Scaled Composites unveiled its privately funded manned
space program here on Apr. 18, displaying largely completed
hardware designed to take three people in a suborbital
trajectory to 100 km. (62 mi.) altitude. It is in essence a
version of the 1960s NASA/USAF X-15 rocket plane program but
with less severe aerodynamic and thermal stresses.
Scaled President Burt Rutan said the main goal of the
program, called "Tier One" internally, is to show that people
can fly to space for very low cost. "All decisions in design
focus on the absolute minimum recurring cost," he said. "We
use the lowest technology possible, not the highest."
The spaceship should have enough performance to meet the
X-Prize, a privately funded competition requiring that three
people be taken to 100 km. and that the ship repeat the flight
within two weeks (www.xprize.org). But Rutan is focused beyond
the X-Prize. "The big message is not to reach the X-Prize, but
to show that space tourism is affordable."
An undisclosed customer is funding the program, and this
includes multiple flights to 100 km. A rough estimate by
Aviation Week & Space Technology is that the program will
cost $20-30 million. The customer may be revealed when the
craft reaches space, Rutan said. Captive carry of the
spaceship will occur "very soon," signifying it is ready for
gliding flight. "I would like to do a manned spaceflight
before the Wright Brothers' anniversary," he said.
The overall system includes:
A turbojet-powered carrier aircraft called the "White
Knight," designed to drop the spaceship from about 50,000 ft.
This unusual configuration was first revealed with a spy photo
in this magazine shortly after its first flight on Aug. 1 last
year (AW&ST Sept. 2, 2002, p. 18).
The winged spaceship, powered by a hybrid rocket engine and
featuring huge pop-up "feather" surfaces for a high
angle-of-attack entry at supersonic speeds. It is called
A cockpit-replica fixed-base simulator and a training
program. This editor had an opportunity to fly the simulator
Ground service equipment.
One of the clever features of the system is that the
carrier aircraft and spaceship have almost identical cockpits
and share system components. This means that the White Knight
can serve to train some elements of the SpaceShipOne profile,
and that spaceship components have their reliability tested on
every flight of the carrier aircraft in the near-space
environment of 50,000 ft.
Scaled is building the rocket engine case and the tank for
the nitrous oxide oxidizer, and two companies are competing to
provide the solid fuel and oxidizer injector and plumbing.
Both have made full-performance, partial-duration runs at an
outside test facility here.
The craft is air-launched and hand-flown like the X-15. The
mission profile starts with the White Knight dropping
SpaceShipOne from level flight at 50,000 ft. The SpaceShipOne
pilot zooms the gliding spaceship up into a slight climb and
lights the rocket. This pushes his back into the seat with
3-4gs of force. Using manual controls and electric trim, he
continues rotating to a nearly vertical climb for the 65-sec.
burn, reaching about Mach 3.5 but only about 240 kt.
equivalent airspeed. Shortly after burnout, the atmosphere
drops to nil, and the spaceship continues in a zero-g coasting
climb, peaking at about 100 km. (328,000 ft.), followed by
In this period, the pilot deploys the feather mechanism,
readying the configuration for entry. The crew has about 3.5
min. to enjoy zero-g and play with the attitude via thrusters,
then the pilot commands the proper entry attitude.
SpaceShipOne goes through peak heating and G forces with
essentially no input from the pilot. The peak loads are a
little over 5gs down into the seat and are above 4gs for more
than 20 sec., with the Mach number reaching 3.3 but equivalent
airspeed staying below 160 KEAS. When the high entry stresses
are over, the configuration is returned from feather to a
normal glider, and the pilot makes a conventional landing at
an airport with an approach speed around 110 kt.
SpaceShipOne is registered as a glider, and its tail number
is N328KF, representing 328,000 ft.--N100KM was already taken.
It is Scaled Model 316, and the White Knight is Model 318.
