[ExI] The amazing Star Raker project that never was....

[Keith Henson]

On Wed, Sep 23, 2015 at 5:00 AM,  John Grigg
<possiblepaths2050 at gmail.com> wrote:

> If only this had been achieved by the United States, or as a joint project
> with other nations!  But how much would it have actually cost?  And was the
> technology mature enough back then to actually do it?

No.

Alan Bond, who designed the Skylon engines, was involved in a rather
similar UK project called HOTOL.  It turns out that those designs have
a major problem.  The center of gravity and center of pressure swap
places as the fuel is expended and, as a result, you can expect the
front end to suddenly (and violently) try to become the back end.

You also don't want the engine inlets inside the vehicle shock wave,
which is why the Skylon engines are out on the wingtips in undisturbed
air.

> "Each Star-Raker was projected to carry a payload of 100 tons, and a fleet
> of Star-Rakers would work day-in, day-out to shuttle into orbit the
> materials and tools and astronauts required to assemble these massive
> (solar energy gathering) satellites."

For the Skylons with a 15 ton payload to LEO, it takes 114 flights per
hour to reach a production rate of two TW of new power per year.  For
a 100 ton payload vehicle, it would take around 17/hour.  That's a
small enough number to get by on one takeoff runway.

Big vehicles have an advantage when using hydrogen as fuel.  LH2 is
really low density, about 70 kg/m^3.  As the vehicles get larger, the
frontal area drag goes up slower than the mass of hydrogen they
contain.

Keith

> http://motherboard.vice.com/read/the-747-to-space-that-never-was
>
>
> John