Woody
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Why aren't spacecraft and spacesuits pressurised to 2.5 psi (17 kPa) of pure oxygen?
Accepted answer
56 votes

The sum of all partial pressures in the lungs must add up to the ambient pressure. The composition of gas inside the lungs includes the vapor pressure of H₂O at body temperature which is about 0.9 psi....

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Would a broken arm/ leg be more painful in zero gravity?
36 votes

Yes, your fracture would still hurt in microgravity. Likely worse. Pain from a fracture comes from inflammation and soft tissue damage around the fracture, not just mechanical loading of the fracture ...

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Shouldn't space junk fall back to Earth on its own? How long will take for a ~1 cm piece of junk in LEO to fall back to Earth on its own for example?
28 votes

Space debris poses a real risk for spacecraft in LEO. From the Technical Report on Space Debris UN Committee on the Peaceful uses of Outer Space (Table 5), a satellite in orbit can expect to collide ...

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JWST - Why unfurl before reaching L2?
23 votes

The commissioning process involves 130+ steps, in a specific order, which takes months. If you never start, you never finish. There is no advantage to delay. Deployment has almost no effect on ...

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Can an ISS module survive reentry?
Accepted answer
22 votes

“Aluminum, rather than steel, comprises most of the outer shell of the modules” https://science.nasa.gov/science-news/science-at-nasa/2001/ast14mar_1 . Aluminum has low melting point and softens ...

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Why did a solar eclipse of the sun as seen from Apollo 11 appear to have an elliptical corona?
21 votes

Answer: The sun has an outrageously strong magnetic field. The corona is highly ionized and interacts with the magnetic field. This produces corona symmetry around the magnetic pole axis. The corona ...

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What is the equation that relates delta v of a rocket to time taken to complete an orbit?
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19 votes

There is actually no relationship between the two. In a simple 2-body problem, each orbit starts and ends in the same place with the same velocity vector. The "delta" in "delta-v" ...

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What are the characteristics of JWST's orbit around L2?
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11 votes

The orbit is more oval than elliptic since it is centered on... well, the center, rather than one focus. It is roughly perpendicular to the Sun-Earth axis. The orbital period 6 months. Radius of the ...

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How will JWST come to rest at L2?
11 votes

Question: will JWST catch up with L2 or will L2 catch up with JWST? Answer: To a first approximation, both. And neither. The answer depends on the frame of reference you chose. Case 1: In a rotating ...

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Is an orbital insertion burn part of any launch from earth
10 votes

Wikipedia defines “orbital insertion” as either acceleration or deceleration to allow entry into a stable orbit. To answer your question, where a spacecraft has been launched into low earth orbit and ...

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Why are the JWST secondary mirror support booms not painted black?
9 votes

A smart-ass answer to the question “Why aren’t the booms painted black?” would be, “Because they are already made of black material.” This doesn’t answer the puzzle of, “Why are supports coated in ...

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Do other planets and moons share Earth’s mineral diversity?
9 votes

According to this dated but enjoyable Scientific American article https://sciences.ucf.edu/class/wp-content/uploads/sites/23/2020/01/Hazen-The-evolution-of-minerals-Scientific-American.pdf, Earth is ...

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Can gas bubbles form in the fuel and oxidizer rocket engine pumps due to insufficient flow from the tanks?
Accepted answer
8 votes

Cavitation occurs when fluid pressure is below the fluid's vapor pressure. In other words, the liquid boils. In a rocket, the propellant tank outlet is pressurized by ullage and acceleration. It is ...

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If we pick any point on the moon (except possibly the poles), is the sun visible for 13.66 days, and then not visible for 13.66 days?
8 votes

It’s interesting that you excluded the poles from your question. If the Moon’s axis was perpendicular to the ecliptic, you could (in theory) mount solar panels on a vertical mast at the poles and ...

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If you release a tool outside the ISS in space will it remain at the "same" place forever?
8 votes

Great question to illustrate small but measurable effects of orbital mechanics! NO, even if both wrench and ISS are idealized point masses in the same circular orbit. The mass of the ISS imposes a non-...

