illnesses. However, some kinds of medical treatments may be appropriate anyway, such as treatment to reduce pain or ease breathing.

Some terminally ill patients stop all debilitating treatments to reduce unwanted side effects. Others continue aggressive treatment in the hope of an unexpected success. Still others reject conventional medical treatment and pursue unproven treatments such as radical dietary modifications. Patients' choices about different treatments may change over time.

Palliative care is normally offered to terminally ill patients, regardless of their overall disease management style, if it seems likely to help manage symptoms such as pain and improve quality of life. Hospice care, which can be provided at home or in a long-term care facility, additionally provides emotional and spiritual support for the patient and loved ones. Some complementary approaches, such as relaxation therapy, massage, and acupuncture may relieve some symptoms and other causes of suffering.

Caregiving

Terminal patients often need a caregiver, who could be a nurse, licensed practical nurse or a family member. Caregivers can help patients receive medications to reduce pain and control symptoms of nausea or vomiting. They can also assist the individual with daily living activities and movement. Caregivers provide assistance with food and psychological support and ensure that the individual is comfortable.

The patient's family may have questions and most caregivers can provide information to help ease the mind. Doctors generally do not provide estimates for fear of instilling false hopes or obliterate an individual's hope.

In most cases, the caregiver works along with physicians and follows professional instructions. Caregivers may call the physician or a nurse if the individual:

• experiences excessive pain.
• is in distress or having difficulty breathing.
• has difficulty passing urine or is constipated.
• has fallen and appears hurt.
• is depressed and wants to harm themselves.
• refuses to take prescribed medications, raising ethical concerns best addressed by a person with more extensive formal training.
• or if the caregiver does not know how to handle the situation.

Most caregivers become the patient's listeners and let the individual express fears and concerns without judgment. Caregivers reassure the patient and honor all advance directives. Caregivers respect the individual's need for privacy and usually hold all information confidential.

Palliative care

Palliative care focuses on addressing patients' needs after disease diagnosis. While palliative care is not disease treatment, it addresses patients' physical needs, such as pain management, offers emotional support, caring for the patient psychologically and spiritually, and helps patients build support systems that can help them get through difficult times. Palliative care can also help patients make decisions and come to understand what they want regarding their treatment goals and quality of life.

Palliative care is an attempt to improve patients' quality-of-life and comfort, and also provide support for family members and carers. Additionally, it lowers hospital admissions costs. However, needs for palliative care are often unmet whether due to lack of government support and also possible stigma associated with palliative care. For these reasons, the World Health Assembly recommends development of palliative care in health care systems.

Palliative care and hospice care are often confused, and they have similar goals. However, hospice care is specifically for terminal patients while palliative care is more general and offered to patients who are not necessarily terminal.

Hospice care

While hospitals focus on treating the disease, hospices focus on improving patient quality-of-life until death. A common misconception is that hospice care hastens death because patients "give up" fighting the disease. However, patients in hospice care often live the same length of time as patients in the hospital. A study of 3850 liver cancer patients found that patients who received hospice care, and those who did not, survived for the same amount of time. In fact, a study of 3399 adult lung cancer patients showed that patients who received hospice care actually survived longer than those who did not. Additionally, in both of these studies, patients receiving hospice care had significantly lower healthcare expenditures.

Hospice care allows patients to spend more time with family and friends. Since patients are in the company of other hospice patients, they have an additional support network and can learn to cope together. Hospice patients are also able to live at peace away from a hospital setting; they may live at home with a hospice provider or at an inpatient hospice facility.

Medications for terminal patients

Terminal patients experiencing pain, especially cancer-related pain, are often prescribed opioids to relieve suffering. The specific medication prescribed, however, will differ depending on severity of pain and disease status.

There exist inequities in availability of opioids to terminal patients, especially in countries where opioid access is limited.

A common symptom that many terminal patients experience is dyspnea, or difficulty with breathing. To ease this symptom, doctors may also prescribe opioids to patients. Some studies suggest that oral opioids may help with breathlessness. However, due to lack of consistent reliable evidence, it is currently unclear whether they truly work for this purpose.

Depending on the patient's condition, other medications will be prescribed accordingly. For example, if patients develop depression, antidepressants will be prescribed. Anti-inflammation and anti-nausea medications may also be prescribed.

Continued treatment

Some terminal patients opt to continue extensive treatments in hope of a miracle cure, whether by participating in experimental treatments and clinical trials or seeking more intense treatment for the disease. Rather than to "give up fighting," patients spend thousands more dollars to try to prolong life by a few more months. What these patients often do give up, however, is quality of life at the end of life by undergoing intense and often uncomfortable treatment. A meta-analysis of 34 studies including 11,326 patients from 11 countries found that less than half of all terminal patients correctly understood their disease prognosis, or the course of their disease and likeliness of survival. This could influence patients to pursue unnecessary treatment for the disease due to unrealistic expectations.

Transplant

For patients with end stage kidney failure, studies have shown that transplants increase the quality of life and decreases mortality in this population. In order to be placed on the organ transplant list, patients are referred and assessed based on criteria that ranges from current comorbidities to potential for organ rejection post transplant. Initial screening measures include: blood tests, pregnancy tests, serologic tests, urinalysis, drug screening, imaging, and physical exams.

For patients who are interested in liver transplantation, patients with acute liver failure have the highest priority over patients with only cirrhosis. Acute liver failure patients will present with worsening symptoms of somnolence or confusion (hepatic encephalopathy) and thinner blood (increased INR) due to the liver's inability to make clotting factors. Some patients could experience portal hypertension, hemorrhages, and abdominal swelling (ascites). Model for End Stage Liver Disease (MELD) is often used to help providers decide and prioritize candidates for transplant.

Physician-assisted suicide

Physician-assisted suicide (PAS) is highly controversial, and legal in only a few countries. In PAS, physicians, with voluntary written and verbal consent from the patient, give patients the means to die, usually through lethal drugs. The patient then chooses to "die with dignity," deciding on his/her own time and place to die. Reasons as to why patients choose PAS differ. Factors that may play into a patient's decision include future disability and suffering, lack of control over death, impact on family, healthcare costs, insurance coverage, personal beliefs, religious beliefs, and much more.

PAS may be referred to in many different ways, such as aid in dying, assisted dying, death with dignity, and many more. These often depend on the organization and the stance they take on the issue. In this section of the article, it will be referred to as PAS for the sake of consistency with the pre-existing Wikipedia page: Assisted Suicide.

In the United States, PAS or medical aid in dying is legal in select states, including Oregon, Washington, Montana, Vermont, and New Mexico, and there are groups both in favor of and against legalization.

Some groups favor PAS because they do not believe they will have control over their pain, because they believe they will be a burden on their family, and because they do not want to lose autonomy and control over their own lives among other reasons. They believe that allowing PAS is an act of compassion.

While some groups believe in personal choice over death, others raise concerns regarding insurance policies and potential for abuse. According to Sulmasy et al., the major non-religious arguments against physician-assisted suicide are quoted as follows:

• (1) "it offends me", suicide devalues human life;
• (2) slippery slope, the limits on euthanasia gradually erode;
• (3) "pain can be alleviated", palliative care and modern therapeutics more and more adequately manage pain;
• (4) physician integrity and patient trust, participating in suicide violates the integrity of the physician and undermines the trust patients place in physicians to heal and not to harm."

Again, there are also arguments that there are enough protections in the law that the slippery slope is avoided. For example, the Death with Dignity Act in Oregon includes waiting periods, multiple requests for lethal drugs, a psychiatric evaluation in the case of possible depression influencing decisions, and the patient personally swallowing the pills to ensure voluntary decision.

Physicians and medical professionals also have disagreeing views on PAS. Some groups, such as the American College of Physicians (ACP), the American Medical Association (AMA), the World Health Organization, American Nurses Association, Hospice Nurses Association, American Psychiatric Association, and more have issued position statements against its legalization.

The ACP's argument concerns the nature of the doctor-patient relationship and the tenets of the medical profession. They state that instead of using PAS to control death: "through high-quality care, effective communication, compassionate support, and the right resources, physicians can help patients control many aspects of how they live out life's last chapter."

