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Author Topic: Reentry possible?  (Read 3341 times)

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Offline Struthio

Reentry possible?
« on: October 08, 2018, 10:59:52 PM »
The ISS (International Space Station) takes roughly 90 minutes to orbit the earth. That's a relative speed with respect to the resting earth of roughly 42,000km per 90minutes or 28,000km/h. A spaceship picking up astronots [sic] and bringing them back to earth basically falls down to earth like a meteor and should burn completely while trying to reach earth passing through the atmosphere, given the high initial radial velocity.

To prevent this, apollo command modules had a heat shield made of phenolic epoxy resin (see wiki: Atmospheric entry / Ablative heat shield).

I admit that I don't believe that such a shield makes a big difference, but for the sake of the argument let's assume that it protects the command module and the astronots inside.

Then, we have the Russian Vostok programme (Yuri Gagarin). Well, they just had a tin can. No heat shield made of phenolic epoxy resin or whatever. How could they return to earth without any shield?

1.) Why don't NASA experts reject the Vostok programme as a conspiracy?
2.) How do ICBMs (intercontinental ballistic missiles) return to earth without burning completely in the atmosphere? (they have no heat shield and a high radial velocity before reentry)
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Offline Stanley N

Re: Reentry possible?
« Reply #1 on: October 08, 2018, 11:56:58 PM »
Quote from: Struthio on October 08, 2018, 10:59:52 PM
1.) Why don't NASA experts reject the Vostok programme as a conspiracy?
2.) How do ICBMs (intercontinental ballistic missiles) return to earth without burning completely in the atmosphere? (they have no heat shield and a high radial velocity before reentry)
1) why? Did the Vostok missions not happen?
2) are you sure they have "no" heat management? ICBMs payloads can be designed to handle higher temperatures than people could.
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Offline Struthio

Re: Reentry possible?
« Reply #2 on: October 09, 2018, 01:00:53 AM »
Quote from: Stanley N on October 08, 2018, 11:56:58 PM
1) why? Did the Vostok missions not happen?
2) are you sure they have "no" heat management? ICBMs payloads can be designed to handle higher temperatures than people could.

1.) Well, as I explained in the OP, I assume that NASA experts would think they could not happen.
2.) There is no known heat management, while impact speed is up to 7 km/s.
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Offline Neil Obstat

Re: Reentry possible?
« Reply #3 on: October 09, 2018, 03:12:21 AM »
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The Russian Soyuz system has two compartments: one for the cosmonauts the other for the space junk they're going to let burn up in the re-entry. It's a sort of figure-8 arrangement with the cosmonauts in the bottom part and the junk in the top part, falling downward.
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You can see this figure-8 shaped Soyuz in the unit attached to the ISS. Soyuz is the dark gray thing in the following image:
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The following diagram shows 6 visiting vehicles in Feb 2011; two Soyuz modules (TMA-01M and TMA-20) as well as a Progress M-09M, HTV-2, ATV-2, and STS-133 Discovery (Space Shuttle), all attached to the ISS:

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There is a heat shield on one end of the crew's compartment:
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The internal quarters for the cosmonauts is very cramped, but they say it's "comfortable." The seats are custom-molded to the shape of each man's body, but they don't have much room to move around inside:
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When it's all over, the Soyuz re-entry unit gets quite charred on the outside from the hot air friction of re-entry:
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Offline Neil Obstat

Re: Reentry possible?
« Reply #4 on: October 09, 2018, 03:32:16 AM »
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Woops. Now I see you're asking about the Vostok system, not the Soyuz.
I found this diagram online:
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Just how the heat shield works they don't make very clear, but here are some photos:
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I have no idea how anyone would want to have Yuri Gagarin's job.
The Soyuz system looks bad enough but this looks like a death trap.
With the Space Shuttle there was a bit of breathing room between the tiles and the astronauts.
But here it's like you're a baby chick in an eggshell -- creepy.
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