Atmospheric Flight to Orbit

Anybody want to talk about Atmospheric Flight to Orbit and what it takes to
get to Orbit?

Personally, I think Atmospheric Flight is the way to get to Orbit.
--
Craig Fink
Courtesy E-Mail Welcome @

Craig Fink wrote:

Anybody want to talk about Atmospheric Flight to Orbit and what it
takes to
get to Orbit?

Personally, I think Atmospheric Flight is the way to get to Orbit.

Then simulate it for us, with Orbiter.

If you can't simulate it for me, I can't take you seriously.

And furthermore, don't ever ever ever followup to sci.space.tech. The
moderator quit, and the group is, for all practical purposes - dead.

--
Get A Free Orbiter Space Flight Simulator :
http://orbit.medphys.ucl.ac.uk/orbit.html

Craig Fink wrote:
Anybody want to talk about Atmospheric Flight to Orbit and what it takes to
get to Orbit?

Personally, I think Atmospheric Flight is the way to get to Orbit.

The automatic response is that this is a silly idea. After all, orbit
requires that there not be an atmosphere, otherwise the orbit will
decay really quickly. So you have to have *left* the think part of the
atmosphere usable for flight for some time before reaching orbit.

But it is true that plane tickets are way cheaper than rocket
launches.

And the *first* stage of a rocket doesn't go very far.

So why not get rid of the first stage, fly a plane as high and fast as
we can, and then have the rocket start its journey from the moving
plane? That way, we build a much smaller rocket for the same payload,
and the big expensive first stage is replaced by an airplane trip.

The X-15 rocket plane was launched from under the wing of another
airplane. So this isn't a completely new, untried idea.

It seems much more achievable, as a way to radically decrease launch
costs, than a "space elevator", or even such relatively modest
proposals, not requiring advanced materials, as a 25-mile-high
artificial mountain with an evacuated railgun tube going gradually up
its side, or even a railgun held aloft by giant helium balloons.

Perhaps the problem is that the first stage of a rocket makes the
rocket go really fast, and an airplane burning atmospheric oxygen
doesn't go nearly that fact, so you can't really eliminate a whole
stage that way, making the benefits not worth the bother.

John Savard

In article . com,
"Quadibloc" wrote:

So why not get rid of the first stage, fly a plane as high and fast as
we can, and then have the rocket start its journey from the moving
plane? That way, we build a much smaller rocket for the same payload,
and the big expensive first stage is replaced by an airplane trip.

The X-15 rocket plane was launched from under the wing of another
airplane. So this isn't a completely new, untried idea.

You might mention SpaceShip1 as well, though of course that doesn't go
to orbit (but then, neither does the X-15). For an orbital example,
look at Pegasus.

It seems much more achievable, as a way to radically decrease launch
costs, than a "space elevator", or even such relatively modest
proposals, not requiring advanced materials, as a 25-mile-high
artificial mountain with an evacuated railgun tube going gradually up
its side, or even a railgun held aloft by giant helium balloons.

More achievable yes; radically decrease launch costs, no.

Perhaps the problem is that the first stage of a rocket makes the
rocket go really fast, and an airplane burning atmospheric oxygen
doesn't go nearly that fact, so you can't really eliminate a whole
stage that way, making the benefits not worth the bother.

That's pretty much it. You do gain some advantages from launching at
altitude. These advantages are quite large for a small or suborbital
rocket, which otherwise spend a lot of their fuel plowing through the
lower atmosphere. For a larger rocket, they're not so great, since they
spend a very small portion of their fuel in the lower atmosphere, and
most of it getting up to orbital speed (including that in the first
stage). However, you do get some extra benefits in that you can tune
your engines to vacuum conditions -- especially significant if you're
trying to do SSTO. If what you're launching is also a plane, then there
are safety advantages in releasing at altitude too.

I suspect that SpaceShipThree, or whichever version goes all the way to
orbit, will still launch from altitude, from what will have to be a
truly titanic carrier plane. It's a help, but it's not a breakthrough
like what a space elevator or railgun would be.

Best,
- Joe

"Joe Strout" wrote in message
...
I suspect that SpaceShipThree, or whichever version goes all the way to
orbit, will still launch from altitude, from what will have to be a
truly titanic carrier plane. It's a help, but it's not a breakthrough
like what a space elevator or railgun would be.

I believe that similar air launch results in the large scale would be
cheaper by a custom design ship compared to an existing aircraft.
Designing a carrier vehicle for the express purpose of providing
airlaunch could have a very different set of trade offs. You can
trade efficient wings and aero surfaces for robust ones that are
lighter and stronger. Aerodynamic efficiency is much less important
to a few vehicles that fly an hour a day at the most, than it is to
large quantities of aircraft that must compete on multiple flights daily.

I believe the carrier plane should be closer to a fly back booster
than a modified airliner.

Best,
- Joe

In article . com,
Quadibloc wrote:
So why not get rid of the first stage, fly a plane as high and fast as
we can, and then have the rocket start its journey from the moving
plane? That way, we build a much smaller rocket for the same payload,
and the big expensive first stage is replaced by an airplane trip.

