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Old 12-14-2011, 04:33 PM   #31
T.Neo
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DARPA wants this type of airlaunch system but for small payloads, ca. 100 pounds:

Curiously they also expect it to fly by 2015. For launches this small it might work to use a WhiteKnight1 or WhiteKnight2 for the carrier aircraft, and Falcon 1 or Falcon 1e for the rocket.
Oh yes, why not use Falcon 1e? Great option... except for the fact that it has a payload of 1010 kilograms, not 40-50...

It also can't fit on a WhiteKnight Two, which has a payload of 17 000 kg (F1e has a mass of over 35 tons).

Quote:
The video does not show it, but I know that they were talking about a 5 engine rocket by spacex. Does this mean that Falcon 5 is re-born?
With wings and slung under a carrier aircraft. It could be.

Though I believe they are looking toward either a four or five engine configuration.

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But, still, 30,000 feet is reached in what, the first 20 seconds of burn time? It can't be worth R&D for a whole carrier vehicle just to save 20 seconds of fuel.
Air launch supposedly gives 5-10% of an advantage. It's more than just saving 20 seconds of fuel... but the question is still "is this advantage worth the extra cost".

Quote:
By the way, you could "launch" from a point 2000 miles south of the US, so even if you assemble the rocket+aircraft at the Cape you could launch from a latitude comparable to Kourou, another few percent more payload.
By flying for 1300 nautical miles at a heading of 116 degrees (you still have to avoid islands), you end up at a launch 'site' at a latitude of roughly 17 degrees. While that would obviously boost payload somewhat, it isn't really comparable to Kourou.

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So how exactly is this different from more classical air-launch concepts? Appart from that it doesn't look nearly as cool, and that I don't quite see how that plane could do anything that a third stage couldn't do a lot better. It can't get very high for launch, and it can't reach significant velocities to help with orbital insertion...
For one, this is actually a (seemingly) serious proposal, and not something silly that looks like it came out of science fiction.

In all seriousness though, air launch isn't one fixed definition. it goes from dropping a rocket out the back of a C-5 to some sort of supersonic or even hypersonic, scramjet assisted proposals.

The "air launch scheme" this is most similar to is Pegasus.
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Old 12-14-2011, 04:48 PM   #32
Arrowstar
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Personally, I'll believe this when I see it. There may be some big names behind it, but I'm just not sure the need and technology is all there.

(That said, I would love to see them succeed: it's a wicked cool concept. I'm just a bit skeptical at the moment.)
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Old 12-14-2011, 07:06 PM   #33
RGClark
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Quote:
Originally Posted by T.Neo View Post
 Oh yes, why not use Falcon 1e? Great option... except for the fact that it has a payload of 1010 kilograms, not 40-50...
It also can't fit on a WhiteKnight Two, which has a payload of 17 000 kg (F1e has a mass of over 35 tons).
Correct. The report:

Report of the Horizontal Launch Study.
http://ntrs.nasa.gov/archive/nasa/ca...2011016245.pdf

on which the DARPA Alasa program was based used an airlaunched Falcon 1e as a baseline for larger launchers using 747-sized carrier aircraft.


Bob Clark

Last edited by RGClark; 12-15-2011 at 12:19 PM. Reason: typo
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Old 12-14-2011, 08:56 PM   #34
orbitingpluto
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Seems like there is enough problems in this to stop it from actually happening. This is an feeling of mine, not backed up by numbers or deep knowledge of the sciences at play in a concept like this. So don't argue me on on it.

That said, just because a concept has problems doesn't mean we can't try it out in orbiter. We don't have a twined 747 airplane around, but we do have a
twined B52
. I can't check how well it might work
Glider's Falcons
at the moment, but we could be flying this thing and debating the relative merits of it before the inevitable configuration change. Which could be two weeks from now
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Old 12-14-2011, 09:04 PM   #35
T.Neo
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I don't think Glider's Falcons include F5, especially winged F5...

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Seems like there is enough problems in this to stop it from actually happening. This is an feeling of mine, not backed up by numbers or deep knowledge of the sciences at play in a concept like this. So don't argue me on on it.
I also have this feeling, but not about the technical aspects- rather the economic ones. But they are just uneducated possibilities, there is obviously a lot going on behind the scenes.

The technical concept has quite a bit going for it, but there are still technical problems of course. How much will the Falcon structure have to be re-engineered to handle the different loads? Will the propellant handling systems face any significant challenges? Etc.
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Old 12-14-2011, 09:12 PM   #36
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Quote:
Originally Posted by Ark View Post
 But, still, 30,000 feet is reached in what, the first 20 seconds of burn time? It can't be worth R&D for a whole carrier vehicle just to save 20 seconds of fuel.
It's not so much about the 20 seconds of fuel. If you launch at surface pressure, you'll have to make compromises in engine design to get enough thrust at lift-off. This makes the engines less efficient at lower pressure.

