Idea for space travel

I am sure someone already had this idea but watching Felix Baumgartner’s capsule gave me the following idea: Why don’t we use massive hellium balloons instead of rockets in order to send a airship into space?

Once in the appropiate altitude, the airship will ignite its engines and fly on its own.

I am a lawyer. I am sure that I am missing something. The SDMB is the place to learn precisely what.

The simple answer to all questions of this form is that it would be really, really expensive.

Helium shortage

It wouldn’t help much. The majority of the energy required to get in to orbit is spent accelerating to orbital velocity. If you simply lifted your ship to orbital altitude and let it go, it would just fall back to earth. Furthermore, a helium balloon can’t quite even get all the way out of the atmosphere, so you wouldn’t be saving much fuel anyway.

It has been tried, and still is done from time to time for small suborbital rockets. Look up ‘rockoon’. But for an orbital or interplanetary mission, you wouldn’t be saving enough fuel to make it worth the hassle of operating such a large balloon.

It’s as simple as this: the atmosphere isn’t very thick.

Look at this photo: http://www.brianhayes.com/images/nasa-earth-atmosphere.jpg
Compare the thickness of the atmosphere and the curvature of the Earth. Getting out of the Atmosphere helps, but it doesn’t help very much.

Here’s a recent thread on the topic.

Actually, it’s a very interesting idea. It may be possible to make it all the way to orbit and back with a balloon and some low thrust ion engines.

There’s a company that’s put together a plan for an orbital balloon concept that works like this:

First, a large lighter-than-air floating station called “Dark Sky Station” is built. This is an interface between earth-bound balloons and a much larger orbital balloon.

From the ground, a large balloon called “The Ascender” transports materials and personnel to dark sky station.

At Dark Sky Station, a much larger balloon, equipped with ion engines, departs for orbit. This balloon isn’t shaped like a standard spheroid balloon, but instead looks like a large ‘V’, and is designed to move horizontally at high speed in the thin upper atmosphere and to use aerodynamic lift as well as lift from lighter-than-air gas.

At first, it uses standard atmospheric lift from being lighter than air. But then it starts to accelerate forward very slowly, and supplements its lift by hitting molecules and pushing them down. Eventually, the atmosphere becomes thin enough that it can’t support the ship, but by then it’s going at orbital speeds and can reach obit on ion propulsion alone.

On the way back, it starts its ion engines to slowly (very slowly) de-orbit. As it hits the first molecules of the atmosphere, it slowly descends and reverses the process, and eventually floats back to Dark Sky Station.

You don’t need heat shielding, because the deceleration through the atmosphere happens so slowly that the ship never heats up.

Is this feasible? As a rough proof of concept, maybe. It seems plausible, anyway. The real question is whether it can be made to work as a practical means of getting into space. If it can, it’s a huge breakthrough that could lower the cost of getting mass to orbit by orders of magnitude.

Wouldn’t that need insane amount of balloons. Didn’t Mythbusters need about 45 weather balloons to lift up just one guy in a lawn chair.

It would need a very large volume of balloons. But it’d probably be more practical to get that volume through a small number of very large balloons, rather than a large number of smaller balloons.

Big balloons would be better for having less heavy fabric compared to volume. It still would take about forty times more helium in volume than the human cargo would be. And metal is many times heavier. So wouldn’t a space shuttle need helium balloons that are bigger than New York itself…

You just need one really, really large balloon. The reason the orbital ascender has to take off from a platform floating in the stratosphere is that it’s so large that it would be torn to pieces by weather were it to attempt to descend to the Earth. So it’s assembled high in the stratosphere and remains there for its entire life.

Here’s a video rendering of the concept: Airship to Orbit

Hydrogen would be ideal over helium, but still, you’d need to achieve ~17,000 mph to stay in low earth orbit, or ~25,000 mph to reach earth’s escape velocity if you planed going elsewhere in the solar system.

I think the savings in fuel because of 50 miles or so of less drag/friction, would be a very tiny fraction of the cost to get to those speeds.

The fuel savings isn’t just from 50 miles of less drag. In general, the most energy-efficient forms of propulsion have very low thrust. This is unacceptable for a rocket, which needs thrust at least equal to its weight, and preferably several times greater. For something that doesn’t need to use its thrust to support its weight, though, it could work.

If you somehow lifted the object straight up all the way to the orbit at which geocentric satellites orbit (through some technological means), wouldn’t this not apply because your current position relative to the ground (stationary)** is orbital velocity with reference to a non-rotating Earth, meaning that you can just lift and go?

If you were to accelerate the object only in the vertical direction, it will keep the same linear horizontal speed - i.e. about 1000 mph at the equator - not the same angular speed. It wouldn’t stay synchronized with the earth’s angular (rotational) speed unless you also accelerated it towards the east so it keeps up.

Actually, lifting a conventional rocket above the atmosphere and getting it started with forward velocity saves a significant amount of weight, which is why so many companies have experimented with air launched vehicles.

Due to the exponential weight requirement of rocket fuel, a rocket actually burns a significant amount of fuel just clearing the tower. As I recall, the space shuttle had burned up tens of thousands of kilograms of fuel by the time it had cleared the tower, at which point it was only going something like 70 mph.

Avoiding that first minute or so of launch gets you a huge fuel savings.

Great thread. I love this stuff.

Gerard O’Neill had an idea for elevating a maglev track to the edge of space using balloons; this has been replaced by a magnetically elevated track in a number of recent concepts, but I am still quite partial to the balloon idea.

Understood, but does ballooning above most of the atmosphere come in comparably cheaper than boosters? You still need the energy to get you up to 17,000 mph, and if you use ion drives, there’s a trade off from minutes to several days of orbital insertion (which, granted, isn’t a deal breaker if it offsets the costs and resources significantly.

But if they do use fuel, you’ll need that much bigger a balloon, hydrogen/helium and overcoming your inertia would still expend a ton of fuel, as gravity isn’t much weaker 50 or 100 miles up.

“Significant amount” is debatable. The Pegasus air-launched rocket weighs 18.5 tons and can place 443 kg into LEO; that’s a ratio of 48.2:1. The Minotaur I is a ground-launched rocket made by the same company; it weighs 36.2 tons and can place 580 kg into LEO, so a ratio of 62.2:1. So the air launch at 40,000 ft altitude only reduces the weight of the launcher by 24%.