GIGANTIC Aviation Week story, Pentagon has been flying 2-stage orbital spaceplane throughout 1990s&# Options

[Guest_BruceMoomaw_*]

It may even have been manned:
http://www.aviationnow.com/avnow/news/chan...ws/030606p1.xml

My God, what a story -- if it's even partially true. And, judging from this article, they are absolutely certain they have proof (along with proof that the thing, although it works, has recently been mothballed as not
cost-effective).

It's important to keep in mind, though, that this thing is NOT a workable prototype of the originally planned 2-stage winged Space Shuttle. The second stage -- the spaceplane that actually achieved orbit -- was relatively small and probably very inefficient as a cargo carrier; its advantage lay in allowing the US to get a military reconaissance (or weapons) satellite into orbit surreptitiously, with no advance warning of the launch going to other countries. Even at that, as I say, AW reports that the thing has been recently canned as not worth its (doubtless huge) black-budget expense.

[Guest_BruceMoomaw_*]

Four more Aviation Week letters on the BlackStar story:

(1) James R. French (Las Cruces, NM), March 27: "Fascinating as it may sound, the BlackStar article does not meet the test of credibility.

"Based upon some quick analysis by my colleague Chuck Deiterich, a vehicle launching due east (to take advantage of the Earth's rotation) at Mach 3.3 would still require a delta velocity of about 21,700 ft/sec. to reach orbit. This doesn't account for drag losses, which even at that altitude probably would be 200 ft./sec.

"The best performance I have seen for a boron fuel, even with highly toxic liquid fluorine as an oxidizer, is a specific impulse of 409-412 sec. using a 95% burn efficiency. This will require a start-of-burn/end-of-burn mass ratio of around 5:2 -- not difficult for a disposable stage, but challenging for a manned vehicle with crew and payload, which must bear the weight of an entry thermal protection system, landing gear, etc. Using more probable oxidizers, the ratio quickly becomes impractical.

"The description of the vehicle goes on at length about apparent inlets on the belly. This is entirely at odds with the discussion of the linear aerospike rocket engine. The only air-breather that might be useful in this flight regime is the scramjet, which, while it does use an external expansion nozzle, does not use a linear aerospike of the type depicted. (Incidentally, the illustrations show a lack of comprehension about how a linear aerospike works.) Also, it seems unlikely that a scramjet would work with a slurry fuel as described, since the solid particles will be slow to mix and burn while rapidity is crucial to a scramjet.

"Finally, the B-70 launch of a '40,000-lb. stage' carrying a '10,000-lb. Dynasoar' surfaces again. Using the delta-V values quoted above, this combination is incapable of reaching orbit. Even if we use the specific impulse of the Space Shuttle Main Engine and assign an improbable 0.9 propellant mass fraction to the stage, it falls about 3000 ft./sec. short.

"One wonders how these ideas persist, without anyone ever really checking the numbers. I could go on at great length about other improbabilities, but this is enough. I really hope I'm wrong and that some super-duper vehicle does reside out there in the black world. I don't think I'll hold my breath, however."

(2) Mike Tinirello (Palmdale, CA), March 27: "The 'XOV' vehicle described in your article looks very close to a very fast aircraft that I observed in the summer of 1999 at Edwards AFB, California.

"I was taking out the trash and was drawn to look overhead (due to a sonic boom from an F-16). Two aircraft were flying due east in relatively close formation down the National Aerospace Corridor. One of the aircraft looked like a smaller version of the space shuttle, but was still larger than the F-16 chase plane. At one point, the space shuttle-type aircraft rapidly accelerated and disappeared off the horizon, leaving the much slower F-16 in its wake.

"Then the mystery craft silently returned, leaving a wake of smoke rings as it slowed down. You could see two nacelles in back, flickering as the puffs of smoke exited the vehicle. I did not observe a 'mother ship SR-3' nearby. Nor did I observe the space shuttle-type craft land at Edwards. I hve always believed this craft may have been the Aurora spyplane or some other secret craft. Perhaps it was the XOV. I also believe it was moving much faster than Mach 3."

(3) A. Leroy Clarke (Santa Fe, NM), April 10: "As a former wind tunnel engineer, the possibility of an 'XB-70 like spaceplane carrier' was of interest.

"The artist's sketch of the mated version certainly would illustrate a challenge for the landing gear group. The spaceplane likely would have to be much smaller or flatter than was pictured to have any hope of being strut-mounted to a large mothership needing to take off from a runway with conventional landing gear.

"The spaceplane could have been partially submerged into the fuselage in place of the bomb bay, similar to the X-planes in B-29s. B-70 bays were large enough to enclose the 1950s generation of nuclear stores, which were big and heavy. Better yet, the spaceplane could have been piggybacked on the aft fuselage, ahead of the vertical tails. Moving the XB-70's vertical tails outboard, as shown, would ease a launch from topside. This idea was studied in the late 1950s. I conducted wind tunnel tests with the B-70 for a spaceplane launch at altitude."

(4) Allan R. Swegle (Seattle), April 10: "Regarding the experimental orbital vehicle, I was a structures technology engineer on studies in the 1970s and 1980s about developing a reusable orbital vehicle system with vehicles of varying payloads. Our team studied vehicles and orbiters that were launched from subsonic and supersonic carriers at various altitudes.

"A common feature of proposals for orbiters has been systems that require lightweight thermal protection systems (TPS) over aluminum (such as the Shuttle Orbiters), or composite structural materials systems that must be protected to 300 deg F or less.

"To save weight, these systems must have limited wing area and hence develop high temperatures during reentry due to high wing loadings. Some concepts have developed higher boost-phase temperatures than for reentry. The materials for thermal protection on leading edges and surfaces needs expensive and time-consuming maintenance. Added weight, slow turnaround, weather sensitivity, increased risk and cost are products of these TPS concepts."