Ballons as the first stage of a launch? It's being attempted.

[vger]

It'll be interesting to see how this goes. I know this concept has been discussed here on numerous occasions.

http://www.aljazeera.com/news/2015/05/balloon-space-launch-system-open-space-150524084640258.html

[Elthy]

A large part of the energy it takes to put an object into space is needed to lift it through the thick lower atmosphere.

Isnt most of the energy spend on moving sideways?

The engines use the near-vacuum conditions found at high altitudes to create pressure. This then feeds liquid natural gas to the engines.

What? I can imagine the want to use pressure fed engines but the vacuum isnt used for the pressure...

[Bill Phil]

Some of the energy required to get to orbit is spent on Gravity losses...

Most of it is going sideways to gain Orbital Speed.

A very small part is the atmospheric drag...

[Shpaget]

Bloostar uses high-altitude helium balloons.

These can carry a payload of up to 75kg to an altitude of 20 kilometers.

So, "payload" in this context includes the orbital insertion stage, which can't leave much room for the useful cargo, can it?

"75% of the cost of a rocket launch happens in the first 75 seconds as its going up

But by the time those 75 seconds are up, the rocket is already going up and sideways quite rapidly. The balloon will be standing still.

[TARDISES]

Attempting to lift stuff with balloons?

I had no idea that our universe worked on Besiege logic.

This... probably isn't going to work.

[Voidryder]

MOAR BLOOSTARS!!

Actually, there is something more civilized in this technique than the brutish barbarism of today's rockets. I can imagine the Mission Control crew in tennis whites all sitting at their iPads, sipping tea, chatting about the Flight Director's summer lawn party as the payload majestically soars heavenward Yep, civilized space flight.

[Camacha]

This... probably isn't going to work.

That is what most people said about almost every first real attempt

[MoffKalast]

Tried this in KSP once with hooligan labs envelopes. Suffice to say that it didnt go well haha

[vger]

So, "payload" in this context includes the orbital insertion stage, which can't leave much room for the useful cargo, can it?

It's definitely NOT a heavy lifter. They say they want to use it mainly for small satellites, and possibly recreational flights.

[r4pt0r]

Cant a bunch of dv be saved by launching from Eve's highest point instead of sea level? Stands to reason that this too would save a boatload of dv, and the rocketwould be smaller and much cheaper. Sure, you arent launching any manned missions this way, but for small probes I dont see why people think this wont work.

[Shpaget]

Eve != Earth

[r4pt0r]

Right but starting a launch from 20k instead of sealevel should still result in some savings.

[Shpaget]

It's not a question of whether there are some savings, it's about how much and if it's worth the loss in capacity and increased complexity.

[vger]

increased complexity.

What the heck is less complex than a balloon?

[WinkAllKerb'']

i have no windea at all ; )

[Fel]

What? I can imagine the want to use pressure fed engines but the vacuum isnt used for the pressure...

Pressure differential. All it really is saying is that ISP improves in vacuum.

The biggest issue I see is whether it actually ends up being cheaper than conventional rockets.

End Altitude is 20km

Payload Mass is 75kg

Altitude: 15000

Temperature ©: -56.50

Air Density: 0.1948 kg/m³

(Air density at 20000m is less than the density of the balloon, and we haven't even cooled it down yet)

source

PV = nRT

P/RT = n/V

(P/RT)*M = density

2 * 1.00793e-3 * 101.325e3/(8.3145*273.15) = 0.089937 kg/m³

(To... simplify and be lazy, I'll assume the rocket is actually a gas or something like that.)

Payload Mass is defined as 75kg and equilibrium is when the two densities are the same, so:

75kg/n(H2) * 101.325e3/(8.3145*273.15) = 0.1948 kg/m³ - 0.089937 kg/m³

n(H2) = 31.9e6 mol

m(H2) = 64.325 kg

Given the skin does have mass and the balloons are suppose to go higher than 15km, I'll tinker the numbers to make the stage one mass be 75kg.

So 50% of the weight of the ship is dedicated to going ~20km.... not certain if it is much of an improvement overall.

[Shpaget]

What the heck is less complex than a balloon?

It's not just a balloon.

Have you ever seen a video footage from a high altitude balloon? The payload, in this case a camera, is usually spinning and swinging uncontrolled (my guess is due to wind shears). You need to stabilize the launch platform and cancel that motion somehow. Dealing with rotation is relatively easy, but swinging will cause the engineers some headache.

[Camacha]

What the heck is less complex than a balloon?

You mean a moving, unstable and very weight limited platform as opposed to a simple, non-moving (or predictably moving, depending on how you look at it), stable piece of earth?

[WinkAllKerb'']

aside the inclination related orbit to reach micro variation course correction and said big/small platform perma/unperma //risk //(")restock(") + location (+others related side matters) @ lambda(t) ...

Edited May 26, 2015 by WinkAllKerb''

[vger]

You mean a moving, unstable and very weight limited platform as opposed to a simple, non-moving (or predictably moving, depending on how you look at it), stable piece of earth?

You're all thinking in terms of amateur-designed micro launches. There's no way a professional rocket tethered to a balloon is going to get whipped around as much as a tiny GoProCam.

[Shpaget]

Even large structures are susceptible to wind.

Agreed, a professional launch system would have means to cancel that motion, but at what cost and by how much would that system reduce the capacity of the launch vehicle?

[Brethern]

Even large structures are susceptible to wind.

Agreed, a professional launch system would have means to cancel that motion, but at what cost and by how much would that system reduce the capacity of the launch vehicle?

If it's engineered to take the sway into account I don't see a problem.

[Shpaget]

Taipei 101 is engineered to take sway into account, by having a 660 ton lump of steel at the top.

How would you counter the sway?

[Slam_Jones]

Whaat, I thought of this idea maybe a year or two ago, but figured it was undo-able due to weight and other constraints... but the real world is proving to be far more awesome than I thought!

[Fel]

Whaat, I thought of this idea maybe a year or two ago, but figured it was undo-able due to weight and other constraints... but the real world is proving to be far more awesome than I thought!

My Hack'n Science still says the gains wouldn't be significant enough to attempt it.