Air launch capability

barrykirk · Nov 16, 2006

halman, I like your vision. There is a tremendous difference between that 1929 Stearman and the 747, but there were a lot of steps in between them. Yes, I would like to see an aircraft that could lift a rocket capable of sending 100+ tons to LEO and doing it cheaply and reliably and repeatedly and often. But, there are a lot of intermediate steps. A lot of those steps are just proof of concept steps. Yes, that is an excellent point that a launch aircraft does provide a lot more flexability for launching than a launch pad. Here is an interesting question. Would it be possible to build a launch aircraft and have a two stage rocket launch from it. The booster stage would have some minimal flyback or glider capability. Enough of a capability that the launch aircraft could catch the booster and bring it back for a landing?

halman · Nov 17, 2006

BarryKirk, As I said earlier, I don't believe that we will see air launched heavy lift vehicles. There are two reasons for this. One is that the carrier wing size would be large enough that only very high launch rates would justify the expense. Conversely, the demand for heavy lift will peak at some point, and then diminish to nothing, as we establish ourselves off planet and begin manufacturing what we need there. Once the infrastructure is in place for mining the Moon, transfering material to orbital factories, and sending the finished goods to Earth, the Moon, Mars, or wherever, the flow of material will reverse, with more stuff coming down than going up. But there will always be demand for access to space to rotate personnel, and to ship advanced technology equipment, so, until the Space Elevator goes into operation, a highly evolved launch system will be used. This concept is not about increasing launch payloads, it is about making most launches simple and routine, which is the real key to bringing launch costs down. Step rockets are going to be around for a while, to provide the brute force needed to send excavating equipment, reactor parts, batteries, and other heavy materials into space. But getting people back and forth is never going to end, (I hope,) and doing that cheaply is essential. A carrier wing will lift a given amount of mass, be it a reusable space plane, or a booster and a satellite or space vehicle. But a payload heavy enough to require an additional booster would probably go on a HLLV, which is like a tractor-trailer rig, made for heavy hauling. My proposal is for a bus, to get people back and forth, as well as small payloads. We are about to see the first steps in this direction, when Bert Rutan's weird looking aircraft haul the Virgin Galactic tourist bus up to launch altitude. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

mikeemmert · Nov 18, 2006

Hi, BarryKirk; halman and I are off on different tracks, but I wonder what he thinks of the idea of incorporating a liquid oxygen generator aboard the launch plane? It utilizes one of the turbofan engines; a clutch disengages the fan part while the launch plane flies to the launch point, then re-engages for the zoom climb. The oxygen generator engine is also available for takeoff. Supercold nitrogen gas is also generated and is used to keep the hydrogen tanks cooler (I think hydrogen is the only fuel that will work for upper stages and is certainly the only fuel for a high-speed airbreathing or partially airbreathing booster stage). The ease and convenience of Single Stage To Orbit is probably a fantasy. Different engines and wings (or parachutes or helicopter blades) are needed for different altitudes. X-33 wasn't going to work. I think they should have replaced the composite fuel tank and flown it anyway, just to see how it would do.

halman · Nov 18, 2006

mikeemmert, Personally, I have no opinion regarding the use of an oxygen generator, but I have to wonder how fast the required amount of oxygen can be obtained. Ideally, a launch profile would allow about 1 hour from lift off to second stage launch, as this requires a climb rate of about 1,000 feet per minute. But that may be unrealistic for a vehicle the size that I imagine would be necessary, so it might take 2 hours. But I don't think that oxygen seperation and compression is an unworkable aspect to air launching, it just might require more generators. Hydrogen is the preferred fuel of upper stages, because it allows the highest IsP values, but it is not necessarily ideal. Storage requirements are extreme, both because of the volume of space required, and the temperatures involved. As motor technology matures, a less demanding fuel may be choosen, such as kerosene. Dealing with the carbon is one of the problems, but I believe that it can be solved. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

