# Apollo 15: What if two parachutes had failed, and how fast? **URL:** \ **Category:** Factual Questions\ **Created:** [July 27, 2023, 8:08pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700 "2023-07-27T20:08:50Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [July 28, 2023, 3:37pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/21 "2023-07-28T15:37:26Z")
> [@Dorjan](#): > > Two publications that may be of interest: > > [https://ntrs.nasa.gov/citations/19740003586](https://ntrs.nasa.gov/citations/19740003586) Thanks for the links. The report on the Earth landing system discusses in detail how the parachute systems work, and also includes a very detailed report on what happened with the parachutes on Apollo 15. Unfortunately, no discussion of splash-down mechanics. The report on land impact tests discusses how things might be expected to play out if there were ever a pad abort or very low altitude abort, which would result in the command module separating from the launch vehicle, deploying its chutes, and touching down on dry land instead of water. They tested a range of potential touchdown attitudes and horizontal velocities along with the expected vertical velocity, and concluded that while the command module might suffer rather severe damage in some scenarios, the crew would only ever be expected to suffer minor injuries. Again, no discussion of splashdown mechanics, since that wasn’t the focus of these tests. ---
**Author:** ![Dorjan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dorjan/32/12440_2.png) [@Dorjan](https://boards.straightdope.com/u/Dorjan)\ **Post date:** [July 28, 2023, 4:15pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/22 "2023-07-28T16:15:32Z")
No discussion of splashdown mechanics, but they do offer some insights. I have another report that i didn’t link because it’s really just development of an analytical model for determining spacecraft impact velocity and orientation relative to an impact surface, and a statistical techniques for determining the probability of survival of different impact conditions, but it’s interesting to note in that publication that even a two-chute deployment was considered a “1-percent” probability. a single-chute deployment isn’t even considered. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [July 28, 2023, 4:21pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/23 "2023-07-28T16:21:10Z")
> [@Dorjan](#): > > a single-chute deployment isn’t even considered. Like, a few decades later, how an SRB burn through wasn’t considered, or a significant re-entry shielding system failure. ---
**Author:** ![Common\_Tater](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/common_tater/32/13846_2.png) [@Common\_Tater](https://boards.straightdope.com/u/Common_Tater)\ **Post date:** [July 28, 2023, 9:48pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/24 "2023-07-28T21:48:43Z")
On 15 the postflight analysis folks concluded the impact was about 15g based on how far the couch impact attenuators stroked. So sayeth [Collectspace.com](http://Collectspace.com) anyway, they have lots of discussion on just this sort of thing. ---
**Author:** ![cincinnatus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cincinnatus/32/7990_2.png) [@cincinnatus](https://boards.straightdope.com/u/cincinnatus)\ **Post date:** [July 29, 2023, 3:02am UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/25 "2023-07-29T03:02:33Z")
> [@Santos\_L\_Halper](#): > > Their capsules fire a thruster right before touchdown to decrease the impact speed. Thanks, Santos. I had never thought of that before. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [July 29, 2023, 3:20pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/26 "2023-07-29T15:20:19Z")
> [@Santos\_L\_Halper](#): > > Their capsules fire a thruster right before touchdown to decrease the impact speed. Assuming everything works as designed. Soyuz 1 had a lot of problems in its mission, so much so that they decided to abort the mission early. The drogue chute was deployed during re-entry, but the main chute did not open. The backup chute was deployed, but the drogue chute hadn’t detached like it was supposed to, and the backup chute tangled in the drogue chute. The end result was that the capsule slammed into the ground at roughly 90 mph. The sole cosmonaut on board, Vladimir Komarov, was killed on impact. The touchdown thruster did not ignite until a rescue helicopter approached the remains of the capsule. Needless to say, the rescue crew was a bit disturbed by the thruster firing on the ground, and delayed their approach to the remains of the capsule. Fire extinguishers were insufficient, and they had to resort to shoveling dirt onto the wreckage to get the fire out. Soyuz 2 and 3 were delayed by the accident, and were further delayed when an un-crewed N-1 rocket decided to undergo rapid spontaneous disassembly on the launch pad. This forced the Soviets to abandon their plan of landing a cosmonaut on the moon. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 29, 2023, 3:36pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/27 "2023-07-29T15:36:17Z")