Other groups such as the American Medical Students Association, the American Public Health Association, the American Medical Women's Association, and more support PAS as an act of compassion for the suffering patient.

In many cases, the argument on PAS is also tied to proper palliative care. The International Association for Hospice and Palliative Care issued a position statement arguing against considering legalizing PAS unless comprehensive palliative care systems in the country were in place. It could be argued that with proper palliative care, the patient would experience fewer intolerable symptoms, physical or emotional, and would not choose death over these symptoms. Palliative care would also ensure that patients receive proper information about their disease prognosis as not to make decisions about PAS without complete and careful consideration.

Medical care

Many aspects of medical care are different for terminal patients compared to patients in the hospital for other reasons.

Doctor–patient relationships

Doctor–patient relationships are crucial in any medical setting, and especially so for terminal patients. There must be an inherent trust in the doctor to provide the best possible care for the patient. In the case of terminal illness, there is often ambiguity in communication with the patient about his/her condition. While terminal condition prognosis is often a grave matter, doctors do not wish to quash all hope, for it could unnecessarily harm the patient's mental state and have unintended consequences. However, being overly optimistic about outcomes can leave patients and families devastated when negative results arise, as is often the case with terminal illness.

Mortality predictions

Often, a patient is considered terminally ill when his or her estimated life expectancy is six months or less, under the assumption that the disease will run its normal course based on previous data from other patients. The six-month standard is arbitrary, and best available estimates of longevity may be incorrect. Though a given patient may properly be considered terminal, this is not a guarantee that the patient will die within six months. Similarly, a patient with a slowly progressing disease, such as AIDS, may not be considered terminally ill if the best estimate of longevity is greater than six months. However, this does not guarantee that the patient will not die unexpectedly early.

In general, physicians slightly overestimate the survival time of terminally ill cancer patients, so that, for example, a person who is expected to live for about six weeks would likely die around four weeks.

A recent systematic review on palliative patients in general, rather than specifically cancer patients, states the following: "Accuracy of categorical estimates in this systematic review ranged from 23% up to 78% and continuous estimates over-predicted actual survival by, potentially, a factor of two." There was no evidence that any specific type of clinician was better at making these predictions.

Healthcare spending

Healthcare during the last year of life is costly, especially for patients who used hospital services often during end-of-life.

In fact, according to Langton et al., there were "exponential increases in service use and costs as death approached."

Many dying terminal patients are also brought to the emergency department (ED) at the end of life when treatment is no longer beneficial, raising costs and using limited space in the ED.

While there are often claims about "disproportionate" spending of money and resources on end-of-life patients, data have not proven this type of correlation.

The cost of healthcare for end-of-life patients is 13% of annual healthcare spending in the U.S. However, of the group of patients with the highest healthcare spending, end-of-life patients only made up 11% of these people, meaning the most expensive spending is not made up mostly of terminal patients.

Many recent studies have shown that palliative care and hospice options as an alternative are much less expensive for end-of-life patients.

Psychological impact

Coping with impending death is a hard topic to digest universally. Patients may experience grief, fear, loneliness, depression, and anxiety among many other possible responses. Terminal illness can also lend patients to become more prone to psychological illness such as depression and anxiety disorders. Insomnia is a common symptom of these.

It is important for loved ones to show their support for the patient during these times and to listen to his or her concerns.

People who are terminally ill may not always come to accept their impending death. For example, a person who finds strength in denial may never reach a point of acceptance or accommodation and may react negatively to any statement that threatens this defense mechanism.

Impact on patient

Depression is relatively common among terminal patients, and the prevalence increases as patients become sicker. Depression causes quality of life to go down, and a sizable portion of patients who request assisted suicide are depressed. These negative emotions may be heightened by lack of sleep and pain as well. Depression can be treated with antidepressants and/or therapy, but doctors often do not realize the extent of terminal patients' depression.

Because depression is common among terminal patients, the American College of Physicians recommends regular assessments for depression for this population and appropriate prescription of antidepressants.

Anxiety disorders are also relatively common for terminal patients as they face their mortality. Patients may feel distressed when thinking about what the future may hold, especially when considering the future of their families as well. It is important to note, however, that some palliative medications may facilitate anxiety.

Coping for patients

Caregivers may listen to the concerns of terminal patients to help them reflect on their emotions. Different forms of psychotherapy and psychosocial intervention, which can be offered with palliative care, may also help patients think about and overcome their feelings. According to Block, "most terminally ill patients benefit from an approach that combines emotional support, flexibility, appreciation of the patient's strengths, a warm and genuine relationship with the therapist, elements of life-review, and exploration of fears and concerns."

Impact on family

Terminal patients' families often also suffer psychological consequences. If not well equipped to face the reality of their loved one's illness, family members may develop depressive symptoms and even have increased mortality. Taking care of sick family members may also cause stress, grief, and worry. Additionally, financial burden from medical treatment may be a source of stress. Parents of terminally ill children also face additional challenges in addition to mental health stressors including difficulty balancing caregiving and maintaining employment. Many report feeling as if they have to "do it all" by balancing caring for their chronically ill child, limiting absence from work, and supporting their family members. Children of terminally ill parents often experience a role reversal in which they become the caretakers of their adult parents. In taking on the burden of caring for their sick parent and assuming the responsibilities they can no longer accomplish, many children also experience significant declines in academic performance. 

Coping for family

Discussing the anticipated loss and planning for the future may help family members accept and prepare for the patient's death. Interventions may also be offered for anticipatory grief. In the case of more serious consequences such as depression, a more serious intervention or therapy is recommended. Upon the death of someone who is terminally ill, many family members that served as caregivers are likely to experience declines in their mental health. Grief counseling and grief therapy may also be recommended for family members after a loved one's death.

Grief counseling and grief therapy may also be recommended for family members after a loved one's death.

Dying

When dying, patients often worry about their quality of life towards the end, including emotional and physical suffering.

In order for families and doctors to understand clearly what the patient wants for themselves, it is recommended that patients, doctors, and families all convene and discuss the patient's decisions before the patient becomes unable to decide.

Advance directives

At the end of life, especially when patients are unable to make decisions on their own regarding treatment, it is often up to family members and doctors to decide what they believe the patients would have wanted regarding their deaths, which is often a heavy burden and hard for family members to predict. An estimated 25% of American adults have an advance directive, meaning the majority of Americans leave these decisions to be made by family, which can lead to conflict and guilt. Although it may be a difficult subject to broach, it is important to discuss the patient's plans for how far to continue treatment should they become unable to decide. This must be done while the patient is still able to make the decisions, and takes the form of an advance directive. The advance directive should be updated regularly as the patient's condition changes so as to reflect the patient's wishes.

Some of the decisions that advance directives may address include receiving fluids and nutrition support, getting blood transfusions, receiving antibiotics, resuscitation (if the heart stops beating), and intubation (if the patient stops breathing).

Having an advance directive can improve end-of-life care.

It is highly recommended by many research studies and meta-analyses for patients to discuss and create an advance directive with their doctors and families.

Do-not-resuscitate

Main article: Do not resuscitate

One of the options of care that patients may discuss with their families and medical providers is the do-not-resuscitate (DNR) order. This means that if the patient's heart stops, CPR and other methods to bring back heartbeat would not be performed. This is the patient's choice to make and can depend on a variety of reasons, whether based on personal beliefs or medical concerns. DNR orders can be medically and legally binding depending on the applicable jurisdiction.

Decisions like these should be indicated in the advance directive so that the patient's wishes can be carried out to improve end-of-life care.

Symptoms near death

A variety of symptoms become more apparent when a patient is nearing death. Recognizing these symptoms and knowing what will come may help family members prepare.

During the final few weeks, symptoms will vary largely depending on the patient's disease. During the final hours, patients usually will reject food and water and will also sleep more, choosing not to interact with those around them. Their bodies may behave more irregularly, with changes in breathing, sometimes with longer pauses between breaths, irregular heart rate, low blood pressure, and coldness in the extremities. It is important to note, however, that symptoms will vary per patient.

