VTVL Airlaunched

guest blogger john hare

I had an interesting conversation with Jon last month about the problems with air launching rocket ships. The various flavors of air launch involve some form of altitude and velocity loss as the rocket ship drops away from the mother ship before it can light it’s engines. In most cases, it also requires wings and other aero surfaces to correct the flight path to the desired vertical. These aero surfaces are not only dead weight from Jon’s point of view, they also induce airframe stresses on the rocket ship that it really doesn’t need.

The most important things for air launch are altitude, attitude, and airspeed, in about that order of importance. A conventional air launch seems to compromise somewhat on all three. Another point Jon didn’t care for is that the rocket cannot light it’s engines until well clear of the mother ship. Ignition or other engine related failure could easily result in loss of vehicle instead of an abort and return to base to examine the problem.

In my opinion, which is not shared by many that I am aware of, the White Knight series are perhaps the best high altitude airplanes in the world by the best designer in the world, but isn’t the optimum mother ship for space craft. The space craft they carry suffer from all the problems mentioned above, with only some mitigation by launching from extreme altitude.

I believe that the best mother ship is one that works for the requirements of the rocket vehicle. The rocket should be able to light the engines and confirm a healthy burn before separation. The release attitude should be such that the rocket ship is vertical or nearly so and doesn’t need any aero surfaces or the loads they impose. And it needs to release from the highest altitude possible at the highest airspeed possible.

I suggest that conventional air launches have been done backwards. The rocket should be lit before separation, and separate from the top of the vehicle at both high subsonic speed, and high altitude. Most of this can be accomplished with a change in operational technique rather than building a brand new super duper mother ship.

Airlaunch

The rocket ship is mounted centerline bottom of an aircraft. At 25,000 feet or so, the mother ship has reached maximum altitude at the loaded condition of full tanks and rocket ship payload. The rockets ignite and feed from tanks on board the mother ship as the two vehicles accelerate and begin to climb. By 30,000 to 40,000 feet, the vehicles begin to roll inverted as you would see in a Shuttle launch. At 50,000 feet, the pair is climbing at 70 degrees and high subsonic airspeed. Then the mother ship lights some RATO type rocket engines and the rocket ship throttles back so that they are accelerating at the same rate as they separate. The switch to internal fuel supply for the rocket ship is confirmed stable at separation. With both vehicles accelerating at the same rate, they fly apart in parallel formation so that neither exhaust impinges the other. The rocket ship rolls from a 70 degree climb to vertical while the mother ship rolls from a 70 degree climb to the horizontal.

When sufficiently clear, the rocket ship  throttles back up for the climb with full tanks and 250+ meters per second velocity at extreme (for aircraft) altitudes. The mother ship reaches horizontal at nearly ‘coffin corner’ altitude for a clean ship with low fuel and no load. Coffin corner is the term I believe applies to an altitude where the  aircraft can’t go faster for engine or airframe reasons, and can’t go slower without stalling and falling out of control with a strong possibility of no recovery.

I believe this method would impart considerably improved performance to a rocket ship compared to the conventional approach. It would not require the rocket ship to have aero surfaces.(VTVL friendly) It would allow abort to base in case of rocket engine problems. It would not require developing the best high altitude aircraft in the world.

The following two tabs change content below.
johnhare

johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
johnhare

Latest posts by johnhare (see all)

This entry was posted in Uncategorized. Bookmark the permalink.

46 Responses to VTVL Airlaunched

  1. John,
    This is somewhat close to what I’ve been thinking. A quick clarification though (I think you’re understanding it right, but your description is semi-ambiguous):

    1-It isn’t “attitude” per se that you care about, but “flight path angle”. Flight path angle is the angle from the horizontal to the *velocity vector*, whereas attitude could just be which way the nose is pointing.
    2-Ideally the flight path angle at separation isn’t purely vertical or purely horizontal. I’m not positive about this (Kirk’s the air launch trajectory guru on the blog), but I think what you want is the flight path angle you would’ve gotten had you ground launched and built up to that speed and altitude. Basically somewhere into the gravity turn portion of the flight. My gut feeling says something in the 30-50 degrees range.
    3-Ideally your attitude and flight path angle at separation would be really close to or identical to each other.