mrmorris · Nov 18, 2006

Many of the concepts mentioned in the past several posts are discussed in the PDF I added to this thread beck here. Mid-Air refueling: "Pioneer Rocketplane. Conceived in the late 1990’s and receiving $2 million in NASA funding, the Pioneer Pathfinder Rocketplane10 concept is a combined jet and rocket powered aircraft that was to be built using existing technology and off the shelf components. It would use its two turbofan engines for take-off, rendezvous, and refueling with a 747 aerial tanker where it would take on 130,000 lbs of LOX, effectively doubling its gross weight to 274,000 lbs." Airborne LOX generation: "Andrews Space Alchemist. Conceived in the late 1990’s and receiving over $3 million in NASA funding, the Andrews Space & Technology (AST) Alchemist TSTO RLV... the Alchemist takes off without any oxidizer on board. An on-board OX production plant makes over 900,000 lbs of LOX from the atmosphere..." ...and more. It's only 16 pages -- 6 of which are for their 'pet' concept, so you can learn all about a bunch of different air-launch concepts and the engineering behind them (and often the lack thereof) with about 10 pages of reading.

halman · Nov 20, 2006

mrmorris, Yes, I read that article, which I found interesting. I think that there is considerable interest in an alternative to vertical launching, but very little money has been spent on developing specialized carrier aircraft. With the exception of the White Knight, all the airborne launches that I am aware of have been done from conventional aircraft. While this is informative in terms of trajectory characteristics, it does not provide much of a picture of what would be possible using an aircraft designed specifically for the purpose of carrying another vehicle to altitude. As ScottB50 has repeatedly pointed out, airborne launches have been limited to rather small vehicles in comparison to the carrier aircraft. I believe that this is because of the drag and weight represented by the fuselage. Experimenting with lox generators and mid-air refueling should wait until we have established the viability of the carrier aircraft concept, I believe, so that we can determine if these steps are really required. I consider development of a flying wing with Boundry Layer Control, extensive flaps, and a heat resistant upper surface to be more critical, so that probing the trajectories possible by flying off the back of the carrier would be possible. This drastically alters the equation of airborne launching, as the second stage does not lose altitude while powering up, nor does it have to experience high g loading while doing so. I dearly wish that I could find the site where a drawing that was posted on a similar thread a couple of years ago came from. It was for a proposed Space Transportation System carrier wing and orbiter by Northrup, as I recall, but I have been unable to find it, and I lost my copy during a screw up while changing disk drives. It depicted a shuttle-type vehicle on the back of a flying wing with at least six engines. Perhaps I am mistaken, but I would think that designing a test vehicle with a capability of carrying <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

gunsandrockets · Nov 20, 2006

"t's only 16 pages -- 6 of which are for their 'pet' concept, so you can learn all about a bunch of different air-launch concepts and the engineering behind them (and often the lack thereof) with about 10 pages of reading." Lack therof being the key phrase. There was a definate agenda being pushed in that document against winged vehicles to the point of cooking the numbers presented. I read part of that document because I was curious what they had to say about the Kelly Space proposal for a tow-launched spaceplane. Some numbers they threw around in their criticism didn't sound right. A quick check shows they misrepresent some data, in point the X-15 mass fraction. The information I find for the X-15a shows an empty weight divided by gross weight anywhere from 39% to 42%. But their graph shows a much worse 55%. Plus they ignore the even more fuel laden X-15a2, because that data would hurt their case against winged vehicles even more.

mrmorris · Nov 20, 2006

"There was a definate agenda being pushed in that document against winged vehicles to the point of cooking the numbers presented." I mentioned that you have to take some of their points with a grain of salt because they're pushing their iwn agenda. However -- the paper did present some solid information about the various air launch concepts and what's been tried. The point I'm trying to push is that I keep seeing on this thread 'What about doing "X"' -- when that paper already has information about such a project. If someone on this thread is interested in onboard-LOX production, that paper mentions the 'Alchemist' project. The interested forum reader then should Google up some information about Alchemist project to see if they can find more information about said concept. I never take *any* one source as gospel. I tend to trust a few sites more than others. Astronautix is one, for example, because they don't really have any agenda to push -- but I'm well aware that Astronautix has inaccuracies in their data even so. I always recommend getting pulling data from multiple sources whenever possible.