Conceptual design started around 1997 and went for four
years, including computational fluid dynamics (CFD) studies
and tests of the thermal protection coating, heat-resistant
windows and drop models of the entry configuration. A lot
changed. The original scheme involved parachute recovery of a
capsule with deployable high-drag "feathers." Rutan wanted to
avoid the careful control of entry angles needed for survival
by winged vehicles like the X-15 and space shuttle. One fatal
X-15 breakup involved improper entry angles. "I wanted to be
able to throw it sideways at the atmosphere," he said.
Nevertheless, a winged vehicle had appeal. However, he also
wanted a manual flight control system--it is cheaper, simpler
and more reliable than a powered, fly-by-wire system. But
Rutan could not find a configuration that had enough relaxed
stability to trim at a high angle of attack for supersonic
entry, yet be stable when the center of pressure moved forward
in subsonic flight, while using manual controls.
The solution is a variation of an old free-flight model
airplane trick--pop the entire tail up to force a high
angle-of-attack steep descent. In this case, the aft part of
the wing pops up along with the tail booms, driven by
pneumatic actuators. The feathered shape gives shuttlecock
stability for carefree reentry, yet handling is acceptable as
a glider. "This gave me the courage for a horizontal lander
instead of a 'chute landing," Rutan said.
Serious development of the Tier One system started after
the customer contract was received in April 2001. With full
funding, work has been rapid since there is no need to pause
for another round of financing, Rutan said. But it is behind
the original schedule, which would have had the craft in space
by now, he said.
SpaceShipOne has monocoque structure with fuselage skin
made mostly of carbon fiber/epoxy honeycomb with a Nomex core.
The skin aft of the horizontal stabilizer pivot is fiberglass
for radio transparency to the antennas there. The wing is
built-up construction with several ribs and honeycomb carbon
fiber/epoxy skin. In a few high-temperature areas a phenolic
resin is used instead of epoxy on the outer face sheet for
50-70F more heat tolerance. Wingspan is 16.4 ft. and wing area
is 160 sq. ft. Weights remain undisclosed.
The spaceship will reach at least Mach 3.5, yet Scaled's
experience has been on Mach 0.6 airplanes. The supersonic
design skill is largely borrowed from reading the "Datacom"
Air Force compendium of aerodynamic information, from
experienced consultants, and from CFD programs. The control
surfaces have thick trailing edges reminiscent of the X-15,
which used 10-deg. wedge tail surfaces for good effectiveness
at hypersonic speed. As is typical, Rutan plans no wind tunnel
tests. They cost money, and real data will be collected during
flight test buildup.
There are no control surfaces on the wing. Roll and pitch
are controlled by elevons on the tail booms driven manually by
the control stick. At the end of the tail booms are upper
rudders that deflect outward only, manually driven by pedals
that have no crossbar--both rudders can deflect outward at the
same time. They are faired to neutral by a strong spring with
an overcenter lock to prevent flutter. Lower rudders are
electrically moved by a cockpit knob and are used for trim and
control at supersonic speed.
At high speed, the stick becomes ineffective--engineers
estimate 300 lb. of pull will be required to produce 1g,
because of both the high dynamic pressure and the drop in
elevator effectiveness at supersonic speed. The full-flying
stabilizers are electrically moved in pitch and roll for
control in this region, as well as trim. The never-exceed
speed is designed to be 260 KEAS.
Outside the atmosphere, attitude is controlled with a
redundant set of pitch, roll and yaw thrusters powered by
6,000 psi. bottles of dry air in the cabin. Full throw of the
stick and pedals electrically valves the gas either full-on or
full-off. For simplicity, there is no stability augmentation
in any of the control systems.
The feather motion is powered by a pair of pneumatic
actuators. The elevons are mechanically locked out in the
shuttlecock configuration, but the rudders and electric stab
trim still work. The feather can be activated after equivalent
airspeed drops below 10 KEAS during ascent, and is retracted
when speed has dropped to subsonic on entry and load factor is
under 1.2g, which occurs at about 80,000 ft. The shuttlecock
angle of attack is 53 deg. at Mach 3 and 65 deg. subsonic.
