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Here is a brief dramatic of the Space Shuttle launch and reentry:

Launch :

  • You get on this plane like thing that is strapped to an orange fuel tank that looks more like a huge bomb.
  • The fuel tank is strapped to 2 missile looking SRBs that actually have explosives charge in them.
  • Takeoff (YAY), but then, your stuck to this constellation of things for 2 minutes until the 2 SRBs gets jettisonned and you know what, there is no abort / launch escape system like Apollo or Soyuz where you press a button then you go flying in the air then fall back down safely.
  • Once the 2 SRBs are gone, you're flying plane with no interior fuel tank is flying with this orange thing until you wanna get rid of it.
  • Congrats, you are now in orbit.

Landing:

  • You're travelling at a speed of... let's just say way too fast.
  • You only have 2 little propusion things that can slow you down because, duh, you threw out the only fuel tank for the main engines like long ago during your way to orbit.
  • Once you get into the atmosphere, you turn around and use the air to slow you down. BUT WAIT, that air is also trying to burn you toast. So NASA helped you by putting on a heat shield.
  • Now that you can get back without being all burned and crunchy, you have wings.
  • Wings provide lift, you have speed, BUT YOU DON'T WANT TO GO BACK INTO SPACE. So you have to do some weird maneover to go down slowly.
  • Now you see KSC runway 33, great, but guess what, you are a flying brick. You know how NASA trains their pilots, by putting them in a small plane, going up high, putting the engines on reverse and opening the gears to augment drag.
  • Now remember, you have no fuel and only one shot to land. Your descent angle is way worse then a 747.
  • You landed.
  • Congrats, you're on earth.

So which one is actually harder??

called2voyage
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Dat Ha
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    They're both hard. They're both engineering problems that can be (and have been) solved. "Hardness," however isn't really something that has a meaningful order to it. For example, which is harder -- olympic tier gymnastics or olympic tier weightlifting? Fighting a horse-sized duck or a hundred duck-sized horses? – Tristan Dec 22 '16 at 17:22
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    The shuttle is a shitty example. It had the worst safety fetures from all manned spacecraft. Looking at Soyuz or Apollo (or Gemini, or Mercury) will probably yield better results. That being said, spaceflight is risky and i'm not sure you can say he one is inherent riskier then the other. – Polygnome Dec 22 '16 at 21:18
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    Two orbiters (and crews) were lost; both due to incidents during launch. Bayesian reasoning suggest that whatever prior you started with you should be leaning toward ascent by now. – dmckee --- ex-moderator kitten Dec 23 '16 at 01:40
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    Sadly, don't you mean "was", not "is"? – Todd Wilcox Dec 23 '16 at 05:04
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    Very related: How could a 90 m/s delta-v be enough to commit the space shuttle to landing? – user Dec 23 '16 at 10:14
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    You don't need the main engines for de-orbit because you are much lighter, because you aren't lugging around the external tank and SRBs anymore. The tyranny of the rocket equation: Most of the thrust generated is necessary just to lift the amount of fuel you need later on in the ascent. You only need a little fuel for the final orbit / de-orbit delta-V, but to get that little fuel up with you, you need more fuel, and to get that more fuel up, you need lots of fuel... – DevSolar Dec 23 '16 at 10:22
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    Define "harder". Do you mean riskier? More technically challenging? More difficult to perform manually? Took most development time and expense? – Innovine Dec 24 '16 at 09:11
  • This is still opinion based, you need to pick a measurable metric to define 'harder'. Like which on requires more fuel, or is more likely to kill the crew, or consumes more time. – OrangePeel52 Jan 03 '17 at 13:54
  • @DatHa If you liked Organic Marble's answer, which your checkmark seems to indicate, you should revise your question to specifically point out that you are looking for the risk factor. – called2voyage Jan 03 '17 at 14:24
  • Getting out requires 100m/s delta-v. Getting in requires 9,400m/s. – Mazura Apr 24 '19 at 10:26

2 Answers2

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Although it seems opinion-based, this is actually answerable if you interpret "harder" to mean "riskier".

After the Columbia accident a Probablistic Risk Assessment was done of shuttle missions. The results show that ascent was riskier.*

(LOCV means Loss Of Crew and Vehicle.)

enter image description here

*The two columns refer to when the LOCV-causing incident actually occurs (on the left) and when it affects the vehicle (on the right). For example, the STS-107 incident occurred during ascent, but did not affect the vehicle until entry. You could sum this up by saying "There is a higher chance that a problem will occur during ascent that will destroy the vehicle. However, it may not show up until entry."

Organic Marble
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    Note that the OP asks about which is harder, not which is riskier. Playing russian roulette is risky, but not hard (in engineering terms). Building a computer CPU is hard, but not exactly risky. If we want to interpret X as Y then communication is useless. Downvoted due to being largely irrelevant. – Innovine Dec 24 '16 at 08:58
  • More accidents have killed the crew on reentry than launch. – Innovine Dec 24 '16 at 09:12
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Humans were able to place objects into space long before they were able to recover them. During ICBM development the launcher technology was widely understood at the time, whereas blunt, ablative heat shields were a highly classified and protected military secret.

More crews have been killed on reentry than any other mission phase.

Innovine
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  • 8 were killed during re-entry, 7 during ascent and 3 in space. While technically most people have ben killed during re-entry, we are talking about a single person more here. thats hardly any statistic to go by. – Polygnome Dec 24 '16 at 13:24
  • Downvoted because the question asks specifically about shuttle, which you do not address. – Organic Marble Dec 24 '16 at 13:55
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    @polygnome the three in space were well into their reentry procedures, and died a few mins prior to landing. Yes, they died in space, but in space performing reentry related manouvers. – Innovine Dec 24 '16 at 16:10
  • No. the Soyuz pilots death had nothing to do with re-entry procedures. they would have been dead even if they did not de-orbit. – Polygnome Dec 25 '16 at 09:56
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    @polygnome they died 12mins AFTER the retrofire, due to a valve failure when separating the descent module, a once-off operation during the descent phase. That has everything to do with re-entry, stop being a jerk. Next you'll say launch has nothing to do with getting into orbit. This discussion is finished. – Innovine Dec 25 '16 at 19:40
  • @Innovine relax, there is no reason to get into rude sidetracks just because someone else has some details wrong in memory. You know, we are all only human. The pressurization valve was part of the capsule subsystems and after reading the report again you seem to be right, the vavle was jolted open because the ejection bolts fired simultanously, a procedure which is definitely part of the re-entry procedure. So yeah I guess they died before re-entry, but still because of re-entry. Still, since the question has ben changed to only the space shuttle, those are irrelevant for the question now. – Polygnome Dec 26 '16 at 09:24