From: vince@offshore.ai (Vincent Cate)
Newsgroups: sci.space.tech
Subject: Is suborbital RLV rather easy at half orbital speed?
NNTP-Posting-Host: 209.88.68.230
Message-ID: <9186edb5.0301201415.2d5b4b23@posting.google.com>

My belief is that SSTT (Single Stage To Tether) makes the task of
designing and building a really reusable rocket far easier than SSTO
while keeping some of the nice aspects.

First, with air-launch and tether the rocket only needs like half the
delta-V.  This means that instead of needing to be 95% fuel it only
needs to be like 75% fuel.  So instead of 5% of takeoff mass for
rocket engines, structure, tanks, heat shielding, and payload we get
maybe 25% to work with.  This just seems far easier to design and
build.

Second, reentry is much easier.  Since the rocket is not going so
fast, there is much less kinetic energy to get rid of as heat (if half
as fast then 1/4 the energy).  In the design I am thinking of we would
have a very small rocket, maybe 700 lbs empty.  The cubed/squared
issue makes small objects slow down much faster with air-resistance,
so much less heat.  Next, because we are doing an air-launch the
rocket does not need to be so long and skinny to get through the
atmosphere.  So we could make it a bit on the short-fat side so it
slows down faster (same nose angle just keep getting wider longer) and
make the reentry heating even less of a problem.

Third, I think that a build-and-test approach will be much cheaper
with a 700 lb rocket than with the usual large rockets.

So it seems to me that if anyone thought we had a chance of making a
reusable single stage to orbit rocket, that making a small reusable
rocket that can go from an air-launch to near a tether should be
rather easy.  Right?

If this rocket can be really reusable, then I am confident we can get
cheap access to space.  There are other technical problems to solve,
but I am more confident they are solvable.  The airplane is cheap to
operate.  The tether is cheap to operate.  My only question is can we
really make a really reusable rocket.  So, I ask you, is this reusable
rocket rather easy to make?

More on my dream design at http://spacetethers.com/

   -- Vince

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Vincent Cate                           Space Tether Enthusiast 
 vince@offshore.ai                      http://spacetethers.com/
 Anguilla, East Caribbean               http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it.    - German Proverb