[ExI] Skylon was New article

[Keith Henson]

On Fri, Sep 12, 2014 at 5:00 AM,  Adrian Tymes <atymes at gmail.com> wrote:

>On Tue, Sep 9, 2014 at 3:24 PM, Keith Henson <hkeithhenson at gmail.com> wrote:

>> New article on power satellites, specifically how to get millions of
>> tons of parts to GEO for less than $200/kg.
>>
>> http://theenergycollective.com/keith-henson/485571/power-satellite-progress

> The same assumptions that one solution is the only possible solution.  What
> happens if the Skylon effort fizzles?  What other options are there that
> might provide equivalent capability?  (Start with other spaceplanes with
> similar lift but being developed by different teams.)

Good questions.  It's always a good idea to have more than one way to
do something. Unfortunately, there are no other spaceplane projects
(that I know about) in the works.  There were others some years ago,
but they all ran into intractable engineering problems or funding
issues or both.

At the moment the Skylon effort is concentrated on the SABRE engine
(redundant since SABRE is Synergetic Air-Breathing Rocket Engine).  It
has two things going for it, it's a relatively lightweight turbo
machine, much lighter per unit thrust than hypersonic ram type engines
because the internal pressures over a large volume are much lower.
The other feature is that it recovers much of the 20 kWh/kg that goes
into liquifying hydrogen.

There are two issues with power satellites, first is cost, second is
the high volume.  The minimum sized power satellite project is around
150,000 tons per year to GEO.  Using ion engines powered from the
ground that takes lifting about 180,000 tons to LEO.  Skylon takes
this up in 15 ton units and needs about 12,000 flights a year to do
it.

SpaceX Falcon Heavy (recoverable) might lift 45-50 tons to LEO so it
would take ~3000 flights a year.  At that rate I am confident they
could get the cost low enough. That rate is about 8 flights a day.
Musk is on the record opposing power satellites, but if someone gets a
chance to ask him, it would be interesting to see if he thinks it is
possible to reach that launch rate.  It would be a heck of a tourist
attraction if they could.

Depending on the specific power in kg/kW, the minimum rate generates
25-30 GW of new power plants per year. The market is *much* larger,
~100 times that large.  10-15 runways and a fleet of ~6500 Skylons
could do that.  I have a hard time imagining 800 FH launches a day and
don't know how large a fleet it would take.

Keith

PS http://withouthotair.blogspot.co.uk/2014/09/solar-power-from-space.html