Less difficult than Skylon - Spacebus?

Einar wrote:

Jeff Findley wrote:
"Einar" wrote in message
ups.com...

There has to be a starting point somewhere. Never said it would be
easy. But, why would a plane with a 15 m. wingspan behave radically
differently from an one with a 35 m wingspan?

Scaling laws. One of the biggest problems here could be takeoffs and
landings. If you have a launch abort, you're stuck having to land your
carrier aircraft with a spacecraft on top that may still be fully fueled.
If the combination is very large and optimized more for supersonic flight
than subsonic landings, your air speed upon landing is going to be a tad
high...

As long as both look
entirelly the same, apart from the scale difference. The smaller plane
migt be carrying a simulated load, small robotic test veicle to test
airlaunching. What is the difficulty in using test veicles to test
real hypersonic flight issues? That´s my assumption, that scaled down
test planes can be built to test the practical aspects of the design
before a fullsize prototype is built, and that way the risk minimized.

Possible, if you can get all the scaling laws to play nice together. But
sometimes that's rather difficult and compromises have to be made on your
test articles.


Mind you, this is a discussion of something which, if ever happens, is
not going to happen soon. The space tourism market would actually have
to look like happening before anyone can seriously think about
developing this thing or a thing somewhat like that.

However, some interim issues could be dealt with at an earlier point,
the same firm is proposing a suborbital plane that will carry a small
number of people, that will have a jet engine for takeoff and landing
and a rocket engine for a high alititude climb but only at mac 2.

While that thing isn´t intended to really fly very fast, a more
ambitious version of it flying a bit faster say mac 4 on rockets,
might serve as a development starting point, i.e. aerodynamics
testbed.

Care to actually adress the issues Jeff and I have raised, or are you
going to just handwave and blow smoke while hoping we don't notice?

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

"Jeff Findley" wrote:


"Derek Lyons" wrote in message
...
Again, something I've never debated and conceded multiple times. And
again, I have pointed out to you mutiple times that an aircraft that
can go hypersonic _and_ carry the loads required _and_ reach the
altitude required while carrying those loads is a very different beast
from a test aircraft that can merely go hypersonic.

No doubt. The XB-70 was pretty big, but may not be big enough considering
that it's got to lift its own rocket engines as well as the spacecraft on
top. That and it was still slow (Mach 3) compared to what we've been
talking about here (Mach 6 separation) and even then, they had serious
structural problems with the first aircraft when they flew Mach 3 flights.

IMO, the XB-70 is just about the right size for a quarter-scale
demonstrator.

The turboramjet engines on the carrier may be possible with existing
technology, even though the SR-71 flew a bit slower than Mach 4), but
they're certainly not off the shelf. You've still got to pay for a very
hefty *development* program to build and fly these engines, since the
problems inherent in them are non-trivial. But you'll keep a lot of
aerodynamics and propulsion engineers happily paid for years...

That's the key problem that airlaunch advocates miss - the carrier
aircraft is going to extremely expensive to develop and build. It's
going to take a hell of a market to even begin to bring the amortized
cost per flight down to something reasonable.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

Fred J. McCall wrote:
Russell Wallace wrote:

:
:Would it be feasible for a winged flyback first stage to get that high,
:if you ditch the ramjets and just climb to 15km on subsonic turbojet and
:then light up rocket engines to climb to separation point?
:

Except that once you get that high your turbojet doesn't work (no air)
and your wings are useless (no air) and you might as well have started
off with a rocket in the first place.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

Interesting, 15km was about the absolute ceiling for prop driven high
altitude research aircraft. Acorrding to my recall the U2 does achieve
20km, with its long narrow wings.

Cheers, Einar

Len wrote:
On Jul 23, 6:05 pm, Russell Wallace wrote:
Jeff Findley wrote:
The supersonic separation problem is very non-trivial. You can't hand wave
it away because no one has done a supersonic separation of two winged
vehicles at Mach 6 before. The danger is your winged spacecraft could end
up out of control as it tries to exit the shock created by the carrier
aircraft. It's not as simple as keeping tail fins on the carrier away from
the spacecraft (e.g. D-21 hand waving argument that such problems are simple
to fix by moving tail fins on the carrier aircraft).