holmec · Nov 22, 2006

Yeah, it would be a big airbreak, not to mention the lauching of the rocket it self will slow the 747 down a lot. So a big hole in the front I don't think is a real problem since from there your coming down. Anyway you could make doors for it . But with the launch of the rocket you want full thrust on your 747 engines because you really don't want to stall. So I think stalling a bigger potential problem than a gapping hole in the front of the plane. Now an easier solution than big doors for the front is to have small doors in the rear so air can come in and out thus reducing drag/suction when the rocket lauches. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

mrmorris · Nov 22, 2006

"So I think stalling a bigger potential problem than a gapping hole in the front of the plane." I find it difficult to conceive a bigger problem than turning your 747 into the biggest windsock in the world. But you go for it. Please be sure to record it thoroughly, I want to see the video.

holmec · Nov 22, 2006

"I find it difficult to conceive a bigger problem than turning your 747 into the biggest windsock in the world. But you go for it. Please be sure to record it thoroughly, I want to see the video." LOL ... too funny. I really was just thinking a probable way to make use of all these extra 747 that is being dumped by the airlines and convert some in to a rocket launcher, but the design of the 747 impedes a lot. So I came up with this forward lauching idea out of the fuselage. This gives the least amount of modification than a dropped rocket. But maybe a rear drop is better. But I think you would have to redesign the tail and reroute hydrolics. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

mikeemmert · Nov 22, 2006

I think you would need to remove the fuselage and redo the landing gear.

holmec · Nov 23, 2006

"I think you would need to remove the fuselage and redo the landing gear. " That is what I'm trying to avoid. If you do that you have massive structural changes that have to be tested. And not only that but you might end up with a very different wheel configuration that might limit you more on the number of runways you can use. Also you would have to relocate the fuel tanks. That's a mess in and of itself. Then with all these changes you have to spend more money on training the pilots. So you see to do all that you might as well not use a 747 in the first place. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

halman · Nov 24, 2006

holmec, These reasons and others are why I keep harping about an aircraft built specifically for air borne launching. We will gain little by using surplus aircraft, in my opinion. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

mikeemmert · Nov 24, 2006

I agree, halman. Brand new sheet of paper. I think, if you're going to launch conventional rockets from your launch plane, that you are being a little overly conservative. You have mentioned 100 ton rockets and an old metal C-5A can carry 122 tons.

mikeemmert · Nov 24, 2006

There's a difference, news; a 747 could backpack a Shuttle. But nobody's ever launched from a 747. VIRTUS was too expensive, yadhah yahdah because there happened to be an existing piece of equipment that could do the job just as well. My advocacy is to figure out how to do the things we can't do today, so that we will be able to do them tomorrow. Flying launchpads and airbreathing boosters are stalled because of a lack of imagination and the financial drain of a nonwinnable war. The country is approaching frozen stasis in several areas (biology, education, energy, lots of things) and I feel it's because of a lack of imagination and willpower. We can do better.

holmec · Nov 25, 2006

I absolutely agree. Composite specialized aircraft is the way to go. I also recently thought that they should be remotely controlled, so to save weight and fuel on less bodies, and also have a rocket and turbine engine combo. That way the mother ship could possibly work as a second stage. This may also serve as a platform for new developments in air breathing and non airbreathing combination engines. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

holmec · Nov 25, 2006

"Today, there is a new generation of engines for the Super-Jumbos like the A-380. Everything else is the same as it was then, and has the same problems." Don't forget composites. Today you can make a plane with just composites main parts...wing, fuselage..etc. Back then the technology my have existed in some form but now its becoming mainstream. I'm sure the cost of composites have come down since then as well. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

holmec · Nov 25, 2006

Enterprise was the only thing that launched from a 747. So it is possible. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

halman · Nov 25, 2006

mikemmert, The Russians already have a design for an aircraft to lift a conventional rocket to altitude. It was posted earlier. Molniya-1000 Heracles This vehicle could probably haul something much heavier than 100 tons to launch altitude. But, again, we are looking at a drop launch, which imposes severe penalties. Flying off the back of the carrier wing provides the optimum performance, I believe. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

