From: Michael Lorrey (mlorrey@datamann.com)
Date: Tue Mar 13 2001 - 14:30:56 MST
Doug Jones wrote:
>
> Spike Jones wrote:
> >
> > Michael Lorrey wrote:
> >
> > > c) scramjet/rocket chem or nuke insertion stage into orbit.
> > >
> > > What is the mass fraction a vehicle would need if it was already
> > > travelling 1000 mph at 15,000 on a 30 degree trajectory, from the
> > > equator?
> >
> > Ill look for my spreadsheet I wrote on this about 8 yrs ago.
> > The 1000 mph and 15000 ft help less than I would have
> > expected, so it was disappointing. As I recall, it reduced
> > fuel needs by around 15%. Doug, do you have an active
> > spreadsheet for this? spike
>
> No, but Dan Delong does (Dan is chief engineer at XCOR). Whether we are
> willing to release it into the public domain is another thing- it is a
> valuable company asset. However, I should be able to get a copy of
> Dan's analysis of the benefits of lobbed altitude launch; there are
> about ten points where that choice allows improvements to the vehicle
> design, from larger nozzles on the engines, to lower stresses on the
> wing at full load (it need only be designed for .8 gee at 1.5 safety
> factor, instead of a 2 gee pullup).
>
> The combination of factors makes subsonic lobbed airlaunch *very*
> attractive.
Gee, would it be possible to make a web interface for this on the
company website to draw traffic? Sort of a way of promoting your
expertise, etc...
BTW: I have a DXF of my proposed launch vehicle I can send up too (not
structurally complex as a full engineering drawing should be, of
course.)
While the fuel needs would be reduced by 15% energy wise for a given
launch vehicle, how much weight savings does that 2 gee to .8 gee
reduction allow in the structure? And how much fuel savings is allowed
by this weight savings?
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