Quote:
Originally Posted by T.Neo View Post
 By flying for 1300 nautical miles at a heading of 116 degrees (you still have to avoid islands), you end up at a launch 'site' at a latitude of roughly 17 degrees. While that would obviously boost payload somewhat, it isn't really comparable to Kourou.
The big advantage is that you can fly to a location where you can launch into the desired direction. Land based sites have many restrictions on launch azimuth.

I hope this thing "gets of the ground" and I'll be in the basement building my own Deltaglider to strap on to it.

Last edited by C3PO; 12-14-2011 at 09:15 PM.
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Old 12-14-2011, 09:59 PM   #37
T.Neo
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It's not so much about the 20 seconds of fuel. If you launch at surface pressure, you'll have to make compromises in engine design to get enough thrust at lift-off. This makes the engines less efficient at lower pressure.
Still, how much of an advantage go you get? And doesn't designing a totally different nozzle mean that SpaceX needs tooling to produce two different (first stage Merlin) nozzles?

Maybe you still get a nice performance boost just by launching at altitude with usual ground-adapted nozzles.

Quote:
Land based sites have many restrictions on launch azimuth.
Can't KSC pretty much support station, GTO and planetary launches and VAFB support retrograde/polar military and Earth sciences payloads?

Wouldn't it cost less to share the same facilities that already exist (or should hopefully soon exist) there for F9/FH?
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Old 12-15-2011, 12:57 AM   #38
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Some things that caught my attention in the NASAspaceflight.com article:

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The company announced they have already acquired two 747s to become the opening hardware for this system.
So that should save some money. They aren't building the aircraft from scratch.

Quote:
Stratolaunch’s carrier aircraft, built by Scaled Composites, weighs more than 1.2 million pounds and has a wingspan of 385 feet. Using six 747 engines, the carrier aircraft will be the largest aircraft ever constructed.
A truly appropriate use for the word AWESOME...

But it makes me think that such a unique aircraft is a big gamble.

The aviation/engineer side of me would love to see this fly but the rational side says it will fail financially.
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Old 12-15-2011, 01:25 AM   #39
T.Neo
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So that should save some money. They aren't building the aircraft from scratch.
But if you look at Stratolaunch, and you look at a 747, they look totally different. One is a high wing, the other is a low wing, for example. The wings are different... the tailplane is totally different...

If they intend to use said 747s, I would imagine they would utilise the engines/engine pods, or other subsystems in the new aircraft if possible.
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Old 12-15-2011, 03:07 AM   #40
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From the looks of it, the landing gear is from a 747. The engines are confirmed to be from one, and the cockpit windows look similar.

Bitzer, anyone?
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Old 12-15-2011, 03:31 PM   #41
RGClark
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The benefits of air launch go beyond just the speed and altitude attained. This is discussed in this report:

Air Launching Earth-to-Orbit Vehicles: Delta V gains from Launch Conditions and Vehicle Aerodynamics.
Nesrin Sarigul-Klijn University of California, Davis, CA, UNITED STATES; Chris Noel University of California, Davis, CA, UNITED STATES; Marti Sarigul-Klijn University of California, Davis, CA, UNITED STATES
AIAA-2004-872
42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, Jan. 5-8, 2004
http://pdf.aiaa.org/preview/CDReadyM...PV2004_872.pdf [first page only]

The conclusions are summarized in this online lecture:

A.4.2.1 Launch Method Analysis (Air Launch).
"For a launch from a carrier aircraft, the aircraft speed will directly reduce the Δv required to attain LEO. However, the majority of the Δv benefit from an air launch results
from the angle of attack of the vehicle during the release of the rocket. An
ideal angle is somewhere of the order of 25° to 30°.
"A study by Klijn et al. concluded that at an altitude of 15250m, a rocket launch with the
carrier vehicle having a zero launch velocity at an angle of attack of 0° to
the horizontal experienced a Δv benefit of approximately 600 m/s while a launch
at a velocity of 340m/s at the same altitude and angle of attack resulted in a
Δv benefit of approximately 900m/s. The zero launch velocity situations can
be used to represent the launch from a balloon as it has no horizontal velocity.
"Furthermore, by increasing the angle of attack of the carrier vehicle to
30° and launching at 340m/s, a Δv gain of approximately 1100m/s
was obtained. Increasing the launch velocity to 681m/s and 1021m/s produced a
Δv gain of 1600m/s and 2000m/s respectively.
"From this comparison, it can be seen that in terms of the Δv gain, an airlaunch is
superior to a ground launch. As the size of the vehicle decreases, this superiority
will have a larger effect due to the increased effective drag on the vehicle."
https://engineering.purdue.edu/AAE/A...%20Launch).doc

A speed of 340 m/s is a little more than Mach 1, while subsonic transport aircraft typically cruise
slightly below Mach 1. So the delta-V saving could still be in the range of 1,000 m/s with air launch,
a significant savings by the rocket equation.