Good death

Patients, healthcare workers, and recently bereaved family members often describe a "good death" in terms of effective choices made in a few areas:

• Assurance of effective pain and symptom management.
• Education about death and its aftermath, especially as it relates to decision-making.
• Completion of any significant goals, such as resolving past conflicts.

In the last hours of life, palliative sedation may be recommended by a doctor or requested by the patient to ease the symptoms of death until they die. Palliative sedation is not intended to prolong life or hasten death; it is merely meant to relieve symptoms.

Death anxiety

From Wikipedia, the free encyclopedia

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

 

Death Anxiety
Other names	Thanatophobia
An illustration from La Fontaine's fable "La Mort et le Mourant" depicting the Grim Reaper
Specialty	Clinical psychology, psychiatry

Death anxiety is anxiety caused by thoughts of one's own death, and is also referred to as thanatophobia (fear of death). Individuals affected by this kind of anxiety experience challenges and adversities in many aspects of their lives. Death anxiety is different from necrophobia, which refers to an irrational or disproportionate fear of dead bodies or of anything associated with death. Death anxiety has been found to affect people of differing demographic groups as well, such as men versus women, young versus old, etc.

Psychotherapist Robert Langs proposed three different causes of death anxiety: predatory, predator, and existential. In addition to his research, many theorists such as Sigmund Freud, Erik Erikson, and Ernest Becker have examined death anxiety and its impact on cognitive processing.

Anxiety caused by recent thought-content about death is sometimes classified by a psychiatrist in a clinical setting as morbid or abnormal, or a combination of the two. This classification pre-necessitates a degree of anxiety which is persistent and interferes with everyday functioning. This high level of death anxiety in the elderly (who perceive themselves as close to death) can cause lower ego integrity, more physical problems as well as an increase in psychological problems.

Death anxiety has also been linked to causing a person to become extremely timid or distressed when discussing anything to do with death and several mental health conditions.

One meta-analysis of psychological interventions targeting death anxiety showed that death anxiety can be reduced using cognitive behavioral therapy.

Types

Robert Langs distinguishes three types of death anxiety:

Predatory death anxiety

Predatory death anxiety arises from the fear of being harmed. It is the oldest and most basic form of death anxiety, with origins in the first unicellular organisms' set of adaptive resources. Unicellular organisms have receptors that have evolved to react to external dangers, along with self-protective, responsive mechanisms made to increase the likelihood of survival in the face of chemical and physical forms of attack or danger. In humans, predatory death anxiety is evoked by a variety of dangerous situations that put one at risk or threaten one's survival. Predatory death anxiety mobilizes an individual's adaptive resources and leads to a fight-or-flight response, consisting of active efforts to combat the danger or attempts to escape the threatening situation.

Predation or predator

Predation or predator death anxiety is a form that arises when an individual harms another, physically and/or mentally. This form of death anxiety is often accompanied by unconscious guilt. This guilt, in turn, motivates and encourages a variety of self-made decisions and actions by the perpetrator of harm to others.

Existential

Existential death anxiety stems from the basic knowledge that human life must end. Existential death anxiety is known to be the most powerful form of death anxiety. It is said that language has created the basis for existential death anxiety through communicative and behavioral changes. Other factors include an awareness of the distinction between self and others, a full sense of personal identity, and the ability to anticipate the future. The existential psychiatrist Irvin Yalom asserts that humans are prone to death anxiety because "our existence is forever shadowed by the knowledge that we will grow, blossom, and inevitably, diminish and die."

Human beings are the only living things that are truly aware of their own mortality and spend time pondering the meaning of life and death. Awareness of human mortality arose some 150,000 years ago. In that extremely short span of evolutionary time, humans have fashioned a single basic mechanism through which they deal with the existential death anxieties this awareness has evoked: denial. Denial is effected through a wide range of mental mechanisms and physical actions, many of which go unrecognized. While denial can be adaptive in limited use, excessive use is more common and is emotionally costly. Denial is the root of such diverse actions as breaking rules, violating frames and boundaries, manic celebrations, directing violence against others, attempting to gain extraordinary wealth and power, and more. These pursuits are often activated by a death-related trauma, and while they may lead to constructive actions, more often than not they lead to actions that are damaging to self and others.

Theories

Thanatophobia

The term thanatophobia stems from the Greek representation of death, known as Thanatos. Sigmund Freud hypothesized that people express a fear of death as a disguise for a deeper source of concern. He asserted the unconscious does not deal with the passage of time or with negations, which do not calculate the amount of time left in one's life. Under the assumption people do not believe in their own deaths, Freud speculated it was not death people feared. He postulated one does not fear death itself, because one has never died. He suspected death-related fears stem from unresolved childhood conflicts.

Thanatophobia is not only death anxiety, but can mean an intense fear, and feelings of overall dread in relation to one's thinking about death. Usually it relates to one's personal death. Death anxiety can mean fear of death, fear of dying, fear of being alone, fear of the dying process, etc. Different people experience these fears in differing ways. Klein in 1948 states that humans are the only species that have a sense of what the limitations associated with life are, and because of this, death is a cause of anxiety. There continues to be confusion on whether death anxiety is a fear of death itself or a fear of the process of dying.

Those who are moving towards death will undergo a series of stages. In Kubhler-Ross's book On Death and Dying (1969), she describes these stages thus: 1) denial that death is soon to come, 2) resentful feelings towards those who will yet live, 3) bargaining with the idea of dying, 4) feeling depressive due to death being inescapable, 5) finally, acceptance.

Wisdom: ego integrity vs. despair

Developmental psychologist Erik Erikson formulated the psychosocial theory that people progress through a series of crises as they grow older. The theory also proposes the concept that once an individual reaches the last stages of life, they reach the level he called "ego integrity". Ego integrity is marked by one coming to terms with both one's life and inevitable death and accepting it. It was also suggested that when a person reaches the stage of late adulthood, they become involved in a thorough overview of their life to date. When one can find meaning or purpose in one's life, one has reached the integrity stage. Conversely, when an individual views their life as a series of failed and missed opportunities, they do not reach the ego integrity stage. They instead experience despair; this variation of the stage is marked by feelings of disdain and unfulfillment. People who have attained the stage of ego integrity rather than despair are believed to exhibit less death anxiety.

In a study performed in 2020, researchers tested to see if psychological need-based experiences affect their death attitudes and to see if ego integrity and despair greatly play a role in these death attitudes. The need-based experiences in this research study are the feelings of autonomy, relatedness, and competence. The researchers found that if the participants needs were satisfied, they would have higher ego integrity in relation to their attitude towards death. This allowed the participants to have an easier time accepting death. If the participants struggled to have their needs met, then they would experience higher despair in relation to death anxiety. This meant that they had more death anxiety overall.

Terror management theory

Main article: Terror management theory

Ernest Becker based his terror management theory (TMT) on existential views that added a new dimension to previous death anxiety theories. His theory states that death anxiety is not only real, but also people's most profound source of concern. He described the anxiety as so intense that it can generate fears and phobias of everyday lifelike fears of being alone, or in confined spaces. According to Becker, many everyday human behaviors consist of attempts to deny death and to keep anxiety under strict regulation.

His theory suggests that as an individual develops mortality salience, or becomes more aware of the inevitability of death, they will instinctively try to suppress this thought out of fear. This behavior may range from simply thinking about death to the development of severe phobias and desperate behavior. Religiosity can play a role in death anxiety through the concept of fear. There are two major claims concerning the interplay of fear and religion: that fear motivates religious belief, and that religious belief mitigates fear. From these, Ernest Becker and Bronislaw Malinowski developed what is called "Terror Management Theory." According to Terror Management Theory, humans are aware of their own mortality which, in turn, produces intense existential anxiety. To cope with and ease the produced existential anxiety, humans will pursue either literal or symbolic immortality. Religion often falls under the category of literal immortality, but at times, depending on the religion, can also provide both forms of immortality. It is theorised that those who are either very low or very high in religiosity experience much lower levels of death anxiety, whereas those with a very moderate amount of religiosity experience the highest levels of death anxiety. One of the major reasons that religiosity plays such a large role in Terror Management Theory, as well as in similar theories, is the increase in existential death anxiety that people experience. Existential death anxiety is the belief that everything ceases after death; nothing continues on in any sense. Seeing how people deeply fear such an absolute elimination of the self, they begin to gravitate toward religion which offers an escape from such a fate. In one specific meta-analysis study that was performed in 2016, it was shown that lower rates of death anxiety and general fear about dying were experienced by those who went day-to-day living their religion and abiding by its practices, compared to those who merely label themselves as members of a given religion, without living according to its doctrines and prescribed practices.

