Get a good Griff on yourself....

On 27/12/2011 1:21 AM, J. Clarke wrote:
In , lid
says...

On 26/12/2011 3:12 PM, bob haller wrote:
On Dec 25, 4:21 pm, David wrote:
Sylvia Else wrote:
On 21/12/2011 3:40 PM, Greg (Strider) Moore wrote:

Separate at altitude may be a bit of an issue, but again, we have
experience doing that subsonically and I don't see major issues
developing, despite the sizes involved. (Now, if they were proposing
supersonic separation, I'd be worried.)

Thing is, six miles, and 1000km/h, are a very small part of the altitude
and delta-V needed for orbit. The benefit may not be worth the cost.

Sylvia.

The point Henry raises on the arocket list and the one that has gathered a bit
a chatter over there is the ability of Stratolaunch to do one-orbit rendezvous.

This would lower transit time and cost associated with that.

However, I largely agree with you on launch costing, unless the one-orbit
option helps offset either on-orbit costs or helps to increase launch rate.

There is also the multiple target option(s) if Bigelow gets going.

Dave

fly south to the equator, gains a bit

possible in flight refueling of the air breathing part means more
weight for orbit.....

If by in flight refueling, you mean a tanker craft makes a rendevous,
and transfers fuel, then it makes no sense in the context of a launcher.
You might as well have the two joined at takeoff, and separate after the
tanker's fuel is depleted.

Has anybody demonstrated a takeoff while linked to a tanker?

The US demonstrated the release of the space shuttle orbiter from the
carrier aircraft during the early flight tests. The carrier aircraft, a
747, wasn't also acting as a tanker, but I can't see that makes any
difference.

In such a configuration, there isn't much point in moving fuel from the
tanker to the orbiter anyway. The carrier aircraft just puts the orbiter
at a suitable place and velocity and releases it, at which time the
orbiter starts its engines and continues the climb.

Supersonic separation might be a different issue entirely, but that's
not what's being discussed here.

You seem
to think that aerial refueling is some kind of big deal, and maybe if
you inhabit some third-world Hellhole it is, but for the US, the EU, the
CIS, and any of their clients, it's all in a day's work for any
military-trained pilot. I agree that there isn't likely any need for it
in the scenario under discussion, but that doesn't make it any kind of
issue to be argued against.

I'm just arguing that it's a pointless complication.

Sylvia.

"Sylvia Else" wrote in message ...

On 21/12/2011 3:40 PM, Greg (Strider) Moore wrote:

Separate at altitude may be a bit of an issue, but again, we have
experience doing that subsonically and I don't see major issues
developing, despite the sizes involved. (Now, if they were proposing
supersonic separation, I'd be worried.)

Thing is, six miles, and 1000km/h, are a very small part of the altitude
and delta-V needed for orbit. The benefit may not be worth the cost.


True. But different argument. :-)

Just saying technically, I don't see any show stoppers.


Sylvia.



--
Greg D. Moore President Green Mountain Software
http://www.greenms.com
Help honor our WWII Veterans: http://www.honorflight.org/
Quidquid latine dictum sit, altum viditur.

On Dec 26, 10:17*pm, "Greg \(Strider\) Moore"
wrote:
"Sylvia Else" *wrote in ...

On 21/12/2011 3:40 PM, Greg (Strider) Moore wrote:

Separate at altitude may be a bit of an issue, but again, we have
experience doing that subsonically and I don't see major issues
developing, despite the sizes involved. (Now, if they were proposing
supersonic separation, I'd be worried.)

Thing is, six miles, and 1000km/h, are a very small part of the altitude
and delta-V needed for orbit. The benefit may not be worth the cost.

True. *But different argument. :-)

Just saying technically, I don't see any show stoppers.

Sylvia.

--
Greg D. Moore * President * * * * * * * * * Green Mountain Softwarehttp://www.greenms.com
Help honor our WWII Veterans:http://www.honorflight.org/
Quidquid latine dictum sit, altum viditur.

this is a good first step towards air launchers, the kinda wright
brothers model.

later versions could take the air breathing stage to near space, say
100,000 feet with rocket assist.....

