GETTING OFF THE GROUND
Did any of you grow up with this book for inspiration? There’s our dream ship, streaking along on a rocket powered sled in the twilight of a day leading to the night of space. There are military vehicles on the ground in those early concepts. In the cold war years we only knew national pride and defense as a motivation for space exploration. Without always knowing why, we pursued the building of the super ship. We are building the super ship today, and we still don’t have a clear mission to justify it.
If we engage the American desire for commerce we can build more than space ships. We can build the economy and jobs for our population. We can’t afford to drain the budget on an expendable launch system that has no value to the economy. We need the reusable systems of horizontal launch for sustainable commerce for mining, science, colonization, and tourism in space. We can facilitate the new ventures that are building a profitable mission for space.
So how do we get off the ground, literally? Horizontal launch to space presents a great challenge for spaceports and safety. If a vessel is of size for future manned settlement and industry it will be a challenge to fly as a conventional aircraft. Its fuel and complexity pose a risk to passengers and ground facilities.
Aircraft are typically at risk during takeoff where impact with the ground is a close potential. Cross winds, aerodynamic stall, tire and landing gear failure can be factors. We have heard proposals to use a rocket powered rail launch or mag-lev to achieve acceleration and controlled launch conditions. Perhaps these are not needed.
Takeoff does not require dramatic acceleration. That may be a step towards the velocity for orbit, but at low altitude it complicates the aerodynamics of supersonic transition. Our first need is just to reach flight speed, perhaps less than 200 miles per hour. If we are able to attain a strong powered flight we can have the first step to a safe launch.
Landing gear are a mass penalty if they must bear the entire mass of a loaded space plane. Full fuel tanks and cargo are a great load to control on a runway. Proposals to use a ramp or rail have some advantages for control during takeoff. They also have a big cost problem with a dedicated rail or ramp infrastructure. This limits flights to a specialized location, the same issue that limits vertical launch. Again the facility may be vulnerable to accidents or sabotage.
How can we use a conventional airstrip without massive landing gear and tire failure risks? The Messerschmitt Me 163 Komet rocket fighter used a nasty disposable undercarriage. After takeoff it simply released the landing gear to go bouncing wildly down the runway. Not a good idea for a massive space plane! However it may lead to a reasonable compromise.
We are witnessing a growth in unmanned aircraft and vehicles today. Cars can drive themselves, and even parallel park. Drones fly over great distances without a crew. The X-37 space plane is operational with the Air Force, and lands on a runway unmanned. It is not unreasonable for an unmanned vehicle to carry great weights as a truck and operate up to 230 miles per hour and stop safely.
THE SPACE TRUCK
By using tires currently in production we can carry up to 11 million pounds of mass fast enough for takeoff with great stability. Now we are envisioning a multi wheeled vehicle that can steer all wheels against a cross wind or pivot in front of the terminal. This cradle truck will eliminate all but minimal landing-only gear and require no airport tractor vehicles. With enough tires blowouts will not threaten safe runway operations. Tire debris can be shielded away from the aircraft by protective shield fenders on the vehicle. Hydraulics can rotate the aircraft when it is appropriate to affect takeoff.
Propulsion could be provided by gas turbine generators driving electric motors at each drive wheel. Turbine exhaust might even aid acceleration. Could these also be equipped with afterburners? How many exotic propulsion systems might be proposed in this system? Small rocket boosters might aid the takeoff roll at higher speeds. All of this can be gradual enough for passenger comfort, and still allow braking power for a launch abort if needed.
ROTATION ASSIST RAMP
I believe robotics are advanced enough to consider placing a carrier truck at an emergency landing strip to meet and land a fully fueled booster. The crew could separate the escape vehicle and land at the original launch site, as that vehicle has much less volatile fuels on board.
The cradle truck could be entirely controlled by the flight crew until separation. At that time it could be operated by its computers or ground control operators, or both. It can return to the terminal to be mated to the next flight vehicle. Fly by wire systems have opened up new potential in aircraft, and do the same for ground vehicles. This would become a cross between the transporters used on the Soyuz and a land speed record race car. Does that sound like an interesting engineering project?