Gargarin ejected from his craft in man’s first spaceflight before landing because the Soviets hadn’t worked out safe landing method yet. The retro rocket method, using rockets mounted at the top of the descending module worked out fairly well for rudimentary hard landings. ---
**Author:** ![Moriarty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/moriarty/32/49_2.png) [@Moriarty](https://boards.straightdope.com/u/Moriarty)\ **Post date:** [July 29, 2023, 8:21pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/28 "2023-07-29T20:21:22Z")
> [@Earl\_Snake-Hips\_Tucker](#): > > I’ll assume that if no chutes had deployed, that very likely would not have been survivable There is evidence that the Astronauts on the Challenger space shuttle survived the initial explosion, but died when their capsule hit the ocean about 2 minutes later. Without anything to slow them down, they would have been pulverized upon impact with the water. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 1, 2023, 4:10pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/29 "2023-08-01T16:10:34Z")
It’s possible for any given component of a spacecraft to fail. You try to decrease that failure rate as much as you can, but it’ll never be zero. If the probability and consequences of a failure are both high enough, you can mitigate it through redundancy. But if it’s possible for one component to fail, it’s possible for two of them, or three, or any number. At some point, you have to just say “well, if that happens, they all die”. Because you can’t eliminate the risk entirely. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 1, 2023, 5:25pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/30 "2023-08-01T17:25:24Z")
> [@Chronos](#): > > At some point, you have to just say “well, if that happens, they all die”. Because you can’t eliminate the risk entirely. Makes me think of the **[Gimli Glider](https://en.wikipedia.org/wiki/Gimli_Glider)**: > Flying with all engines out was never expected to occur, so it had never been covered in training. Which is weird, because all engines out has happened several other times: **[British Airways 009](https://en.wikipedia.org/wiki/British_Airways_Flight_009)** **[Air Transat 236](https://en.wikipedia.org/wiki/Air_Transat_Flight_236)** **[US Airways 1549](https://en.wikipedia.org/wiki/US_Airways_Flight_1549)** **[TACA 110](https://en.wikipedia.org/wiki/TACA_Flight_110)** > [@Moriarty](#): > > > [@Earl\_Snake-Hips\_Tucker](#): > > > > I’ll assume that if no chutes had deployed, that very likely would not have been survivable > > There is evidence that the Astronauts on the Challenger space shuttle survived the initial explosion, but died when their capsule hit the ocean about 2 minutes later. Without anything to slow them down, they would have been pulverized upon impact with the water. Going back to the simple difference in the density of air and water (a factor of 800): If the challenger astronauts were falling at terminal velocity, then when they hit the water, they’d experience an impact deceleration of about 800 g. The same would be true for an Apollo command module descending without parachutes. In either case, the impact would pretty much pancake them. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 1, 2023, 7:37pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/31 "2023-08-01T19:37:18Z")
FAA has a standard of 10E-10 for unmitigatable risks. Nobody survives a wing falling off. Having redundant load paths within the wing / fuselage join is doable and required. But carrying a spare wing isn’t. Redundancy only goes so far. After that, sux to be you. Even in very safe commercial aviation. For space exploration, “sux to be you” is set a LOT closer to “normal ops”. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 1, 2023, 7:43pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/32 "2023-08-01T19:43:40Z")
> [@LSLGuy](#): > > FAA has a standard of 10E-10 for unmitigatable risks. Is that a weird way of writing 1E-9, or a typo? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 1, 2023, 7:45pm UTC](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700/33 "2023-08-01T19:45:49Z")
It’s kinda both. D’oh!! :smack: What I meant was 1E-10. [Previous page](https://boards.straightdope.com/t/apollo-15-what-if-two-parachutes-had-failed-and-how-fast/987700.md?page=1)