How high would you have to go before the shock wave thins out enough to
make it substantially easier?

We currently plan to stage our Space Van 2011 at
mach 2 at 40 km--where the dynamic pressue is only
about 750 Pa. The loaded orbiter is essentially
insensitive to this dynamic pressure; however, the
extremely low wing loading of the carrier makes the
carrier very sensitive. We don't anticipate a significant
separation problem. This is one of the major advantages
of our patent-pending approach.

Would it be feasible for a winged flyback first stage to get that high,
if you ditch the ramjets and just climb to 15km on subsonic turbojet and
then light up rocket engines to climb to separation point?

Even much higher altitudes and lower [staging]
speeds are no problem for a rocket and our
patent-pending approach. Lift is not the problem,
only [airbreathing] propulsion.

However, return is basically glide back. The turbofan
landing engines are running only at subsonic speeds
and relatively low-altitude. They are restarted for
approach and landing. They are basically sized
for engine-out powered landing. The derated
rocket engines are sized for engine-out takeoff
and only need provide thrust levels far less than
would be needed for vertical takeoff. I have always
maintained that wing maintenance can be cheaper
than rocket-engine maintenance.

BTW, some configurational similarity to Skylon
is incidental. The basic concept could hardly be
more different.

It may not be possible to solve technical problems
through the conceptual design process--however,
is quite possible to avoid problems.

Len


--
"Always look on the bright side of life."
To reply by email, replace no.spam with my last name.

Hello, I must admit I don´t know much about "Space Van 2011". Do you
have any links with pictures or drawings?

Cheers, Einar

On Jul 24, 8:16 am, Einar wrote:
Len wrote:
On Jul 23, 6:05 pm, Russell Wallace wrote:
Jeff Findley wrote:
The supersonic separation problem is very non-trivial. You can't hand wave
it away because no one has done a supersonic separation of two winged
vehicles at Mach 6 before. The danger is your winged spacecraft could end
up out of control as it tries to exit the shock created by the carrier
aircraft. It's not as simple as keeping tail fins on the carrier away from
the spacecraft (e.g. D-21 hand waving argument that such problems are simple
to fix by moving tail fins on the carrier aircraft).

How high would you have to go before the shock wave thins out enough to
make it substantially easier?

We currently plan to stage our Space Van 2011 at
mach 2 at 40 km--where the dynamic pressue is only
about 750 Pa. The loaded orbiter is essentially
insensitive to this dynamic pressure; however, the
extremely low wing loading of the carrier makes the
carrier very sensitive. We don't anticipate a significant
separation problem. This is one of the major advantages
of our patent-pending approach.

Would it be feasible for a winged flyback first stage to get that high,
if you ditch the ramjets and just climb to 15km on subsonic turbojet and
then light up rocket engines to climb to separation point?

Even much higher altitudes and lower [staging]
speeds are no problem for a rocket and our
patent-pending approach. Lift is not the problem,
only [airbreathing] propulsion.

However, return is basically glide back. The turbofan
landing engines are running only at subsonic speeds
and relatively low-altitude. They are restarted for
approach and landing. They are basically sized
for engine-out powered landing. The derated
rocket engines are sized for engine-out takeoff
and only need provide thrust levels far less than
would be needed for vertical takeoff. I have always
maintained that wing maintenance can be cheaper
than rocket-engine maintenance.

BTW, some configurational similarity to Skylon
is incidental. The basic concept could hardly be
more different.

It may not be possible to solve technical problems
through the conceptual design process--however,
is quite possible to avoid problems.

Len

--
"Always look on the bright side of life."
To reply by email, replace no.spam with my last name.

Hello, I must admit I don´t know much about "Space Van 2011". Do you
have any links with pictures or drawings?