    Not sure if the inversion is necessary or not. It would be interesting to simulate and see which is better. I don’t have really good intuition for how wingy things work…

    ~Jon

  2. johnhare john hare says:

    The relatively shallow angle would certainly be easier and safer for the aircraft. I was fixated on an up and down suborbital flight when I wrote that which would be a much higher flight angle.

  3. A_M_Swallow says:

    Do any precautions need taking to ensure that the rocket exhausts do not damage the other vehicle?

  4. johnhare john hare says:

    Many precautions. What I described could only happen after a considerable testing phase. Some thermal protection might be required on the aft section of the mother ship. The effects of the rocket plume on the mother ship flight controls will need considerable attention. The release mechanism with two vehicles thrusting at high subsonic speeds will be critical. And so on. This post is a potential lead on substantial improvement, not a blueprint for action.

  5. What would you simulate something like this in?

  6. One thing worth remembering, is that there is experience with launching rocket like things off of wingy things… People have been doing it for at least 50 years… Recently even off of carbon fiber wingy things. Some of the peopled variety and some of the unpeopled variety. There may be scaling issues, but it’s not entirely unknown territory.

    ~Jon

  7. C Garner says:

    Since we’re going to need a rocket(s) on the mothership anyway, leave the RATOs alone, and use a proper, throttle-able rocket in the tail. Modifying an existing airframe to do the job probably isn’t going to happen, I don’t think using a WK2 would be wise given the considerably different profile we’re flying (besides the difficulty of ‘where do we put the rockets?’ I wouldn’t like the idea of offsetting them from the centerline too far!). So assume a purpose-built machine, probably not as efficient as a WK2, but we can trade off on that for the benefits of optimal launch speeds and angles.

    As before, fly up to a suitable ignition altitude, then light the rocket on the mothership and spacecraft. The mothership’s motor could perhaps throttle to minimize the load on the pylon. Since we have a clean-sheet design, we’ve probably dealt with the issue of rocket exhausts. Alternatively, we could extend the pylon, placing the spacecraft further away from the mothership; this would also help with the pitch-up.
    As the pair accelerates, they pitch up, converting horizontal velocity to vertical velocity. Once the desired launch angle is reached, the craft separate. Now the spacecraft is developing little or no lift, but the mothership is still developing lots of lift. As well as this, the pair are still pitching up as separation occurs, so they naturally ‘fly apart’, in much the same way as fighter-bombers ‘toss’ bombs towards a target. So separation is no issue.
    The spacecraft continues on it’s own trajectory now, but the mothership continues pitching over onto it’s back, probably with some thrust still coming from the rocket (to avoid slowing down and stalling over the top in the thin air). Once level, it rolls back upright, shuts down the rocket, and returns to base.

    This should provide good flexibility of launch angle, launch speed (by using an appropriate pitch rate), and makes separation a non-issue.

    But then I’m just a pilot, not an engineer…

  8. Chris (Robotbeat) says:

    My idea would be a carrier that is essentially all jet engine (perhaps even augmented with LOX a bit)… It takes off vertically, reaches maybe close to Mach 1 (actually could be Mach 2), then ignites/releases (or releases/ignites) the upperstage at very high altitude so you can effectively use a vacuum-optimized nozzle. The carrier then lands, either horizontally or vertically. This would be like an unmanned air-breathing first stage, not really a proper airplane.

  9. jsuros says:

    Not liking the need for TPS on the mothership. How about separating mothership and rocket using a tow rope before lighting the rocket engines? Maybe you could put “aero surfaces” on the mothership side of the tow rope connector that stay with the mothership after separation.

  10. Brad says:

    Perhaps a technique similar to nuclear bomb delivery, “toss bombing”, would be best.

    http://www.statemaster.com/encyclopedia/Toss-bombing

    Instead of complicated propellant storage on the carrier aircraft and airframe modifications to absorb rocket thrust, release the rocket before ignition. The aircraft climbs steeply trading airspeed for altitude and releases the rocket in a near vertical attitude. The aircraft completes the half-loop after releasing the rocket to gain separation before the rocket ignites.

  11. Pete says:

    Conventional aircraft are not necessarily the best match for air launch. They have a high upfront cost, require very high flight rates, are not high rocket “accident” rate compatible, have limited and constrained payloads, and are, well, aircraft (not rockets). How far could Masten or XCOR have got for the cost of a Whiteknight?

