Commercial Nearearth Launchers Enable The First Step

Incorporation of air breathing offers many propulsion options; however, vehicle design choices are not arbitrary, since requirements and propulsion performance define the practical (technologically and commercially feasible) solution space. A priori decisions can doom success before starting on an otherwise solvable problem. One of the difficulties is the identification of need, and this at a time when there is an overabundance of expendable launchers that do not have the capability of high fly-rates with the accompanying reduction of payload cost (see Figure 3.1). This issue brings back the Conestoga wagon versus Railroad comparison. Commerce with the Western United States was never possible with the Conestoga wagons, as none ever returned, becoming instead building materials for the settlers. All of projections of future space business for expendable or limited reuse launchers are as valid for future space business as the business projections for the future railroad based on Conestoga wagons. Dr William Gaubatz, formerly of McDonnell Douglas Astronautics and Manager of the Delta Clipper program, has addressed this issue in his briefings on space development. Figure 2.22 represents our current status. Remember, however, that since Dr Gaubatz made his presentation, MIR has deorbited and crashed into the Pacific Ocean and the International Space Station (ISS) has replaced it in 55-degrees inclination orbit. Expendable launchers

Planets Q

Planets Q

Figure 2.22. Our current space infrastructure, but without MIR is limited to specific LEO and GSO without significant intra-orbit operations. Hubble is in the space-based warning orbit, and is not shown.

L-5 colony

Asteroid mining

Planets

Planetary exploration

L-5 colony

Asteroid mining

Planets

Planetary exploration

Geostationary orbit

Communications

Warning

Power

Solar farm

Operations center

Low and medium Earth orbits

Spaceways Servicing the Space Frontier

Figure 2.23. One US look to the future space infrastructure that fully utilizes the space potential by Dr William Gaubatz when director of the McDonnell Douglas Astronautics Delta Clipper Program, circa 1999.

Space-based tracking

Space deployment/ retrieval excursion vehicle Hotels

Geostationary orbit

Communications

Warning

Power

Solar farm

Operations center

Low and medium Earth orbits

Spaceways Servicing the Space Frontier

Figure 2.23. One US look to the future space infrastructure that fully utilizes the space potential by Dr William Gaubatz when director of the McDonnell Douglas Astronautics Delta Clipper Program, circa 1999.

can of course readily meet the military and commercial need that is suited to expendable launcher. Until a sustained use launch system is operational, the payloads that warrant a high launch rate system will remain the subject of design studies only. In other words, without the railroad there will be no railroad-sized payloads for Conestoga wagons. Perhaps if the Space Shuttle main propellant tank was slightly modified to permit its use as a space structure, like the Saturn S-IVB, an infrastructure might begin to build [Taylor, 2000]. However the Shuttle main tank is intentionally not permitted to enter Earth orbit and is deliberately crashed into the ocean.

For a true space transportation system to exist, a transportation system network has to be built, just as it was for the United States Transcontinental railroad. Dr Gaubatz attempted to anticipate what the future might hold, if a space transportation system actually did exist, as shown in Figure 2.23. The future space world envisioned becomes then a crowded, busy place. One of the key enabling space structures is the Fuel Station Spaceport network. Without these Fuel Stations movement between orbital planes and altitudes is limited to specific satellites, such a GSO communication satellites with integral geo-transfer propulsion. Note the Construction Module Storage, that can supply components for orbital, lunar and deep space vehicle assembly in space. The Operations Center and Space Station

Figure 2.24. Waiting time is costly for commercial space operations.

provide a system to launch and control missions to the Moon, planets and deep space. The Power Station Warehouse provides hardware for the power satellites in Geo-Earth Orbit, that, coupled with an Orbital Servicing Vehicle, can maintain this and other space resources. As in the USSR plan, there are lunar spaceports and lunar orbiting satellites. There are also space deployment and retrieval vehicles as well as a waste storage and processing facility in high orbit. So, Figure 2.23 provides a very comprehensive projection of future space if a suitable scheduled, frequent, sustained transportation and heavy-lift capability is available. That is what is needed to plan for the future, not the current status quo.

There is a first step that can be made in propulsion to anticipate the future much as Steve Wurst has done. The key first step is off-loading some of the carried oxidizer by utilizing even partially airbreathing rockets, and designing for sustained operations over a long operational life with normal maintenance, not continuous overhaul and rebuilding. Design space solvable with current industrial capabilities and materials is readily identifiable. A cross-section of propulsion options that are based on available, demonstrated hardware and materials is presented and discussed with its pros and cons in Chapter 3. The propulsion systems that are necessary to reach LEO are evaluated in Chapter 4, including pulse detonation

Table 2.1. Return from orbit performance is configuration-dependent.

LR (nautical miles) DR (nautical miles) Waiting time at 28.7° (orbits)

200 1,080 1,700 2,600 3,540

5,800 9,900 12,900 17,100 21,600

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