Zeppelin Rocket Carrier to reduce orbital cost

[Guest]

Just an idea I was wondering about,

Most of the fuel in rockets is used to escape the low atmosphere,

why not build a huge zeppelin, a bit like aircraft carrier but for rockets, that could go at the upper limit of the stratosphere to launch spaceplanes?

Powered mostly by just heating the air in the balloon. (maybe electric motors would be enough)

Rockets/Spaceplanes could be a lot smaller and cheaper launched directly high up.

Edited March 1, 2015 by RevanCorana

[Yukon0009]

I think this was an actual concept by some space agency in Europe.

[shynung]

Most of the fuel in rockets is used to escape the low atmosphere,

Common misconception. Most of the fuel in rockets is used not to gain altitude, but to gain orbital velocity.

http://what-if.xkcd.com/58/

Launching the rocket from higher locations (top of a mountain, or from some sort of airship) will reduce the needed delta-V, but not dramatically.

[wumpus]

Again, orbital velocity is the key. Even without the atmosphere, a rocket will still burn half of its mass just to get to mach ~3 (assuming typical rocket fuels). And then half again to get to mach ~6.Orbital Sciences Corp launches the Pegasus. This rocket launches from a airplane (and has been launching since the 90s). Typically, the smaller the rocket the higher the gains for avoiding the atmosphere are, but don't expect more air launched vehicles. I suspect that Orbital customers are more interested in that it is easier to launch closer to the equator (and thus avoid inclination changes). Remember K[erbal]SC is on the equator. K[ennedy]SC is not even tropical. Getting an equatorial (or on the solar elliptic) orbit can be expensive.Play the game some more (especially with more realistic aerodynamics) and all will be clear.

[Kryten]

Orbital has only had one customer for Pegasus quite some time-NASA. Their priority is getting small science payloads in odd orbits that can't be covered with secondary payloads, or cheap small launchers from existing launchsites.

[RainDreamer]

Well, you know what? You can test your hypothesis in KSP! Get Procedural Airship and then launch your rocket from an airship!

[Ten Key]

Again, orbital velocity is the key. Even without the atmosphere, a rocket will still burn half of its mass just to get to mach ~3 (assuming typical rocket fuels). And then half again to get to mach ~6.Orbital Sciences Corp launches the Pegasus. This rocket launches from a airplane (and has been launching since the 90s). Typically, the smaller the rocket the higher the gains for avoiding the atmosphere are, but don't expect more air launched vehicles.

Aircraft also provide a small advantage in that they impart some horizontal velocity to the rocket before they release it. It looks like the Pegasus gains about 3% of its orbital velocity from its carrier aircraft.

An airship wouldn't do that.

[Robotengineer]

Well, you know what? You can test your hypothesis in KSP! Get Procedural Airship and then launch your rocket from an airship!

KSP is a terrible analogy for applicable rocketry. Do to the fact that 'The Soup' adds about a kilometer of DV to the total DV to orbit, so launching from an airship at 10km on Kerbin would save you a lot more DV than it would IRL. RSS requires 9.4km/s DV to get to orbit, if orbital velocity is 8km/s, that means you lose about 1.4km/s of DV to ascent and atmosphere. While that is a not insignificant amount of DV, it is not worth the cost building a large airship to launch from, or a launch facility that is at a significantly higher altitude, unless you are planning on using it quite often and building slightly smaller rockets to save cost on production and fuel.

[Laie]

Common misconception. Most of the fuel in rockets is used not to gain altitude, but to gain orbital velocity.

http://what-if.xkcd.com/58/

That is key (and I recommend that What If to everyone who hasn't seen it so far).

Smaller issue, but probably still enough to kill the concept before it reaches the drawing board: How will you get the airship back to the ground after it has deployed it's payload? I can only think of venting gas; helium is incredibly expensive. Lifting 1t to 10km with helium will cost you like 100k USD. Hydrogen would be a lot cheaper, but if you try to use hydrogen everybody will scream Hindenburg and the project is doomed from the start.

[rtxoff]

Combining zeppelins and rockets is a bad idea. Very explosion.

[magnemoe]

Combining zeppelins and rockets is a bad idea. Very explosion.

Would probably not be any more dangerous than a plane, at least you could land again with the rocket if you have to abort, with an plane you would need a way to dump the rocket fuel to land again without loosing the rocket.

Main downside is that the zeppelin would not be able to go neither high nor fast compared with an plane. Its main benefit is VTOL with heavy cargo something who is of limited use during a rocket launch.

[PB666]

Well, you know what? You can test your hypothesis in KSP! Get Procedural Airship and then launch your rocket from an airship!

Nice plug, but I built a jet powered launch pad powered by stock jet engines and a modified 0.5 factor jet fuel tanks to life the Space Eagle landing pad to 34km and launch a 12M fully open space telescope. Note the surface verticle speed of 202 m/s, I've actually got it down to 50 m/s. Post launch velocity is ~10 m/s.

Now that I have scewered the competition, the bigger question is why they don't launch from Kilamonjaro or Cotopaxi, as this would be idea for most interplanetary for 3 reasons. I suspect the reason is cost, its simply cheaper to assemble and launch from canaval than elsewhere, but with a new spaceport being built in boca-chica (been there, its a waste land) that may change the equation. Blimp, not enough altitude launch trajectory off by 90' and still does not give velocity as mentioned by other poster.

