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 ± ...
- 54.9k
67
votes
Accepted
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 ...
- 18.2k
65
votes
Accepted
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 ...
- 1,954
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 ...
- 943
59
votes
Accepted
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 ...
- 167k
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 ...
- 148k
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 ...
- 167k
49
votes
Accepted
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 ...
- 7,322
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 ...
- 167k
47
votes
Accepted
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 ...
- 11.5k
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 ...
- 178k
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 ...
- 178k
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 ...
- 126k
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 ...
- 18k
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 ...
- 167k
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")...
- 178k
38
votes
Accepted
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 ...
- 14.6k
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 ...
- 2,267
37
votes
Accepted
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 ...
- 167k
36
votes
Accepted
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 ...
- 178k
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, ...
- 178k
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 ...
- 126k
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 ...
- 148k
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
...
- 178k
33
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 ...
- 126k
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 ...
- 11.5k
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 ...
- 6,427
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 ...
- 48.8k
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 ...
- 521
29
votes
Accepted
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 ...
- 178k
Only top scored, non community-wiki answers of a minimum length are eligible