# Could an astronaut fart himself back to the space capsule? **URL:** \ **Category:** Factual Questions\ **Created:** [January 27, 2009, 1:58pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223 "2009-01-27T13:58:03Z")\ **Posts on this page:** 12\ **Page:** 3
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [January 31, 2009, 5:55am UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/41 "2009-01-31T05:55:06Z")
> [@flex727](#): > > Correct. It’s all about momentum transfer. Momentum is mass times velocity, so they’re equally important. I don’t think they are equaly important. If you throw away a massive object, then your new momentum loses the mass you threw. Suppose you had a 60 kg anvil and you threw that. You would get a ton of velocity out of that. On the other hand, if you held on to the 60 kg anvil and ejected high velocity gas (ie killer IBS) with equal momentum, you wouldn’t gain as much velocity because you would still be 60 kg more massive. ---
**Author:** ![Dervorin](https://avatars.discourse-cdn.com/v4/letter/d/eb8c5e/32.png) [@Dervorin](https://boards.straightdope.com/u/Dervorin)\ **Post date:** [January 31, 2009, 8:28am UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/42 "2009-01-31T08:28:02Z")
> [@WarmNPrickly](#): > > I don’t think they are equaly important. If you throw away a massive object, then your new momentum loses the mass you threw. Suppose you had a 60 kg anvil and you threw that. You would get a ton of velocity out of that. On the other hand, if you held on to the 60 kg anvil and ejected high velocity gas (ie killer IBS) with equal momentum, you wouldn’t gain as much velocity because you would still be 60 kg more massive. Ah, but how fast can you throw a 60kg mass? I suspect that this is where the various forces involved need to be examined more carefully. I don’t have a definitive answer, but I think the overall momentum transfer from a long sustained burst of IBS might be more than that from a single throw of a large object. ---
**Author:** ![daval12](https://avatars.discourse-cdn.com/v4/letter/d/838e76/32.png) [@daval12](https://boards.straightdope.com/u/daval12)\ **Post date:** [February 1, 2009, 1:50pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/43 "2009-02-01T13:50:02Z")
Wouldn’t “throwing” any size mass result in spin due to the torque and rotation involved in this? If you had a 60 kg object, wouldn’t you be better off putting under foot and “jumping” off of it? ---
**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:** [February 1, 2009, 7:01pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/44 "2009-02-01T19:01:47Z")
> [@](#): > > Wouldn’t “throwing” any size mass result in spin due to the torque and rotation involved in this? If you had a 60 kg object, wouldn’t you be better off putting under foot and “jumping” off of it? Well, spin wouldn’t be so terrible, since you’d still get thrust out of it, and no matter how you’re spinning, you’ll probably be able to flail around to grab your spaceship or whatever. But a “jumping” motion probably would be better, if only because most peoples’ legs are stronger than their arms. ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [February 6, 2009, 2:46pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/45 "2009-02-06T14:46:38Z")
Not a physics-ian and about to prove it. . . This makes no sense to me at all. If you’re in the vacuum of space, a fart would simply be sucked into the void. I mean, on Earth it would provide a small bit of force because it would push against the air which was previously occupying that space; that’s why it has to be under a certain amount of pressure to escape at all. But in space, there’s nothing to create friction, nothing to push against, so how do they create any propulsion at all? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 6, 2009, 2:53pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/46 "2009-02-06T14:53:19Z")
> [@TruCelt](#): > > But in space, there’s nothing to create friction, nothing to push against, so how do they create any propulsion at all? Propulsion such as jets, rockets and farts don’t push against anything to provide thrust. Thrust comes from reaction, as in Newton’s “equal and opposite.” The gas inside the engine, be it rocket or rectum, pushes outwards in all directions. With an opening, the gas rushes through without pushing against anything; this is balanced by the force of the gas pushing on the opposite side. Thus, the engine is propelled in the opposite direction to the flow of gas. ---
**Author:** ![Dervorin](https://avatars.discourse-cdn.com/v4/letter/d/eb8c5e/32.png) [@Dervorin](https://boards.straightdope.com/u/Dervorin)\ **Post date:** [February 6, 2009, 2:53pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/47 "2009-02-06T14:53:20Z")
> [@TruCelt](#): > > Not a physics-ian and about to prove it. . . > > This makes no sense to me at all. If you’re in the vacuum of space, a fart would simply be sucked into the void. I mean, on Earth it would provide a small bit of force because it would push against the air which was previously occupying that space; that’s why it has to be under a certain amount of pressure to escape at all. > > But in space, there’s nothing to create friction, nothing to push against, so how do they create any propulsion at all? Quite simply, [Newton’s Third Law](http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion) - famously summarised as “every action has an equal and opposite reaction”. It’s true that you need a force on an object to produce motion, but that force doesn’t have to be friction. Think of a pair of ice-skaters standing in the middle of a lake - there’s very little friction there, but they can move in opposite directions by pushing against off each other. In the same way, you and the fart push against each other, but since you are so much more massive than the fart, your velocity is very, very small, while the fart whizzes off in the opposite direction. You are, in effect, a very small rocket, and larger rockets work on the same principle of expelling mass behind them to gain forward momentum. ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [February 6, 2009, 2:58pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/48 "2009-02-06T14:58:39Z")
> [@Jolly\_Roger](#): > > In space no one can smell you fart. Thanks! I now have coffee all over my desk! That’s the greatest Alien reference I’ve ever heard! You’ve made my morning!😃 ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [February 6, 2009, 9:06pm UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/49 "2009-02-06T21:06:23Z")
> [@TruCelt](#): > > This makes no sense to me at all. If you’re in the vacuum of space, a fart would simply be sucked into the void. I mean, on Earth it would provide a small bit of force because it would push against the air which was previously occupying that space; that’s why it has to be under a certain amount of pressure to escape at all. See everyone, I \*told \*you rockets didn’t work and they faked the moon landing. ---
**Author:** ![robardin](https://avatars.discourse-cdn.com/v4/letter/r/43a26b/32.png) [@robardin](https://boards.straightdope.com/u/robardin)\ **Post date:** [February 7, 2009, 12:22am UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/50 "2009-02-07T00:22:51Z")
> [@Chronos](#): > > One of the physics professors here has a friendly rivalry with one of the engineering profs… Not a page goes by in the physics prof’s problem book that the engineer doesn’t fall to his death or \*\*get eaten by a grizzly \*\*or crash an experimental rocket sled or suffer some other such gory fate, and I understand that the engineer uses the physicist in a similar way in his classes. Everything made sense except the grizzly. What kind of physics problem involves a bear? 😕 😕 ---
**Author:** ![bonitahi](https://avatars.discourse-cdn.com/v4/letter/b/7993a0/32.png) [@bonitahi](https://boards.straightdope.com/u/bonitahi)\ **Post date:** [February 7, 2009, 12:53am UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/51 "2009-02-07T00:53:33Z")
:eek: bump ---
**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:** [February 7, 2009, 1:48am UTC](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223/52 "2009-02-07T01:48:13Z")
> [@](#): > > Everything made sense except the grizzly. > > What kind of physics problem involves a bear? The grizzly starts off such-and-such a distance away from Prof. Eiger, and has a given maximum speed and acceleration. Prof. Eiger also has a given maximum speed and acceleration, and is a given distance from his house. Does he make it into his house before the bear catches up to him? [Previous page](https://boards.straightdope.com/t/could-an-astronaut-fart-himself-back-to-the-space-capsule/483223.md?page=2)