Just some wild speculation....

06/03/05 00:00:00    

By Michael Mealling

I'm sure someone has already thought of this but here it is anyway….

So lets say we don't find large amounts of hydrogen stored as frozen water at the lunar poles. But there's all that great oxygen there! Its such a shame to let all of it go unused as oxidizer. Yea, we could have fun with the aluminum and other minerals but those would be as solids and those just don't do well in areas where you need small and precise burns for orbital corrections. So that means you still really want hydrogen (and possibly carbon) to either make some nice hydrocarbons for easy tanking and storage or you still want pure hydrogen for those long burns to Mars.

So that means, at least until we can mine comets and such, that we still need to bring some hydrogen up from the surface with us. But why do we have to “bring” that stuff up on big boosters. I mean that stuff floats anyway. Who needs an engine?

So here's the question for all the engineers reading this: given what JP Aerospace is doing with its balloons, why can we fill up some REALLY FREAKING BIG BALLONS with insane gobs of hydrogen and let them float up high were they can be grabbed by a teather in LEO and boosted up higher and then cryogenically stored or converted? How big of a balloon could you make that wouldn't get ripped to shreads by winds?

Just a thought… Comment from Charles Radley:

bq.

The devil is in the details.

Air drag primarily……

The highest a balloon can go is about 60 km, there is still a ton of air

drag at that altitude.

Objects like orbiting balloons decay rapidly, need to be in an orbit at

least 10,000 km altitude to be reasonably stable.

Getting up from floating in the stratosphere at 60 km to a 10,000 km orbit

requires a lot of acceleration and delt-vee, the propellant consumed would

probably exceeed the amount of hydrogen recovered….need to run some

numbers and do some simulations.

Also the air drag during acceleration to orbit will cause the ballon to get

very hot, it will melt unless made of some thick heavy refractory

materials….the weight penalty for that will be a killer, many times more

weight than the weight of the H2 itself.

The structural loads on something as flimsy as a balloon would rip it to

shreds, loads due to two sources, first the acceleration, second the air

drag. Making a balloon strong enough would be a challenge, the added

weight would probably mean the balloon would not get off the ground. Have

to be made of some exotic material, like the stuff proposed for a lunar

tether (cf Jerome Pearson).

That gets expensive.

Also……

Rendevous between an orbiting tether and an object in the atmosphere is

tricky, and confined to the equatorial plane. Changing inclinations is

prohibitive. Getting a balloon to stay in the right place for long enough

will be challenging, winds will tend to blow it every which way.

Interesting concept, but probably not economic due to the practicalities.