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68 votes
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Why don't we know exactly where the Chinese rocket will fall?

If the orbital period is about 90 minutes, that means ±45 minutes error at predicting the moment of landing means randomizing that point all around the globe. At the moment the prediction error is ± ...
SF.'s user avatar
  • 55k
67 votes
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Why not increase contact surface when reentering the atmosphere?

I've done a lot of work on this subject with researchers and engineers at JPL, NASA Langley, and NASA Ames. There are some interesting things that come out of high-fidelity CFM (Computational Fluid ...
Tom Spilker's user avatar
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65 votes

Why didn’t the Spacecraft used for the Apollo 11 mission melt in the Earth’s Atmosphere?

Although the temperature at altitude can be several thousands of degrees, the atmosphere is so thin it does not transfer heat efficiently. Wikipedia explains it very well - The highly diluted gas ...
david_c's user avatar
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65 votes
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Why didn't the Space Shuttle bounce back into space as many times as possible so as to lose a lot of kinetic energy up there?

Skipping reentries aren't unheard of. The Apollo command module performed a single skip when returning from lunar missions. However, there are several reasons why a skipping reentry (especially one ...
Bret Copeland's user avatar
59 votes

Why didn't the Space Shuttle bounce back into space as many times as possible so as to lose a lot of kinetic energy up there?

I think bounce back causes intermittent heating so heat shield tiles get a lot of time of radiate heat out. Your thinking is reasonable as far as it goes... But once you lose too much velocity and ...
uhoh's user avatar
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53 votes
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Is it harder to enter an atmosphere perpendicular or at an angle

“Bouncing off the atmosphere” is a misleading turn of phrase. When returning to the Earth from the Moon, a spacecraft is on an elliptical orbit with the high end somewhere around the moon’s altitude ...
Russell Borogove's user avatar
48 votes
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Why does the SpaceX Falcon 9 rocket do a 180 flip for reentry?

Hobbes has already showed you a diagram of the Falcon 9 launch profile, so I won't repeat that. Note: This answer is not intended to be a complete, scientific treatment of the subject. I knowingly ...
user's user avatar
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47 votes
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What eliminates the velocity when occupants return from ISS to earth, and how much?

Nearly all the velocity is cancelled by atmospheric deceleration of the descent module, before its parachutes are deployed. ISS orbital velocity is around 7700 m/s. An initial retro-burn of the ...
Russell Borogove's user avatar
47 votes
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What impact will the deorbiting of thousands of satellites have on the atmosphere?

Not much research has been done on this question in recent years, but some researchers are worried enough to research into wooden satellites. The question on the environmental impact of deorbiting ...
gerrit's user avatar
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46 votes
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Did the astronauts seated on the space shuttle mid-deck have responsibilities during reentry and landing?

There were no nominal activities for the middeck crew related to flying the vehicle. There were no switches or controls on the middeck accessible to seated crewmembers in the ascent/entry seats. The ...
Organic Marble's user avatar
45 votes

Why does the SpaceX Falcon 9 rocket do a 180 flip for reentry?

Trajectory of the Falcon 9 first stage: Graphic courtesy ZLSA Design (zlsa.github.io) As you can see, before the boostback burn, the stage flips so the engines point in the direction of travel. When ...
Hobbes's user avatar
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45 votes
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Space Shuttle Challenger bringing back Salyut-7

No work was ever done on this in the Shuttle Mission Simulator (SMS), so they were nowhere "close to an actual mission". Not even any testing. Source: I worked to some extent on all missions ...
Organic Marble's user avatar
42 votes

During spacecraft reentry why is heatshield side down the most stable orientation?

We’re accustomed to seeing things travel pointy-end-first (bullets, rockets, arrows, Lamborghinis) so it seems “natural” that Entry Vehicles (EV) should be most stable traveling pointy-end-first as ...
Woody's user avatar
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41 votes
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Gagarin not ejecting from capsule

Initially, the USSR insisted that Gagarin had landed with the spacecraft, because of requirements for FAI certification of spaceflight records: One of the stipulations for spaceflight requires that ...
Russell Borogove's user avatar
39 votes

Apollo Command Module heatshield tube - what was it for?

