Frequently
Asked Questions - General
VISION
What does Burt Rutan think
of the other X-Prize designs?
Burt prefers to discuss this only after the X-Prize
is won.
How long has Burt been working on all this?
The concept dates back to April 1996. Design work and
some limited testing was started 3.5 years ago. The
full development program began in May of 2001.
What's going to be next in Burt's bag of tricks?
Scaled has completed 34 manned research aircraft. None
were announced until they were ready to fly.
When will the first X-Prize
flight take place?
The first flight has been scheduled for
September 29, 2004.
BUSINESS
How much will it cost to
get a ride into space?
Rides will not be offered in SpaceShipOne. The price
of a ride will have to take in consideration the cost
of certification and establishing an airliner-like operation.
One goal of this research program is to see how low
it might be without the burden of regulatory costs.
At program completion we will have good data for operational
costs and may publish them.
Is it physically stressful?
It is expected to be on the order of some modern theme
park rides. The highest forces occur during reentry
but build up gradually and peak above 5 G's for less
than 10 seconds. With the pilot and passengers reclined,
these forces should be quite tolerable for anyone in
reasonable health.
WHITE KNIGHT
Why did the 1st flight last
only 2 minutes?
The airplane had outboard spoilers on the wings to help
improve roll control in the event of gusty crosswind
landings. They were pneumatically actuated (using the
same tanks, valves and fittings as the RCS system on
SpaceShipOne) and returned to recesses in the wings
by springs. On the first flight, the low air pressure,
at rotation was sufficient to "suck" the spoilers
out which killed the lift and caused the return springs
to slam them closed. Four of these surfaces chattering
out on the wingtips during the climb out produced significant
airframe vibrations and the pilot elected to turn downwind
and land immediately rather than aggravate the condition
any longer than necessary. The spoiler system has since
been disabled, since the ailerons provide adequate control.
How can you see where you're going?
The visibility is actually much better than you might
imagine. By moving your head slightly you can piece
together an acceptable picture of the outside world
and maintain adequate "situational awareness".
What is more difficult is spotting other airborne traffic.
However, between radar advisories from ground controllers
and an onboard traffic alert system, this limitation
is minimized.
Isn't it hard to land with
all those wheels?
No. The pilot doesn't notice that he has two nose wheels
up front and with excellent elevator control he can
hold them off until about 45 knots during the landing
roll.
Why is the cockpit called
a "pressure vessel"?
The cockpit is airtight and the air is not freely exchanged
with the outside air. So, like a submarine, the structure
must be able to withstand large forces due to the pressure
differential. In the case of this vehicle, there is
high pressure air inside compared to the near vacuum
outside.
How do you keep the air
breathable?
There are three components to keeping the cockpit environment
suitable for flight. One, oxygen needs to be added at
a small rate for that used by breathing. This is done
with a small bottle carried in the cabin. Two, the carbon
dioxide from the exhaled air needs to be removed and
this is done by using an absorber system. Finally, the
humidity is controlled by passing the air through another
absorber material that removes water vapor, keeping
the cabin cool and dry.
Have there been any surprises during flight test?
Right from the start the White Knight has been one of
Scaled's best handling aircraft. It has good control
harmony and is surprisingly responsive for a large airplane.
Despite its high wing, the airplane's dihedral effect
(being able to pick up a wing with rudder only control)
was too low and, therefore, angled winglets have been
added.
SPACESHIPONE
What's with all those funny
windows?
The windows must be small to keep the weight of the
vehicle down and they must be round to minimize the
structural loads. This configuration is also the least
expensive to manufacture. Each portal consists of two
windows to provide redundancy for the integrity of the
pressure vessel should one window crack or fail. The
number and location of the windows were selected to
provide the pilot a view of the horizon throughout SpaceShipOne's
mission profile.
How high do you go?
The goal is to get to 100 kilometers or about 62 miles
up. This altitude was established by the X-Prize foundation
as a target to stimulate commercial interest in the
technology to achieve it. $10M will be awarded to the
first team to make it before the end of 2004.
Why do you "fold" the wings to come back down?
In space, the wings are folded up to provide a shuttle-cock
or "feather" effect to give the ship extremely
high drag for reentry. This allows the reentry deceleration
to occur at a higher altitude and greatly reduces the
forces and heating on the structure. Also, the ship,
in the feathered configuration, will align itself automatically
such that the pilot has a less-critical flight control
task. We refer to this as "care-free reentry".
The atmosphere orients the vehicle to a belly-first
attitude without pilot input. Another benefit is that,
since the altitude is higher, the pilot can glide further
after the entry deceleration. A SpaceShipOne pilot can
glide more than 60 miles after he converts back to the
non-feathered glider shape.
Why isn't the pilot in a
space suit?
You can think of the design of the cockpit with its
dual seals and window panes as essentially a space worthy
cockpit surrounded by a second outer space worthy shell.
This redundancy eliminates the need for a space suit
and allows the crew to operate and test the vehicle
in comfort knowing that any major single failure will
not result in loss of cabin pressure.
