Russell Borogove
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Was the ship decompression scene in the movie Aliens realistic?
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36 votes

I did a quick extrapolation from Organic Marble's data (1.5" diameter hole = lose 1500 lbs of air per hour from 14.7 psi; flowrate proportional to the square root of the pressure differential) and my ...

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Is it possible to create a relativistic space probe going at least 0.1c with present day technology?
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35 votes

No. 10% of the speed of light is about 30,000,000 m/s. Our fastest space probe to date, New Horizons, left Earth at less than 1/1000 of that speed. With a large propellant tank and a high-efficiency ...

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What's the largest single object payload ever lifted into space?
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35 votes

Depending on your definitions, the contenders seem to be the US Space Shuttle, Buran, Apollo 17, or Skylab. Apollo 17 + S-IVB translunar 143 t? STS, maximum payload 115 t Discovery ...

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Did Apollo leave poop on the moon?
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I believe used fecal bags from the LM were normally supposed to be transferred back to the CSM and returned with the crew to Earth for analysis. In the Apollo 15 flight journal, in the annotation ...

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How can a rocket approaching the Karman Line then return to earth faster than 53 m/s terminal velocity?
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35 votes

53 m/s is the approximate terminal velocity of a human skydiver. The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than ...

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How would astronauts brave a 19 hour trip to ISS inside Crew Dragon capsule?
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34 votes

After the initial launch into orbit, the crew will be weightless, which will make things a little more comfortable. The Crew Dragon isn't as cramped as you might think; it has room for 4 crew members ...

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Is Mars more at risk than Earth for asteroid collisions?
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34 votes

There are three factors which contribute to the difference in “apparent crateredness” between Earth and Mars. By far the most significant is ongoing erosion from weather. In Mars’ thin atmosphere, a ...

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Why is there a hole in solid rocket engines?
34 votes

It depends on the particular engine. Thrust from a solid rocket is approximately proportional to the burning surface area of the fuel (also called the grain). A long solid rocket motor with a ...

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Difference between BlueOrigin and SpaceX rocket landings?
34 votes

Blue Origin's flight was straight-up, straight-down, with a fairly small rocket that can't carry much useful payload. It's a great demonstration of technology, but it's only practical for space ...

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Why was the engine of the launch vehicle recently tested in Iran "not a very good missile engine"?
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33 votes

What actual engine are they talking about Organic Marble has identified it as the S5.2/9D21. in what way is it "not a very good missile engine"? The old Soviet engine on the Scud-B uses a ...

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How did astronauts using rovers tell direction without compasses on the Moon?
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33 votes

The Lunar Roving Vehicle did have a (form of) compass. It was gyroscopic rather than magnetic, thus it needed calibration when first powered up using the sun angle as a reference. It's in the upper ...

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Apollo simulator practical jokes
33 votes

Not exactly a prank, but from an article on Ellison Onizuka: “We were doing simulations of engine-out aborts,” Buchli said. “Most of those wound up in what we called the ‘black zone’ — the area where ...

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What was the result of the propellant predictions in the last chapter of "Ignition!"?
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33 votes

Chemical rockets will never have more than 600 seconds specific impulse. Storing free radicals in propellant to defeat this limit is impractical. Validated. Chemical rockets in use top out at 450-460 ...

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Interstellar Travel Thought Experiment
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32 votes

Does this logic make sense? Has anyone thought of this before? Yes, it's been considered. In the literature it's known as the "incentive trap". There are a couple of academic papers on it, ...

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Why was it necessary to program InSight with an ability to land in dust storms?
32 votes

InSight doesn't enter Martian orbit before EDL; it plows straight into Mars' atmosphere from interplanetary space. Thus, the time of landing is pretty much un-alterable after its final midcourse ...

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Could an Apollo astronaut stand up if they fell on the moon?
32 votes

Despite Charlie Duke's concern about it, given that the PLSS is massive, and would shift an astronaut's center of gravity far back from their natural distribution, it would be surprising if the ...

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Why was InSight planned to launch from Vandenberg?
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32 votes

According to the article "Seven Ways Mars InSight is Different", the driver was launch site availability: InSight will ride on top of a powerful Atlas V 401 rocket, which allows for a planetary ...

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Why is fuel ratio different for upper stage of a rocket?
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31 votes

The J-2 engine used on the second and third stages of the Saturn V has a "PU valve" (propellant utilization) on the oxidizer turbopump. Adjusting the mixture ratio with this valve primarily ...

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What's this creature on the Canadian Space Agency coat of arms, and why is it there?
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31 votes

It's not a unicorn, but a pantheon: The Pantheon is a mythical or imaginary creature used in heraldry, particularly in Britain. They are often depicted as white deer with the tail of a fox and ...

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Why were seven astronauts selected when there were only six crewed Mercury flights?
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31 votes

It wasn’t originally intended for the astronauts to be matched 1-to-1 with the flights; four additional crewed Mercury-Redstone (suborbital) and three more Mercury-Atlas (orbital) flights were planned ...

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How often do other space vehicles visit the international space station?
31 votes

Since the retirement of the US Space Transportation System (aka space shuttle) in 2011, the only crewed transportation to ISS has been in Russian-operated Soyuz spacecraft -- even for American ...

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Are there photos of the Apollo LM showing disturbed lunar soil resulting from descent engine exhaust?
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31 votes

Most of the Apollo photo libraries have a few shots of the surface under the descent engine bell; I think A14 has some interesting ones: The disturbance of the soil is very subtle; compared with the ...

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Why do some rockets not ignite all their engines during liftoff? (GSLV MK3 LV)
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31 votes

Besides limiting aerodynamic stress and drag losses as you and Antzi mention, using the core engine only at high altitude means the engine can be optimized for low-pressure use by putting a larger ...

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How could a 90 m/s delta-v be enough to commit the space shuttle to landing?
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31 votes

If you're just looking for an intuitive handle on it, try this: In circular LEO, your orbital period is about 90 minutes. If you apply a velocity change of 90 m/s, then wait half an orbit -- 45 ...

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Who were the youngest and oldest persons in space?
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30 votes

As of October 13, 2021, the oldest person to fly in space is Canadian actor William Shatner (T.J. Hooker, Boston Legal), aged 90. This was a brief suborbital flight above the Kármán line on Blue ...

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Would an astronaut experience a force during a gravity assist maneuver?
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30 votes

If the only acceleration is due to the large mass's gravity, and the mass is not exceptionally large, or exceptionally close (i.e. close approach to a black hole or a neutron star), the astronaut will ...

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What are the Grid fins on the Soyuz escape system used for?
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30 votes

The grid fins passively stabilize the spacecraft while the LES is firing during an abort. They deploy by pivoting outward but aren't otherwise movable. In an abort situation, the booster may be in the ...

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Why did Apollo 11 land at the sea of tranquility?
30 votes

The set of landing sites considered for all the Apollo missions was driven by a desire to sample a wide variety of lunar geology, but the order for them was chosen to make the first landings easiest ...

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Did any of the Apollo lunar modules land significantly off level?
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All the LMs landed a few degrees off-level. Apollo 11 was closest to level at about 4 degrees. The design limit for LM ascent stage lift-off is variously stated as 12 or 15 degrees. Apollo 15 was ...

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What is and what isn't ullage in rocket science?
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30 votes

But I still don't completely understand what is or isn't ullage in rocket science context. Ullage technically is the space in a tank of liquid which is gas-filled instead of liquid-filled. For a ...

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