Re: [gurps] [VEHICLE] of the week 674 – Improved Spaceplane

[Onno Meyer]

> On Wed, 2007-09-26 at 12:48 -0600, Wyrm wrote:
> > Onno Meyer wrote:
> [snip]
> > Reentry takes the 
> > > spaceplane into the upper atmosphere, where drag brings it down for a 
> > > dead stick landing.
> > >   The turbofans burn 1,200 gallons of jet fuel per hour and the
> rockets 
> > > burn 1,375 gallons of HO per second. A full load of fuel is $23,600.
> > 
> > Why a dead stick? Can't the turbofans be used for landing as well?
> 
> Every gallon of jet fuel you don't burn has to be carried to orbit by
> the rockets and comes directly out of your payload weight.  I wouldn't
> be surprised if the jets are run at full power right up to the last of
> the fuel, before rocket ignition.
> 
> Just like commercial airlines don't load all the fuel they can carry.
> Extra weight doesn't pay.
> -- 
> Zan Lynx <zlynx at acm.org>

My delta-V figures assume dry jet fuel tanks, but I added a
guesstimated drag penalty to the required delta-V, so there
might be payload capacity for a few extra gallons - or a 
few more m/s in orbit.