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National Aerospace Plane (X-30) announced 20 years ago



 
 
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  #21  
Old March 15th 06, 08:42 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

In article ,
"H2-PV NOW" wrote:

Wings are cheaper than fuel. Before last year's oil price gouging
carbon-fiber fabric was down to $0.94 square foot for 6kx6k 2,000,000
psi, wholesale in volume lots. The cost of 10,000 square feet of wings
in material costs was less than buying a Piper Cub used. Now Exxon got
their price raise and it costs a NEW Piper Cub.


Comparing an air breathing winged vehicle to a VTVL all rocket vehicle
the VTVL has the following advantages. Low landing speed of about 3
mph, vs 220 mph for a winged lander. The vehicle has about 10% less
hardware (no wings or wheels). Because there are no wings or wheels
they can't fail (Shuttle). Hardware costs are in the neighborhood of
$1000 per kilogram, and propellents $0.50 per kilogram. With these
numbers the break even point for cost is at 250 flights per year for a
vehicle designed for a ten year life, and it will be a long time before
we have shuttles running that schedule. No specialized runways required
to land. In an emergency it can land on any firm level ground (DC-X).
Wings are of use only for the first two minutes of a mission, and the
last one minute. Wheels are used only the last 30 seconds of the
flight.
Many engineers and managers like wings and wheels because they are a
known quantity. They don't like the Buck Rogers stuff, at least until
someone else does it, then it will be all the rage.

--
Mike Swift

Two things only the people anxiously desire, bread and circuses.
Decimus Junius Juvenalls
  #22  
Old March 15th 06, 08:42 PM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

mike Williamson wrote:
Wings do not allow for less energy to be used to orbit a craft- while
they provide lift they do not provide any energy. In fact, since they
also generate drag, a winged vehicle would almost certainly require
more fuel to reach orbit, since the tubular design will have less
drag to overcome.


Careful here. Wings do indeed save energy; this is because wings have a
lift/drag ratio, the drag is approximately equal to the engine thrust,
and so thrust can be reduced- reducing the propellant needed to carry
the vehicle whilst within the atmosphere.

The root cause of the energy saving is that the vehicle uses wing to
throw air downwards relatively slowly; the slow speed represents lower
energy needed to carry the vehicle; the high exhaust speed of rocket
engines uses more energy (since energy goes as a square law on the
exhaust velocity), although it saves propellant mass.

Even with Apollo, studies showed that a lifting approach did indeed
increase payload (although the payload increase was very marginal.)

The big downside of wings is after you leave the atmosphere- wings push
up dry mass, and then it is very easy to lose everything that was
gained during ascent and then some; a good mass ratio is essential
particularly toward the end of the burn.

Mike


  #23  
Old March 25th 06, 10:50 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago


"dan" wrote in message
ups.com...
Various attempts have been made to design hypersonic airbreathing
engines. The X-43 is probably the only one to fly, even briefly. The
problem with scramjets is that they tend to be efficient only in a
narrow range of speeds; great for a cruise missile but not for orbital
launch. The liquid air cycle (i.e. hotol) is less speed sensitive but
there's no easy way to carry enough cooling capacity to actually
liquify all the air you need. Best bet might essentially be a
cooled-inlet turbojet. Wings can be useful for thrust-limited designs,
but a launch vehicle goes through the speed regiemes quickly and above
about 30 KM wings aren't much use. After attacking the SSTO problem
for awhile, at some point a two-stage solution begins to look more
practical.


Why bother with air breathing, winged vehicles at all? Why not consider a
conventional, rocket powered VTVL TSTO? Such a design wouldn't even need an
altitude compensating engine (i.e. aerospike), since the first stage would
be optimized for low altitudes and the second stage for vacuum.

Jeff
--
Remove icky phrase from email address to get a valid address.


  #24  
Old March 25th 06, 10:50 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago


"dan" wrote in message
oups.com...
In other words, the high cost of fuel isn't what makes spaceflight
expensive

when launch costs fare more than the cost of fuel for the launch.

Exactly. Almost all the cost for the Shuttle is the maintenance needed
between flights. Some parts, like the SRBs, are completely
disassembled, stripped to bare metal (even the nuts and bolts),
inspected for cracks, and remanufactured. The Orbiter requires months
of inspections and maintenance. But these aren't the inevitable result
of the vehicle being reusable; they're with us because the Shuttle was
designed before we had any actual flight experience with many of the
critical systems, particularly the TPS and SRBs.


Actually, the problem really was with the SRB's themselves. As with many
orbiter systems, they were chosen because of their low development costs,
not because NASA thought they would have low per flight costs. Also, the
TPS on the orbiter isn't the only labor intensive system. There are also
the SSME's (their high chamber pressure drove them to a design that's
bleeding edge), the APU's (toxic propellants), the RCS/OMS systems (which
use toxic propellants), and etc.

Jeff
--
Remove icky phrase from email address to get a valid address.