That is the remnant of one of the attachments between the Command and Service modules (there were three). Here is a cutaway drawing showing the bolt penetrating the heat shield (labeled "tension tie")...
Organic Marble's user avatar
39 votes
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Person falling from space

Your question is under-specified (you don't give the size or posture of your subject), so I'm assuming an average-sized woman falling in the classic face-down skydiver posture. I'm also modeling this ...
Mark's user avatar
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37 votes
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Why did early satellites (e.g. China's Fanhui Shi Weixing) re-enter the atmosphere narrow end (nose)-first?

The advantages of the blunt end first design were known well before either vehicle was launched (1958, a few years earlier for spy satellite designers). However, pointy end first is the simplest ...
Quentin Clarkson's user avatar
37 votes
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Is there such thing as plasma (from reentry) creating lift?

This appears to be a garbled recounting of a problem that occurred during STS-1 entry due to a mis-match between predicted and actual hypersonic pitch trim. Image Source All that happened was that ...
Organic Marble's user avatar
37 votes
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Could one skydive from a space capsule that just had a parachute failure during re-entry?

Would you even be able to open the door? It would depend on the capsule, but since the Apollo 1 fire, one expects crewed American capsules to have explosively-jettisoned hatches that can be ...
Russell Borogove's user avatar
36 votes

Apollo 13's plutonium RTG re-entry into the Tonga Trench: Good shootin' or good luck?

Good shooting. Chuck Deiterich, lead retrofire officer, was responsible for the impact point. From Henry S. F. Cooper's book Moonwreck aka Thirteen: The Flight That Failed: Deiterich, however, ...
Organic Marble's user avatar
34 votes

What impact will the deorbiting of thousands of satellites have on the atmosphere?

The mass of Earth's atmosphere is 5E+18 kg and the Troposphere alone has 3/4's of that. With an average height of 13 km that makes its volume $4 \pi r^2 h$ or about 6.6E+18 m^3. If we break up one ...
uhoh's user avatar
  • 149k
34 votes
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What if a Space Shuttle entered the atmosphere of Venus?

Can't speak to the trajectory aspects but the Orbiter crew compartment was very intolerant of crush pressure loading. The two negative pressure relief valves protect the crew compartment from being ...
Organic Marble's user avatar
33 votes

Why didn’t the Spacecraft used for the Apollo 11 mission melt in the Earth’s Atmosphere?

It's not the temperature that matters, it's the heat transfer. The density of the atmosphere up in the thermosphere is very very thin. There simply isn't nearly enough mass to transfer any ...
gerrit's user avatar
  • 11.7k
32 votes

Why does the heatshield have to be on the outside?

To answer the title: Why does the heatshield have to be on the outside? Because most materials commonly used in spacecraft construction melt at the temperatures encountered during reentry. And most ...
Hobbes's user avatar
  • 128k
30 votes

Why will the BFS reenter broadside rather than engine first?

F9 can enter engine first because it isn't returning from orbital speeds. While fast, it's a fraction of the speeds something returning from orbit (or further) comes in at. So the engines are out as ...
Saiboogu's user avatar
  • 6,417
30 votes

Could sheets of stacked graphene be used as part of a heat shield, since its melting point is 3000k to 5000 K

For a non ablative heat shield you need a material with a very high melting point and a very low thermal conductivity. It should not burn in hot air. Unfortunately graphene seems to have a high ...
Uwe's user avatar
  • 49k
29 votes

Apollo Command Module heatshield tube - what was it for?

Service module attachment point The service module (SM) was attached to the command module (CM) using tension members which pulled the two modules towards each other. The SM used cups that rest on ...
Aaganrmu's user avatar
  • 521
29 votes
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Testing of rocket heat shield on Earth

Ground testing of heatshield components and materials can and has been done in arcjet facilities. (image source) An arcjet typically combines a super- or hyper- sonic wind tunnel with a large ...
Organic Marble's user avatar
29 votes

Has SpaceX chosen to drop the Transpiration cooling of Starship? If so, why?

Despite SpaceX's high-tech reputation, SpaceX aren't where they are today because they made massive technological leaps or pushed the envelope of science--after all, just doing science doesn't earn ...
Dragongeek's user avatar
  • 19.1k
29 votes
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Did any Columbia debris continue orbiting Earth?

No. Even the highest ballistic coefficient debris (engine turbopumps, etc) only made it to Louisiana. Heavier objects with higher ballistic coefficients, a measure of how far objects will travel in ...
Organic Marble's user avatar

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