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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 ± ...
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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 ...
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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 ...
64 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 ...
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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 ...
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58 votes
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How does the Falcon 9 first stage avoid burning up on re-entry?

The heat of re-entry is highly dependent on speed. The second stage of the rocket is responsible for providing most of the speed needed for orbit, after the first stage lifts it out of dense ...
53 votes
Accepted

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 ...
49 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 ...
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48 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 ...
46 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 ...
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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 ...
46 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 ...
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46 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 ...
44 votes
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Why are spaceship capsules frustum shaped?

The capsules designed to reenter the atmosphere have to slow down from about 8 km/s to zero by the time they get to the ground. They actually don't use the part that looks like a cone to do that. They ...
44 votes
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If I drop a feather from orbit, would it burn up or "hit" the ground?

Throwing it down at 5 m/s will do basically nothing. That will simply cause it to advance in its orbit a bit. To deorbit, you need to throw it backwards, not down. However in this case, since the ...
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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 ...
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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 ...
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")...
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 ...
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 ...
36 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 ...
35 votes
Accepted

Why do spacecraft enter the atmosphere violently instead of a smooth spiral?

Spiraling down in the sense you mean is not possible, the reason is that when a spaceship is orbiting Earth, it is travelling extremely fast relative to the surface, it is not that space is so high up,...
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35 votes

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

Page 331 in the Shuttle Crew Operations Manual, an official NASA astronaut training document, confirms that The deorbit burn usually decreases the vehicle's orbital velocity anywhere from 200 to ...
35 votes

How does the Falcon 9 first stage avoid burning up on re-entry?

Here's an image of the bottom of the stage before launch. As you can see, the entire bottom is covered in white panels. I suspect those panels are a heat shield. This SpaceX press release on the ...
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34 votes
Accepted

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 ...
33 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 ...
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32 votes
Accepted

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

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 ...
32 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 ...
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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 ...
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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 ...
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