Even though the shuttlecock lift-to-drag ratio is 0.7, the
downward velocity is generally so high that the descent
remains essentially vertical, with only 2-3 mi. of offset,
The shuttlecock mode has a draggy terminal velocity of 60
KEAS, equivalent to a ballistic coefficient of 12 psf. This
means that entry deceleration will start early and high,
spreading out the G and thermal loads over a greater period
and making SpaceShipOne design easier. The Mercury capsule had
a ballistic coefficient of about 60 psf., creating more
There is no hydraulic system in SpaceShipOne other than the
wheel brakes. There is a set of 6,000 psi. dry air bottles for
the feather actuator, attitude jets, window defogging, and to
maintain cabin pressure. Springs extend the landing gear and
are manually released. Independent wheel brakes activate at
full extension of the rudder pedals. The nose has a skid with
a maple tip. Electrical power comes from lithium batteries.
The time from leaving the carrier aircraft until landing is
under 30 min.
The cabin is sealed, with a pressure relief valve. Rutan
expects it will be maintained at about 6,000 ft. with a little
flow from the air bottles to offset about 100-fpm. leakage.
This is done by hand, watching a cabin altimeter. A "Sodasorb"
carbon dioxide scrubber is used, though it may not be
necessary for short flights, and no makeup oxygen is required.
A three-man crew has done a 3-hr. test in the sealed cabin.
The crew will not wear pressure suits--Rutan believes the
overbuilt structure of the cabin provides the same safety
backup as a spacesuit. There are oxygen bottles and masks for
emergency use. While carried under the White Knight, cabin
heat comes from engine bleed air directed at the outside of
the aft pressure bulkhead. Otherwise temperature is free to
vary--the sidewalls are insulated and engineers expect it will
remain within ± 20-30F of room temperature.
There are 4-in. hole plugs on the left and right walls that
can be removed at lower altitudes to let in fresh air.
Otherwise, the cabin quickly gets hot below 10,000 ft. in
summer. The plugs will pop in if outside pressure becomes
greater than inside during descent. One plan may be to keep
them out until 10,000 ft. during climb, then use the air
bottles to pressurize the cabin to 6,000 ft.
The nosecone is a big keyed hatch that comes off after a
7.5-deg. turn, leaving a 36-in.-dia. opening. An internal ring
gear gives the leverage to turn and lock it. The rudder pedals
and many of the instruments come off with the hatch, and the
crew crawls in and out the front. There also is a 26-in. plug
door on the left side, which is usually left open during taxi
The 16 9-in. windows are double-paned with a 1/4-in. gap.
The outer panes are 5/16-in. Lexan polycarbonate to withstand
heat, and the inner panes are 5/16-in. Plexiglas. The outer
panes have several small holes, putting all the pressurization
on the cooler-running Plexiglas, which deflects 0.2 in. under
The biggest environmental problem seen on White Knight's
similar cabin has been humidity that fogs the windows, coming
from the crew's breath and sweat. Ice forms on cold parts like
the front hatch ring. While most of the mission can be flown
on instruments, landing requires a good view out the windows.
Attempts to combat fog include running air through a "13X"
desiccant, flowing bottled dry air through the window pane gap
and overboard via the outer holes, directing electric heat at
them, using peel-off films of plastic and wiping with a cloth.
The problem still isn't completely solved, said Douglas B.
Shane, Tier One director of flight operations. It may be that
reentry heating will automatically defog the SpaceShipOne
windows. Some windows were moved back from the nose to avoid
The stagnation temperature at peak heating is about 1,100F,
with heat loads roughly similar during ascent and entry. About
25% of the surface is covered with a proprietary ablative
material about 0.035-in. thick that can be recoated between
flights. The rest of the skin will be white paint. The lip of
the feathered surface will have thermal protection and is
partially protected by the cove at the hingeline. If there
were no ablative, calculations and tests show only the outer
two plies of structural composite would be damaged and the
thicker inner face of the honeycomb would be intact, keeping
the craft safe, Rutan said.
