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Old 12-16-2011, 10:53 PM   #46
C3PO
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Originally Posted by T.Neo View Post
 How is it reusable? The rocket gets thrown away every time.
Are you serious?

The general idea is to land the aeroplane once the rocket is released.

Feel free to ask if there are some other things you need explained.
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Old 12-16-2011, 11:41 PM   #47
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Are you serious?
Yes. I said the rocket gets thrown away. I never said anything about the airplane.

One can look at the airplane as something that is in a 'grey area' between 'stage' and 'launch infrastructure'. It's arguably both, but you don't usually see launch facilities getting thrown away with each launch. They're reused (what extent of repair/maintenance they require after use is another issue, but I'm willing to bet it is relatively minimal) just like the aircraft would be.

The rocket, which not only provides most of the climb to orbit energy wise but represents a good deal of technological complexity and cost, is thrown away with each launch. One could go as far as to say that STS was more 'reusable' than this is.

Last edited by T.Neo; 12-16-2011 at 11:44 PM.
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Old 12-17-2011, 02:30 AM   #48
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Originally Posted by T.Neo View Post
 Yes. I said the rocket gets thrown away. I never said anything about the airplane.

One can look at the airplane as something that is in a 'grey area' between 'stage' and 'launch infrastructure'. It's arguably both, but you don't usually see launch facilities getting thrown away with each launch. They're reused (what extent of repair/maintenance they require after use is another issue, but I'm willing to bet it is relatively minimal) just like the aircraft would be.

The rocket, which not only provides most of the climb to orbit energy wise but represents a good deal of technological complexity and cost, is thrown away with each launch. One could go as far as to say that STS was more 'reusable' than this is.
I'm not going into a quote-swapping match with you.

My point is that this way you can completely reuse the first stage of the system without a major overhaul.

Because the rocket provides almost all of the DV to get into orbit, it's important that it is optimized for operating at very low pressure/vacum.

As for STS, reusing the SRBs was more expensive then building new ones. In fact that was one of the options considered when the plan to continue STS flights commercially was in the works.

And the STS is history, so everything the US launches is not reused, and it will stay that way for many years.

Whether you chose to designate the plane a "first stage" or a "launch pad" is of no interest to me, as are labels like Reusable and SSTO. I'm only interested in the reliability and competitiveness of the complete system.

But IMHO the most exciting part of this project is that we might get some experience in air-launching larger rockets, which is practically non-existing today. While we've been using launch pads for decades, nothing larger then a Pegasus has been air-launched into orbit.
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Old 12-17-2011, 11:54 AM   #49
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My point is that this way you can completely reuse the first stage of the system without a major overhaul.
Where? The first stage is thrown away each time. The aircraft is reused.

Aircraft are often reused multiple times, no breakthrough here.

Quote:
Because the rocket provides almost all of the DV to get into orbit, it's important that it is optimized for operating at very low pressure/vacum.
But what does that have to do with reusability?

Quote:
As for STS, reusing the SRBs was more expensive then building new ones. In fact that was one of the options considered when the plan to continue STS flights commercially was in the works.
That isn't relevant. We're not talking about how (badly) something is reused, but how much of it is reused.

Far more is expended here than is expended on STS. The issue is not how the STS stuff was reused, I can also say that Falcon 5 has smaller, less complex engines for example... but that is irrelevant.

The carrier aircraft can be regarded as technically analogous to the MLP/FSS of the shuttle (the analogues of the crawler, the RSS and other pad infrastructure are located elsewhere here).

The fact is, the launch vehicle here is thrown away each time. The actual, technical, complex bit. The bit that you need to reuse if you want to get close to the hypothetical 1-2 order of magnitude cost reduction. It isn't any improvement over STS in terms of pioneering reusability, because it simply isn't reusable.

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I'm only interested in the reliability and competitiveness of the complete system.
Why then did you seem so excited about it being "reusable, and reusable in a good way"? The vehicle isn't reusable, the launch infrastructure is, but this isn't special.