A rendering at the mach 2 / 40-km staging point
at a flight path angle of 27 degrees (carrier at a
high negative angle-of-attack) can be seen at:

http://www.tour2space.com

Our price goal is $2,200,000 per flight in 2007
dollars--including return on investment. Payload
to a 450-km, 60 degree orbit with a single pilot is
2000 kg. Tourism payload in a large oversize
cabin for 11 orbits is 10 passengers--not including
pilot, copilot and flight attendant--to a 48 degree,
165-km by 450-km (or 285-km circular) orbit.
Other drawings and data are not being
disclosed at this time.

Len


Cheers, Einar

Len wrote:
On Jul 24, 8:16 am, Einar wrote:
Len wrote:
On Jul 23, 6:05 pm, Russell Wallace wrote:
Jeff Findley wrote:
The supersonic separation problem is very non-trivial. You can't hand wave
it away because no one has done a supersonic separation of two winged
vehicles at Mach 6 before. The danger is your winged spacecraft could end
up out of control as it tries to exit the shock created by the carrier
aircraft. It's not as simple as keeping tail fins on the carrier away from
the spacecraft (e.g. D-21 hand waving argument that such problems are simple
to fix by moving tail fins on the carrier aircraft).

How high would you have to go before the shock wave thins out enough to
make it substantially easier?

We currently plan to stage our Space Van 2011 at
mach 2 at 40 km--where the dynamic pressue is only
about 750 Pa. The loaded orbiter is essentially
insensitive to this dynamic pressure; however, the
extremely low wing loading of the carrier makes the
carrier very sensitive. We don't anticipate a significant
separation problem. This is one of the major advantages
of our patent-pending approach.

Would it be feasible for a winged flyback first stage to get that high,
if you ditch the ramjets and just climb to 15km on subsonic turbojet and
then light up rocket engines to climb to separation point?

Even much higher altitudes and lower [staging]
speeds are no problem for a rocket and our
patent-pending approach. Lift is not the problem,
only [airbreathing] propulsion.

However, return is basically glide back. The turbofan
landing engines are running only at subsonic speeds
and relatively low-altitude. They are restarted for
approach and landing. They are basically sized
for engine-out powered landing. The derated
rocket engines are sized for engine-out takeoff
and only need provide thrust levels far less than
would be needed for vertical takeoff. I have always
maintained that wing maintenance can be cheaper
than rocket-engine maintenance.

BTW, some configurational similarity to Skylon
is incidental. The basic concept could hardly be
more different.

It may not be possible to solve technical problems
through the conceptual design process--however,
is quite possible to avoid problems.

Len

--
"Always look on the bright side of life."
To reply by email, replace no.spam with my last name.

Hello, I must admit I don´t know much about "Space Van 2011". Do you
have any links with pictures or drawings?

A rendering at the mach 2 / 40-km staging point
at a flight path angle of 27 degrees (carrier at a
high negative angle-of-attack) can be seen at:

http://www.tour2space.com

Our price goal is $2,200,000 per flight in 2007
dollars--including return on investment. Payload
to a 450-km, 60 degree orbit with a single pilot is
2000 kg. Tourism payload in a large oversize
cabin for 11 orbits is 10 passengers--not including
pilot, copilot and flight attendant--to a 48 degree,
165-km by 450-km (or 285-km circular) orbit.
Other drawings and data are not being
disclosed at this time.

Len


Cheers, Einar

Thanks, looks a bit like the Valkyrie that artist´s impression of the
carryer.

Cheers, Einar

Einar wrote:

:
:Fred J. McCall wrote:
: Russell Wallace wrote:
:
: :
: :Would it be feasible for a winged flyback first stage to get that high,
: :if you ditch the ramjets and just climb to 15km on subsonic turbojet and
: :then light up rocket engines to climb to separation point?
: :
:
: Except that once you get that high your turbojet doesn't work (no air)
: and your wings are useless (no air) and you might as well have started
: off with a rocket in the first place.
:
:
:Interesting, 15km was about the absolute ceiling for prop driven high
:altitude research aircraft. Acorrding to my recall the U2 does achieve
:20km, with its long narrow wings.
:

Yep. And you'll notice what the wing loading and power to weight
ratios have to be to fly up there. There's a reason cargo aircraft
don't fly at 120,000 feet.