What pilot qualifications
are required to fly it?
Scaled's pilots come from a variety of backgrounds and
experiences. It is the training provided by in-house
assets and program-specific resources that provide confidence
in our ability to fly the space ship. This training
includes glide approaches in our twin engine Duchess,
acrobatic and unusual attitude training in an Extra
300, a sophisticated simulator with tailored flight
displays for each distinct phase of flight and, finally,
the in-flight exposure to the same cockpit environment
provided by the White Knight aircraft.
How does the pilot control
the rocket motor?
Rocket controls are very simple. Two switches, one to
Arm it and a second to Fire it. The avionics suite has
a dedicated propulsion display that shows various critical
motor parameters that can be monitored both by the pilot
before launch and by a ground station during flight.
Can the pilot throttle the rocket?
No. There is no provision for the pilot to modulate
the rocket thrust.
Has any other vehicle gone
supersonic with manual flight controls?
Yes. Chuck Yeager's "Glamorous Glennis" or
the Bell X-1 had manual flight controls. Like SpaceShipOne
it also had electric trim for supersonic flight. SpaceShipOne
may be the first supersonic aircraft that was not developed
by an Aerospace Prime.
Did you do wind tunnel testing?
No. All design refinements and performance predictions
have been derived from Computational Fluid Dynamic tools.
PROPULSION
Why is it called a hybrid
motor?
It is called a "hybrid" because it is has
characteristics that utilize features from both solid
and liquid rocket motors.
Who designed the rocket motor?
While hybrid motors are not new, the configuration designed
by Scaled for SpaceShipOne is unique with its fuel case
and nozzle cantilevered off the main oxidizer tank,
which in turn, forms part of the vehicle's aft fuselage.
Burt has applied for a patent for the new configuration.
Its largest components, the oxidizer tank and fuel casing,
are Scaled-designed composite structure. The development
and testing of the rocket hardware - injectors, valves,
controls, ignition systems and fuel characteristics
- is being done by two competing, independent rocket
companies, eAc
and SpaceDev.
What is the rocket's thrust and Isp?
As of April 2003 we are still competing two different
rocket designs and we will not advertise any rocket
performance data until after down-select and space flights
have commenced.
What's the deal with laughing
gas and rubber?
All rocket motors have some form of "fuel"
and an "oxidizer". In solid rocket motors
the oxidizer is embedded into the fuel (like an Estes
rocket motor) and when lighted will burn until depleted.
In liquid rockets the oxidizer is usually liquid oxygen
and the fuel another liquid like hydrogen or kerosene.
In our hybrid motor we use Nitrous Oxide (N2O or laughing
gas) as an oxidizer and hydroxy-terminated polybutadiene
(HTPB or rubber) as the fuel. Both of these can be safely
stored without special precautions and will not react
when put together. Finally N2O has the nice quality
of self-pressurizing when at room temperature so that
the space ship doesn't need complicated turbo pumps
or plumbing to move the oxidizer into the combustion
chamber.
How do you start it?
To start a hybrid motor first requires introducing a
significant source of heat into the fuel and then introducing
the oxidizer. A hybrid motor does not start by accident
and, thus, it is a safe and simple alternative to its
liquid and solid cousins.
Does it pollute the atmosphere?
The products of combustion are mostly benign (water
vapor, carbon dioxide, hydrogen and nitrogen and some
carbon monoxide) and certainly much more friendly than
any other class of rocket propulsion.
Is the rocket re-useable?
Partly. The oxidizer tank is reusable and the same fuel
casing can support several short firings or one long
one. The intent is to replace the fuel casing and nozzle
between high altitude flights.
SIMULATOR
How did you validate the
simulator?
The simulator is based on CFD analysis and updated by
flight test data. Since the space ship is first flown
as a glider it will provide the opportunity to iterate
the subsonic aero characteristics before
the powered supersonic flights.
Does it simulate stick forces?
Not in real time. We are able to change the stick force
gradients to simulate different flight regimes. Thus
we can practice flying with a "heavy" stick
for supersonic conditions and a lighter one for the
glide landing return.
Can you rehearse normal
and emergency procedures?
Yes. The cockpit has most of the functionality of the
actual vehicle. Emergencies and faults can be introduced
by a console operator.
Who developed the controls
and displays?
All of the controls and displays were developed in-house
and reflect many iterations and fit-ups in the simulator
as well as in-flight assessments during White Knight
flights.
How do you simulate rocket
accelerations and weightlessness?
We don't attempt to do this in the ground based simulator,
but we are able to expose the pilots to most of the
expected flight envelope from flying the White Knight
and the acrobatic Extra 300.
MORE
How can I get more technical
information?
The April 21, 2003 issue of Aviation Week & Space
Technology magazine is an excellent source.
How can I send fan mail
and well wishes to the SpaceShipOne team?
Use our online contact
form or use our mailing address:
Scaled Composites, LLC
1624 Flight Line
Mojave, CA 93501
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