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Falcon HTV Hypersonic Project Update  
User currently offlineLumberton From United States of America, joined Jul 2005, 4708 posts, RR: 20
Posted (7 years 9 months 4 weeks 1 day 15 hours ago) and read 2947 times:

http://www.defenseindustrydaily.com/...n-htv-hypersonic-project/index.php

Quote:
DARPA and prime contractor Lockheed Martin have decided not to build and fly the two planned HTV-1 craft after subcontractor C-CAT experienced delamination problems with the curved leading edges of the carbon-based aeroshell. Instead, they have shifted efforts to a different HTV-2 design whose multi-piece aeroshell has thinner leading edges and will be easier to build because it's less of a technical stretch. Meanwhile, thermal protection research will continue, as will research into the scramjet engines required.

DID's updated anchor article here:
http://www.defenseindustrydaily.com/...ane-program-inches-along/index.php


"When all is said and done, more will be said than done".
6 replies: All unread, jump to last
 
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 1, posted (7 years 9 months 4 weeks 1 day 8 hours ago) and read 2902 times:



Contours of the fuselage length-ways near the bay doors appear to me as misleading, would you think they are flat horizontal (parallel to freestream) or inclined (boat like fuselage)?



The meaning of life is curiosity; we were put on this planet to explore opportunities.
User currently offlineGrandTheftAero From United States of America, joined Nov 2003, 254 posts, RR: 5
Reply 2, posted (7 years 9 months 4 weeks 1 day 6 hours ago) and read 2887 times:

Quoting Lehpron (Reply 1):
would you think they are flat horizontal (parallel to freestream) or inclined (boat like fuselage)?

Perhaps you are making comparisons to the X-43? That had an "inclined" forebody because it was the inlet to the SCRAMJET engine. This machine appears to have to separate engines with their own inlets. Without the kind of airframe/engine integration found on the X-43 you are free to use just about anything with a sharp leading-edge to generate lift like a waverider at hypersonic speeds, if you don't melt it first. My apologies if I'm telling you something you already know.


User currently offlineLumberton From United States of America, joined Jul 2005, 4708 posts, RR: 20
Reply 3, posted (7 years 9 months 4 weeks 1 day 5 hours ago) and read 2880 times:

Apologies if this question is dumb, but doesn't a scramjet need oxygen? How can it be a space plane if it's powered by scramjets?


"When all is said and done, more will be said than done".
User currently onlineStarlionblue From Greenland, joined Feb 2004, 17015 posts, RR: 67
Reply 4, posted (7 years 9 months 4 weeks 1 day 4 hours ago) and read 2873 times:

Quoting Lumberton (Reply 3):
Apologies if this question is dumb, but doesn't a scramjet need oxygen? How can it be a space plane if it's powered by scramjets?

Well, all reaction engines need oxygen  Wink

Yes, I know what you meant. Ramjets and scramjets are airbreathers and thus do not carry their own oxidizer like rockets. For a spaceplane this can still be useful during the atmospheric boost phase. Also, I understand this is not a spaceplane, just a fast atmospheric transport.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 5, posted (7 years 9 months 4 weeks 1 day 1 hour ago) and read 2863 times:

Quoting GrandTheftAero (Reply 2):
My apologies if I'm telling you something you already know.

Don't worry about it, I had a more detailed question and was running late to class, so I shortened it.

You are right though, I was relating this to just about every other hypersonic wave-rider concept that I have seen which had the ramp up front to lift and for the engines to compress the air. For all the data I could find, none refer ed to subsonic performance with these configurations. I had to try to estimate a body based on a delta wing, with a high dihedral and an angle of attack equalling the body's ramp angle. My results: A plane of mass similar to a 757 with twice the wing area wouldn't takeoff until about 265kts!

With performance like this, its subsonic cruise would be shotty. Since the B-1 slows to subsonic to drop bombs (which it takes care of the AoA issue with its swinging-wings), my questions are:

  • Does the payload disperse below Mach 1 requiring the vehicle to waste valuable energy to slow and re-accelerate?

  • Does the payload get dropped 'in space', like a projectile?

  • If, heaven forbid (at least in my mind), the bay doors open while in the atmosphere and sonic, would payload dropped experience a kind of ground effect resulting the sudden change from the still-air bay environment to the high pressure compression zone of the lower body outside? Would the munition 'float' for a a second (potential bay recontact) before dropping away?


  • Quoting Lumberton (Reply 3):
    How can it be a space plane if it's powered by scramjets?

    Air gets thinner as you go up higher, it doesn't go to zero, per se. For a scramjet powered plane to work it must already be in motion many times the speed of sound. Air compresses approximately per square of the Mach number. Thin air combined with really high speed thickens the air for the engines to use and lifting the plane. The higher you go the faster you need to be. This was/is the idea behind SSTO (Single Stage To Orbit) vehicles that used hybrid engines of rockets and scramjets.

    Speed isn't the only thing; Aeroenvironment (funded by NASA) built a solar-electric-powered airplane that flew above 25 miles up at around 20 KTAS, that plane compensated by having a massive aspect ratio and was really light.



    The meaning of life is curiosity; we were put on this planet to explore opportunities.
    User currently offlineGrandTheftAero From United States of America, joined Nov 2003, 254 posts, RR: 5
    Reply 6, posted (7 years 9 months 4 weeks 8 hours ago) and read 2820 times:

    Quoting Lehpron (Reply 5):
    With performance like this, its subsonic cruise would be shotty.

    You bring up a good point. High-speed weapons release was what I first thought of when I saw this configuration. I'm an engine guy so this topic far outside my comfort zone but just what I know about aerodynamics tells me that opening up a weapons bay at hypersonic speeds is a bad idea.


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