Spaceflights
Manned spaceflight on an individual basis has only been achieved with experimental aircraft such as the X-15.

# Cosmic rays
"Thus far, astronauts have not been exposed to the high doses of radiation that can be received by exposure to SPE radiation , but exposure to  SPE radiation will be considerably more likely for astronauts during the exploration class missions (with the necessary extended times in space travel) planned by NASA and other space agencies for the future."

# Protons
"Mice were suspended prior to and after proton radiation exposure (2 Gy dose) and total leukocyte numbers and splenic lymphocyte functionality were evaluated on days 4 or 21 after combined HU and radiation exposure. Total white blood cell (WBC), lymphocyte, neutrophil, and monocyte counts are reduced by approximately 65%, 70%, 55%, and 70%, respectively, compared to the non-treated control group at 4 days after combined exposure. Splenic lymphocyte subpopulations are altered at both time points investigated. At 21 days post-exposure to combined HU and proton radiation, T cell activation and proliferation were assessed in isolated lymphocytes. Cell surface expression of the Early Activation Marker, CD69, is decreased by 30% in the combined treatment group, compared to the non-treated control group and cell proliferation was suppressed by approximately 50%, compared to the non-treated control group. These findings reveal that the combined stressors (HU and proton radiation exposure) result in decreased leukocyte numbers and function, which could contribute to immune system dysfunction in crew members. This investigation is one of the first to report on combined proton radiation and simulated microgravity effects on hematopoietic, specifically immune cells."
"Hematological and immune system effects from ionizing radiation exposure (similar to the expected or estimated spaceflight doses) are established. Previous data indicate a dose-dependent decrease in peripheral blood cell counts, particularly lymphocytes, after whole body proton radiation exposure . Bone marrow derived lymphocyte numbers are also decreased after whole body proton radiation exposure . Limited studies have been reported on the function and activation of lymphocytes after proton radiation exposure , and there are no available reports on lymphocyte function and activation in response to ground-based microgravity simulation with combined proton radiation exposure."

# Solar cycle effects
"Protons and heavier ions accelerated at the termination shock, after pickup from photo-ionization of interstellar gas neutrals, are called anomalous cosmic rays (ACR)."
"Near solar minimum the ACR ions, including protons, are dominant components of radiation dosage outward from 40 AU to the outer heliosphere, while these ions largely disappear at solar maximum. There is a 22-year cycle in the polarity of the solar dipole magnetic field, which is frozen into the solar wind plasma within several radii of the Sun and thereby carried outward into the heliosphere. Due to sign-dependent transport effects, the ACR ions accelerated at the termination shock have larger fluxes, and more positive radial gradients, at 40 to 85 AU near the Ecliptic when the solar dipole moment is directed southward (qA  0 polarity)."

# Theoretical spaceflights
Def. an "act of flight" is called flying.
Def.
- the "act of flying",
- an "instance of flying", or
- a "journey made by an aircraft, eg a balloon, plane or space shuttle, particularly one between two airports, which needs to be reserved in advance" is called a flight.
Def. a flight "into, from or through space" is called a space flight or spaceflight.
Def. any "region of space beyond limits determined with reference to boundaries of a celestial system or body, especially the region of space immediately beyond Earth's atmosphere" is called outer space.
""Flyings" could vary considerably in complexity and lavishness and could involve an actor or property being either lifted from the stage into the flies above or vice versa. As Colin Visser has observed, flyings and sinkings are both "associated with supernatural manifestations of various kinds""