The White Knight's gull wing provides room underneath for
SpaceShipOne, and the outboard tail booms give aft clearance
for the drop. Wing area is about 468 sq. ft. at the current
82-ft. span. It was originally 79 ft. with flat wingtips but
flying showed there wasn't enough dihedral to bank the plane
with rudder alone, and when tip dihedral was added, the span
grew to 82 ft. Further extension to 92.5 ft. is possible if
more ceiling is required, at the cost of some G capability.
The aircraft is powered by a pair of afterburning General
Electric J85-GE-5 turbojets taken from a Northrop T-38
supersonic trainer, rated at 3,850 lbf. static thrust each.
The White Knight never-exceed speed is 160 KEAS and Mach 0.6,
making it perhaps the slowest aircraft equipped with
afterburners. "It is the only aircraft with a panted nosewheel
and twin afterburners," Rutan said. All this thrust is to
achieve a ceiling above 53,000 ft. at light weight. The used
engines can run a little erratically there. If more thrust is
required, the 5,000-lbf. J85-GE-21 engine from the Northrop
F-5 fighter could be installed. Or a small hybrid rocket could
be placed in the fuselage tailcone, Rutan said.
Internal fuel capacity is up to 6,400 lb., carried in the
wing leading edge bay and boom tanks above the main landing
gear. The White Knight can carry and drop payloads up to
8,000-9,000 lb. Scaled doesn't want to disclose other weights,
but when the spaceship drops, the carrier aircraft will pull
almost 2gs due to the instantaneous loss of weight, Rutan
said, meaning that the carrier weighs slightly more than the
Primary flight controls are all manual. The ailerons are
outboard of the tail booms, and the rudders and elevators are
on the T-tails, with a trimmable horizontal stabilizer.
Pneumatically powered "spoil flaps" inboard of the booms can
be activated separately in inboard and outboard pairs for
steep descent. Shane said the aircraft has a big
center-of-gravity range and "flies remarkably well. Without a
yaw damper it has good Dutch roll at 50,000 ft."
The main landing gear are pneumatically retracted and have
a rubber biscuit strut for springing and damping, since
experience with the company's Proteus aircraft at high, cold
altitude showed the oleo struts were prone to leakage. The
panted nosewheels at the tip of each boom don't retract. The
left one is free-castoring and the right one is steered, which
already has proven useful when a main wheel brake failed.
The White Knight has a sealed cabin and environmental
systems similar to SpaceShipOne. Construction is almost
completely of composite materials, primarily carbon
fiber/epoxy. It has a dual pitot-static system. One probe is
on the removable nosecone and supplies backup instruments that
are mounted there. The second probe is just aft of the
nosecone joint and feeds the avionics system.
The aircraft has made about 20 flights as of Apr. 14 and
accumulated 40-50 hr.
The spaceship is suspended from a fore-aft pair of hooks
and is stabilized by cone fittings in line with the hooks, and
sway bars pressing on the wings. Following electrical arming
by both the White Knight and SpaceShipOne crews, a manual pull
in White Knight activates a big spring to retract the hooks
toward one another, releasing the craft. The spaceship is
above its stall speed so the trim is carefully set to not fly
back into the carrier. No wind tunnel modeling of separation
has been done, but CFD shows there should be little
interference. Mounted, there is only 1-ft. clearance between
the two craft.
The White Knight and SpaceShipOne cabins are nearly
identical. Both have the same 60-in. maximum outside diameter.
Where there are throttles in White Knight, there is the
feather actuator and lock controls in SpaceShipOne, and
turbojet instruments are replaced with rocket instruments.
