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.
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.
Is
Burt Rutan going to ride in the vehicle?
Yes, as soon as the opportunity presents itself.
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.
For more current
information visit: www.scaled.com
(Photos and Content
Reprinted with Permission)
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