Team Enterprise undertook the challenge of the Kepler Prize competition not just to design a spacecraft to go to Mars and return with a crew, but to create a system based on creative combinations of realistic engineering results. As such, our solution results in a hybrid of “tried and true” aerospace methods, augmented by newest discoveries specifically in the arenas of materials, propulsion methods, computing and communications design, as well as the latest information on Martian Geology. Some of these combinations, although unique to spacecraft design, are tested and implemented in other fields. We took great care to ensure that mathematically, this solution is ready for testing and implementation.

The unique advantage to this ERV design stems from the multiple uses of the solar thermal collector. Solar thermal collectors, in the right conditions, produce as much heat as a nuclear thermal plant. As such, this ERV design uses that to advantage propulsion and electrical power systems, using the same plant, and removing the many complexities involved with developments using nuclear power and RTGs, both of which have high shielding mass requirements to protect the crew and components from massive amounts of radiation produced. Nuclear Thermal plants also have a high degree of physical complexity as well as crew educational requirements. A solar thermal ERV design is physically simpler—has far fewer moving parts; likewise, it is much easier to maintain, and crewmembers will not need the traditional 2-4-years intensive training required to handle complex nuclear power systems.

Our propulsion system uses chemical propellant combined with heat and electricity generated from the solar-thermal reactor assisted for energy efficiency – the spaceship equivalent of a hybrid, solar-powered car. This also allows for throttling of the thrust so the system produces a high thrust at low efficiency or low thrust at a high efficiency. By superheating the propellant and ionizing the resulting gas, we achieve an Isp into the thousands at the high efficiency end. This will have the nearly the same efficiencies as nuclear thermal, with a modest thrust of 59 Newtons. This represents two areas of tested and developed technologies combined into one efficient package. Although this unique and innovative combination has never before been attempted, we show mathematically the result with this design as being very much advantaged over using either solar thermal alone (which has lower thrust), or chemical propulsion alone (having lower Isp).

The largest challenge integrating these two technologies had to do with the design of the ERV as a “spacecraft system” itself. Placement of the solar collector is strategic—it must be placed in as direct sunlight as possible for best result. Designing the spacecraft for either transit (Earth to Mars and Mars to Earth) in this case, was not difficult, even with a spin for artificial gravity on the return trip. This constrained us to place the solar collector at the CG (also center of rotation) facing the Sun. Surface operations, however, presented a challenge, as the best position for the ERV is to land “sideways”, a.k.a., lengthwise, so the solar thermal collectors can face the Sun at all times over the horizon.

A sideways surface operations configuration, however, proved infeasible. Landing can still be accomplished—the collector requires retraction regardless of landing configuration, so that is not a problem. But how do we take off? Once fueled, the bulky 51,000kg ERV fills out to a whale of 183,000kg, and becomes difficult, if not impossibly complicated to launch after landing on its side. It takes a tremendous amount of fuel to bring it to the upright position, so that is a poor option. Bringing cranes/lifts for operation by the human crew (or complicated robotics) is a possibility but adds a high degree of complexity as well as unnecessary risk. All in all, this was looking like a very poor option.

The solution presented itself however, in modular simplicity and home design. Because of the above reasons we decided to take off and land in the “upright” position, like any other conventional rocket. The solar collector now retracts and extends from the South side, to maximize solar collection in the same manner as any house in the Northern Hemisphere on Earth. Although this requires a well-controlled landing and loses a few hours of direct sunlight per day, these challenges are easily mitigated. A controlled landing is required anyways—and is conducted by the robust neural network AI presented in the Navigation and Attitude Control section. Some sunlight-hours can be recovered with control mechanisms to point the primary collector, guiding light to the secondary collector. Both the primary and secondary collectors as well as pointing mechanisms already have several years of development applied and as such, are considered for this study as Common-Off-The-Shelf (COTS) products.

Several other innovations are important to mention upfront. The integrated communication subsystem includes the premier of emergent laser communications technologies with advanced error correction coding to reach bandwidth in the area of 50 gigabits per second. Infrastructure systems will all be managed through controller area networks (CAN) to provide a highly integrated system of expendable components. Likewise, the ships computer architecture features Bluetooth wireless technology for integrated, on-board local area networks.

Finally, our method of space weather mitigation and protection combines several innovative technologies from different areas of industry. As the first line of defense we use a persistent-current superconducting coil to mimic the function of the Earth’s magnetic field by deflecting solar particles and cosmic radiation. Stowed inside a compartment in the hull of the crew compartment, the 1 x 5 meter cylindrical assembly extends outward and parallel to the dark-side of the ERV once in deep space. Liquid nitrogen is circulated through the coil in order to maintain a constant 77K and the continuous flow of current through the coil’s closed loop. Although outer space may get as cold as 2.72K, the liquid nitrogen provides a buffer against radiant and conducted heat. Loss should be minimal throughout the duration of the mission, however if needed, additional liquid nitrogen may be produced by compressing nitrogen from the crew compartment atmosphere supply. Also, in the event of a loss of current, power may be rerouted from the EPS system, as shown in the power budget.

To prevent leaks caused by micro meteors and gamma particles (neutral particles unaffected by magnetic fields), a thin layer of ferrofluid (a stable colloidal suspension of ferromagnetic mono-domain particles in a liquid carrier) is sandwiched between two thin layers of iron-nickel surrounding the crew compartment. These iron-nickel foil layers also serve to amplify the magnetic field and keep it stable during solar storms and power fluctuations. Once magnetized, the ferrofluid bonds to the iron-nickel foil layers creating a sealant capable of plugging holes up to 1-cm in diameter. Due to the enormous pressure difference between the crew compartment at 1 atm and the vacuum of space, a gel would quickly leak out. But the magnetic bond between the ferrofluid molecules provides a secure seal even under very high-pressure differences.

The final layer of space weather mitigation comes from creative placement of the crew’s water supply. Lining the inner hull of the crew compartment is a multi-chambered polyethylene balloon with each chamber connected by capillary tubes to a water monitor and control system. Water is drawn from only one chamber at a time through a system of solenoid valves. Should any chamber ever become contaminated, that chamber is immediately shut off and quarantined. Similarly, if a chamber ever develops a leak, the remaining water can be pumped to an empty chamber. The astronauts-explorers in Team Enterprise’s ERV will find themselves with the best protection and conditions of any space travelers in human history.