    I have also got the impression that going supersonic with a carrier aircraft gets very expensive, so if one is going to make a rocket carrier aircraft, probably best to go the whole hog and make a full stage out of it. Interestingly in this scenario, horizontal takeoff only needs about half the rocket engine thrust of vertical takeoff, this may be a significant cost saving. An idea here is that the carrier aircraft might be a simple and otherwise unpowered glide back fuel tank, using the upper stage rocket engine from takeoff.

    The proportion of funding that is spent on a carrier aircraft should perhaps correlate somewhat with how much it would otherwise cost to provide that proportion of effective delta v with extra rocket. So for an orbital vehicle maybe one could perhaps justify spending 5-10% of the budget on the carrier vehicle :-). Designing a carrier aircraft within such constraints sounds like a fun challenge. In support of air launch I would note that we tend to use aircraft not rockets to get to 40.000 ft – for that section of the journey they cost less, but this generally assumes high flight rates.

  12. johnhare john hare says:

    C Garner,
    That might be a safer, more comfortable profile to fly. Either way, keeping the vehicles out of each other’s exhaust/wake turbulance without excessive manuevering at high altitude is a good thing.

    Jsuros and Brad,
    The benifits of good health monitoring before release allows abort to base. Relasing the rocket before ignition is a potential loss of vehicle situation if the rocket ship has any problems after separation.

    Chris,
    I think something like this might come later. At this time, I am thinking in terms of getting high aircraft performance launch out of surplus conventional aircraft with some mods.

    Pete,
    This would assume a conventional aircraft with minimal modifications to allow it to fly the different profile. I think a supersonic carrier with rockets is a good idea for later on. The late 1990s concepts by Len Cormier were very good.

  13. Tim says:

    Going completely vertical reminded me of the Pop-up TSTO that Jon mentioned in the Orbital Access Methodologies post. Apparently the first stage of a pop-up vehicle is mass insensitive, so I have to wonder whether you could get away with adding lifting surfaces and airbreathing engine to a conventional first stage to create something in between a carrier aircraft and a proper stage. Am I right in thinking that if the rocket is going straight up, no lift is required, which means you can fly at an attitude that minimises drag and therfore airframe stress, allowing you to push a lighter vehicle faster?
    Rolling a conventional aircraft with a bottom mounted rocket is mentioned in the paper referenced here
    http://selenianboondocks.com/2008/09/air-launch-paper/

  14. MG says:

    Conceptually, this proposal reminds me of the Gryphon:

    http://www.andrews-space.com/content-main.php?subsection=MTA4

    In flight propellant transfer
    High gamma release

    with the added innovation of in-flight LOX production.

  15. John Hare is right. I’ve been arguing for starting the rocket engines before separation for years. If you use LH2/LOX propellant and a regeneratively-cooled engine, the plume is transparent and won’t radiatively heat the airplane significantly. Flight-path angle is a metric of surpassing value in air-launch and I have simulated the performance of many air-launched trajectories to verify this. Igniting the rocket engines before separation solves SO MANY of the problems of both the rocket and the carrier aircraft.

  16. Roderick Reilly says:

    Sounds too complicated. That’s my instinctive reaction. Too many things that can go wrong in the process.

    It’s n ot the basic concept, but the complex fueling and rolling, igniting and throttling and stuff.

    But then, I are not a rokkit sinetist.

  17. Bob Steinke says:

    Great idea overall.

    Rather than “altitude, flight path angle, airspeed” I would state the priority order as “vertical velocity, altitude, horizontal velocity”. From the crude simulations I’ve done I would rather start at 25,000 ft (7600 meters) altitude going straight up at 250 m/s vertical velocity (which I think military aircraft should be able to do with afterburners on) than start at 50,000 ft (15,200 meters) going horizontal.

    On another point, I think one of the biggest advantages of air launch is not to have to build a dedicated vehicle form scratch, and to be able to fly it under normal FAA certification when it’s not launching rockets. So I would scrap the RATO, start the rocket at idle, or throttled down, and launch from an altitude where the airplane has enough thrust to match the rocket’s acceleration with it’s jets alone. I would also scrap the cross feed and accept that some of the rocket’s propellant is going to be used up for the separation manuver. I really do like igniting the rocket before separation form an operations standpoint.

