Maglev assisted launch SSTO

"Ross C. Bubba Nicholson" wrote:

(Gordon D. Pusch) wrote in message ...
"Roger Stokes" writes:

"Gordon D. Pusch" wrote in message
...
"Roger Stokes" writes:

I have read in this newsgroup that chemical fuel SSTO proposals have
a mass ratio of around 8:1, leaving very little left over for payload.
However if the launch could be assisted by an initial velocity of about
2 km/sec the vehicle mass ratio would drop to about 4:1, permitting a
much bigger payload.

2 kps is Mach 5. Mach 5 is a bit fast inside an atmosphere. Even at the
top of the highest mountain on Earth, the air will still be thick enough
that the vehicle will need a thermal protection system ON THE WAY UP, as
well as on the way down.

If the vehicle is SSTO, it will already posess a thermal protection system
for reentry at mach 25, which should be only lightly loaded at mach 5-10
for a few 10's of seconds on the way up, even at greater air density.
(Although this is just intuition, since I don't know how to calculate it)

There is a =BIG= difference between doing Mach 25 through the near-vacuum
at 250,000 feet versus through a substantial fraction of an atmosphere.
Even Mach 5 is =WAY= to fast at the pressures you find on mountaintops !!!


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Well, troopers, a mag lev launcher might do for returns from
planets/moons without atmospheres, eh? Now all we need it 'da juice.


and more money than has ever been made.

In article ,
Peter Fairbrother wrote:
I can't see Mecapa being a problem. It's about 1800 miles downrange from
Quito. There are no boosters to land on them. It would be a bit like
Europeans complaining about launches from Kennedy.

More precisely, like the citizens of St. John's, Newfoundland, objecting
to high-inclination shuttle launches overflying them (which has happened,
I believe).

Note also that at that distance, quite a small change in ascent trajectory
will take you well to one side of Macapá. Such avoidance maneuvers are
not uncommon; e.g., Sea Launch flew slightly north of due east on its
first few launches, to eliminate any chance of a failure dropping debris
on the Galapagos.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
Ross C. Bubba Nicholson wrote:
Well, troopers, a mag lev launcher might do for returns from
planets/moons without atmospheres, eh?

On such a body, you'd want to use a catapult technology that achieved much
higher velocity, reducing the demands on the rocket end. By rocketry
standards, maglev is a low-speed technology. Hotter catapult systems
achieve levitation almost incidentally.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

"Henry Spencer" wrote:
In article ,
Ross C. Bubba Nicholson wrote:
Well, troopers, a mag lev launcher might do for returns from
planets/moons without atmospheres, eh?

On such a body, you'd want to use a catapult technology that achieved much
higher velocity, reducing the demands on the rocket end. By rocketry
standards, maglev is a low-speed technology. Hotter catapult systems
achieve levitation almost incidentally.

Technically, sure. But otherwise I'm not so sure. A planetary
body without an atmosphere means almost certainly that the
surface gravity is a lot less than Earth's. Plus, no atmosphere
means no drag losses, easier insulation, and better Isp. I would
be shocked if there were a planetary body with no atmosphere for
which an SSTO using roughly our current state of technology
weren't very easy. It'd almost be foolish not to use rocketry
when you can get such huge leverage with it. But perhaps other
concerns (especially, I'm thinking, resource abundance locally)
might elevate an alternative to a higher level of practicality and
cost effectiveness than rocketry.

Christopher M. Jones wrote:
"Henry Spencer" wrote:

In article ,
Ross C. Bubba Nicholson wrote:

Well, troopers, a mag lev launcher might do for returns from
planets/moons without atmospheres, eh?

On such a body, you'd want to use a catapult technology that achieved much
higher velocity, reducing the demands on the rocket end. By rocketry
standards, maglev is a low-speed technology. Hotter catapult systems
achieve levitation almost incidentally.


Technically, sure. But otherwise I'm not so sure. A planetary
body without an atmosphere means almost certainly that the
surface gravity is a lot less than Earth's. Plus, no atmosphere
means no drag losses, easier insulation, and better Isp. I would
be shocked if there were a planetary body with no atmosphere for
which an SSTO using roughly our current state of technology
weren't very easy. It'd almost be foolish not to use rocketry
when you can get such huge leverage with it. But perhaps other
concerns (especially, I'm thinking, resource abundance locally)
might elevate an alternative to a higher level of practicality and
cost effectiveness than rocketry.



Say an asteroid colony is exporting to another asteroid colony
via a Hohmann transfer orbit. There would be two burns: one to enter
the transfer orbit and the other to match velocities with destination.
If the burns are done with fuel mined at the asteroid, they could be
expensive burns. But if the transfer orbit insertion delta v could be
accomplished by other means, much mass and fuel could be saved. I think
you'd still need rockets to match velocities with your destination, but
much less onboard fuel.

Hop
http://clowder.net/hop/index.html