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Cyclical Visits to Mars via Astronaut Hotels


Global Aerospace Corporation developed a revolutionary concept for an overall interplanetary rapid transit system architecture for human transportation between Earth and Mars which supports a sustained Mars base of 20 people circa 2035.

This innovative design architecture relies upon the use of small, highly autonomous, solar-electric-propelled space ships, we dub Astrotels for astronaut hotels and hyperbolic rendezvous between them and the planetary transport hubs using even smaller, fast-transfer, aeroassist vehicles we shall call Taxis.

Astrotels operating in cyclic orbits between Earth, Mars and the Moon and Taxis operating on rendezvous trajectories between Astrotels and transport hubs or Spaceports will enable low-cost, low-energy, frequent and short duration trips between these bodies.

The results of this study effort provides a vision of a far off future which establishes a context for near-term technology advance, systems studies, robotic Mars missions and human spaceflight.

In this fashion, Global Aerospace Corporation assists NASA in preparing to conduct human missions of exploration to planetary and other bodies in the solar system, expanding scientific knowledge, providing safe and affordable access to space, and establishing a human presence in space. Key elements of this innovative, new concept are the use of:

  • Five month human flights between Earth and Mars on cyclic orbits,
  • Small, highly autonomous human transport vehicles or Astrotels:
    - In cyclic orbits between Earth and Mars
    - Solar Electric Propulsion for orbit corrections
    - Untended for more than 20 out of 26 months
    - No artificial gravity
  • Fast-transfer, aeroassist vehicles, or Taxis, between Spaceports and the cycling Astrotels,
  • Low energy, long flight-time orbits and unmanned vehicles for the transport of cargo,
  • In situ resources for propulsion and life support, and
  • Environmentally safe, propulsion/power technology.




In 1985 the National Commission on Space (NCOS) published their plans for the future of space exploration, which included support to a sustained Mars base. The NCOS plan assumed the existence of a sustained Mars base of 20 humans circa 2035, which required significant support in the form of crew replacement and cargo. The NCOS Mars base was supported by the use of large (>460 metric tonnes [mt]) interplanetary space ships for transporting humans and their material back and forth between the planets originally conceived by William Hollister at MIT in 1967. In addition, an entire support infrastructure was envisioned that includes human, cargo and propellant transfer vehicles, transport hubs and propellant manufacturing plants.

The new innovative Mars transportation system architecture concept being developed by Global Aerospace Corporation uses small, highly autonomous, solar-electric-propelled space ships, we dub Astrotels for astronaut hotels, for transporting humans to and from Earth and Mars on cyclic orbits between these planets, that were originally conceived by former Apollo astronaut, Buzz Aldrin. Human transfer between planetary Spaceports and Astrotels is by means of hyperbolic rendezvous trajectories using new, even smaller, fast-transfer, aeroassist vehicles called Taxis. Figure 1 illustrates one concept for an Astrotel along with a Taxi docked at one end.

Astrotel and Taxi Concepts
Figure 1. Astrotel and Taxi Concepts

These basic systems combined with other elements of the Mars transportation infrastructure and a new analysis of the celestial mechanics and aeroassist options will enable low life cycle costs, low-energy, frequent and short duration trips between these bodies. Figure 2 shows a schematic of the overall concept for regular human visits to Mars via an Astrotel concept that uses cyclic interplanetary orbits.

The innovative design architecture developed by Global Aerospace Corporation departs from the concepts in the mid-1980s in several fundamental ways, and these are described below.

Figure 2. Mars Transportation Architecture Schematic
(Click figure for larger image.)

Our visions for a Mars base circa 2035, its transportation support concept, and its elements are discussed later.


What Makes This Concept Revolutionary?


First, this new transportation systems architecture assumes the use of highly autonomous on-board systems to a) reduce the number of crew and b) their occupation time of the transfer space ships to only five months in interplanetary space. Experience with untended space flight on the Russian Mir and the construction phase of the International Space Station make it clear that crew are not essential to maintain support systems. Reducing the size of crew and reducing the duration of their time spent in space reduces the size of the space vehicle and its complexity and the amount of logistics supporting the daily needs of the crew. In addition, by eliminating crew on long flight legs, we eliminate the need for additional Taxis for return to Spaceports thus reducing the number required by one half. Because these Taxis are not carried on these long trajectory legs, Astrotel propulsion requirements are therefore reduced.

