# [ExI] Inflatable tower could climb to the edge of space

hkhenson hkhenson at rogers.com
Fri Jun 12 16:30:17 UTC 2009

```At 05:00 AM 6/12/2009, Jeff Davis wrote:

snip

>The structure will involve truly immense quantities of gas.  Air is
>free, whereas generating hydrogen in the quantities needed would be
>costly.  Exactly how costly needs a calculation.

snip

From water, 48 MWh/t current, perhaps as low as 33 MWh/t for
advanced systems.  Penny a kWh is \$10/MWh, scale from there. A mole
of H2 occupies 22.4 l, a kg is 500 moles or 11.2 cubic meters.

Has anyone actually done an engineering analysis of an inflatable tower?

http://en.wikipedia.org/wiki/Scale_height

Hydrogen is close to 1/15 the molecular mass of air.  Scale height of
air is ~7.6 km.

For a serious structure, drag from wind is going to be immense.  Some
places on the equator have a fairly steady wind out of the east.

If the structure was 50 km high, the saving in delta v would be

50,000 = 1/2 gt^2
100,000/g -t^2
t=101 seconds
V=gt
V = ~1 km/sec.

so if you launched off the top of this thing, you could gain about
ten percent over a ground launch plus about five percent for air drag.

Anyone think this deserves more analysis?

Keith

```