# Bone mineral losses
Def. the "amount of mineral per square centimeter of" bone is called bone density (in clinical practice).
"Actual bone density would be expressed in grams per milliliter."
Areal bone mineral density "BMD (aBMD) measurements by  DXA showed that cosmonauts making flights of 4- to 12-month duration on the Soviet/Russian MIR spacecraft lost bone at an average rate of 1%/month from the spine and 1.5%/month from the hip."
From "a study of crewmembers (13 males and 1 female; age range, 4055 years) on long-duration missions (46 months) on the International Space Station (ISS). We used DXA to obtain aBMD of the hip and spine and volumetric QCT (vQCT) to assess integral, cortical, and trabecular volumetric BMD (vBMD) in the hip and spine. In the heel, DXA was used to measure aBMD, and quantitative ultrasound (QUS) was used to measure speed of sound (SOS) and broadband ultrasound attenuation (BUA).  aBMD was lost at rates of 0.9%/month at the spine (p < 0.001) and 1.4 1.5%/month at the hip (p < 0.001). Spinal integral vBMD was lost at a rate of 0.9%/month (p < 0.001), and trabecular vBMD was lost at 0.7%/month (p < 0.05). In contrast to earlier reports, these changes were generalized across the vertebrae and not focused in the posterior elements. In the hip, integral, cortical, and trabecular vBMD was lost at rates of 1.21.5%/month (p < 0.0001), 0.40.5%/month (p < 0.01), and 2.22.7%/month (p < 0.001), respectively. The cortical bone loss in the hip occurred primarily by cortical thinning. Calcaneal aBMD measurements by DXA showed smaller mean losses (0.4%/month) than hip or spine measurements, with SOS and BUA showing no change."
"Long-term spaceflights induce bone loss as a result of profound modifications of bone remodeling"
"We measured intact parathyroid hormone (PTH) and serum calcium; for bone formation, serum concentrations of bone alkaline phosphatase (BAP), intact osteocalcin (iBGP), and type 1 procollagen propeptide (PICP); for resorption, urinary concentrations (normalized by creatinine) of procollagen C-telopeptide (CTX), free and bound deoxypyridinoline (F and B D-Pyr), and Pyr in a 36-year-old cosmonaut (RTO), before (days 180, 60, and 15), during (from days 10 to 178, n = 12), and after (days +7, +15, +25, and +90) a 180-day spaceflight, in another cosmonaut (ASW) before and after the flight. Flight PTH tended to decrease by 48% and postflight PTH increased by 98%. During the flight, BAP, iBGP, and PICP decreased by 27%, 38%, and 28% respectively in CM1, and increased by 54%, 35%, and 78% after the flight. F D-Pyr and CTX increased by 54% and 78% during the flight and decreased by 29% and 40% after the flight, respectively. We showed for the first time in humans that microgravity induced an uncoupling of bone remodeling between formation and resorption that could account for bone loss."

# Carotid baroreceptor-cardiac reflexes
"Spaceflight is associated with decreased orthostatic tolerance after landing. Short-duration spaceflight (45 days) impairs one neural mechanism: the carotid baroreceptor-cardiac reflex. To understand the effects of longer-duration spaceflight on baroreflex function, we measured R-R interval power spectra, antecubital vein plasma catecholamine levels, carotid baroreceptor-cardiac reflex responses, responses to Valsalva maneuvers, and orthostatic tolerance in 16 astronauts before and after shuttle missions lasting 814 days. We found the following changes between preflight and landing day: 1) orthostatic tolerance decreased; 2) R-R interval spectral power in the 0.05 to 0.15-Hz band increased; 3) plasma norepinephrine and epinephrine levels increased; 4) the slope, range, and operational point of the carotid baroreceptor cardiac reflex response decreased; and 5) blood pressure and heart rate responses to Valsalva maneuvers were altered. Autonomic changes persisted for several days after landing."

