Easier route to orbit..what's wrong with it?

Hello all,

Total (yet interested) amateur here with a question. What exactly is
wrong with the following method of getting to orbit?

Build a decent plane that will fly fairly high (and will survive a
vacuum, has radiation shielding, etc.)
Stick some small-ish booster rockets on it.
Fly is as high as it will go (until the air gets too thin for lift,
don't need more than mach 1?).
Stick the nose in the air a bit at the ceiling (say 50,000 feet?).
Fire boosters to escape velocity and enjoy space!

As far as can see, the possible major problems with this might be:

A plane that can *fly* and carry the required equipment, shielding,
etc., would need wings too large to survive the stresses of escape
velocity and/or re-entry.

At 50,000 feet (or whatever the sensible ceiling might be) there is
still too far to go to need anything other than HUGE boosters, leading
to same problem as before.

Please enlighten someone not in the field with the reasons why this
can't be done!

Thanks!

Chandy

"Chandy" wrote in message
om...
Hello all,

Total (yet interested) amateur here with a question. What exactly is
wrong with the following method of getting to orbit?

Build a decent plane that will fly fairly high (and will survive a
vacuum, has radiation shielding, etc.)
Stick some small-ish booster rockets on it.
Fly is as high as it will go (until the air gets too thin for lift,
don't need more than mach 1?).
Stick the nose in the air a bit at the ceiling (say 50,000 feet?).
Fire boosters to escape velocity and enjoy space!

As far as can see, the possible major problems with this might be:

A plane that can *fly* and carry the required equipment, shielding,
etc., would need wings too large to survive the stresses of escape
velocity and/or re-entry.

At 50,000 feet (or whatever the sensible ceiling might be) there is
still too far to go to need anything other than HUGE boosters, leading
to same problem as before.

Please enlighten someone not in the field with the reasons why this
can't be done!

Thanks!

Chandy

Good thinking. I think it's the "fire boosters to escape velocity" that is
the hard part; we're talking 17,000 mph, if I remember right. Takes a lot
of fuel.

Google for information on the X-15 rocket plane flown back in the 1960's,
and then on SSTO (single stage to orbit) designs.

Wayne

Chandy wrote:

Hello all,

Total (yet interested) amateur here with a question. What exactly is
wrong with the following method of getting to orbit?

Build a decent plane that will fly fairly high (and will survive a
vacuum, has radiation shielding, etc.)
Stick some small-ish booster rockets on it.
Fly is as high as it will go (until the air gets too thin for lift,
don't need more than mach 1?).
Stick the nose in the air a bit at the ceiling (say 50,000 feet?).
Fire boosters to escape velocity and enjoy space!

As far as can see, the possible major problems with this might be:

A plane that can *fly* and carry the required equipment, shielding,
etc., would need wings too large to survive the stresses of escape
velocity and/or re-entry.

At 50,000 feet (or whatever the sensible ceiling might be) there is
still too far to go to need anything other than HUGE boosters, leading
to same problem as before.

Please enlighten someone not in the field with the reasons why this
can't be done!

It's not so much that it can't be done, but that it doesn't make an enormous
difference. You see, getting into orbit doesn't just require getting high
up, but more importantly requires going fast enough that when you fall down
you miss the earth (that's basically what an orbit is : you fall down, but
you are moving so fast sideways that you actually miss the earth and keep
on falling indefinetly). Since you need to be going at least 28800km/h
(18000mph) to be in orbit, and Mach 1 is only about 1200km/h (750mph), you
aren't even going at 1/20th of the speed you really need. This means that
you actually haven't gained all that much in launching from a plane, and
would still need a considerable rocket to get further.

That doesn't mean it's completely useless, an important part of the fuel at
the start is "wasted" pushing against the thick atmosphere near sea-level,
so going higher will certainly gain some advantage. As a matter of fact,
there are studies considering creating a launch platform suspended from
huge ballons, allowing a launch from the stratosphere.

