Landing heavier payloads with pinpoint precision on the surface of Mars is a known challenge for future missions to Mars. Supersonic retropropulsion has been proposed as a means to deliver higher-mass payloads to the surface, traditionally with the sole intent of deceleration. By adding range control capability during the supersonic retropropulsion maneuver by means of thrust vectoring, it has been found that a substantial amount of propellant can be saved in a precision landing scenario when compared with traditional architectures. Decreasing the propellant mass necessary for the mission increases the amount of payload mass that can be brought to the surface. Propellant mass savings greater than 30% are possible if thrust vectoring is unconstrained during the supersonic phase of flight. Propellant mass fraction is found to be sensitive to the divert direction and also the altitude and flight-path angle at ignition, favoring low altitudes and shallow flight-path angles. Decreased nozzle cant angles and aerodynamic drag preservation have also been found to reduce propellant usage.= reference area, m 2 s = range, m T∕W = thrust-to-weight ratio, referenced to Mars surface gravity V = velocity, m∕s β = ballistic coefficient, kg∕m 2 ΔV = change in velocity, m∕s = flight-path angle, defined as positive above the horizon,°θ = off-velocity thrust angle,°∞ = freestream conditions
The Small Probes for Orbital Return of Experiments (SPORE) flight system will provide low-cost on-orbit operation, Earth return and recovery for small payloads. The SPORE flight system design includes a service module for orbital operations and de-orbit capability, and an entry vehicle to perform entry, descent and landing. The SPORE system architecture is scalable, allowing payload sizes ranging from the CubeSat standard one-unit (1U) configuration 2U and 4U configurations. Experiments including biological science, materials science, and thermal protection system flight demonstrations are targeted applications for SPORE. The flight system can be launched as either a primary or secondary payload into low-Earth orbit or geosynchronous transfer orbit. It can also be deployed from the International Space Station. This paper describes the driving requirements for the SPORE system architecture. Conceptual designs for the service module and entry vehicle are provided, and launch vehicle and ISS interfaces are discussed. Future work leading to SPORE commercialization is described.
NomenclatureEDL = entry, descent and landing EELV = Evolved, Expendable Launch Vehicle ESPA = EELV secondary payload adapter GTO = geosynchronous transfer orbit I sp = specific impulse ISS = International Space Station LEO = low-Earth orbit RCS = reaction control system RF = radio frequency SPORE = Small Probes for Orbital Return of Experiments
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