  18. Pete says:

    Building aircraft is hard, building rockets is hard, building aircraft and rockets both at once is really hard. There is a suspect a lot to be said for limiting a development program to the minimum number of core competencies possible.

    I have spent some time looking at the air launch design space and it always seemed to converge on something simple and subsonic that primarily gives one launch freedom (the very significant non direct delta v benefits like lower range costs, incremental testing, better aborts, non atmospheric compensating engines, etc), or a full minimalistic fly back rocket booster stage. Designs in the middle always seemed to converge to one of those two extremes.

    Of late I have come around to the following type of air launch platform (all electric multi prop helicopter platform):
    http://vimeo.com/6194911
    Much cheaper to develop and operate than a WhiteKnight, scales better and much more rocket vehicle compatible (it does not burn capital when not continuously flying) – generally a much better test platform. It is an inexpensive way to divide and conquer the launch problem into largely ideal atmospheric and exo-atmospheric stages, making each stage much simpler. I would also favor this as a capsule landing system – I suspect well worth the perhaps slightly higher mass penalty. If only this stuff was available in the days of Roton…

  19. Charles Grimm says:

    In order to get the largest mass rocket off the ground, consider in flight refueling. If there is a cross feed, then send up the carrier aircraft with minimum fuel, and tank for its fuel, or the rocket’s fuel. The carrier aircraft is light on takeoff to haul the rocket from 0-200 mph and get airborn, while airborne and generaring lots of lift, it can “mass up” with fuel for itself and/or the rocket. Even if there’s no crossfeed, however many tons of fuel are needed for the duration of the flight can be used as liftoff mass instead.
    Charles Grimm

  20. Tom D says:

    I agree with Pete. Building both a carrier aircraft and a rocket at the same time is hard (i.e. expensive). What can we do with what is already available?

    Len Cormier studied the trade spaces for quite a few variations on air launching to orbit over the years. Everything from dropping from a converted bomber to a rocket powered kite launcher. I saw one of his presentations at a Space Access Conference a few years ago. I wonder if any of that stuff is archived anywhere?

    His main conclusions seemed to be that launching your vehicle from an airplane or kite of some kind makes SSTO much more doable, but still not easy. He felt that developing a special purpose launcher aircraft should be avoided if you can to keep initial development costs down. Obviously Scaled Composites/Virgin Galactic felt otherwise, but I was pretty disappointed at how small their White Knight II aircraft is.

    Orbital Sciences converted a used L-1011 jumbo jet into a launcher for their Pegasus launch vehicle. The L-1011 worked out very well since its “dual-keel” design allowed them to put a slot in the airliner for the Pegasus’ tail fin. The only problem with this launch scheme is that it limits the size of the launch vehicle to something that can fit under the L-1011. On the plus side dropping the Pegasus avoids the problem of roasting your carrier aircraft. Could a liquid-fueled SSTO be developed to fit under the L-1011? The Pegasus can put 500 kg into LEO. What could a liquid-fueled SSTO do?

  21. Pete says:

    Had to resort to the way back machine:
    http://web.archive.org/web/20061205044524/http://tour2space.com/

    Modifying existing aircraft, and re-certifying them is incredibly expensive and usually results in a severely compromised rocket designs. The last thing one needs is the carrier aircraft adding yet further constraints to a difficult rocket design. T-Space was I thought a very good attempt at using an exiting aircraft, large aircraft need to be operating 24/7 to pay for themselves, so a carrier aircraft kind of needs to be able to slot into that.

    Len ultimately went full circle and came back to a full HTHL TSTO system. Something like what the shuttle nearly ended up being. There is a lot to be said for such a design.

  22. Jim Howard says:

    Was not the Shuttle originally intended to be launched off the top of a reusable rocket plane, in a very similar manner to that proposed here?

  23. Paul Breed says:

    Wouldn’t a rocket engine on the plane be simpler than high speed fuel transfer to the upper stage/rocket? Let the plane do most of the pushing and only light the vehicle rocket late in the process, before release, but not as the first thing either.