  #25  
Old March 25th 06, 10:50 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago


"Mike Swift" wrote in message
...
In article ,
David Given wrote:

[...]
SpaceShipOne only got 1/3rd the way there and that wasn't SSTO, it was
two staged, carried on White Knight.


No. No, it didn't. SS1 reached Mach 3. Orbit is about the equivalent of
Mach
25. That's 1/8 of the way.


Actually it much worse than 1/8 of the way. In terms of energy that
eight to one velocity increase takes 128 times more energy. As you can
see SpaceShipOne was far from getting to orbit.


The intention was never to get it into orbit. The question to ask yourself,
is if NASA were given the task to create a reusable vehicle to carry three
people to 50 miles altitude and back, what would *that* have cost? Ask the
same question only substitute any large aerospace contractor for NASA.

Jeff
--
Remove icky phrase from email address to get a valid address.


  #26  
Old March 25th 06, 10:51 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

dan wrote:
The liquid air cycle (i.e. hotol) is less speed sensitive but
there's no easy way to carry enough cooling capacity to actually
liquify all the air you need. Best bet might essentially be a
cooled-inlet turbojet.


Alternately, there is SABRE.
http://en.wikipedia.org/wiki/SABRE

Which might be that "cooled inlet turbojet" you mentioned.

After attacking the SSTO problem
for awhile, at some point a two-stage solution begins to look more
practical.


Yes, though sometimes the SSTO looks tempting, like when you find a
very lightweight dense fuel design.

Mike Miller

  #27  
Old March 25th 06, 10:52 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

Ian Woollard wrote:

mike Williamson wrote:


The big downside of wings is after you leave the atmosphere- wings push
up dry mass, and then it is very easy to lose everything that was
gained during ascent and then some; a good mass ratio is essential
particularly toward the end of the burn.

Mike


Which is another excellent reason to look at TSTO rather than STSO with
current technology.

--
Malcolm Street
Canberra, Australia
The nation's capital
  #28  
Old March 25th 06, 10:53 AM posted to sci.space.tech
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Default National Aerospace Plane (X-30) announced 20 years ago

*From:* "Ian Woollard"
*Date:* Wed, 15 Mar 2006 19:42:39 -0000

mike Williamson wrote:
Wings do not allow for less energy to be used to orbit a craft-
while
they provide lift they do not provide any energy. In fact, since
they
also generate drag, a winged vehicle would almost certainly require
more fuel to reach orbit, since the tubular design will have less
drag to overcome.


Careful here. Wings do indeed save energy; this is because wings have
a
lift/drag ratio, the drag is approximately equal to the engine thrust,
and so thrust can be reduced- reducing the propellant needed to carry
the vehicle whilst within the atmosphere.

The root cause of the energy saving is that the vehicle uses wing to
throw air downwards relatively slowly; the slow speed represents lower
energy needed to carry the vehicle; the high exhaust speed of rocket
engines uses more energy (since energy goes as a square law on the
exhaust velocity), although it saves propellant mass.

Even with Apollo, studies showed that a lifting approach did indeed
increase payload (although the payload increase was very marginal.)

The big downside of wings is after you leave the atmosphere- wings
push
up dry mass, and then it is very easy to lose everything that was
gained during ascent and then some; a good mass ratio is essential
particularly toward the end of the burn.

Mike


So the obvious approach is a two-stage one - fly the wings and
atmospheric engines away once they no longer serve a good purpose.

Spaceship One on steroids...
  #29  
Old March 26th 06, 05:43 AM posted to sci.space.shuttle,sci.space.history,sci.space.tech,rec.aviation.military
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Default National Aerospace Plane (X-30) announced 20 years ago

In article .com,
"dan" wrote:

Exactly. Almost all the cost for the Shuttle is the maintenance needed
between flights. Some parts, like the SRBs, are completely
disassembled, stripped to bare metal (even the nuts and bolts),
inspected for cracks, and remanufactured.


Could you please give an example of an SRB segment that has been reused,
including the flight on which it was first used, and the flight on which
it was reused.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------
  #30  
Old March 28th 06, 02:00 AM posted to sci.space.tech
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Default National Aerospace Plane (X-30) announced 20 years ago

Derek Clarke wrote:
So the obvious approach is a two-stage one - fly the wings and
atmospheric engines away once they no longer serve a good purpose.


The problem is that the optimum staging speed is about 3km/s. But the
wings are normally only good for maybe mach 3 or so (1km/s); after that
structural heating problems start to really get interesting.

So you're compromising your first stage when you stick wings on in
several different ways.

Spaceship One on steroids...


Yes, but it might be observed that Spaceship One took two stages to do
what one stage can do. Even Rutan admitted that a lot of the tech he
used was because it was stuff that *he* knew how to do, rather than
because it was inherently better (but he did have some good ideas, the
pivoting tail structure seems to be a reasonably good idea.)

 




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