Bart

In article ,
(Chandy) writes:
...
Total (yet interested) amateur here with a question. What exactly is
wrong with the following method of getting to orbit?

Build a decent plane that will fly fairly high (and will survive a
vacuum, has radiation shielding, etc.)
Stick some small-ish booster rockets on it.
Fly is as high as it will go (until the air gets too thin for lift,
don't need more than mach 1?).
Stick the nose in the air a bit at the ceiling (say 50,000 feet?).
Fire boosters to escape velocity and enjoy space!

The other posters have explained some of the problems
with this approach, but I think that a variant of it could
work.

Have the plane fly as fast as possible, as a plane, i.e.
at considerably more than mach 1.

As the plane gets higher, the air gets thinner; on the other
hand, as the speed increases, the volume of air scooped
into the engines per second increases. The upward trajectory
can be chosen to make these two effects balance out as
far as possible, so that the air intake is nearly constant for
as long as possible.

At the very highest levels of the atmosphere, the air should
be thin enough to avoid the excessive heating which occurs
on re-entry, but still dense enough to supply an engine.

Getting to orbit is expensive using rockets because not
only the payload but also the fuel and oxidant need to be
lifted to great heights. For a plane, the oxidant can be
extracted from the atmosphere but still fuel needs to be
lifted. this problem can be negated by having the power
source firmly located on the ground at all times; e.g. have
a succession of ground-based lasers, spaced along the
planned flight path, beaming power to the plane.
The lower surface of the plane can have an arrangement
of mirrors which concentrates energy from the lasers onto
a reaction chamber in the plane, in which air is heated.

Eventually the plane will have to rise above the atmosphere,
and so it will have to carry some material which can be
used as a reaction mass. This needn't be conventional
rocket fuel and oxidant, it could be just some inert material
such as water, to be transformed into superheated steam.
In that case, the energy would have to continue to come
from a ground-based installation, or maybe from an orbiting
station beaming energy downwards. At this point the plane
could flip upside down to collect energy from the orbiting
station, since aerodynamics would have ceased to be a
significant factor,

Once in orbit, the plane can drop passengers off at the
orbiting station, from where they can transfer to a different
craft, one equipped with large arrays of solar cells to
provide an autonomous power source. This can use a
highly efficient ion motor to take the passengers gradually
to higher and higher orbits, spiralling outwards to the moon
and beyond. Ion motors would probably extend the duration
of a moonflight to an unacceptable degree, but they would
be acceptable for mars flights, which are bound to take a
long time anyway, and also for sending cargo to the moon.

Can anyone see anything wrong with this method?

"C" == Chandy writes:

C What exactly is wrong with the following method of getting to
C orbit?

C Build a decent plane that will fly fairly high (....) Stick some small-ish
C booster rockets on it. Fly is as high as it will go (...). Stick the
C nose in the air a bit at the ceiling (say 50,000 feet?). Fire
C boosters to escape velocity and enjoy space!

Others have already explained some problems. I'll just point out that
the Pegasus launcher uses exactly this principle. A rocket is carried
underneath an airplane's wing and launched from some altitude.

Thus, there's nothing per se wrong with this idea. From a practical
standpoint, though, does this method produce any cost savings? It
costs something like US$10,000 to get a single pound into space.
Unless the proposed method is significantly better, one doesn't gain
much over just launching it from the ground.

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Build a decent plane that will fly fairly high (and will survive a
vacuum, has radiation shielding, etc.)
Stick some small-ish booster rockets on it.
Fly is as high as it will go (until the air gets too thin for lift,
don't need more than mach 1?).
Stick the nose in the air a bit at the ceiling (say 50,000 feet?).
Fire boosters to escape velocity and enjoy space!


It never got off the ground, but in the 80s there was the HOTOL project.
e.g. http://www.geocities.com/CapeCanaver...133/hotol.html


DaveL