Otherwise they are very similar, letting spaceship pilots get
training time in the carrier aircraft. At light weight, the
White Knight has a thrust-to-weight ratio greater than 1, so
pilots can practice flying near-vertical profiles. It can give
20 sec. of zero-g, and windup turns can simulate the G-loading
of entry. Activating the spoil flaps gets the lift-to-drag
ratio down to about 5 to practice the spaceship's gliding
The White Knight also tests the spaceship's systems. The
avionics and environmental system are the same, as are the
stabilizer and rudder trim actuators. The actuators that
retract the landing gear are the same as those that feather
The first flight was plagued with banging spoilers that
were a test of the spaceship's attitude control jet system.
The pressure bottle and valve were remotely located in the
wing and electrically signaled, as was the plan for the
spaceship roll jets at the time. Instead of a jet, the valve
drove an actuator that raised an outboard spoiler. The
actuator had an intentional leak so a spring could retract the
spoiler. But the aerodynamic loads were misestimated and
larger than the spring force, causing the spoiler to flap up
and down and shake the airframe. The spoilers were then bolted
shut and later removed, and the spaceship roll control system
was modified so the pressure bottle and valve are in the
warmed cabin, and only the nozzle and a feed tube are in the
The White Knight will also be used as a flying wind tunnel
with the spaceship in captive carry, to measure control
surface hinge moments. And spaceship systems can be tested
inflight using umbilical power from the carrier.
The first spaceship flight is to be a glide from 46,000 ft.
The first rocket-powered flight will have just a brief burn,
probably accelerating to Mach 1.2. Several more powered
climbing flights will expand the Mach envelope before going
for an altitude flight. The advantage of an air launch is that
if the motor hiccups it can be shut off and there are 15
minutes to dump oxidizer while gliding to base, Rutan said.
The equivalent airspeed envelope is to be expanded by diving
in glides. There will be ground vibration tests to search for
Rutan believes flight test will pose little threat to the
test range. The rocket motor can be shut off, and the kinetic
energy in a terminal dive is about half that of a light twin
like the Beech Baron, and about 2% that of the X-15.
Spaceship launch and entry are to occur in the Edwards AFB,
Calif., restricted areas, but takeoffs and landings will be at
Scaled's home base at Mojave, 5 mi. outside the Edwards
airspace. "It will be the first time a commercial airport is
used for space flight," Rutan said.
The first flight to 100 km. is to be with one person, but
there are plans for several flights with two or three people.
The cockpit is high-workload and the second person can run the
environmental system, read the checklist, and be a backup set
of eyes. A mobile van is fitted to be mission control.
There are no ejection seats, these being judged too heavy,
complex and expensive. To bail out, the front hatch is cranked
open to fall away and the crew climbs out, Rutan said.
The four pilots that will be testing the Tier One system
are Shane, Brian Binnie, Michael W. Melvill and Peter Siebold.
Rutan pointed out that there was no government involvement
in this project. "I believe the government is the reason it's
unaffordable to fly into space. We didn't want them to know;
their 'help' causes cost problems." Two weeks ago he briefed
his congressman, the FAA Commercial Space Transportation
office and USAF space officials at the Pentagon and Edwards
AFB about Tier One.
After the end of the funded program, Rutan would like to
fly once a week to 100 km. for five months to discover
operational issues and gauge recurring costs. He doesn't know
if this will happen. His current guess is that costs would be
under $80,000 per flight. But he can't charge for rides
because the aircraft are not FAA-certified. Rutan guesses
certification would cost $100-300 million--"How can you
amortize that?" he asks. "I'm not interested in certifying it,
but I'd supply parts to someone who is." Marketing studies
show there would be thousands of people who would pay $100,000
for a suborbital ride, but a tourist craft would need at least
6-8 seats and more windows to be economical.
"I want to do something different and fun, and show it can
be cheap," Rutan said. "The next step is unknown now. Going to
orbit has been done before. Maybe go to the Moon or planets.
Maybe a figure eight around the Moon."
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