by Dave Dietzler
How will we fly up to LEO in the future? The Space Island Group wants to improve the Shuttle and use it to carry tourists, but the future of the Space Shuttle is dim since the Columbia disaster. Boarding the Shuttle before launch and disembarking after landing would also be problems with the Shuttle and any other vertical take-off and horizontal landing spacecraft. Horizontal take-off and landing spaceplanes that take-off and land like airliners are the stuff dreams are made of. We imagine huge delta winged planes launching from mag-lev traks, flying to the lower levels of the ionosphere with hydrogen powered turbo-ram-SCRAMjets and then rocket power to LEO. These exotic machines may be exciting to engineers, but they might also be so complex and expensive to develop and operate that they are never practical. Vertical take-off and landing rockets could be the simplest and most practical. These VTOLs would look like large space capsules. They would only endure stress in the vertical direction and they would not need wings, control surfaces, jet engines or landing wheels. They could use disposable blunt heat shields rather than high maintainence tiles like the Shuttle or other spaceplanes would. Aerospike or "plug nozzle" engines would allow high efficiency. The VTOL rockets could parachute down to Earth or sea and use some vertical rocket thrust for a very soft touchdown. They couldn't land at conventional airports and would require expansive landing fields, but that's not too much of a problem. Some control during descent could be had by toggling the parachutes with servoactuators. The VTOLs could always splash down at sea but this would complicate recovery operations, so land touchdown is preferable.
If we go with VTOLs we should be able to reduce operating costs thanks to cheap disposable heat shields and avoidance of aircraft systems. Since the rockets don't have to haul the dead weight of wings to orbit, decent payload masses should be possible. Passengers will board the rocket before liftoff and return in the same attitude upon landing as comfortably as they would on an airliner. A duck-billed platypus VTHOL (vertical take-off horizontal landing) vehicle like the Shuttle doesn't have this advantage. We must question the use of liquid hydrogen for routine flights. Liquid hydrogen is a deep cryogen that is much more difficult to work with than soft cryogens like liquid oxygen, liquid methane or liquid nitrogen. The best fuel for routine rocket launches might be cheap liquid natural gas (methane). Methane has the highest specific impulse of any hydrocarbon fuel and is commerically available. A rocket fueled with methane (CH4) could obtain a higher mass ratio than a LH2 powered rocket of similar volume because LCH4 is much denser. The only problem is that the rocket will be heavier. Strap-on boosters that parachute back could be needed for a 1.5 stage VTOL. Hybrid rocket boosters would probably be best for this application. The VTOLs would be made of lightweight lithium-aluminum alloy. They would not have to move large payload masses. Fifty people only amass about five tons.
The only drawback seems to be that fully reusable VTOLs won't provide the bonus of an external tank in orbit as the Shuttle would. The Space Island Group might still build large space hotels from external tanks (E.T.s) by launching cargos with heavy lift vehicles (HLVs) derived from the Shuttle like Zubrin's Ares rocket. The Russian Energia also has possibilities. These HLVs won't fly as often as passenger VTOLs, so the use of LH2 which will be trickier than LCH4 to work with will be justified to obtain maximum payload mass. Several hundred HLV launches could provide E.T.s in orbit to build space hotels, cycling stations and spaceships as well as thousands of tons of cargo to build a Moon mining base with mass drivers for solar power satellite (SPS) construction. Helium 3 mining machines would also be built at the Moon mine to harvest this valuable fusion fuel of the future ( if we keep our fingers crossed!). Materials from the Moon could also be used to build space hotels far beyond the E.T. hotels envisioned presently. The purpose of space colonization is not just to create space tourism but to provide plentiful environmentally benign energy from space and save the planet. Other industries like orbital manufacturing and astronomical research in observatories on the far side of the Moon could ride along with space energy and tourism. Eventually, there could be the colonization and terraforming of Mars and the creation of a space faring civilization that reaches the stars. It looks like HLVs based on the Shuttle E.T., SRBs and SSMEs in addition to all new 1.5 stage passenger VTOLs are the starting points on this road to a galactic civilization. This seems to follow common sense, as most of us would think that rockets are for space travel and jetplanes are for air travel. I'm sure kids would see it that way!!
