X-51 Status Update

1. The principal application appears to be for higher-speed cruise missiles.

2. This is a incremental development of hypersonic propulsion, stability and flight dynamics. Its predecessor X-43 had issues with separation as well, but was able to use a simpler but short term fuel.

   By using dense hydrocarbon fuel, greater speed / range / duration may result.

   Next, you’d like a means to accelerate to hypersonic combustion speed without abandoning the vehicle.
   The uses of this technology could be hypersonic cruise missiles (easiest), fast deploy strike teams vehicles, … and fully reusable boosters.

   add:
   … practical use if you want to STAY in the atmosphere ..
   … til Mach 10-12 at 140-160,000ft using NO oxider tank, higher energy density propellant, acceptable gravity losses on second stage given HIGHER expansion nozzle for ALTITUDE. Duh – different scheme entirely for responsive launch.

   1. For “fully reusable boosters”? – Hardly. This kind of propulsion is only of practical use if you want to STAY in the atmosphere. For any kind of practical orbital delivery system (booster, SSTO, or inbetween), you want to get out  of the thick atmospheric soup as quickly as possible – not waste propellant staying in it.

      1. B52 \ X-15

         L-1011 \ Pegasus

         WhiteKnight \ SpaceShipOne

         WhiteKnightTwo \ SpaceShipTwo

         Stratolaunch \ Falcon 9 derivitive

         These are (were, or will be) viable space launch systems for their particular purpose.

         It seems that being in the atmosphere is okay during the phase while you are utilizing air-breathing engines and lift. The time when you want to “get out of the thick atmospheric soup as quickly as possible” is after you light the rockets.

         1. You probably want to get out of the atmosphere when you’re going as fast as your design lets you in the atmosphere. When either friction prevents acceleration or heating would start to destroy the vehicle. The longer you can use oxygen out of the atmosphere, the less you have to carry with you.

         2. Of that list of carrier aircraft/rocket combinations, only the Pegasus has gone into orbit.  The others are all suborbital.
            And once the Pegasus is released from the carrier, it gets out of the atmosphere is quickly as possible.

            1. “And once the Pegasus is released from the carrier, it gets out of the atmosphere is quickly as possible.”

               I guess you’re saying you agree with me?

               Although actually Pegasus doesn’t get out the atmosphere as absolutely fast as possible, it has some small wings to generate some lift on its way up which means that it takes a little longer to get out the atmosphere than it would otherwise, but I’m guessing not much longer.

               “The others are all suborbital.”

               Stratolaunch will be an orbital delivery system.

   2. It’s ultimately a matter of cost. Hypersonic airbreathers for launch system first stage have to be compared directly with rocket-propelled reusable VTOVL (SpaceX concept) and reusable VTOHL (DOD winged Reusable booster stage concept) which have a similar role, although flight profile and staging altitude may be different. For conventional lauch aircraft like the WK2 costs are reasonably well understood. Foy hypersonic launch aircraft the complexity of the engine (including starting at zero airspeed) and the losses in efficiency one encounters at very high speeds due to compression heating and similar effects have to be balanced against the mass of the oxydizer. Propellant grade LOX at LC-39 costs only 65 cents a gallon.

   3. What separation issues did X-43 have? The first X-43 launch failed due to the Pegasus rocket having to be flight terminated when it went out of control…the other flights were flawless.

      1. The first X-43 launch failed due to the Pegasus rocket having to be flight terminated when it went out of control.
         Due to a bending moment on the stack.

         Suggest you read some of the papers on it.

         Start with:
         http://hapb-www.larc.nasa.g…

         1. No need to read what I already know.  The separation sequence of X-43 worked cleanly…even in the FTS event, the X-43 separated and continued to send data to impact.

            1.  The first one didn’t.

3. I would rather we have a hypersonic cruise missile than any potential opponent. However, the big application may still be space launch, since, even during a war, unlike artillery shells, you do not normally launch cruise missiles on an hourly basis. Production could not keep up! There are a number of technologies, which when combined, may give us a truely efficient and re-usable airbreathing launcher.  Good luck to the X-51 team.

   1. Only the US will dare this. SCRAM has been around since the 60’s. Its hard and costly as this illustrates.

      1. Mr. C.,

         I’m still thinking that if we finally get it right, the cost aspect will reverse and this will become a cost-effective main “component” of high-volume, quick-turnaround, reusable launch systems for small to medium payloads.  Heavy lift, I’m sure, will continue to make its own rules.

         If we ignore the “losses” due to program cancellations and cutbacks, there have not actually been that many test flights of scram systems compared to any other launch technology.  As you say, only the US will dare this, but the US keeps cutting it off before it’s really begun.  I think the US had better hope that no one else picks up on it, or the US is going to get left behind.  Yep! I’m a scram fan.

         Steve

4. http://www.businessinsider….

   1. I found the problem within the referenced BusinessInsider.com article above.  Robert A. Mercier said they were “standing in the door waiting to go into that arena”  If they were to stand in the doorway, instead of the door, they might find it easier to move forward.  Perhaps the problem isn’t technical at all but rather an inability to speak proper English.

      Remember what Redstone accomplished after the dismal results of Vanguard.  Remember what Robert Goddard and Sergei Korolev accomplished only after endless seemingly heart-breaking failures.  Take a look at the history of aircraft and aerospace technology and calculate the average time between technology revolutions.  SCRAM and the other technologies required to support it are barely out of the starting gate historically.  Let’s hope that maybe this time Congress will back off and let the pros do their work for long enough to cross a new barrier.