Ok, I was a little hyperbolic with regard to the altitude where things
stop working, but just starting off high and slow doesn't gain you
much.

If your goal is to get into orbit, you're better off just starting
with rockets in the first place.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

"Russell Wallace" wrote in message
...
Jeff Findley wrote:
The supersonic separation problem is very non-trivial. You can't hand
wave it away because no one has done a supersonic separation of two
winged vehicles at Mach 6 before. The danger is your winged spacecraft
could end up out of control as it tries to exit the shock created by the
carrier aircraft. It's not as simple as keeping tail fins on the carrier
away from the spacecraft (e.g. D-21 hand waving argument that such
problems are simple to fix by moving tail fins on the carrier aircraft).

How high would you have to go before the shock wave thins out enough to
make it substantially easier?

Would it be feasible for a winged flyback first stage to get that high, if
you ditch the ramjets and just climb to 15km on subsonic turbojet and then
light up rocket engines to climb to separation point?

That's one approach, so let's follow that line of thinking.

Since the shock is an issue, it would be desirable to get completely out of
the atmosphere to eliminate the problem entirely. But then your first stage
is essentially a suborbital spacecraft, which begs the question, why include
the complex turbo-ramjet engines at all if you need rocket engines to get to
the proper speed and altitude for separation? Rockets are far better at
acceleration than turboramjets, which are typically optimized for supersonic
cruise.

Taking this line of thinking one step further, why should the first stage be
an aircraft at all? Why not make it a purely rocket powered first stage?
If it's all rocket powered, why launch from a runway at all since landing
gear really eats into payload?

So this leads you to vertical takeoff on pure rocket power. Once you've
made that choice, why bother with horizontal landing at all? Why not make
the thing vertical takeoff and (powered) landing like DC-X? This eliminates
those pesky wings, which cause drag on launch, and are a pesky thing to
design for the entire flight regime (e.g. reentry).

In the end, I think this drives you to a fully reusable, liquid rocket
powered first stage that operates in a VTVL mode.

I tend to agree with Derek. Air launch is a solution in search of a
problem. When you look at the actual problem you're trying to solve, I
think you're driven to all rocket powered designs. They're the best
*proven* engines out there for the high acceleration needed to get into
orbit.

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)

"snidely" wrote in message
oups.com...
On Jul 23, 1:39 pm, "Jeff Findley"
wrote:
[...]
Boeing has been looking into these sorts of designs for a *long* time,
and
nothing has come of it yet. Their customers are a conservative lot,
especially since 9/11 and since oil prices shot up.

Which is why the test program is so important. But they do seem to be
bending composite for test items. "Long Lead Time" was partly
euphemistic, though even the 7E7 takes a while, but isn't Blended Wing
supposed to be needed to maintain fuel efficiency as passenger count
goes up?

OTOH, Boeing recently scored points in the market by not matching the
size of the A380, so raw cattle count isn't the only factor involved.

Ultimately Boeing builds what customers want to buy. Until the customers
start showing *real* interest in blended wing designs, we won't see many
test items. In other words, customers have to be willing to place acutal
orders in order for Boeing to justify the funding of actual development.
Until then, these blended wing designs are really just concepts waiting for
actual development.

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)

"Einar" wrote in message
ups.com...

Interesting, 15km was about the absolute ceiling for prop driven high
altitude research aircraft. Acorrding to my recall the U2 does achieve
20km, with its long narrow wings.

At the altitude that the US flies, the stall speed is so high it's close to
the maximum speed of the aircraft.

http://en.wikipedia.org/wiki/Lockheed_U-2 (look for stall speed)

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)