Some questions on the Space Show, Floating to Space

The Space Show callers had a few technical questions which I thought I'd
comment upon briefly. One caller asked about energy source and John's
answer was a solar electric combination- most likely using batteries.

My comment is that it may not be the best idea because batteries are
quite heavy. That adds a weight penalty that you may want to avoid in
attempting to get to space.

The second question was about shock waves as you approach supersonic
speeds at high altitudes. John's answer was to manage that problem
at altitudes. The higher the altitude, the less the problem was. He
said the following altitudes were targeted to attain the velocities listed:

Below 200k ft. subsonic: begin to lose buoyancy, begin aerodynamic lift
240-260k 300 mph up to supersonic
above 240 k supersonic, not clear here; assume below 240k ft is subsonic
300 k supersonic; above 300k is supersonic to hypersonic, I gather
316 k hypersonic At this altitude, you are approaching space itself.


The third question was the most challenging. The questioner, named
Charles, asked how do you impart the necessary energy with batteries.
The most powerful batteries known could not come close to the
energy requirement of getting to space. He observed that the
energy requirement is 33 megajoules per kg mass no matter how you
do it. A battery cannot deliver that kind of power,he says. He
was also doubtful about solar too.

I ran some numbers on that. According to the wikipedia, there
are about 10 kilowatt hours per kilogram according to the number
that Charles gave. A kilowatt hour is over 3 million joules.
Therefore 10 kilowatt hours per kilogram satisfies Charles claim.

Incidentally, this is not the answer that John gave. It is the
one I looked up myself. Not that the source that I've given is
accurate or correct. If what I cite is correct, then the power
requirements seem daunting. But not necessarily impossible.

I don't know the mass of his airship, but it is quite large.
If the weight is 100 times his Ascender airship that he described,
it would only weigh 600 lbs times a hundred, or 60,000 pounds.

That figures to 272,000 kilowatt hours.
Or 2.84 megawatt continuous power over 4 days that he anticipates
that it will take to get to orbital speed.

Charles may be right in that it may take more than batteries
to do the job, but that kinda what I figured in the first place.


Update: Sun. 1/16/11, approx 9:15 am cst

In case the above seems rather unfavorable to this concept, I should note that John
mentioned that he has turned down investment offers in his enterprise.  The reason,
from what I gather, is that he would prefer to keep independent.  Any investors would
want return on their money according to some timetable which may not be feasible.  I
would only add that if a timetable could be plausible to make this concept's feasibility into
a more highly probable favorable outcome, that he may want to reconsider any new
investment offers that may come along.  That's because trying to do this solo may take
longer than he has left in terms of his own lifespan.  He has been at this for over 20 years,
according to the show.  So, he may want to reconsider since he won't live forever.