      Steve

5. It failed. Surmise that they can’t achieve JP-7 combustion. Theory of combustion … doesn’t match practice?

   1. No, an apparent control surface failure.

      The critics will say “Why can’t they get a simple fin to work. That’s old school”. The experienced would say “Moving parts are always difficult to work with on space vehicles.”

      1.  When you see the complexity of what Curiosity did landing on Mars and then within a couple of weeks see two test failures (Morpheus being the other), it’s natural to ask why others seem to be having so much trouble.  #1: Aeronautics and Aerospace are hard.  Period.  #2: Comparing Curiosity with these programs is totally apples and oranges.  MSL is a flagship NASA mission with thousands of people working on it.  These others programs are orders of magnitude smaller and as a result likely have very limited resources to commit to mission assurance.

         1. Not to mention that Curiosity is a mission flight, i.e.  a final deliverable.

            X-51 and Morpheus are test articles, emphasis on “test”.  Obviously, you’d rather they not fail, but tests are by their nature experimental with a high probability of failure.  Pragmatically, even a “failed” test is successful, as you gain data on potential failure modes.

            1. “Obviously, you’d rather they not fail“

               gofast,

               Actually, I think in the earlier tests it’s actually better if you do have failures (just not total disasters). I figure that if you don’t get early failures, then you’ve got marginal problems waiting to bite you later on when you think you’re off and running. Bad news at the right time can be good news. Every time an engineer says damn it, we tend to learn something important.

               Steve

6. How would a hypersonic cruise missile be better than a rocket-powered ballistic missile?

   1. It doesnt set off ICBM early warning systems, and it can abort launch and return – hence no MAD 

      1. But they can be seen from space more easily than can a ballistic missile, starting at launch and through their entire powered flight.  Any target that could not see a hypersonic cruise missile coming could not see a ballistic missile coming either.  This wipes out the “no MAD” argument.       

         1. I submit that “no MAD” holds. After boost phase, ICBM  lands on target, no choice about it. The only thing you can do is not arm the warhead – but your adversary is not going to wait to see if you did and would be forced to launch.
            Cruise missiles, including supersonic and future hypersonic ones are a bit more flexible.Their launch platforms and sites are a bit more flexible too.

            1. If the ability to say “oops” and recall a weapon is an advantage then going slower would seem to be a feature, not a bug.  In any case the thing has been an experiment for six decades now.  I expect we’ll tire of putting money into it before it can be deployed for any purpose.

            2. Believe it or not this is the cheapest way to do this kind of research – it’s very difficult.

               For a long time many barriers to even trying these experiments.

               Eventually, one needs to get a more effective fuel like JP-7 to work so as to have practical flight times. Incrementally, you build out to expand the envelope, solving many issues and increasing capability.

               So why do this? Hypersonic might have more application/usability than supersonic, strange as it may seem.

               It’s the next big challenge in aircraft propulsion / stability / aerodynamics /  performance.

            3. What’s the major benefit of supersonic combustion for application in cruise missiles? Is it really that important to have Mach 10 scramjets instead of Mach 5-6 plain old subsonic ramjets?

            4. mmeijeri, denying your adversaries the opportunity to say “oooh shii..” has to be worth something.

         2. It’s all about “event horizon”, or in this case actual horizon.  

            Ballistic missiles are on a high, protracted arc.
            Cruise missiles are low and fast; fast-moving objects near the ground are difficult to track or destroy, and by the time it pops over the horizon you have seconds to respond.

      2. myth,

         Telemetry and trajectory monitoring and projection have been around for a while now, a least as long as the MAD concept. Cold War thinking and procedures are a thing of the past. By the logic you suggest, fighter jets would be shot down every day as mistaken missile attacks and the Concorde would never have flown. Once you hit supersonic, I think it hardly matters if you then make hypersonic. How many countries have defense systems in place that can actually tell the difference?

         Steve

   2.  Well, it can’t be confused with an ICBM. Other than that… it isn’t.

7. Again I ask the question, If you use air breathers/jets wings with rockets at low speeds like up too 5000 miles per hour or so and use throtterable rockets to keep your jet in that pressure sweet spot then  turn up and rocket stage after that. Is that viable??? Why worry about being in the atmosphere at high high speeds. when second stages are pretty cheap. and shield recoverable. Don’t you want to use the air to reduce first stage tank size and cost by using air to gain extra lift??? Yes I know scram and ram jets work best at different speeds and altitudes.

   1. The cost of this is largely materials and development.

   2. DTARS,

      I, for one, can’t answer your question because, as far as I know, there are science aspects for which we don’t yet have any answers, and others that are more empirical than properly understood.  Even though it’s a fairly old concept, scram is still a young technology in the sense that not that much work/testing has been done with it yet.  One reason for this is that the test “failures” tend to be rather more extreme than for other flight technologies, so (as a generalization) each test is very expensive in return for only a little knowledge gained. It’s going to take time and money, since the materials that the aircraft/spacecraft are made of and how they are joined together are also factors still in need of new developments.  Even things as simple as hinges and clamps need to be better than current options at hypersonic speeds, especially in vibration situations.  There are thermal issues as well.

      Steve

      1. Thanks Mr. C, Steve that helps

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