# Using large helium balloon to assist space craft launch **URL:** \ **Category:** Factual Questions\ **Created:** [September 11, 2012, 1:03am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363 "2012-09-11T01:03:05Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![bldysabba](https://avatars.discourse-cdn.com/v4/letter/b/ecccb3/32.png) [@bldysabba](https://boards.straightdope.com/u/bldysabba)\ **Post date:** [September 11, 2012, 1:03am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/1 "2012-09-11T01:03:05Z")
[This](http://www.huffingtonpost.com/2012/09/10/adam-cudworth-british-tee_n_1871502.html) story got me thinking - Is it viable from a technological and/or economic perspective to use very large helium balloons to get (at least part of the way) out of the earth’s atmosphere? Is it possible for this method to result in any sort of cost saving? ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [September 11, 2012, 1:16am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/2 "2012-09-11T01:16:28Z")
Certainly possible. I’m not sure how much benefit you’ll get from it. On the plus side, you’ll save a little bit of fuel that you would have spent gaining altitude and fighting drag. You can’t get completely out of the atmosphere, and most of the energy cost of getting to orbit lies in gaining speed, not altitude, so you won’t be gaining much, but every little bit counts. Also, your first-stage engines can be optimized for near-vacuum rather than sea level, which helps. On the minus side, you will be much, much more at the mercy of favorable winds. The balloon will take a not completely predictable amount of time to climb to altitude, and will be pushed around by upper-altitude winds as it does so. This makes it much, much harder to exactly match a target orbit, so you probably wouldn’t be able to use this for ISS cargo supply missions. Also, you need to keep the rocket in ready-to-launch condition during the entire balloon climb. Many modern rockets use cryogenics - liquid oxygen and sometimes hydrogen. Rockets don’t have internal refrigeration systems and the fuel tank insulation isn’t quite good enough to keep some heat from leaking in, so there’s constant boil-off. Ground-launched rockets have topoff systems that pump in a trickle of extra fuel to compensate for this until right before launch. The second and higher stages still lose some fuel and oxygen to boiloff during first stage burn, but that’s a much shorter time than it will take a helium balloon to climb to launch height. Still something you can deal with, but it eats into the savings you get from launching at high altitude. ---
**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:** [September 11, 2012, 1:17am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/3 "2012-09-11T01:17:14Z")
Some early rocket experiments used this technique. I recall it was for sounding rockets that didn’t leave the atmosphere though. With the increasing cost of helium and limited supplies it doesn’t sound very practical. But considering it’s an extremely dangerous activity to start with maybe hydrogen could be used somehow. In a different approach, one hypothetical technique would be to have a balloon carry aloft a long strip of solid fuel. A rocket would consume this fuel as it climbed. The rocket wouldn’t need to carry the weight of it’s fuel. But that would only work up to around 100,000 feet or so. I don’t think anybody has an idea of how to do this practically for actual space flight. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [September 11, 2012, 8:10pm UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/4 "2012-09-11T20:10:20Z")
> [@AndrewL](#): > > On the plus side, you’ll save a little bit of fuel that you would have spent gaining altitude and fighting drag. But the large balloon (and the expensive helium it contains) would be destroyed when the rocket is ignited. That would seem to outweigh any cost saving from reduced fuel due to the rocket being farther up from the surface. Also, how large would the balloon have to be to lift an Apollo rocket? Somebody could calculaste that, but I think it would be huge! And is there enough helium left on earth to fill such a big balloon? Helium is a very limited, irreplacable element on earth, and is disappearing all the time. ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [September 11, 2012, 9:23pm UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/5 "2012-09-11T21:23:07Z")
It was done in the early 1950’s-it was called (not strangely) a “rockoon”. AS you said it was a small solid fuel rocket called a “Deacon”, lifted by a helium balloon. It was a VERT small rocket. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [September 11, 2012, 9:36pm UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/6 "2012-09-11T21:36:16Z")
It would provide negligible help if you are trying to get into orbit, which is all about speed, not altitude. It might reduce drag a bit, but you still have to get up to 17,500 mph to achieve orbit. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [September 11, 2012, 9:56pm UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/7 "2012-09-11T21:56:30Z")