A 2009 study on death anxiety in the context of religion showed that Christians scored lower for death anxiety than non-religious individuals, which supports the main tenets of terror management theory, that people pursue religion to avoid anxiety about death by finding comfort in the ideas about afterlife and immortality. Interestingly, the study also found that Muslims scored much higher than Christians and non-religious individuals for death anxiety. These findings do not support terror management theory, as the belief in an afterlife caused more anxiety for the Muslim participants than those with no belief in an afterlife. This finding highlights a need for further examination into TMT in the context of different religions/sects as well as the impact of varying beliefs about the afterlife on levels of death anxiety.

Heidegger's being-for-death

The German philosopher Martin Heidegger wrote about death as something conclusively determined, in the sense that it is inevitable for every human being, while on the other hand, it unmasks its indeterminate nature via the truth that one never knows when or how death is going to come. Heidegger does not engage in speculation about whether being after death is possible. He argues that all human existence is embedded in time: past, present, future, and when considering the future, we encounter the notion of death. This then creates angst. Angst can create a clear understanding in one that death is a possible mode of existence, which Heidegger described as "clearing". Thus, angst can lead to a freedom about existence, but only if people can stop denying their mortality (as expressed in Heidegger's terminology as "stop denying being-for-death").

The American philosopher Sidney Hook criticized Heidegger's view of death anxiety in his review of Heidegger's book Being and Time when it was translated into English in 1962. Hook noted that for Heidegger, death anxiety "is a primordial anxiety, not something that waxes and wanes with changes in nature, history or society", and the anxiety is about "the possibility that one's existence may at any moment become finally impossible". Hook argued that Heidegger's claims were wrong:

Now even when we become aware of this possibility, there is no evidence that we normally become anxious about it, unless the possibility is concretized and seems probable. Nor does Heidegger advance any reasons why we should be anxious. After all, because we cannot imagine ourselves dead, this hardly justifies the inference that our existence is necessary. What we know about human attitudes towards death indicates that Heidegger's generalization is false. Some men, and not only figures like Socrates and Spinoza, have no anxiety in the face of death. Men have believed that there are many things which could happen to them that are far worse than death. Any sensitive person can think of a variety of circumstances that would make death a happy release, almost a privilege.

Meaning management theory

Paul T. P. Wong's work on the meaning management theory indicates that human reactions to death are complex, multifaceted and dynamic. His "Death Attitude Profile" identifies three types of death acceptance as Neutral, Approach, and Escape acceptances. Apart from acceptances, his work also represents different aspects of the meaning of death fear that are rooted in the bases of death anxiety. The ten meanings he proposes are finality, uncertainty, annihilation, ultimate loss, life flow disruption, leaving the loved ones, pain and loneliness, prematurity and violence of death, failure of life work completion, judgment and retribution centered.

Existential theories

The existential approach, with theorists such as Rollo May and Viktor Frankl, views an individual's personality as being governed by continuous choices and decisions in relation to the realities of life and death. Rollo May theorized that all humans are aware of the fact that they must one day die, reminiscent of the Latin adage memento mori. However, he also theorized that humans must find meaning in life, which led to his main theory on death anxiety: that all humans face the dichotomy of finding meaning in life, but also confronting the knowledge of approaching death. May believed that this dichotomy could lead to negative anxiety that hindered life, or a positive anxiety that would lead to a life full of meaning and living to one's fullest potential and opportunities.

Other theories

Other theories on death anxiety were introduced in the late part of the twentieth century. Another approach is the regret theory which was introduced by Adrian Tomer and Grafton Eliason. The main focus of the theory is to target the way people evaluate the quality and/or worth of their lives. The possibility of death usually makes people more anxious if they feel that they have not and cannot accomplish any positive task in the life that they are living. Research has tried to unveil the factors that might influence the amount of anxiety people experience in life.

Personal meanings of death

See also: Meaning-making

Humans develop meanings and associate them with objects and events in their environment which can provoke certain emotions. People tend to develop personal meanings of death which could be either positive or negative. If the formed meanings about death are positive, then the consequences of those meanings can be comforting (for example, ideas of a rippling effect left on those still alive). If the formed meanings about death are negative, they can cause emotional turmoil. Depending on the certain meaning one has associated with death, positive or negative, the consequences will vary accordingly. The meaning that individuals place on death is generally specific to them; whether negative or positive, and can be difficult to understand as an outside observer. However, through a phenomenological perspective, therapists can come to understand their individual perspective and assist them in framing that meaning of death in a healthy way.

Religiosity

See also: Religious views on death

A 2012 study involving Christian and Muslim college-students from the US, Turkey, and Malaysia found that their religiosity correlated positively with an increased fear of death.

In 2017 a literature review found that in the US, both the very religious and the not-at-all religious enjoy a lower level of death anxiety and that a reduction is common with old age.

In 2019 a study further examined the aspect of religiosity and how it relates to death and existential anxiety through the application of supernatural agency. According to this particular study, existential anxiety relates to death anxiety through a mild level of preoccupation that is experienced concerning the impact of one's own life or existence in relation to its unforeseen end. It is mentioned how supernatural agency exists independently on a different dimensional plane than the individual and, as a result, is seen as something that cannot be directly controlled. Oftentimes, supernatural agency is equated with the desires of a higher power such as God or other major cosmic forces. The inability for one to control supernatural agency triggers various psychological aspects that induce intense periods of experienced death or existential anxiety.  One of the psychological effects of supernatural agency that is triggered is an increased likelihood to attribute supernatural agency toward causality when dealing with natural phenomena. Seeing how people have their own innate form of agency, the attribution of supernatural agency to human actions and decisions can be difficult. However, when it comes to natural causes and consequences where no other form of agency exists, it becomes much easier to make a supernatural attribution of causality.

Death acceptance and death anxiety

Researchers have also conducted surveys on how being able to accept one's inevitable death could have a positive effect on one's psychological well-being, or on one's level of individual distress. A research study conducted in 1974 attempted to set up a new type of scale to measure people's death acceptance, rather than their death anxiety. After administering a questionnaire with questions regarding the acceptance of death, the researchers found there was a low-negative correlation between acceptance of one's own death and anxiety about death; meaning that the more the participants accepted their own death, the less anxiety they felt. While those who accept the fact of their own death will still feel some anxiety about it, this acceptance could allow them to form a more positive perspective on it.

People who are exposed to those who are near death or who have already died seem to have a paradigm shift in their way of thinking about death.

A more recent longitudinal study asked cancer patients at different stages to fill out different questionnaires in order to rate their levels of death acceptance, general anxiety, demoralization, etc. The same surveys administered to the same people one year later showed that higher levels of death acceptance could predict lower levels of death anxiety in the participants.

Death row phenomenon

Main article: Death row phenomenon

The death row phenomenon is the distress and anxiety seen in inmates awaiting execution, which can cause an increased risk for suicidal tendencies and psychotic delusions. A contributing factor to this phenomenon is solitary confinement, lack of social interaction, as well as the psychological impact as a result of their crimes. One study collected data on death row suicides from 1978 to 2010 and found the rate of death row suicides to be higher than suicides in the male prison population as well as males in society, regardless of the increase in supervision of death row inmates.