    The B-58 would go mach 2 and climb to 63K ft with 20K lbs of load.
    Seems like the idea airframe for this, its supersonic so coffin corner.
    constraints are relaxed. The rarer XB-70 would be even better. If you look at the wiki article for the XB-70 it originally had the concept of subsonic tankage that “flew” away before the supersonic p3enitration portion of the flight.

  24. johnhare john hare says:

    Rockets on the carrier would probably be simpler. I was thinking about air turborockets at some point. I think supersonic release will happen eventually. I think it is a financial bridge too far at this time. I think mach3 at 100,000 plus feet is a good eventual target for an assisted SSTO. For the near term though, I think a subsonic air launched TSTO is a more financially feasible goal.

  25. C Garner says:

    For subsonic launch, you’re going to be reasonably constrained to lower-altitude launch if you intend to impart any significant vertical speed to the rocket. Once you start getting up around 50,000ft or more, Mach 1 isn’t much over 200kts indicated, less as you go higher.
    Near term I wouldn’t expect any serious supersonic launches as that complicates things a lot more (read $$$).
    If you are willing to launch at supersonic speed, then the next ‘barrier’ is probably mothership ‘re-entry’ and the line beyond which you need TPS, which again pushes up cost and complexity. You’re probably past that line if you’re at Mach 3 and 100,000ft.

  26. Pete says:

    Subsonic air launch is not necessarily a bad thing, most of the advantage of air launch comes from avoiding the extremely high costs of launching from the ground and having to design a compromised dual mode rocket vehicle that can operate both within and without the atmosphere. If the objective is pure delta v, then use a rocket, it is what they are good at. Airplanes do not make for good rockets.

    I would also note that current launch vehicles use a rocket to get off the pad – because it is the cheapest way of doing it (within that context). Point being, for air launch to add up, that context would have to somehow change (breakthrough air launch technology, very high flight rates, etc).

    The rocket equation makes for a good start, but the economic equation makes for a better finish. 🙂

  27. Mike Lorrey says:

    Note there was a proposal in the 80’s for an air launched minishuttle which would launch from the back of a 747. The 747 would have an SSME in its tail that would be used to put the mothership into a zoom climb for LV separation, or alternatively would have had afterburners on the turbofan engines. Ah here it is: the Air Launched Sortie Vehicle:

    http://www.thespacereview.com/article/1580/1

    There was an article on this in AWST back in the day that showed the tank config slightly different, more in line with the teardrop shape that was planned for the Soviet equivalent project.

    I agree regarding lighting the candle before separation. Military pilots have been launching missles from their planes for decades. The separation issue is IMHO something imposed by insurance providers to manage risk, something the air force doesn’t have to deal with. You would think given the long experience launching missiles from rails on aircraft that the risk managers would consider that ignition while attached is demonstrably safer.

    Particularly with regard to space launch, consider the ASAT missle launched from an F-15. The F-15 flew just this sort of flight profile: zoom climb, trajectory acquisition, launch from the rail. As I understand it, there are Russian or Ukrainian efforts to create a space launch system using a Mig-31 or 35 flying a similar profile that would compete against Falcon 1 for customers in the lower mass range..

  28. Mike Lorrey says:

    Here’s the version with the SSME on the 747 and the teardrop tank:

    http://www.pmview.com/spaceodysseytwo/spacelvs/sld053.htm

  29. Mike Lorrey says:

    C Garner,
    How is a TPS necessary at mach 3 and 100kft beyond merely using materials that need to withstand the pressures of that speed anyways?
    The “thermal thicket” really doesn’t get to be a serious problem until you get to the mach 7-10 range. Anything less than that can be reasonably dealt with.

  30. Paul Breed says:

    >How is a TPS necessary at mach 3 and 100kft
    The max speed of the Concorde was about Mach 2,
    Faster and it would melt. So with “Traditional” aerospace materials and no TPS mach 2 is about the limit. If you now go to hot structures and the like you are no longer traditional.

  31. C Garner says:

    Mike: My thinking was in a similar vein to what Paul mentioned, plus I assumed you are on a trajectory similar to what was discussed in the initial post, ie you’re going uphill really fast when you launch at Mach 3 and 100k ft. So by the time you start coming down, you’re going to be REALLY high, and will probably be coming back down rather steeply and quickly indeed.
    If your craft is ‘fluffy’ enough, SS1 style, it may not be a problem.