The most common reason for delaying a rocket launch is weather. Delays are expensive - [this article](http://www.foxnews.com/story/0,2933,533280,00.html) says it cost $1.2 million to cancel a Shuttle launch after fueling had started. Using a balloon for rocket launch would make the rocket flight _more_ prone to weather delays. It’s probably not an economical option. An air launch (from a winged aircraft), on the other hand, _reduces_ weather delays because an airliner can handle low-altitude weather conditions (turbulence, crosswind, etc) much better than a rocket can. And it provides the same benefit (i.e. reducing air resistance during initial part of the rocket flight). So that’s a much better approach. The [Pegasus](http://en.wikipedia.org/wiki/Pegasus_(rocket)) rocket has been highly successful and reliable. ---
**Author:** ![Rain\_Soaked](https://avatars.discourse-cdn.com/v4/letter/r/e19adc/32.png) [@Rain\_Soaked](https://boards.straightdope.com/u/Rain_Soaked)\ **Post date:** [September 11, 2012, 11:33pm UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/8 "2012-09-11T23:33:30Z")
> [@TriPolar](#): > > Some early rocket experiments used this technique. I recall it was for sounding rockets that didn’t leave the atmosphere though. With the increasing cost of helium and limited supplies it doesn’t sound very practical. But considering it’s an extremely dangerous activity to start with maybe hydrogen could be used somehow. Methinks you have this backwards. I would expect that helium would be safer than hydrogen. ---
**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:** [September 11, 2012, 11:48pm UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/9 "2012-09-11T23:48:49Z")
> [@Rain\_Soaked](#): > > Methinks you have this backwards. I would expect that helium would be safer than hydrogen. I was talking about rocketry being dangerous, not the helium. The giant balloon full of hydrogren isn’t as dangerous as the giant tanks of liguid hydrogen and oxygen a rocket would have. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [September 12, 2012, 12:30am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/10 "2012-09-12T00:30:14Z")
What about a balloon lifting up a rope into space, and then using that as the start of the space elevator, is that possible? Would it go high enough for a vehicle like the Space Shuttle\* to catch it, and then take it out to 35,786 KM? - I know the shuttle has been discontinued. Whatever replaces 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:** [September 12, 2012, 12:42am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/11 "2012-09-12T00:42:58Z")
If it were technologically and economically practical, we’d be doing it already. We’re not, ergo apparently it isn’t. But there _have_ been proposals for heavy-lift balloon rockets, and the estimates are that it would be cost-effective _if_ you’re willing to lay out the initial investment and have enough customers to amortize it (both pretty big ifs, of course). The big advantage is that, if you can get up above 99+% of the atmosphere, you can use low-thrust, high-efficiency engines to gradually get up to orbital speed. In the proposals I’ve seen, you end up bringing the entire vehicle, balloon and all, up to orbit, and come down the same way to re-use it. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [September 12, 2012, 1:17am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/12 "2012-09-12T01:17:05Z")
> [@Chronos](#): > > If it were technologically and economically practical, we’d be doing it already. We’re not, ergo apparently it isn’t. Is that a response to the OP, or my question? ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [September 12, 2012, 1:32am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/13 "2012-09-12T01:32:08Z")
[Here’s an interesting previous thread on this subject.](http://boards.straightdope.com/sdmb/showthread.php?t=210785) ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [September 12, 2012, 1:34am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/14 "2012-09-12T01:34:40Z")
> [@Peter\_Morris](#): > > What about a balloon lifting up a rope into space, and then using that as the start of the space elevator, is that possible? Would it go high enough for a vehicle like the Space Shuttle\* to catch it, and then take it out to 35,786 KM? > > - I know the shuttle has been discontinued. Whatever replaces it. The shuttle won’t be able to catch it, because the shuttle will be moving at about 8 kilometers per second relative to the upper end of the rope. Most of the energy cost of getting to orbit is in reaching velocity, not gaining altitude. This is true even of geostationary orbit. An object in geostationary orbit is always over the same spot on the earth, but it’s still moving at a much higher speed, since it’s much further from the center of the earth. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [September 12, 2012, 3:02am UTC](https://boards.straightdope.com/t/using-large-helium-balloon-to-assist-space-craft-launch/634363/15 "2012-09-12T03:02:07Z")
> [@Peter\_Morris](#): > > What about a balloon lifting up a rope into space, and then using that as the start of the space elevator, is that possible? You can’t build a space elevator from the ground up - there’s nothing holding it up until it’s completed and reaches beyond the geostationary orbit. Construction needs to start at geostationary orbit and built (or extended) downwards.