Children

Death anxiety typically begins in childhood. The earliest documentation of the fear of death has been found in children as young as age 5. Psychological measures and reaction times were used to measure fear of death in young children. Recent studies that assess fear of death in children use questionnaire rating scales. There are many tests to study this including The Death Anxiety Scale for Children (DASC) developed by Schell and Seefeldt. However the most common version of this test is the revised Fear Survey Schedule for Children (FSSC-R). The FSSC-R describes specific fearful stimuli and children are asked to rate the degree to which the scenario/item makes them anxious or fearful. The most recent version of the FSSC-R presents the scenarios in a pictorial form to children as young as 4. It is called the Koala Fear Questionnaire (KFQ). The fear studies show that children's fears can be grouped into five categories. One of these categories is death and danger. This response was found amongst children age 4 to 6 on the KFQ, and from age 7 to 10. Death is the most commonly feared item and remains the most commonly feared item throughout adolescence.

A study of 90 children, aged 4–8, done by Virginia Slaughter and Maya Griffiths showed that a more mature understanding of the biological concept of death was correlated to a decreased fear of death. This may suggest that it is helpful to teach children about death (in a biological sense), in order to alleviate the fear.

Relationship to adult attachment

Death anxiety refers to the fear of death and the unknown that comes with it. Adult attachment, on the other hand, refers to the emotional bond between two individuals, often romantic partners, that provides a sense of security and comfort. Research has shown that there is a complex relationship between death anxiety and adult attachment.

According to the attachment theory, people exhibit different attachment patterns. Several studies have found that individuals who are more anxious about death tend to have less secure attachment styles. Insecure attachment styles are characterized by a fear of abandonment and a lack of trust in others, which can make it difficult for individuals to form close, supportive relationships. These individuals may also have difficulty coping with the idea of death, as they may feel a lack of support and security in their relationships.

On the other hand, individuals who have more secure attachment styles tend to have lower levels of death anxiety. This may be because they feel more supported and connected to others, which can provide a sense of comfort and security when dealing with the idea of death.

There is evidence that suggests increasing one's social curiosity, which plays a role in interpersonal relations, can reduce and subdue death anxiety. In the context of particular study, social curiosity and its tendency to foster social connection and relatedness with others acts as a form of symbolic immortality. Symbolic immortality is a conceptual model that can help reduce the fear of death.

Sex

The connection between death anxiety and one's sex appears to be strong. Studies show that females tend to have more death anxiety than males. In 1984, Thorson and Powell did a study to investigate this connection, and they sampled men and women from 16 years of age to over 60. The Death Anxiety Scale, and other scales such as the Collett-Lester Fear of Death Scale, showed higher mean scores for women than for men. Moreover, researchers believe that age and culture could be major influences in why women score higher on death anxiety scales than men.

Through the evolutionary period, a basic method was created to deal with death anxiety and also as a means of dealing with loss. Denial is used when memories or feelings are too painful to accept and are often rejected. By maintaining that the event never happened, rather than accepting it, allows an individual more time to work through the inevitable pain. When a loved one dies in a family, denial is often implemented as a means to come to grips with the reality that the person is gone. Closer families often deal with death better than when coping individually. As society and families drift apart so does the time spent bereaving those who have died, which in turn leads to negative emotion and negativity towards death. Mothers hold greater concerns about death due to their caring role within the family. It is this common role of women that leads to greater death anxiety as it emphasize the 'importance to live' for her offspring. Although it is common knowledge that all living creatures die, many people do not accept their own mortality, preferring not to accept that death is inevitable, and that they will one day die.

Age and gender

Using the Collett-Lester Fear of Death scale, studies can be performed to examine the age and gender effects on death anxiety. In 2007, two studies were compared to support these claims and they discovered the evidence that was needed. The studies claim that death anxiety peaks in men and women when in their 20s, but after this group, gender plays a role in the path that one takes. Either gender can experience a decline in death concerns with age, but the studies show an unexpected second spike in women during their early 50s. Regardless of gender, once the age of 60 is reached death anxiety levels seem to decrease and stabilize to a low level.

From a study done on elderly men and women in a care facility they were able to see that many older people were not as worried about what happens to their soul beyond death, but more, what they will have to go through in order to get to that process. In relation to their personal health/deterioration, self esteem, etc. From this study, it was also seen that women seem to be more concerned with others they will be leaving behind and the loss of those around them, in many cases even more-so than themselves.

Another study that was performed on specifically black and white men and women over the age of 65 found that race and gender tend to not have the most effects on death anxiety in elderly age. The age of the individuals ended up being a greater predictor of death anxiety than the other two variables previously mentioned. Age was the greatest predictor in how much death anxiety women had, but not in men. This study also found that this difference in death anxiety between genders may be caused due to the different ways men and women communicate with other people specifically about death.

Measuring

There are many ways to measure death anxiety and fear. In 1972, Katenbaum and Aeinsberg devised three propositions for this measurement. From this start, the ideologies about death anxiety have been able to be recorded and their attributes listed. Methods such as imagery tasks to simple questionnaires and apperception tests such as the Stroop test enable psychologists to adequately determine if a person is under stress due to death anxiety or post-traumatic stress disorder.

The Lester attitude death scale was developed in 1966 but not published until 1991 until its validity was established. By measuring the general attitude towards death and also the inconsistencies with death attitudes, participants are scaled to their favorable value towards death.

One systematic review of 21 self-report death anxiety measures found that many measures have problematic psychometric properties.

Fear of COVID-19 during the pandemic

Death anxiety and COVID-19

Millions of people around the world died from COVID-19 during the COVID-19 pandemic. The pandemic presented a psychological stressor for already present death anxiety fears. COVID-19 death anxiety was found to influence people's judgement throughout their lives. In an Australian study, those who fear that they are more prone to contracting and dying from COVID-19 have higher levels of death anxiety. The study finds a positive correlation with death anxiety and general psychological disturbances such as depression, anxiety, stress, and paranoia. Participants were also found to have greater fears of death from COVID-19 (average 22%) than the Australian fatality case rate (2%). Elderly individuals, who were already likely to experience death anxiety outside of a pandemic situation, now find their fear of death largely exacerbated. The fear of dying from COVID-19 has also been one of the leading factors in psychological distress among many countries during the course of the pandemic. It has particularly affected women and those with a lower level of education. During the COVID-19 pandemic, death anxiety has been a large contributor to declining mental wellbeing among those working in helping professions such as nursing and social work.

Solid-propellant rocket

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Solid-propellant_rocket

The Space Shuttle was launched with the help of two solid-fuel boosters known as SRBs

A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Chinese, Indians, Mongols and Persians as early as the 13th century.

All rockets used some form of solid or powdered propellant up until the 20th century, when liquid-propellant rockets offered more efficient and controllable alternatives. Solid rockets are still used today in military armaments worldwide, model rockets, solid rocket boosters and on larger applications for their simplicity and reliability.

Since solid-fuel rockets can remain in storage for an extended period without much propellant degradation and because they almost always launch reliably, they have been frequently used in military applications such as missiles. The lower performance of solid propellants (as compared to liquids) does not favor their use as primary propulsion in modern medium-to-large launch vehicles customarily used to orbit commercial satellites and launch major space probes. Solids are, however, frequently used as strap-on boosters to increase payload capacity or as spin-stabilized add-on upper stages when higher-than-normal velocities are required. Solid rockets are used as light launch vehicles for low Earth orbit (LEO) payloads under 2 tons or escape payloads up to 500 kilograms (1,100 lb).

Basic concepts

A simplified diagram of a solid-fuel rocket.

1. A solid fuel-oxidizer mixture (propellant) is packed into the rocket, with a cylindrical hole in the middle.
2. An igniter combusts the surface of the propellant.
3. The cylindrical hole in the propellant acts as a combustion chamber.
4. The hot exhaust is choked at the throat, which, among other things, dictates the amount of thrust produced.
5. Exhaust exits the rocket.

A simple solid rocket motor consists of a casing, nozzle, grain (propellant charge), and igniter.

The solid grain mass burns in a predictable fashion to produce exhaust gases, the flow of which is described by Taylor–Culick flow. The nozzle dimensions are calculated to maintain a design chamber pressure, while producing thrust from the exhaust gases.

Once ignited, a simple solid rocket motor cannot be shut off, because it contains all the ingredients necessary for combustion within the chamber in which they are burned. More advanced solid rocket motors can be throttled, and also be extinguished, and then re-ignited by control of the nozzle geometry, or through the use of vent ports. Further, pulsed rocket motors that burn in segments, and that can be ignited upon command are available.

