NASA dusts off X15-successor rocket hyperplanes
Mach 8 X34s, mothballed in 2001, to fly at last?
NASA has dusted off a pair of prototype hypersonic rocket-planes it has had lying around since the 1990s with a view to getting them flying. The X-34 project was cancelled in 2001 "for both technical and budgetary reasons", but now the mothballed rocket ships are being checked out to see if they are "potentially viable as flight demonstrators".
Eat my smoke, X-15
The 60-foot-long X-34, under 1990s plans, was to be a very hot ship indeed - a successor to the famous X-15 rocketplane, which was dropped from a B-52 bomber mothership to reach speeds of Mach 6.7 back in the 1960s. NASA engineers expected the unmanned X-34 to top this handily and achieve Mach 8 after being released from a modified L-1011 jetliner, before coming in to an autonomous runway landing.
In the event, the X-34 project got no further than a couple of early test flights with the rocketplanes mounted under the L-1011 mothership: the prototypes were never released to fly free before the programme was cancelled. Since then, the two X-34s and parts for a third have sat in storage at NASA's Dryden research centre and Edwards airforce base.
Now, however, according to a NASA statement released last week, the X-34s have been moved to the Mojave Air and Space Port and placed in a hangar at the National Test Pilot School. There they will be examined by contractor Orbital Sciences, which originally built them and which operates the L-1011 mothership jet (this is normally used as a reusable first stage for Orbital's Pegasus rocket).
"Orbital will tell us whether these existing vehicles are potentially viable as flight demonstrators," says John Kelly, NASA bigwig.
The idea of the X-34s was and remains that they would be testbed technology-development craft aimed at a reusable orbital launcher that would follow them. The planes were designed from the outset to be cheap and simple to maintain and operate: their specially-developed "Fastrac" rocket engines burn kerosene rather than troublesome cryogenic hydrogen (though still using liquid oxygen as oxidiser) and they incorporate various other low-maintenance, low-cost technologies. The X-34 planned test programme had the goal of achieving costs of $500,000 per flight.
The X33 failure
Was NASA's attempt to demonstrate that while they had destroyed the DC-X through careless ground handling they *could* build a vehicle and demonstrate the pre-cursor of a true Single Stage To Orbit transport.
Note a *true* X programme aims to demonstrate *capability* in the simplest possible way. It's *key* requirements are very short and direct. build it, test it to near destruction (or sometimes beyond) and use the data to build the *real* vehicles of the future. You might recall the X1's mission. Exceed the speed of sound without falling apart and/or killing the pilot. *Everything* else is negotiable.
NASA management types then proceeded to tag on a load of unnecessary requirements *including* that the winning contender stump up a chunk of cash into the design to be developed *after* X33 had proved the concept.
Lockmart won with the most complicated, least tested (indeed the original shaped failed in later wind tunnel tests *after* they won the contract) design with the *most* amount of bleeding edge tech *coupled* with the highest planned cash injection for their follow on vehicle design.
Because they had *no* plans to get to a follow on vehicle.
They had (and as ULA still have) a *very* substantial expendable launch business. Hoovering up *all* the available money choked off both North American(the people who built the shuttle) and McDonald Douglas (The people who built DC-X for c$50m, an unheard of price for high tech R&D) proposals.
X33 burnt through its build budget *and* its planned test budget (as NASA *very* generously allowed them to use that also) and *still* stayed in pieces on the ground. BTW an Aluminum tank which *matched* the shape and weight of the composite tank *was* built but a design "expert" stated that using would have destroyed the chain of component usage (demo multi-lobed composite H2 tank -> full size H2 tank), needed to build "investor confidence." (I'll bet LockMart management had a few ROFLMAO moments at that one).
As the design was "refined" its weight ballooned like a compulsive eater who had their stomach stapled to win Slimmer of the Year and having won has decided to let themselves go a bit.
Again in a *true* X programme the object is *data*. short cuts, single string control systems, looting old bits out the retired hardware warehouse are *all* acceptable *if* it keeps the schedule on target.
Lockmart choked off any *serious* competition for a generation, got some of their staff some on the job training and walked away from Uncle Same with better than $1.1 Bn having delivered virtually *nothing*.
And no one got arrested.
Cutting-edge tech from NASA.
Specifically, 1990's cutting-edge tech from NASA.
Sounds like an admission that they've done fuck-all of any consequence in the rocket science department for the last 10 years, if brushing the dust off these hanger queens and flying them is supposed to prove anything useful.
"I'd like to know why they discontinued development of the X33 linear aerospike motor. "
There were hopes its development would be continued after the X33 went down the pan but since the X33 *was* the only vehicle whose geometry matched the size and shape of the engine it didn't happen.
"It seemed to have all the right answers. for an uncomplicated rocket motor"
It's "simplicity" is only relative to something like the SSME. You're looking at an engine with 10 thrust chambers designed to eliminated gimbal steering by differential throttling. This needs faster valves *combined* with a fast responding thrust chamber design that remains *stable* to substantial throttling. . But it's pretty impressive for something in store since about 1974.