In article , lid
says...

On 21/12/2011 3:40 PM, Greg (Strider) Moore wrote:

Separate at altitude may be a bit of an issue, but again, we have
experience doing that subsonically and I don't see major issues
developing, despite the sizes involved. (Now, if they were proposing
supersonic separation, I'd be worried.)

Thing is, six miles, and 1000km/h, are a very small part of the altitude
and delta-V needed for orbit. The benefit may not be worth the cost.

To be fair, it's got 4 less (rocket) engines than Falcon 9. It's not a
huge savings, to be sure, but it's still less money spent on rocket
engines.

Besides, there are other advantages to air launch. Far more
opportunities for first orbit rendezvous are possible with air launch
than with ground launch, which would be an advantage for future
potential markets.

Also, removing yourself from the headaches associated with launch from a
fixed, shared, government operated, launch site is worth something.
Just how much that's worth depends on who your customers are and what
their requirements are.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker

On 28/12/2011 1:04 AM, bob haller wrote:
On Dec 26, 10:17 pm, "Greg \(Strider\) Moore"
wrote:
"Sylvia Else" wrote in ...

On 21/12/2011 3:40 PM, Greg (Strider) Moore wrote:

Separate at altitude may be a bit of an issue, but again, we have
experience doing that subsonically and I don't see major issues
developing, despite the sizes involved. (Now, if they were proposing
supersonic separation, I'd be worried.)

Thing is, six miles, and 1000km/h, are a very small part of the altitude
and delta-V needed for orbit. The benefit may not be worth the cost.

True. But different argument. :-)

Just saying technically, I don't see any show stoppers.

Sylvia.

--
Greg D. Moore President Green Mountain Softwarehttp://www.greenms.com
Help honor our WWII Veterans:http://www.honorflight.org/
Quidquid latine dictum sit, altum viditur.

this is a good first step towards air launchers, the kinda wright
brothers model.

later versions could take the air breathing stage to near space, say
100,000 feet with rocket assist.....

100,000 feet isn't much better unless it's also hypersonic, in which
case you're dealing with separation in untried circumstances, with
shockwaves doing nasty things. There is also the issue of getting the
first stage back given that by that time it's a long way down range and
at a high velocity. It could land somewhere downrange, refuel and
return, but that pushes up the infrastructure costs.

Sylvia.

"Sylvia Else" wrote in message ...


100,000 feet isn't much better unless it's also hypersonic, in which

Sure it is, it's getting you above a big part of the atmosphere. That
helps.


case you're dealing with separation in untried circumstances, with
shockwaves doing nasty things. There is also the issue of getting the first
stage back given that by that time it's a long way down range and at a high
velocity. It could land somewhere downrange, refuel and return, but that
pushes up the infrastructure costs.

(I'm assuming your "first stage" is the rocket, not the plane)

Actually if anything this negates that disadvantage. Fly westward, and then
before launch turn eastward and launch. You're now 500 miles or more (1000
if you land your craft and refuel) and less downrange then if you launch
from a fixed location that you want to return to.


Sylvia.



--
Greg D. Moore President Green Mountain Software
http://www.greenms.com
Help honor our WWII Veterans: http://www.honorflight.org/
Quidquid latine dictum sit, altum viditur.

Greg (Strider) Moore wrote:
"Sylvia Else" wrote in message ...

100,000 feet isn't much better unless it's also hypersonic, in which

Sure it is, it's getting you above a big part of the atmosphere. That
helps.

The lower total air friction until out of the atmosphere is the biggest
difference but the potential energy difference between 0 and 100K feet
is not zero. There's that much less gravity well to leave. Much lower
effect than the air resistance at that point but not zero. The forward
flight of the launch platform at mach 0.5ish matters as well.

On Dec 28, 12:25*pm, Doug Freyburger wrote:
Greg (Strider) Moore wrote:
"Sylvia Else" *wrote in ....

