Date: Wed Sep 15 1993 13:33:04
From: Allen Robinson
Subj: "new rocket" 1/2
In the interest of clearing up some misconceptions about what
was and was not involved in last month's initial flight of the
DC-X, please take a look at the following information. My
principal sources are various weekly "DC-X Update" postings
made to the UseNet newsgroup sci.space by Henry Vanderbilt,
exec. dir. of the Space Access Society (firstname.lastname@example.org
or 602-431-9283: voice/fax). Much of the following is quoted
directly from his postings in July and August.
DC-X is a low-speed flight regime testbed for a proposed reusable
rocket-powered Single Stage to Orbit (SSTO) transport, McDonnell-
Douglas Aerospace's "Delta Clipper." DC-X is intended to prove
out rocket-powered vertical takeoff, nose-first lifting-body to
tail-first flight transition, and tail-first landing. It is also
intended to prove out rapid turnaround of a reusable rocket by a
minimal ground support crew. DC-X is being tested and flown by
approximately thirty people.
DC-X has already pretty much proved out rapid low-cost develop-
ment of an advanced aerospace X-vehicle type engineering testbed
by a small highly-motivated engineering team on a tight budget.
DC-X was built by less than two hundred people, in less than two
years, for about $60 million.
DC-X stands 40 feet tall, is 13 feet across the base, and is
roughly cone-shaped, with a circular cross-section blending into
a square base. The vehicle has four maneuvering flaps, one set
into each side near the base, and sits on four landing legs.
DC-X masses 22,300 lbs empty and 41,630 lbs fully fuelled, and
is powered by four 13,500 lb thrust Pratt & Whitney RL-10-A5
liquid oxygen/liquid hydrogen rocket motors, each able to gimbal
+/- 8 degrees. The RL-10-A5 is a special version of the RL-10-A
designed for wide throttling range (30% to 100%) and sea-level
The single DC-X vehicle was rolled out of its construction hangar
at MDA's Huntington Beach, CA, plant in early April of this year,
and trucked to White Sands, NM, for for ground and flight tests.
Between May 20 and June 17, DC-X underwent a series of nine
engine firings/vehicle systems exercises, including two firings
in one day with complete defueling/vehicle servicing/refueling
On June 18, the DC-X crew began breaking down the ground support
equipment and moving it to the WSMR flight test site. Meanwhile
the DC-X was stored in a hangar. On July 16, the ground support
equipment move was completed. DC-X was taken out of storage,
trucked out to the flight test site, and hoisted upright onto
its launch pad. On July 19, the DC-X crew began running a series
of ground tests to make sure everything had made it intact and
was reassembled properly.
On Wednesday, August 18, at 4:43:53 local time, DC-X's engines
ignited, and the cloud of white vapor silhouetting the ship's
mottled gray shape turned into a brief billow of orange flame
around the vehicle. A second later, the flame cloud had turned
to gray smoke as the vented engine precool hydrogen finished
burning off and the rocket exhaust started the concrete under
the launch stand smoking. Two seconds more for the engines to
settle down to a steady burn, and the DC-X reusable rocket test-
bed lifted off on its first flight.
DC-X, flying with a partial fuel load, jumped off the pad quickly
before easing back on the acceleration and drifting to a stop 150
feet up. As the ship climbed away from the ground, the rocket
exhaust cleared up, and by the time she was hovering the exhaust
flames were (typically for a hydrogen rocket) almost invisible,
showing only an occasional streak of orange as engine throttling
produced transient changes in the fuel mix.
Thirteen seconds after liftoff, DC-X tilted over a few degrees
and began "translating," (sliding sideways at a brisk walking
pace) while holding holding altitude, occasional puffs of vapor
from a cryo tank vent on her side punctuating her stately pro-
gress toward the landing site, 350 feet away.
Once over the touchdown point, DC-X drifted to a halt and hovered
briefly, then began her careful tail-first descent. At a hundred
feet, the landing legs popped out. At about thirty feet, the
rocket plumes began kicking up dust from the landing pad, and the
clear exhaust flames quickly turned to incandescent pillars of
fire, as concrete smoke glowed in burning hydrogen.
By ten feet, DC-X was almost hidden by the smoke and dust boiling
up, inching down into a swirling white-hot cushion of flame.
When the landing legs finally touched ground and triggered engine
cutoff, one last billow of vapor rolled out from underneath, then
silence fell. DC-X stood there, at first only the nose showing
through the smoke, the rest of the ship gradually coming into
view as the breeze cleared the smoke away.
That was it! Sorry if that disappoints some. No diversion.
Nothing suspicious. No electromagnetic gravimetric neutrali-
zation at work.
The worst thing that happened to DC-X during its first flight was
that one side of the fiberglass nose cone was scorched. There
are several spares. This probably happened right after engine
start, when the cloud of vented hydrogen around the vehicle
ignited. This looked scary, but it is a routine part of opera-
ting DC-X, albeit one that turned out to be a bit more spec-
tacular than planned. Liquid hydrogen is run through the en-
gines to precool them before startup, then vented to the air,
producing the vapor clouds visible engine start. When the en-
gines start, unless there's a strong breeze, the hydrogen con-
centration nearby is high enough to ignite, producing a half-
second fireball around the bottom of the vehicle. This is how
DC-X lost its McDonnel-Douglas decals and had its white factory
paint job turned to mottled gray during the test stand engine
firings back in May and June. Everything below the nose cone
is designed to stand the heat, and, of course, in any space-
worthy descendant of DC-X the nose cone will not be made of
The current DC-X program is funded through flight test and data
analysis this fall, and ends after that. There is an ongoing
effort to get Congress to fund a three-year followon program,
currently called SX-2. This tentatively looks like being a
reusable suborbital vehicle powered by 8 RL-10-A5 engines,
capable of reaching Mach 6 and 100 miles altitude, built with
orbital-weight tanks and structure, and able to test orbital-
The SX-2 program goal would be to demonstrate all remaining
technology needed to build a reusable SSTO vehicle. Once SX-2
has been tested, all that should be necessary to produce a
functioning reusable SSTO is to scale up the SX-2 structures
and install more powerful rocket engines.
--- GEcho 1.00
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