Modern designs may also include a steerable nozzle for guidance, avionics, recovery hardware (parachutes), self-destruct mechanisms, APUs, controllable tactical motors, controllable divert and attitude control motors, and thermal management materials.

History

A battery of Katyusha rocket launchers fires at German forces during the Battle of Stalingrad, 6 October 1942

Aerojet 260 motor test, 25 September 1965

The medieval Song dynasty Chinese invented a very primitive form of solid-propellant rocket. Illustrations and descriptions in the 14th century Chinese military treatise Huolongjing by the Ming dynasty military writer and philosopher Jiao Yu confirm that the Chinese in 1232 used proto solid propellant rockets then known as "fire arrows" to drive back the Mongols during the Mongol siege of Kaifeng. Each arrow took a primitive form of a simple, solid-propellant rocket tube that was filled with gunpowder. One open end allowed the gas to escape and was attached to a long stick that acted as a guidance system for flight direction control.

The first rockets with tubes of cast iron were used by the Kingdom of Mysore under Hyder Ali and Tipu Sultan in the 1750s. These rockets had a reach of targets up to a mile and a half away. These were extremely effective in the Second Anglo-Mysore War that ended in a humiliating defeat for the British East India Company. Word of the success of the Mysore rockets against the British triggered research in England, France, Ireland and elsewhere. When the British finally conquered the fort of Srirangapatana in 1799, hundreds of rockets were shipped off to the Royal Arsenal near London to be reverse-engineered. This led to the first industrial manufacture of military rockets with the Congreve rocket in 1804.

In 1921 the Soviet research and development laboratory Gas Dynamics Laboratory began developing solid-propellant rockets, which resulted in the first launch in 1928, that flew for approximately 1,300 metres. These rockets were used in 1931 for the world's first successful use of rockets to assist take-off of aircraft. The research continued from 1933 by the Reactive Scientific Research Institute (RNII) with the development of the RS-82 and RS-132 rockets, including designing several variations for ground-to-air, ground-to-ground, air-to-ground and air-to-air combat. The earliest known use by the Soviet Air Force of aircraft-launched unguided anti-aircraft rockets in combat against heavier-than-air aircraft took place in August 1939, during the Battle of Khalkhin Gol. In June 1938, the RNII began developing a multiple rocket launcher based on the RS-132 rocket. In August 1939, the completed product was the BM-13 / Katyusha rocket launcher. Towards the end of 1938 the first significant large scale testing of the rocket launchers took place, 233 rockets of various types were used. A salvo of rockets could completely straddle a target at a range of 5,500 metres (3.4 mi). By the end of World War II total production of rocket launchers reached about 10,000. with 12 million rockets of the RS type produced for the Soviet armed forces.

In the United States modern castable composite solid rocket motors were invented by the American aerospace engineer Jack Parsons at Caltech in 1942 when he replaced double base propellant with roofing asphalt and potassium perchlorate. This made possible slow-burning rocket motors of adequate size and with sufficient shelf-life for jet-assisted take off applications. Charles Bartley, employed at JPL (Caltech), substituted curable synthetic rubber for the gooey asphalt, creating a flexible but geometrically stable load-bearing propellant grain that bonded securely to the motor casing. This made possible much larger solid rocket motors. Atlantic Research Corporation significantly boosted composite propellant I_sp in 1954 by increasing the amount of powdered aluminium in the propellant to as much as 20%.

Solid-propellant rocket technology got its largest boost in technical innovation, size and capability with the various mid-20th century government initiatives to develop increasingly capable military missiles. After initial designs of ballistic missile military technology designed with liquid-propellant rockets in the 1940s and 1950s, both the Soviet Union and the United States embarked on major initiatives to develop solid-propellant local, regional, and intercontinental ballistic missiles, including solid-propellant missiles that could be launched from air or sea. Many other governments also developed these military technologies over the next 50 years.

By the later 1980s and continuing to 2020, these government-developed highly-capable solid rocket technologies have been applied to orbital spaceflight by many government-directed programs, most often as booster rockets to add extra thrust during the early ascent of their primarily liquid rocket launch vehicles. Some designs have had solid rocket upper stages as well. Examples flying in the 2010s include the European Ariane 5, US Atlas V and Space Shuttle, and Japan's H-II.

The largest solid rocket motors ever built were Aerojet's three 6.60-meter (260 in) monolithic solid motors cast in Florida. Motors 260 SL-1 and SL-2 were 6.63 meters (261 in) in diameter, 24.59 meters (80 ft 8 in) long, weighed 842,900 kilograms (1,858,300 lb), and had a maximum thrust of 16 MN (3,500,000 lbf). Burn duration was two minutes. The nozzle throat was large enough to walk through standing up. The motor was capable of serving as a 1-to-1 replacement for the 8-engine Saturn I liquid-propellant first stage but was never used as such. Motor 260 SL-3 was of similar length and weight but had a maximum thrust of 24 MN (5,400,000 lbf) and a shorter duration.

Design

Design begins with the total impulse required, which determines the fuel and oxidizer mass. Grain geometry and chemistry are then chosen to satisfy the required motor characteristics.

The following are chosen or solved simultaneously. The results are exact dimensions for grain, nozzle, and case geometries:

• The grain burns at a predictable rate, given its surface area and chamber pressure.
• The chamber pressure is determined by the nozzle throat diameter and grain burn rate.
• Allowable chamber pressure is a function of casing design.
• The length of burn time is determined by the grain "web thickness".

The grain may or may not be bonded to the casing. Case-bonded motors are more difficult to design, since the deformation of the case and the grain under flight must be compatible.

Common modes of failure in solid rocket motors include fracture of the grain, failure of case bonding, and air pockets in the grain. All of these produce an instantaneous increase in burn surface area and a corresponding increase in exhaust gas production rate and pressure, which may rupture the casing.

Another failure mode is casing seal failure. Seals are required in casings that have to be opened to load the grain. Once a seal fails, hot gas will erode the escape path and result in failure. This was the cause of the Space Shuttle Challenger disaster.

Grain geometry

Solid rocket fuel deflagrates from the surface of exposed propellant in the combustion chamber. In this fashion, the geometry of the propellant inside the rocket motor plays an important role in the overall motor performance. As the surface of the propellant burns, the shape evolves (a subject of study in internal ballistics), most often changing the propellant surface area exposed to the combustion gases. Since the propellant volume is equal to the cross sectional area $A_s$ times the fuel length, the volumetric propellant consumption rate is the cross section area times the linear burn rate ${\displaystyle \dot{b}}$, and the instantaneous mass flow rate of combustion gases generated is equal to the volumetric rate times the fuel density $\rho$:

${\displaystyle \dot{m}=\rho \cdot A_s\cdot \dot{b}}$

Several geometric configurations are often used depending on the application and desired thrust curve:

• 

  Circular bore simulation

• 

  C-slot simulation

• 

  Moon burner simulation

• 

  5-point finocyl simulation

• Circular bore: if in BATES configuration, produces progressive-regressive thrust curve.
• End burner: propellant burns from one axial end to other producing steady long burn, though has thermal difficulties, center of gravity (CG) shift.
• C-slot: propellant with large wedge cut out of side (along axial direction), producing fairly long regressive thrust, though has thermal difficulties and asymmetric CG characteristics.
• Moon burner: off-center circular bore produces progressive-regressive long burn, though has slight asymmetric CG characteristics
• Finocyl: usually a 5- or 6-legged star-like shape that can produce very level thrust, with a bit quicker burn than circular bore due to increased surface area.

Casing

The casing may be constructed from a range of materials. Cardboard is used for small black powder model motors, whereas aluminium is used for larger composite-fuel hobby motors. Steel was used for the space shuttle boosters. Filament-wound graphite epoxy casings are used for high-performance motors.

The casing must be designed to withstand the pressure and resulting stresses of the rocket motor, possibly at elevated temperature. For design, the casing is considered a pressure vessel.

To protect the casing from corrosive hot gases, a sacrificial thermal liner on the inside of the casing is often implemented, which ablates to prolong the life of the motor casing.