100,000 feet isn't much better unless it's also hypersonic, in which

Sure it is, it's getting you above a big part of the atmosphere. *That
helps.

The lower total air friction until out of the atmosphere is the biggest
difference but the potential energy difference between 0 and 100K feet
is not zero. *There's that much less gravity well to leave. *Much lower
effect than the air resistance at that point but not zero. *The forward
flight of the launch platform at mach 0.5ish matters as well.

every ounce saved is greater payload capacity and less cost per pound
to orbit....

In sci.space.history message , Tue, 27
Dec 2011 12:15:52, Sylvia Else posted:

The US demonstrated the release of the space shuttle orbiter from the
carrier aircraft during the early flight tests. The carrier aircraft, a
747, wasn't also acting as a tanker, but I can't see that makes any
difference.

In such a configuration, there isn't much point in moving fuel from the
tanker to the orbiter anyway. The carrier aircraft just puts the
orbiter at a suitable place and velocity and releases it, at which time
the orbiter starts its engines and continues the climb.


An orbiter burns its fuel in ten minutes. But a carrier aircraft, even
if fuelled on the runway, will take an hour or more to get it from there
to the separation point. For cryogenic fuels, one could use heavier
insulation in the aircraft (with a little cryogen in the orbiter,
perhaps, to have it pre-chilled).

With the orbiter fuelled at take-off, that fuel mass must be supported
along a longer load path leading to a hard and imperfectly smooth
runway. But with the orbiter fuelled at altitude, the fuel load path
then leads to a pair of somewhat elastic wings supported on soft air.

Even with an orbiter fully-fuelled in the runway, it could be useful to
provide top-up fuel from the tanker aircraft before separation.

One might even consider an air-to-air transfer of orbiter fuel from
another tanker aircraft.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms and links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

On 29/12/2011 7:05 AM, Dr J R Stockton wrote:
In sci.space.history , Tue, 27
Dec 2011 12:15:52, Sylvia posted:

The US demonstrated the release of the space shuttle orbiter from the
carrier aircraft during the early flight tests. The carrier aircraft, a
747, wasn't also acting as a tanker, but I can't see that makes any
difference.

In such a configuration, there isn't much point in moving fuel from the
tanker to the orbiter anyway. The carrier aircraft just puts the
orbiter at a suitable place and velocity and releases it, at which time
the orbiter starts its engines and continues the climb.


An orbiter burns its fuel in ten minutes. But a carrier aircraft, even
if fuelled on the runway, will take an hour or more to get it from there
to the separation point. For cryogenic fuels, one could use heavier
insulation in the aircraft (with a little cryogen in the orbiter,
perhaps, to have it pre-chilled).

With the orbiter fuelled at take-off, that fuel mass must be supported
along a longer load path leading to a hard and imperfectly smooth
runway. But with the orbiter fuelled at altitude, the fuel load path
then leads to a pair of somewhat elastic wings supported on soft air.

Even with an orbiter fully-fuelled in the runway, it could be useful to
provide top-up fuel from the tanker aircraft before separation.

One might even consider an air-to-air transfer of orbiter fuel from
another tanker aircraft.


In the situation where the orbiter is attached to the carrier aircraft
at take off, there seems little point in running the orbiter's engines.
Doing so just requires them to operate over a wider range of ambient
pressures, and also to operate for longer.

If they are not operating, then no fuel is being consumed, so there's
nothing to top up except perhaps some boil-off, but I find it hard to
believe that the it would be worth carrying the mass of the extra
machinery in the orbiter to allow that.

In the case where the orbiter takes off independently, it needs landing
gear, or other arrangements, capable of handling its takeoff weight.

In addition, it would need inflight refuelling equipment that presumably
gets carried to orbit. To me it seems improbable that that would mass
less than the extra structure required to allow the fully fuelled
orbiter to sit on its carrier aircraft.

In any case, whether the orbiter takes off seperately, or attached to
its carrier aircraft, the system appears to be 'SSTO' from 1000km/h and
a few tens of thousands of feet. Where are the numbers showing that
that's feasible without using a new type of engine?

Sylvia.