  32. Mike Lorrey says:

    Um, I’ve worked on USAF aircraft using “traditional’ aerospace materials (F-15, F-111, some others ‘cough’), don’t try to pull that wool over on me. While the official top speed for the F-15 was Mach 2.5, I can say for a fact that I’ve witnessed them returning from flights on multiple occasions with the mach meters pegged over mach 3. Significantly over.

  33. Mike Lorrey says:

    Speed tolerance with aircraft and materials is highly subjective relative to altitude and time exposed…. Note, for instance, the FIRST project, a rogallo wing, inflated spar, made from steel wire cloth impregnated with silicone. Yeah, ‘fluffiness’ is very important.

    That said, titanium skin and frame with SHARP leading edge and nose cone materials allows for mach 7 flight at 100k ft.

    Or weren’t you counting titanium as a traditional aerospace material? (and SHARP has been in use since the early 70’s in some ‘cough’ aerospace applications, so thats a pretty good tradition too)

  34. C Garner says:

    “I’ve witnessed them returning from flights on multiple occasions with the mach meters pegged over mach 3. Significantly over.”
    I have not heard this before, but it does not surprise me! I know ex-A-4 pilots who flew them beyond Mach-1 on occasion. Getting certified to do this regularly on a commercial operation is another matter, perhaps!

    I wasn’t considering titanium; I would consider that a material for thermal resistance if not thermal protection. It’s use would drive up costs significantly anyway, wouldn’t it? (compared with say, aluminium or conventional composites) No doubt it could be used, if the cost wasn’t a concern.

  35. johnhare john hare says:

    Of course, cost should always be a concern. I really like Pete’s line.

    The rocket equation makes for a good start, but the economic equation makes for a better finish.

  36. jv says:

    What would be the required range of the carrier aircraft to be able to launch to the space station every day of the year?

  37. Pete says:

    Quick in the head estimate, I think the orbital track should only miss by a few hundred mile on average once a day, depending. Not that this would have to all be mitigated by the carrier aircraft.

    If launching to an equatorial space station, it could potentially do so every say three hours from one launch site without any range.

  38. Mike Lorrey says:

    C Garner


    Mike said:
    “I’ve witnessed them returning from flights on multiple occasions with the mach meters pegged over mach 3. Significantly over.”

    I have not heard this before, but it does not surprise me! I know ex-A-4 pilots who flew them beyond Mach-1 on occasion. Getting certified to do this regularly on a commercial operation is another matter, perhaps!

    I wasn’t considering titanium; I would consider that a material for thermal resistance if not thermal protection. It’s use would drive up costs significantly anyway, wouldn’t it? (compared with say, aluminium or conventional composites) No doubt it could be used, if the cost wasn’t a concern.”

    Titanium isn’t that expensive a material. Especially not today. My father, before he retired, was an engineer at Sturm Ruger, who, in addition to firearms, made Calloway’s Big Bertha golf club heads, in investment cast titanium. Smith & Wesson and Taurus both make pistol frames from titanium in a few models. Theres plenty of consumer products that use the metal today, from watches to golf clubs and beyond. The Russians in particular have some serious expertise in manufacturing with it. Once the cold war ended the cost of titanium material and knowledge about its manufacture dropped in cost in the west significantly.

    You do have to know how to machine it, tooling for that can be a little more expensive, but really, the cost of materials and mill bits is hardly a percent of a percent in the grand scheme of a development project. Personally in my experience, composites are the expensive items.

  39. Godzilla says:

    IIRC the F-15 ASAT was launched from a high angle as well. Like 65 degrees. However the second stage rocket ignited after being dropped. Probably not a good idea to ignite a solid while it is still attached to the carrier aircraft. Ahem. I suspect the stresses on the airframe (or even worse, the pilot) would be too great.

    The Mig-25 also reached Mach 3 and IIRC it did not use a lot of titanium. They used nickel steel instead. Heavier but cheaper. Nickel alloys are used in turbine blades so they can withstand a lot of heat. However going at that speed destroyed the engines. SR-71 had a hybrid turbojet/ramjet, not a turbojet.