Second, in previous plans, a means to generate artificial gravity was required due to the lengthy crew stay time (up to 2 1/7 years). The Mir experience, Russian (one year) and US (Shannon Lucid's 6 month flight), indicates 6 months of zero-g are clearly tolerable. When transit times are reduced to no more than 5 months, artificial gravity is no longer necessary thus reducing mass, complexity and risk.

Third, in past planning, conventional propulsion has been envisioned for the crew transport space ships using a Taxi's rockets. We are proposing instead to use solar electric propulsion for the periodic course corrections that are required for Astrotels (major corrections will generally occur during untended periods). Utilization of low-thrust Solar-powered Ion Propulsion reduces propellant mass requirements by a factor of 9. The cost in propellant mass for conventional chemical propulsion for course corrections for the large 460-mt vehicle over 15 years is more than 173 mt (more than twice our entire proposed Astrotel vehicle!). If we combine the interplanetary vehicle size reductions with SEP, the total reduction in propellant required for the Astrotel in 15 years is less by a factor of sixty! This reduction has a tremendous mass and cost multiplying effect since all this propellant must also be mined, manufactured and stored, transported to the Spaceport and injected onto high-energy trajectories required for rendezvous with the Astrotels. See Table 1 for a comparison of several NCOS and preliminary NIAC study results including propellant requirements. As they are developed, evolutionary improvements in propulsion technologies will further reduce propellant requirements, but they probably will not change the fundamental architecture explored in this study.

Table 1. Comparison of NCOS and NIAC Study Results
NIAC Improvement Factor
Cyclic Transport Vehicle Size, mt
70 7
Total 15-year Propellant and Consumables, mt
Lunar LOX Production Rate, kg/day
Phobos LOX Production Rate, kg/day
Primary Power Generation Mode

Finally, in previous planning, all cargo except certain propellants needed at Mars, went via the same large crewed interplanetary space ship. The implication was that a lot of propulsive energy was being expended on hardware and supplies that could take a lot longer to get to Mars without detrimentally effecting the operation of the base.

All of these departures from the plans originally envisioned by the NCOS result in significant reductions in mass requirements and therefore they have enormous implications to overall energy requirements of a Earth-to-Mars transportation system. Reduced energy requirements impact the design of other elements of the transportation infrastructure and the cost of their development and operations. Since this new concept for support of a future Mars base results in a significant reduction in operations cost over previous concepts, a Mars base could be much the closer to reality. In fact, elements of this concept could be implemented at the very beginning of Mars exploration insuring that the first humans to Mars begin the permanent inhabitation of this our nearest, most hospitable neighbor.

The key elements of the overall Earth-to-Mars interplanetary rapid transit infrastructure in support of a permanent Mars base are listed below:

  • Cycler orbits between Earth and Mars that enable fast, frequent transfers between these planets
  • Small, human transport space ships, or Astrotels, on cycling orbits between planets,
  • Orbital Spaceports at the planets
  • Very small, fast, hyperbolic transfer vehicles, or Taxis, between Spaceports and Astrotels.
  • Propellant and life support in situ resource manufacturing plants
  • Cargo vehicles that utilize low-energy, long-flighttime orbits to transport propellant and low value cargo to and from planets
  • Shuttles to and from Spaceports and planetary surfaces


Potential Significance To NASA


The proposed concept provide a means to expand human exploration to Mars and by providing a transportation architecture that could be put in use to explore other planetary bodies, potentially near-Earth and Main Belt asteroids. It could also enable frequent, short visits to Mars by scientists. Opportunities for extended direct and teleoperated field science (e.g. geology) by scientists at Mars will swiftly expand scientific knowledge of the planet and increase our understanding of its similarities and differences with our own planet. This transportation architecture offers transport to and from Mars at an expected very low life cycle cost. High life cycle costs will limit Mars exploration by Apollo-like expeditions. If life cycle costs can be significantly reduced, permanent exploration and inhabitation of Mars can be argued as being cost effective. This concept contributes to the establishment of a permanent human presence on the planet Mars. Finally, this concept could also provide future direction to NASA regarding flight system technology development that could set the stage for Mars expeditions in the future.