The idea is not ridiculous, but whether you can get big cost reductions
that way is unproven, at best. A rocket first stage is not particularly
costly, especially if you can recover and reuse it; it is the upper stage
that's expensive to build and maintain. And big airplanes are expensive,
and *custom-built* big airplanes are very expensive.

My feeling is that it's potentially a sensible idea, if you can fit on an
existing aircraft. Building your own aircraft, it's much more difficult
to see a net gain.

Even with an existing aircraft, it's by no means clear that you save
money. The example of Pegasus and Taurus is not encouraging. Pegasus is
air-launched from under a slightly-modified ex-airliner TriStar. Taurus
is essentially a wingless Pegasus on top of a big existing solid rocket
motor, for ground launch. Taurus's price is about 50% more than Pegasus's,
but it has about 3x the payload. (Of course, cost and price are different
things, but cost is harder to assess...)

Perhaps the problem is that the first stage of a rocket makes the
rocket go really fast, and an airplane burning atmospheric oxygen
doesn't go nearly that fact, so you can't really eliminate a whole
stage that way, making the benefits not worth the bother.

An aircraft, especially an off-the-shelf airliner, indeed doesn't give you
as much boost as a good rocket first stage. However, it probably is
*enough* to eliminate a stage -- even people who don't think SSTO is
possible will reluctantly concede that a really good upper stage doesn't
need a *lot* of initial boost to reach orbit with a modest payload.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In article ,
john hare wrote:
I believe the carrier plane should be closer to a fly back booster
than a modified airliner.

Trouble is, the more you start designing for robustness and simplicity
rather than aerodynamic efficiency, the more interested you get in engines
that are far lighter and much less fussy and much more powerful than jet
engines, if somewhat less fuel-efficient -- that is, rocket engines. What
lies at the end of that evolutionary path *is* a recoverable rocket stage,
not an airplane.

An awful lot of design concepts that start out with an airbreathing lower
stage and a rocket upper stage quietly drop that idea when the designer,
just for completeness, does a comparison to an all-rocket system... and
discovers that the all-rocket system performs better and would be easier
to develop and cheaper to operate.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

"Henry Spencer" wrote in message
...
In article ,
john hare wrote:
I believe the carrier plane should be closer to a fly back booster
than a modified airliner.

Trouble is, the more you start designing for robustness and simplicity
rather than aerodynamic efficiency, the more interested you get in engines
that are far lighter and much less fussy and much more powerful than jet
engines, if somewhat less fuel-efficient -- that is, rocket engines. What
lies at the end of that evolutionary path *is* a recoverable rocket stage,
not an airplane.

My thinking is use enough airbreathing engine to safely fly the stage
back from serious down/cross range distances. Any advantage in
airbreathing engines will not be in performance. It will be in operational
flexibility. If the trades do not give serious advantages in that aspect,
then the airbreathing engines should be dropped.

An awful lot of design concepts that start out with an airbreathing lower
stage and a rocket upper stage quietly drop that idea when the designer,
just for completeness, does a comparison to an all-rocket system... and
discovers that the all-rocket system performs better and would be easier
to develop and cheaper to operate.
--
I think the best lower stage will have some mix of the two engine types.
When you require high flight rates to a variety of orbits, it may be
worthwhile to develop a vehicle that can get the near SSTO vehicle to
a launch location clear of the thunderstorm that cropped up an hour
before the limited launch window of the fixed pads.

The lower stage/flyback booster should replace the launch pads
and reduce third party risks and paperwork, like Sealaunch, not
the Tristar.

spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

I would think that the advantages of airbreathing engines are tremendous. A
payload increase in the 100% to 1000% range. There is a huge performance
gap (ISP to SPF Specific Fuel Consumption) between rocket engines and
airbreathing engines. From 600 for the best chemical rockets to the
1000-4000 for airbreathing engines. Doubling the ISP of the best rocket
engine will more than double the payload.

In my opinion, not much has been done or studied to bridge this gap. If your
trades don't give a serious advantage then something is wrong with your
trades. Like, maybe they had the wrong engine.

--
Craig Fink
Courtesy E-Mail Welcome @
--

john hare wrote:

My thinking is use enough airbreathing engine to safely fly the stage
back from serious down/cross range distances. Any advantage in
airbreathing engines will not be in performance. It will be in operational
flexibility. If the trades do not give serious advantages in that aspect,
then the airbreathing engines should be dropped.

On Fri, 02 Mar 2007 14:51:11 GMT, in a place far, far away, Craig Fink
made the phosphor on my monitor glow in such a
way as to indicate that:

I would think that the advantages of airbreathing engines are tremendous.

You'd be wrong.

A payload increase in the 100% to 1000% range. There is a huge performance
gap (ISP to SPF Specific Fuel Consumption) between rocket engines and
airbreathing engines. From 600 for the best chemical rockets to the
1000-4000 for airbreathing engines. Doubling the ISP of the best rocket
engine will more than double the payload.

In my opinion, not much has been done or studied to bridge this gap. If your
trades don't give a serious advantage then something is wrong with your
trades. Like, maybe they had the wrong engine.

No, it's been studied extensively, by many competent people. The cost
of staying in the atmosphere long enough to take advanage of
airbreathing always tends to outweigh (often by a lot) any benefit
gained thereby.