Bob Clark

Last edited by RGClark; 12-16-2011 at 02:42 PM. Reason: typo
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Old 12-15-2011, 10:18 PM   #42
T.Neo
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So the delta-V saving could still be in the range of 1,000 m/s with air launch,
a significant savings by the rocket equation.
With a potentially significant cost increase from the "gigantic airplane and associated rocket facilities" equation...

Last edited by T.Neo; 12-15-2011 at 10:21 PM.
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Old 12-16-2011, 01:26 AM   #43
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Quote:
Originally Posted by T.Neo View Post
 With a potentially significant cost increase from the "gigantic airplane and associated rocket facilities" equation...
But it's reusable, and reusable in a good way. Not rebuildable like the STS.
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Old 12-16-2011, 02:52 AM   #44
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The funniest comment I've seen about this so far:
"Who would want to spend 2+ hours in an "eyeballs down" position??"



It's as if some people see Mike Griffin's name and have some sort of uncontrollable reflex. And there seems to be some sort of strange backlash against Paul Allen for not spending his own fortune on their individual spaceflight fantasies. "He should have announced a private expedition to Mars/ a manned mining base on the Moon/ a Venture Star like SSTO/ point-to-point suborbital travel/ a space hotel complex/ a network of orbital propellant depots/ a reusable Moon lander etc..." Boo hoo, a billionaire can spend his money how he wants to, stop being petty.

About the concept, I like it. Sure it's a big aeroplane, but the costs for maintating a big aeroplane are at least an order of magnitude less than maintainting a traditional rocket launch complex, and the operational advantages appear to make up for it. It's not just about providing the lowest cost per kg to orbit, it's about providing the best sevice for the lowest cost. The fact that the Air Force have sponsored several studies of similar air launch concepts is a fair indicator that a reasonable demand exists.

So, just because a super rich chap may not be answering all of your spaceflight desires in one leap doesn't mean it's not a nice step in the right direction.
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Old 12-16-2011, 12:33 PM   #45
T.Neo
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But it's reusable, and reusable in a good way. Not rebuildable like the STS.
How is it reusable? The rocket gets thrown away every time.

Quote:
It's as if some people see Mike Griffin's name and have some sort of uncontrollable reflex.
Yes, but after Constellation, what can you expect?

Quote:
And there seems to be some sort of strange backlash against Paul Allen for not spending his own fortune on their individual spaceflight fantasies. "He should have announced a private expedition to Mars/ a manned mining base on the Moon/ a Venture Star like SSTO/ point-to-point suborbital travel/ a space hotel complex/ a network of orbital propellant depots/ a reusable Moon lander etc..." Boo hoo, a billionaire can spend his money how he wants to, stop being petty.
I agree, it's quite annoying.

But to be honest, while it is indeed Allen's money, it's only fair to critique his rationale behind the whole excersise.

Quote:
Sure it's a big aeroplane, but the costs for maintating a big aeroplane are at least an order of magnitude less than maintainting a traditional rocket launch complex, and the operational advantages appear to make up for it.
Where are the numbers behind this statement?

Also, you need a lot of the elements of a traditional rocket launch complex anyway- vehicle integration facilities, payload integration facilities, LOX and fuel supplies, other supporting infrastructure, etc. It's more intensive than you think.

The aircraft itself isn't just your average cargo or passenger airplane, either. It could have onboard hardware for handling propellants, for example. As well as a quick-disconnect umbilicals.

And also; the costs of a launch facility are high, but are pretty much fixed, so the cost per launch is reduced if you launch more often.

If you built F5 for example, and launched it from SLC-40 and SLC-4, you would not only share the costs with F9 and FH, but those vehicles would share their costs with F5... making the launch facility cost per launch lower for all vehicles using those sites.

Maybe SpaceX plans to use some of their SLC-40 facilities (such as the integration hangar) for Stratolaunch operations and then transport the vehicle to the SLF, but there are still going to be some facilities that are needed elsewhere and some facilities at the normal launch site that aren't used (and that then presumably don't have their costs shared).

It is also possible that the SpaceX launch facilities are very lean (they do look like it), meaning that cost-sharing does not change overall launch price much, but in that case you have the option of "other launch facilities and launch pad" or "other launch facilities and launch aircraft". I don't know, but I'm willing to guess that the erector arm/hold-down post aren't more expensive to operate than a gigantic aircraft (especially since the airplane has a lot of similar infrastructure onboard).

Quote:
It's not just about providing the lowest cost per kg to orbit, it's about providing the best sevice for the lowest cost.
How is this service better than a land launch? Sure, you can supposedly do a polar orbit from the cape... but you can also do a polar orbit from Vandenberg.

It even isn't as safe, since you can't have a hold-down prior to launch; every rocket engine firing is now an air-start event...

Last edited by T.Neo; 12-16-2011 at 12:44 PM.
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