[Nibb31]

Now that I have scewered the competition, the bigger question is why they don't launch from Kilamonjaro or Cotopaxi, as this would be idea for most interplanetary for 3 reasons. I suspect the reason is cost, its simply cheaper to assemble and launch from canaval than elsewhere, but with a new spaceport being built in boca-chica (been there, its a waste land) that may change the equation. Blimp, not enough altitude launch trajectory off by 90' and still does not give velocity as mentioned by other poster.

We already had this discussion a few weeks ago:

http://forum.kerbalspaceprogram.com/threads/107595-DeltaV-savings-from-equatorial-Mountain-launch

If a blimp doesn't have enough horizontal velocity, then I think that a mountain has even less. And it is typically much cheaper to launch rockets from a coastal wasteland than to haul them up the side of a mountain.

[K^2]

Launch in KSP from sea level is over 4km/s, of which 2km/s are due to drag and gravity losses. Launching from high altitude in KSP is huge savings.

Launching from an aerostat on Earth would save you at most 1-2km/s out of ~9km/s budget. It's not bad, if you can make the costs of this minimal, but this is nowhere near the margin you'd get in KSP, and I have a feeling that the operating costs won't actually be any lower.

[magnemoe]

Launch in KSP from sea level is over 4km/s, of which 2km/s are due to drag and gravity losses. Launching from high altitude in KSP is huge savings.

Launching from an aerostat on Earth would save you at most 1-2km/s out of ~9km/s budget. It's not bad, if you can make the costs of this minimal, but this is nowhere near the margin you'd get in KSP, and I have a feeling that the operating costs won't actually be any lower.

You earn far more on launching high up in KSP than in real world, orbital speed is just 2.4 km/s and the soup atmosphere make it cost 1000 m/s to get up to 7000.

Eve is an even more extreme example. It's not so much worse than Kerbin once you reach 1 bar pressure.

On earth the drag is less and the orbital speed are higher. On large rockets the drag is pretty insignificant.

[K^2]

Eve escape from 1 bar will still cost you over 4.5km/s in aerodynamic and gravity losses. That's more than twice what it would be from Kerbin's surface. This is due to combination of increased scale height and surface gravity. Of course, that's still a steal compared to 8km/s extra dV you need when lifting from sea level.

Likewise, our own Venus is going to be enormously difficult to lift from, even if we can manage to build hardware that survives presence on the surface. If we are ever to have a sample return mission from Venus, an aerostat or blimp might be the best option of accomplishing this.

[cantab]

Keep in mind that although the ascent through the lower atmosphere is a small portion of the delta-V it's a disproportionately large portion of the fuel. This is magnified by the atmosphere reducing the efficiency of the engine; 1 km/s is even more costly at 280 s Isp than at 340 s. So while the gains from an air launch aren't Earth-shattering they're more than you might expect.

The biggest drawback is that even with the shaved mass requirements from the air launch rockets are still heavy. So it works well for light payloads, such as are launched by Pegasus, but for anything bigger you'd need a truly huge airship.

[Jovus]

Plus, we already have enough trouble with rocket launches from a stable platform where you can build as much supporting equipment as you like and the rocket generally continues to sit exactly the way you propped it up until ignition. I shudder to think what the instability of an airship might do to launch operations.

[magnemoe]

Plus, we already have enough trouble with rocket launches from a stable platform where you can build as much supporting equipment as you like and the rocket generally continues to sit exactly the way you propped it up until ignition. I shudder to think what the instability of an airship might do to launch operations.

It will work like an plane first stage but with some downsides. No heavy lift airships exist, its some plans however they focus on the VTOL features like taking modules of pretty much any shape and a weight up to 100 ton, move to an area who might be remote and place the module accurately. They will not go high or fast high will require an far different system.

I don't see that this has any benefit over stratolauncher who can reach high attitude, close to the speed of sound and is fast enough to go close to equator.

[AngelLestat]

I love airships... And I think the hydrogen rigid airships needs to comeback to solve many of the freight or commercial transport issues in some areas, they can be the most eco friendly and efficient way of transport.

Saying this, I dont think that they can bring significant cost/deltav improve in the rocket business.

[PB666]

I think if one had an unlimited amount of money to spend on infrastructure, find an equitorial highspot close to the equator, dig a shaft down about 10,000 feet, then a horizontal shaft and transport the rocket to the lift, load the peeps, lift and launch.

[Kryten]

You'd either have to have a lift big enough to support all the payload and lv electronics, or do payload processing at the top of a mountain.

[PB666]

You'd either have to have a lift big enough to support all the payload and lv electronics, or do payload processing at the top of a mountain.

Gear driven lift on the slope is one option.

The other option to be real sci-fi is make the platform seal the launch tube and hyperpressurize under the chamber to 10 ATM, use lasers that vibrate at the frequency of O2 and N2 in the upper tube and atmosphere and super heat the air (increasing mach speed and lowering density), trigger the main engine throttle up to concide to with chamber exit and hope the mountain does not blow up like Mt. St. Helens. you probably get 100 dV from that.

[magnemoe]

It would be far more effective to do the launch somewhere you could soft land the first stage and boosters following an ballistic trajectory like Indonesia, you could probably find islands for both.

Russia has an benefit in that they launch over land, problem will be to get large stages back, they probably need to do an new burn to get back.