# Immune system changes
"The results of immunological analyses before, during and after spaceflight, have established the fact that spaceflight can result in a blunting of the immune mechanisms of human crew members and animal test species. There is some evidence that the immune function changes in short-term flights resemble those occurring after acute stress, while the changes during long-term flights resemble those caused by chronic stress. In addition, this blunting of the immune function occurs concomitant with a relative increase in potentially infectious microorganisms in the space cabin environment. This combination of events results in an increased probability of inflight infectious events. The realization of this probability has been shown to be partially negated by the judicious use of a preflight health stabilization program and other operational countermeasures."
"It is now well established that spaceflight alters immune function  by mechanisms which are poorly understood. The changes in the immunological parameters studied thus far occur within a few days of exposure to the space environment. Factors in the space environment contributing to immune dysregulation during and post-spaceflight include exposure to microgravity, stress, deconditioning (reduced physical activity and shift of fluids), and radiation. Primary immune defense heavily relies on immune cell distribution and function, and is clearly influenced by a combination or synergy of any of the factors described above that exist in the space environment."
"Of the blood cell types, lymphocytes are the most sensitive to ionizing radiation exposure. T cells, or T lymphocytes, processed in the thymus, secrete lymphokines, which orchestrate signaling to lymphocytes and other immune cells to promote cell activation, proliferation, destroy target cells, and incite macrophages. Blood lymphocytes isolated from astronauts upon re-entry after a prolonged spaceflight exhibit decreased responses in mitogen reactivity, T-lymphocyte proliferation, and IL-2 production . Space laboratory studies using rat splenocytes indicate dramatic shifts in T lymphocyte subsets as well as decreased cell division in bone marrow cells post-flight . A follow up study using bone marrow cells isolated from rhesus monkeys upon landing indicated decreased cytokine production and cytokine receptor expression ."
"When human lymphocytes are exposed to microgravity in a rapidly rotating clinostat, Concanavalin A (ConA) stimulated T cell activation is depressed , . During flight, the activation of cultured human lymphocytes is depressed to less than 3% of the ground controls when exposed to ConA . Microarray analysis of T lymphocytes exposed to mitogen in a vectorless gravity environment (using a random positioning machine) revealed that early T cell activation-associated gene expression is in fact, suppressed ."

# Muscle mass losses
"Muscle strength and limb girth measurements during Skylab and Apollo missions suggested that loss of muscle mass may occur as a result of spaceflight. Extended duration spaceflight is important for the economical and practical use of space. The loss of muscle mass during spaceflight is a medical concern for long duration flights to the planets or extended stays aboard space stations. Understanding the extent and temporal relationships of muscle loss is important for the development of effective spaceflight countermeasures."
"Statistical analyses demonstrated that  the soleus-gastrocnemius (-6.3%), anterior calf (-3.9%), hamstrings (-8.3%), quadriceps (-6.0%) and intrinsic back (-10.3%) muscles were decreased, p < 0.05, compared to baseline, 24 h after landing. At 2 weeks post recovery, the hamstrings and intrinsic lower back muscles were still below baseline, p < 0.05."

# Orthostatic intolerances
Def. symptoms "of cerebral hypoperfusion or autonomic overaction which develop while the subject is standing, but are relieved on recumbency" are called orthostatic intolerance.
The types of orthostatic intolerance "include NEUROCARDIOGENIC SYNCOPE; POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME; and neurogenic ORTHOSTATIC HYPOTENSION."
Def. a "transient loss of consciousness and postural tone caused by diminished blood flow to the brain" is called a syncope.
Def. loss "of consciousness due to a reduction in blood pressure that is associated with an increase in vagal tone and peripheral vasodilation" is called vasovagal syncope or neurocardiogenic syncope.
Def. a "syndrome of ORTHOSTATIC INTOLERANCE combined with excessive upright TACHYCARDIA, and usually without associated ORTHOSTATIC HYPOTENSION" is called Postural Orthostatic Tachycardia Syndrome.
"All variants have in common an excessively reduced venous return to the heart (central HYPOVOLEMIA) while upright."
Def. "a 20-mm Hg decrease in systolic pressure or a 10-mm Hg decrease in diastolic pressure 3 minutes after the person has risen from supine to standing" is called orthostatic hypotension.
"Symptoms generally include DIZZINESS, blurred vision, and SYNCOPE."
"Orthostatic intolerance occurs commonly after spaceflight, and important aspects of the underlying mechanisms remain unclear."
"After spaceflight, 9 of the 14 (64%) crew members could not complete a 10-min stand test that all completed preflight."
The "postural vasoconstrictor response was significantly greater among the finishers (P < 0.01)."

# Hypotheses
- A method to place a 5,000 kg object in orbit by using the natural electric field of the Earth may be possible.

# Acknowledgements
The content on this page was first contributed by: Henry A. Hoff.
Initial content for this page in some instances came from Wikiversity.