Nozzle

Main article: Rocket engine nozzle

A convergent-divergent design accelerates the exhaust gas out of the nozzle to produce thrust. The nozzle must be constructed from a material that can withstand the heat of the combustion gas flow. Often, heat-resistant carbon-based materials are used, such as amorphous graphite or carbon-carbon.

Some designs include directional control of the exhaust. This can be accomplished by gimballing the nozzle, as in the Space Shuttle SRBs, by the use of jet vanes in the exhaust as in the V-2 rocket, or by liquid injection thrust vectoring (LITV).

LITV consists of injecting a liquid into the exhaust stream after the nozzle throat. The liquid then vaporizes, and in most cases chemically reacts, adding mass flow to one side of the exhaust stream and thus providing a control moment. For example, the Titan IIIC solid boosters injected nitrogen tetroxide for LITV; the tanks can be seen on the sides of the rocket between the main center stage and the boosters.

An early Minuteman first stage used a single motor with four gimballed nozzles to provide pitch, yaw, and roll control.

Performance

An exhaust cloud engulfs Launch Pad 39A at NASA's Kennedy Space Center as the Space Shuttle Endeavour lifts off.

A typical, well-designed ammonium perchlorate composite propellant (APCP) first-stage motor may have a vacuum specific impulse (I_sp) as high as 285.6 seconds (2.801 km/s) (Titan IVB SRMU). This compares to 339.3 s (3.327 km/s) for RP1/LOX (RD-180) and 452.3 s (4.436 km/s) for LH₂/LOX (Block II RS-25) bipropellant engines. Upper stage specific impulses are somewhat greater: as much as 303.8 s (2.979 km/s) for APCP (Orbus 6E), 359 s (3.52 km/s) for RP1/LOX (RD-0124) and 465.5 s (4.565 km/s) for LH₂/LOX (RL10B-2).

Propellant fractions are usually somewhat higher for (non-segmented) solid propellant first stages than for upper stages. The 53,000-kilogram (117,000 lb) Castor 120 first stage has a propellant mass fraction of 92.23% while the 14,000-kilogram (31,000 lb) Castor 30 upper stage developed for Orbital Science's Taurus II COTS (Commercial Off The Shelf) (International Space Station resupply) launch vehicle has a 91.3% propellant fraction with 2.9% graphite epoxy motor casing, 2.4% nozzle, igniter and thrust vector actuator, and 3.4% non-motor hardware including such things as payload mount, interstage adapter, cable raceway, instrumentation, etc. Castor 120 and Castor 30 are 2.36 and 2.34 meters (93 and 92 in) in diameter, respectively, and serve as stages on the Athena IC and IIC commercial launch vehicles. A four-stage Athena II using Castor 120s as both first and second stages became the first commercially developed launch vehicle to launch a lunar probe (Lunar Prospector) in 1998.

Solid rockets can provide high thrust for relatively low cost. For this reason, solids have been used as initial stages in rockets (for example the Space Shuttle), while reserving high specific impulse engines, especially less massive hydrogen-fueled engines, for higher stages. In addition, solid rockets have a long history as the final boost stage for satellites due to their simplicity, reliability, compactness and reasonably high mass fraction. A spin-stabilized solid rocket motor is sometimes added when extra velocity is required, such as for a mission to a comet or the outer solar system, because a spinner does not require a guidance system (on the newly added stage). Thiokol's extensive family of mostly titanium-cased Star space motors has been widely used, especially on Delta launch vehicles and as spin-stabilized upper stages to launch satellites from the cargo bay of the Space Shuttle. Star motors have propellant fractions as high as 94.6% but add-on structures and equipment reduce the operating mass fraction by 2% or more.

Higher performing solid rocket propellants are used in large strategic missiles (as opposed to commercial launch vehicles). HMX, C₄H₈N₄(NO₂)₄, a nitramine with greater energy than ammonium perchlorate, was used in the propellant of the Peacekeeper ICBM and is the main ingredient in NEPE-75 propellant used in the Trident II D-5 Fleet Ballistic Missile. It is because of explosive hazard that the higher energy military solid propellants containing HMX are not used in commercial launch vehicles except when the LV is an adapted ballistic missile already containing HMX propellant (Minotaur IV and V based on the retired Peacekeeper ICBMs). The Naval Air Weapons Station at China Lake, California, developed a new compound, C₆H₆N₆(NO₂)₆, called simply CL-20 (China Lake compound ^#20). Compared to HMX, CL-20 has 14% more energy per mass, 20% more energy per volume, and a higher oxygen-to-fuel ratio. One of the motivations for development of these very high energy density military solid propellants is to achieve mid-course exo-atmospheric ABM capability from missiles small enough to fit in existing ship-based below-deck vertical launch tubes and air-mobile truck-mounted launch tubes. CL-20 propellant compliant with Congress' 2004 insensitive munitions (IM) law has been demonstrated and may, as its cost comes down, be suitable for use in commercial launch vehicles, with a very significant increase in performance compared with the currently favored APCP solid propellants. With a specific impulse of 309 s already demonstrated by Peacekeeper's second stage using HMX propellant, the higher energy of CL-20 propellant can be expected to increase specific impulse to around 320 s in similar ICBM or launch vehicle upper stage applications, without the explosive hazard of HMX.

An attractive attribute for military use is the ability for solid rocket propellant to remain loaded in the rocket for long durations and then be reliably launched at a moment's notice.

Propellant families

Black powder (gunpowder) propellant

Black powder (gunpowder) is composed of charcoal (fuel), potassium nitrate (oxidizer), and sulfur (fuel and catalyst). It is one of the oldest pyrotechnic compositions with application to rocketry. In modern times, black powder finds use in low-power model rockets (such as Estes and Quest rockets), as it is cheap and fairly easy to produce. The fuel grain is typically a mixture of pressed fine powder (into a solid, hard slug), with a burn rate that is highly dependent upon exact composition and operating conditions. The specific impulse of black powder is low, around 80 s (0.78 km/s). The grain is sensitive to fracture and, therefore, catastrophic failure. Black powder does not typically find use in motors above 40 newtons (9.0 pounds-force) thrust.

Zinc–sulfur (ZS) propellants

Composed of powdered zinc metal and powdered sulfur (oxidizer), ZS or "micrograin" is another pressed propellant that does not find any practical application outside specialized amateur rocketry circles due to its poor performance (as most ZS burns outside the combustion chamber) and fast linear burn rates on the order of 2 m/s. ZS is most often employed as a novelty propellant as the rocket accelerates extremely quickly leaving a spectacular large orange fireball behind it.

"Candy" propellants

In general, rocket candy propellants are an oxidizer (typically potassium nitrate) and a sugar fuel (typically dextrose, sorbitol, or sucrose) that are cast into shape by gently melting the propellant constituents together and pouring or packing the amorphous colloid into a mold. Candy propellants generate a low-medium specific impulse of roughly 130 s (1.3 km/s) and, thus, are used primarily by amateur and experimental rocketeers.

Double-base (DB) propellants

DB propellants are composed of two monopropellant fuel components where one typically acts as a high-energy (yet unstable) monopropellant and the other acts as a lower-energy stabilizing (and gelling) monopropellant. In typical circumstances, nitroglycerin is dissolved in a nitrocellulose gel and solidified with additives. DB propellants are implemented in applications where minimal smoke is required yet a medium-high I_sp of roughly 235 s (2.30 km/s) is required. The addition of metal fuels (such as aluminium) can increase performance to around 250 s (2.5 km/s), though metal oxide nucleation in the exhaust can turn the smoke opaque.