    It is a shame they destroyed the tooling for the SR-71. Perhaps we would have less sedate fighter planes now. There was a kind of regression on fighter speed since then, although thrust-to-weight ratios in jet engines got so much better.

  40. johnhare john hare says:

    I’ve been thinking about doing a post on an air launched two stage concept. Fly north or south out of Hawaii to get the right launch inclination for the first rocket stage to land in Mojave with the upper going to the right orbit with minimal plane change losses. For various high inclination launches, fly east or west out of Hawaii and recover at Kodiak. If the first stage can land well down range and be flown back with minimal hassle, then the attractions of supersonic air launch fade fairly rapidly.

  41. Randy Campbell says:

    As an FYI as someone with 15+ years experiance with Air Force aircraft missiles a few things:
    Unlike you see in a lot of animations and drawings/art the missiles on an aircraft don’t normally “drop-the-fire” the exception being some of the larger missiles such as the Phoenix, ASAT, LGM-30 etc.
    The majority of relativly smaller missiles (AGM-65, AMRAAM, AIM-9X, etc) all fire thier motors while attached to an aircraft launch rail and THEN accelerate away from the aircraft.

    The larger missiles have more powerful rocket engines and therefore larger and hotter exhaust plumes that do “BAD” things to rather sensistive things like aircraft skin panels.

    Some of the earlier aircraft missile systems, (Genie, FALCON, and RASCAL come to mind) where launched using an extending rail system to place the missile at a slight distance from the aircraft to lessen the exhausts plume effects while still retainaing “positive” launch control of the missile during firing.
    It should be noted that for a NON-COMBAT airframe you can add such things as spray-on ablative to ward off damage but you still want at least SOME distance between the airframes when the rockets light because of the interactions between the airframe slipstreams and the exhaust plume can have the hot exhaust following the slipsteam in some weird directions.
    (This is a major reason you can’t ‘fire-up’ a rocket INSIDE an airframe like a C-141/5/17 because the slipstream around the open cargo bay tends to funnle the exhaust into a nice recirculation plume back into the cargo bay :::bleH:::)

    The current “lanyard-and-trapeze” system of the AirLaunch/T-Space paper on choosing a carrier aircraft seems about the best system since it reveals how modifications to the 747-200 carrier aircraft are very similar to those need for conversion to an airial fire-tanker leading to a possilbe “triple-income” between launches with using the carreir aircraft as a fire-tanker, air freighter or launch carrier.

    I should mention that both Glenn Olson and Dani Eder both proposed using a jet-powered VTVL (Olson) and jet-launch-assist (Eder) to enhance the abilitiys of launch vehicles. AS soon as I can unearth my information on the concepts I’ll post the summeries here.

    Randy

  42. Redchrome says:

    The concept reminds me of a sci-fi story I read once, written in the very early 50s. The story was about the pilot of a toroidal rocketship that carried the actual space vehicle inside the ‘hole’ in the center. The downside of this design of course is that you need a large number of engines on the toroidal ship; and thrust needs to be balanced across them. Not sure how practical it is; but it’s definitely been considered for a long time.

  43. Doug Gard says:

    Subsonic horizontal drop seemed to work well for a lifting body like the X-15. Given the number of successful drops to failures I do not see an issue all methods have potential failure modes.

    Non-lifting bodies would be better launched more vertical if the second stage is fully fueled. Given the higher vehicle density the momentum force alone will help compensate for a 3-5 seconds of unpowered flight I do not see a major performance loss concern which would justify the risk of igniting the second while still attached to the booster.

    Speaking of boosters the T-38 Talon modified (like the N-205) with a 30K pound thrust throttle-able TVG RT-30 rocket (replacing the three AR4 motors originally purposed) would get-er-done low cost and minimal development. Fly back booster ready made.
    N-205 : “Space trainer” variant proposed in May 1958, with triple rocket engines for vertical launch. Capable of Mach 3.2 on its way to an altitude of 200,000 feet .

  44. johnhare johnhare says:

    Not much performance loss from lighting the stage after the drop, but a massive reliability loss from dropping a stage before ignition. Check out the various comments on this issue.

  45. Pingback: Boomerang Air-Launched TSTO RLV Concept (Part I) | Selenian Boondocks

Leave a Reply

Your email address will not be published. Required fields are marked *