[ExI] Power sats and payload size was Small solar satellites

[Keith Henson]

On Sun, Feb 26, 2012 at 5:00 AM,  Adrian Tymes <atymes at gmail.com> wrote:

> On Sat, Feb 25, 2012 at 10:42 PM, Keith Henson <hkeithhenson at gmail.com> wrote:

snip

>> I don't exactly know what you mean in this context by "cheaper." ?Just
>> about any existing launch rocket is "cheaper" for a one off launch
>> than designing, building and testing a new one.
>
> The research effort this stems out of, is proposing to design, build, and
> test a new launch system anyway.  This inquiry is just gauging how
> useful it would be toward this end.  Answer: you wouldn't be running
> many flights on it - a few at most, more likely just one.

There are scale problems.  The drag on the vehicle goes up by the
frontal area, square of the linear dimensions, the mass of fuel by the
cube of dimensions.  There are also tracking problems because the
target shrinks and the pointing and tracking problems for the laser
get worse.  I think a 30 ton with a 5 ton delivery to GEO will work.
Not sure where it becomes too hard to work.

> Careful, though: 1 launch per month is the fastest turnaround time many
> in the rocket business can imagine.  This says more about how
> ingrained they are in the slow, costly, and rather wasteful launch
> procedures that exist today, than about what's actually possible.  But
> asking them to push beyond that before you're actually launching at
> that rate will get you dismissed out of hand.  You'd have to get to
> 1/month, keep that rate up for a few months, then start broaching the
> topic of daily launches, then multiple-per-day.

While there might very well be a month between the first test launch
and the second, the project makes no sense without a rapid ramp up to
3 per hour.  It just takes that many for it to make economic sense.
And there are people, at Reaction Engines in particular, who already
think in these terms.

If the Chinese do it, they will be solving their energy problems.  If
the US does it, the main reason will be the secondary use of the
propulsion laser--even if it *never* used for that.

Keith