The only difference is that the launch 'pad' flies. If the flying launchpad costs more than the static one for its performance, it isn't competitive.

And it's already less reliable than a land-launch, since you can't have a hold-down before engine ignition. You drop the thing and you ignite the engines, if there's any problem the vehicle and its payload just plummets to oblivion.

Quote:
But IMHO the most exciting part of this project is that we might get some experience in air-launching larger rockets, which is practically non-existing today. While we've been using launch pads for decades, nothing larger then a Pegasus has been air-launched into orbit.
Air launch has disadvantages to go with its advantages. I think it would make more sense in the case of an existing carrier aircraft with minor modifications (or none) and a wholly new vehicle without any existing infrastructure, rather than a scenario with a new aircraft and an existing launch infrastructure.

Also, hasn't an ICBM been dropped out the back of a C-5 before? I've read that something like this was tested out in the past.

EDIT:


EDIT #2:


Last edited by T.Neo; 12-17-2011 at 12:15 PM.
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Old 12-17-2011, 09:52 PM   #50
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Burt Rutan is an aerospace engineer renowned for designing Voyager (the first plane to fly around the world without refueling) and the Paul Allen-funded SpaceShipOne (the first manned civilian craft in space). He is also the founder of Scaled Composites and a board member of Stratolaunch.

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Jim Halsell is a retired NASA astronaut and US Air Force officer who now serves as Technical Director for Dynetics Inc. Dynetics will make the rocket/plane itegration system for Stratolaunch.

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Mike Griffin is a former NASA Administrator (2005-2009), physicist, and aerospace engineer. He is also a board member of Stratolaunch Systems.

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David A. King is a former Director of the NASA Marshall Space Flight Center, a Stratolaunch board member, and Executive Vice President of Dynetics Inc.
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Old 12-19-2011, 07:34 PM   #51
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Parabolic Arc: Some Thoughts — Random and Otherwise — on Stratolaunch:
Quote:
{...}

What problem does this solve? This has been puzzling a few people, who tend to view this as an incremental step forward that doesn’t quite solve anything.

The company’s answer is its motto, “any orbit, any time.” Instead of sitting on a fixed launch pad and waiting for that one brief window per day when the International Space Station (or a private Bigelow facility) is in the right position, you launch at your own convenience. Rendezvous might take two hours instead of two days.

{...}


The plane that can’t taxi. The carrier aircraft will be built an tested at the Mojave Air and Space Port. However, the word among Mojave insiders is that the taxiways there can’t handle an aircraft of that size. Thus, the hanger will have to be build right off the runway.


Can the runway handle the load? The carrier aircraft will have a gross weight of more than 1.2 million pounds, a wingspan of 385 feet, and the capacity to carry a booster weighing up to 490,000 pounds. For takeoff and landing, it will require a 12,000 feet long runway.

Mojave’s Runway 12-30 is long enough, although it has weight restrictions far below what is required for the Stratolaunch carrier.

Mojave Runway 12-30
Dimensions12,500 feet long, 200 feet wide
SurfaceConcrete/asphalt, excellent condition
TaxiwaysParallel on southwest side; four exit taxiways
Weight LimitationsSingle wheel: 200,000 lbs
Double wheel: 300,000 lbs
Double tandem: 400,000 lbs
Source: Mojave Air and Space Port

The upper limit of 400,000 lbs. is sufficient to accommodate the operating empty weight of a Boeing 747, which are routinely flown to Mojave’s Boneyard to be scrapped.

{...}
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Look! Up in the sky! It’s a bird! It’s a plane! It’s…. Birdzilla?
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Old 12-19-2011, 08:15 PM   #52
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The company’s answer is its motto, “any orbit, any time.” Instead of sitting on a fixed launch pad and waiting for that one brief window per day when the International Space Station (or a private Bigelow facility) is in the right position, you launch at your own convenience.
Is this advantage really worth the cost of the gigantic aircraft though?