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Why is NASA choosing such a large “halo” orbit at L2 for JWST?
Accepted answer
7 votes

Answer: to avoid eclipses by the Moon. See: Why are eclipses of the James Webb by the Earth or Moon not permitted during the mission? . It discusses NASA's decision not to allow any lunar eclipses of ...

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Why did Luna 1 enter a heliocentric orbit?
6 votes

According to the Wikipedia article on Luna 1, “The Soviet engineers did not trust automated systems for controlling the engine burns, so they communicated to the rocket via radio. The signal to stop ...

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How does gravity change beyond L2?
5 votes

The key here is that the graph shows acceleration in a rotating frame of reference. The line shows the sum of gravitational acceleration and centrifugal acceleration, which are opposite in direction. ...

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Why end-of-life GPS satellites given orbits that seemingly still intersect active satellite orbits but with a different period? Recipe for disaster?
5 votes

“As of Feb 2019, there are 31 satellites in the GPS constellation, 27 of which are in use with the rest allocated as stand-bys… More decommissioned satellites are in orbit and available as spares.” ...

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Experience of breathing regular air vs. Nitrox vs pure oxygen at 4.3 psi?
Accepted answer
5 votes

Respiratory gasses interact with the respiratory system, hemoglobin and respiring tissues through their partial pressures. Room air is 21% O2 @ 760mmHg, or a partial pressure of 160mmHg. So, at first ...

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Can there be color blind astronauts?
4 votes

Yes. There has been at least one color blind pilot astronaut. “Color Blindness” covers such a wide range of conditions, the term is almost useless. It would be counterproductive to disqualify all ...

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Isometrics in zero gravity
3 votes

Spaceflight Associated Neuro-Ocular Syndrome (SANS) (formerly called visual impairment and intracranial pressure syndrome) is a group of findings and symptoms that have been found in astronauts who ...

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What was the flight path of China's hypersonic missile that circumnavigated sometime in summer 2021?
3 votes

The Chinese missile/glider was in LEO for some of its path, then re-entered the atmosphere as a glider. There is a good article in the Economist: https://www.economist.com/china/2021/10/23/chinas-test-...

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Are any space agencies working on an (essentially) 100% reliable sterilization technique for spacecraft bound for subsurface ocean worlds?
3 votes

“100% reliable” may be unattainable, but “Dang close” is already routine in hospitals. Dry heat sterilization is possible, but requires long exposure times which can damage many materials. Etylene ...

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Could you survive very high G's if your whole body was accelerated uniformly?
3 votes

To just answer your question, Einstein says “yes”. All uniformly accelerating frames of reference are the same. A sort of related topic used in SF plots is flotation tanks used to protect crew from ...

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How does SpaceX plan to deal with boiloff on the trip to Mars?
3 votes

Liquids boil when their vapor pressure exceeds ambient pressure. The structure of Starship tanks limits ambient pressure to 6 bar. Therefore, to prevent boiling you must refrigerate to below -170 °C (...

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How does it feel to breathe 100% oxygen at low pressure?
3 votes

Respiratory gasses interact with the respiratory system through their partial pressures. Room air is 21% O2 @ 760mmHg, or a partial pressure of 160mmHg. So, at first glance, it would seem that ...

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Could astronauts jump from a spaceship onto a spacestation and how would it be like if yes?
2 votes

It is not mandatory that the two vessels have zero relative velocity, but it would make the operation more controlled (and therefore less exciting). Having vessels in close proximity with significant ...

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Methane internal combustion engines for rovers on Mars and Moon. Feasibility?
2 votes

SpaceX has developed a CH4/O2 ICE: The Raptor. We don’t usually think of liquid fueled rockets as ICEs, but they are: compression, ignition, expansion and all that. It is very difficult to run an ICE ...

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Accomodations for blood transfusion
2 votes

Crewed space missions are very unlikely to need transfusions. Most people will never need a transfusion during their lives. And if they do, it will likely be when they are elderly. Most transfusions ...

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