Composite propellants

A powdered oxidizer and powdered metal fuel are intimately mixed and immobilized with a rubbery binder (that also acts as a fuel). Composite propellants are often either ammonium-nitrate-based (ANCP) or ammonium-perchlorate-based (APCP). Ammonium nitrate composite propellant often uses magnesium and/or aluminium as fuel and delivers medium performance (I_sp of about 210 s (2.1 km/s)) whereas ammonium perchlorate composite propellant often uses aluminium fuel and delivers high performance: vacuum I_sp up to 296 s (2.90 km/s) with a single-piece nozzle or 304 s (2.98 km/s) with a high-area-ratio telescoping nozzle. Aluminium is used as fuel because it has a reasonable specific energy density, a high volumetric energy density, and is difficult to ignite accidentally. Composite propellants are cast, and retain their shape after the rubber binder, such as Hydroxyl-terminated polybutadiene (HTPB), cross-links (solidifies) with the aid of a curative additive. Because of its high performance, moderate ease of manufacturing, and moderate cost, APCP finds widespread use in space, military, and amateur rockets, whereas cheaper and less efficient ANCP finds use in amateur rocketry and gas generators. Ammonium dinitramide, NH₄N(NO₂)₂, is being considered as a 1-to-1 chlorine-free substitute for ammonium perchlorate in composite propellants. Unlike ammonium nitrate, ADN can be substituted for AP without a loss in motor performance.

Polyurethane-bound aluminium-APCP solid fuel was used in the submarine-launched Polaris missiles. APCP used in the space shuttle Solid Rocket Boosters consisted of ammonium perchlorate (oxidizer, 69.6% by weight), aluminium (fuel, 16%), iron oxide (a catalyst, 0.4%), polybutadiene acrylonitrile (PBAN) polymer (a non-urethane rubber binder that held the mixture together and acted as secondary fuel, 12.04%), and an epoxy curing agent (1.96%). It developed a specific impulse of 242 seconds (2.37 km/s) at sea level or 268 seconds (2.63 km/s) in a vacuum. The 2005-2009 Constellation Program was to use a similar PBAN-bound APCP.

In 2009, a group succeeded in creating a propellant of water and nanoaluminium (ALICE).

High-energy composite (HEC) propellants

Typical HEC propellants start with a standard composite propellant mixture (such as APCP) and add a high-energy explosive to the mix. This extra component usually is in the form of small crystals of RDX or HMX, both of which have higher energy than ammonium perchlorate. Despite a modest increase in specific impulse, implementation is limited due to the increased hazards of the high-explosive additives.

Composite modified double base propellants

Composite modified double base propellants start with a nitrocellulose/nitroglycerin double base propellant as a binder and add solids (typically ammonium perchlorate (AP) and powdered aluminium) normally used in composite propellants. The ammonium perchlorate makes up the oxygen deficit introduced by using nitrocellulose, improving the overall specific impulse. The aluminium improves specific impulse as well as combustion stability. High performing propellants such as NEPE-75 used to fuel the Trident II D-5, SLBM replace most of the AP with polyethylene glycol-bound HMX, further increasing specific impulse. The mixing of composite and double base propellant ingredients has become so common as to blur the functional definition of double base propellants.

Minimum-signature (smokeless) propellants

One of the most active areas of solid propellant research is the development of high-energy, minimum-signature propellant using C₆H₆N₆(NO₂)₆ CL-20 nitroamine (China Lake compound #20), which has 14% higher energy per mass and 20% higher energy density than HMX. The new propellant has been successfully developed and tested in tactical rocket motors. The propellant is non-polluting: acid-free, solid particulates-free, and lead-free. It is also smokeless and has only a faint shock diamond pattern that is visible in the otherwise transparent exhaust. Without the bright flame and dense smoke trail produced by the burning of aluminized propellants, these smokeless propellants all but eliminate the risk of giving away the positions from which the missiles are fired. The new CL-20 propellant is shock-insensitive (hazard class 1.3) as opposed to current HMX smokeless propellants which are highly detonable (hazard class 1.1). CL-20 is considered a major breakthrough in solid rocket propellant technology but has yet to see widespread use because costs remain high.

Electric solid propellants

Electric solid propellants (ESPs) are a family of high performance plastisol solid propellants that can be ignited and throttled by the application of electric current. Unlike conventional rocket motor propellants that are difficult to control and extinguish, ESPs can be ignited reliably at precise intervals and durations. It requires no moving parts and the propellant is insensitive to flames or electrical sparks.

Hobby and amateur rocketry

Solid propellant rocket motors can be bought for use in model rocketry; they are normally small cylinders of black powder fuel with an integral nozzle and optionally a small charge that is set off when the propellant is exhausted after a time delay. This charge can be used to trigger a camera, or deploy a parachute. Without this charge and delay, the motor may ignite a second stage (black powder only).

In mid- and high-power rocketry, commercially made APCP motors are widely used. They can be designed as either single-use or reloadables. These motors are available in impulse ranges from "A" (1.26 Ns– 2.50 Ns) to "O" (20.48 kNs – 40.96 kNs), from several manufacturers. They are manufactured in standardized diameters and varying lengths depending on required impulse. Standard motor diameters are 13, 18, 24, 29, 38, 54, 75, 98, and 150 millimeters. Different propellant formulations are available to produce different thrust profiles, as well as special effects such as colored flames, smoke trails, or large quantities of sparks (produced by adding titanium sponge to the mix).

Use

Sounding rockets

Almost all sounding rockets use solid motors.

• Astrobee
• Black Brant
• S-310, S-520
• Skylark (rocket)
• Terrier-Orion, Terrier-Malemute
• VSB-30

Missiles

Due to reliability, ease of storage and handling, solid rockets are used on missiles and ICBMs.

• Air-to-air missiles: AIM-9 Sidewinder
• Ballistic missiles: Jericho, Sejjil
• ICBMs: LGM-30 Minuteman, UGM-133 Trident II, LGM-118 Peacekeeper, RT-2PM Topol, DF-41, M51 SLBM

Orbital rockets

Solid rockets are suitable for launching small payloads to orbital velocities, especially if three or more stages are used. Many of these are based on repurposed ICBMs.

• Scout
• Athena
• Mu
• Pegasus
• Taurus
• Minotaur
• Start-1
• PSLV - alternating solid and liquid stages
• Shavit
• Vega
• Long March 11
• OmegA

Larger liquid-fueled orbital rockets often use solid rocket boosters to gain enough initial thrust to launch the fully fueled rocket.

Main article: Solid rocket booster

• Delta II
• Titan IV
• Space Shuttle
• Space Launch System
• Ariane 5
• Atlas II
• Atlas V (optionally 1-5 boosters)
• Delta IV (optionally 2 or 4 boosters)
• H-IIA, H-IIB
• PSLV - optional solid boosters to lift heavier payloads
• GSLV Mk III

Solid fuel is also used for some upper stages, particularly the Star 37 (sometimes referred to as the "Burner" upper stage) and the Star 48 (sometimes referred to as the "Payload Assist Module", or PAM), both manufactured originally by Thiokol, and today by Northrop Grumman. They are used to lift large payloads to intended orbits (such as the Global Positioning System satellites), or smaller payloads to interplanetary—or even interstellar—trajectories. Another solid-fuel upper stage, used by the Space Shuttle and the Titan IV, was the Boeing-manufactured Inertial Upper Stage (IUS).

• Pioneer 10 and Pioneer 11 were both sent out of the solar system by Star 37E upper stages from Atlas-Centaur rockets.
• Voyager 1 and Voyager 2 were both sent out of the solar system by Star 37E upper stages from Titan IIIE rockets.
• Magellan was sent to Venus on an IUS after being deployed from Space Shuttle Atlantis on STS-30.
• Galileo was sent to Jupiter on an IUS after being deployed from Space Shuttle Atlantis on STS-34.
• Ulysses was sent to Jupiter on an IUS and a Star 48 PAM after being deployed from Space Shuttle Discovery on STS-41. It then was placed in a polar orbit around the Sun following a gravity assist around Jupiter.
• New Horizons was sent out of the solar system on a Star 48 PAM from an Atlas V rocket.

Some rockets, like the Antares (manufactured by Northrop Grumman), have mandatory solid-fuel upper stages. The Antares rocket uses the Northrop Grumman-manufactured Castor 30 as an upper stage.

Advanced research

• Environmentally sensitive fuel formulations such as ALICE propellant
• Ramjets with solid fuel
• Variable thrust designs based on variable nozzle geometry
• Hybrid rockets that use solid fuel and throttleable liquid or gaseous oxidizer