And what about things like propellant handling, passenger considerations and payload limitations? Surely they've got to limit the practicality of a "launch anytime" mindset.

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Rendezvous might take two hours instead of two days.
Isn't the major time factor catching up to the target, rather than matching planes with it?
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Old 12-19-2011, 10:24 PM   #53
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Rendezvous might take two hours instead of two days.
Isn't the major time factor catching up to the target, rather than matching planes with it?
Yes, if you can vary your launch location you can minimise that time to within one or two orbits.
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Old 12-19-2011, 11:19 PM   #54
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Yes, if you can vary your launch location you can minimise that time to within one or two orbits.
I'd appreciate if you elaborated. How does your launch site affect the time it takes to rendezvous with the target? Isn't it mostly dependant on orbit phasing?
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Old 12-19-2011, 11:43 PM   #55
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Originally Posted by T.Neo View Post
 I'd appreciate if you elaborated. How does your launch site affect the time it takes to rendezvous with the target? Isn't it mostly dependant on orbit phasing?

It is because a given objects (ISS) orbital path doesn't always fall exactly on the launch pad when said given object is within short (one or two orbits) rendezvous distance 1-2k km, that object might be several thousand Km around the earth which requires more orbits to catch up with.

Does that make any sense?

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Old 12-19-2011, 11:56 PM   #56
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Does that make any sense?
It makes perfect sense, but I don't see why you can't simply use a more aggressive rendezvous technique. It may use more propellant, but you could sacrifice payload capability for transit time- or make the vehicle smaller because it doesn't have to support the crew/passengers for a longer duration.

It would still pay off if you had to mount the spacecraft on a larger launch vehicle... as long as the larger launch vehicle and its facilities had a cost advantage over the gigantic airplane and its support facilities...

And there are other options, like dog-leg trajectories. Maybe requirements get pretty messy if you include those, but they could have other benefits (higher payload for the system on other missions).

Last edited by T.Neo; 12-19-2011 at 11:58 PM.
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Old 12-20-2011, 12:02 AM   #57
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Um, let me see if I can explain in a way that makes sense.

You need to launch when the target's orbital plane crosses your launch site. But for a quick rendezvous you also need to launch when the target is about to pass overhead, so that after you reach orbit the target is very near.

For example, assume a launch at KSC when the target is in plane, but the station happens to be over the other side of the planet at the time. But abound 45 minutes earlier the station passed over the same latitude as KSC at some point out over the ocean to the east. So if you launch from that site further to the east at that earlier time, you would be in the optimal position for a very short rendezvous. A carrier aircraft has the flexibility to fly out to the ideal position every time.

EDIT: Play around with launch locations yourself in Orbiter to see what the various penalties for dog-legs and "agressive rendezvous" are.

Last edited by Wood; 12-20-2011 at 12:10 AM.
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Old 12-20-2011, 12:30 AM   #58
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A carrier aircraft has the flexibility to fly out to the ideal position every time.
...And the inflexibility of being a gigantic carrier aircraft.

Quote:
EDIT: Play around with launch locations yourself in Orbiter to see what the various penalties for dog-legs and "agressive rendezvous" are.
If I actually had the time for playing around like that, I would do it. Sadly I don't.

An aggressive rendezvous has nothing to do with launch location but rather the amount of dV expended in orbit. And it is a trade-off: do you want a shortened rendezvous time, if it results in even a 50% payload reduction?

Regardless, vehicles have been tending to space stations and other spacecraft for decades without a 2-hour transit requirement.
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Old 12-20-2011, 12:52 AM   #59
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Those "dog-legs" are usually called plane changes, and I think you'll find that most launchers will have a bit more then a 50% payload reduction.
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Old 12-20-2011, 01:00 AM   #60
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Those "dog-legs" are usually called plane changes, and I think you'll find that most launchers will have a bit more then a 50% payload reduction.
Depends on how severe a dog-leg you fly.
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