halman · Nov 25, 2006

holmec, I has occurred to me that many of you probably think that I am advocating building a huge wing and an orbiter to launch from it, as soon as possible. Well, sure, why not? But seeing as the technology of airbourne lunching will have to be demonstrated and proven, small steps will have to be taken at first. So, an orbiter with a self-contained fuel supply which weighs in at 60 metric tons, built using composite technology, might conceivably be able to reach orbit with a crew of three and four passengers, or one metric ton of payload, if launched at 12,000 meters. But it would launch from the back of the wing, to avoid losing altitude, having started its engines while still mated to the wing. The wing would be about 50 meters wide, and about 15 meters long at the center. Probably 4 turbofan engines would be enough to power it, although using a 4 kilometer long catapult would ensure the vehicle getting airborne well above stall speed. This design can be enlarged as a system, if reliability and efficiency are demonstrated. Now that the B-2 has demolished the myths about the flying wing being inherently unstable, by using computers to monitor the airflow over the wing, it is possible to avoid the drag and weight of a large fuselage, as well as the problem of the tail surfaces being in the path of the rocket exhaust. The wing can pitch up for separation, as opposed to diving, as the 747 had to do when launching Atlantis, as I recall. So, we build a wing, test it, then build an orbiter, drop test it, then go sub-orbital, if desired, and then all the way to orbit. No huge commitment of capitol all at once, we can take our time, build the wing, then the catapult, and then mothball them until the orbiter is ready. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

holmec · Nov 26, 2006

Cool, but, Put a rocket on the wing and have it light up and take the space craft ballistic then unhook and have the space craft start its rocket and go into orbit. I think that would be the groundbreaking part. Because we have never done that, and it seems reasonable to separate while going ballistic (like normal rockets). The problem would be getting high enough to reduce the air pressure on the mother ship while going ballistic, and constructing the mother ship in a way that it won't tear apart with the increased speed. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

rocketman5000 · Nov 26, 2006

Stability at high altitude would be an issue that would have to be worked out. Wouldn't want the aircraft to go into an unrecoverable spin like the one that almost killed Yeager

halman · Nov 27, 2006

holmec, The way that I understand all of this, the benefits of trying to get the carrier aircraft to reach supersonic speeds are very marginal, while the costs are very high. Again, this is all about the simplest way to reach orbit, not about enhancing payloads. The carrier wing should be designed to haul an orbiter up to an altitude where the orbiter can accelerate at full throttle, at a low angle. This allows for most of the propellant to be used in gaining velocity, not fighting gravity and air resistance. The orbiter is the only vehicle that needs to go really fast, so souping up the wing with additional motors will not result in much improvements in the overall performance of the system. And the only real reason to develop a system such as this is to get away from vertical launches, which are extremely expensive, require tremendous precision in timing, and incur penalties due to fixed launch location. The system that I envision is what I believe will be the most efficient method of putting routine payloads and crews in orbit. The heavy stuff will still fly on a step rocket, because there is almost certainly not going to be enough demand to warrant building a horizontal take off heavy lift launch vehicle. I keep coming back to the vision of an orbiter accelerating at 2 or more gravities, while its nose is aimed a few degrees above the horizon, having reached this point without burning any of its fuel. If there were no atmosphere, or if we were launching a rocket on the Moon, we would probably not launch vertically, but at a low angle to the horizon. Of course, most rockets will have to land vertically, so they will take off that way. But to launch a rocket for the first time, we don't want to send it straight up, we want to get it moving around the planet. Instead of fighting the atmosphere where it is the densest, we can utilize it to provide lift, as well as oxidizer, by using plain old turbofans and a wing. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

vulture2 · Aug 13, 2007

>>Of course, you could probably get a similar effect of an air launch by adding a couple of SRB's to your core liquid first stage. And it might be cheaper to do that. Even the small nonsteerable SRBs used on the EELVs cost $1 million apiece. That would buy a lot of flying hours.

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