A simple analytic multistage model is presented for combined chemical-electric orbit-raising missions. Expressions for transportation rates and optimum electric specific impulse are derived for two-stage, three-stage, variable-efficiency, and tank-limited missions of up to 100 days duration. The optimum electric specific impulse is shown to depend strongly on the specific impulse of the chemical thruster. A low-thrust-trajectory optimization model is combined with launch-vehicle performance data to derive end-to-end optimized three-dimensional chemical-electric orbit-raising profiles to geostationary orbit. Optimized profiles are derived for the Sea Launch, Ariane 4, Atlas V, Delta IV, and Proton launch vehicles. Optimum electric orbit-raising starting orbits and payload mass benefits are calculated for each vehicle. The mass benefit is shown to be between 6.1 and 7.6 kg/day with two SPT-140 thrusters, or up to 680 kg for 90 days of electric orbit raising. The optimized profiles are combined with the analytic model to a create simple parametric performance model describing multiple launch vehicles. The model is a good tool for system level analysis of electric orbit-raising missions and is shown to match calculated performance to within 13%. Nomenclatureb = fitting constant c lv = effective launch-vehicle exhaust velocity, m/s c 1 = effective on board chemical thruster exhaust velocity, m/s c 2 = effective electric thruster exhaust velocity, m/s c * 2 = optimum electric thruster effective exhaust velocity, m/s d = fitting constant, m/s g = 9.81 m/s 2 m 0 = spacecraft mass, beginning of orbit raising, kg m 1 = spacecraft mass, end of chemical orbit raising, before electric orbit raising (EOR), kg m 2 = spacecraft mass, end of orbit raising (payload mass), kġ m 2 = electric propulsion mass flow rate, kg/s P = thruster input power, W T 2 = electric propulsion device thrust, N t = time, s v chem = v for all-chemical orbit raising, m/s= v for chemical portion of a C-EOR mission, m/s v 2 = v for electric portion of a C-EOR mission, m/s v 2eff = chemical v effectively replaced by electric v, m/s η p = thruster efficiency η v = mission planning efficiency

The NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) Technology Demonstration Mission (TDM) will demonstrate an operational AF-M315E green propellant propulsion system. Aerojet-Rocketdyne is responsible for the development of the propulsion system payload. This paper statuses the propulsion system module development, including thruster design and system design; Initial test results for the 1N engineering model thruster are presented.

A sustainable space logistics system for robotic and human exploration of the Moon, asteroids, Mars, and other deep space destinations has been identified. Following the key tenets of launch and in-space commonality, efficient in-space transportation, and phased capability development drives the overall cost of missions to the Moon, NEOs, Phobos, and the surface of Mars to fall within achievable budgets while ensuring that risks to the crew and mission are minimized. Using high power solar electric freighters to preposition all nontime critical cargo and using conventional LOX/H2 high thrust systems for crew transportation enables the use of smaller SLS class launch vehicles with great commonality across missions, distributing fixed launch costs across a broad customer base and dramatically reducing exploration costs. Both 300kW and 600kW SEP freighters are used for pre-placement of habitats, exploration equipment, and return vehicles at the destinations, allowing complete systems verification prior to crew Earth departure, significantly reducing the risks from the crewed portion of the mission. Missions are phased to spread development, production, and mission operations costs and enable incremental expansion of demonstrated exploration capabilities and modular infusion of new technologies, culminating in a human mission to the surface of Mars in 2033.

Aerojet Rocketdyne has completed mission analysis trade studies to support near-term NASA cislunar exploration mission concepts by comparing cargo delivery to the EarthMoon Lagrange points (EML1 or EML2) using a solar electric propulsion (SEP) stage (or "tug") versus the most efficient all-chemical approach. The study examined the relationship between total delivered mass to the destination, trip time required, and power level at the SEP thrusters and focused on flight-proven performance regimes for thruster and solar array performance. The results show how SEP enables the delivery of significantly more total mass versus all-chemical approaches, with the benefits increasing as SEP trip time is allowed to increase. SEP solutions can actually deliver up to twice as much mass to EML2 versus a chemical solution or the same mass on a lower cost launch vehicle. Aerojet Rocketdyne also examined the relationships between transfer time, delivered cargo, and campaign costs versus chemical solutions, finding that incorporating SEP tugs in the campaign can reduce cost per delivered cargo mass ($/kg) by over 50% compared to chemical. The results showed that SEP tugs reduce the number of launch vehicles required for the campaign, which is by far the largest campaign cost driver. Overall, using SEP tugs for space exploration and cargo delivery dramatically increases mission flexibility over allchemical solutions, and can enable significant campaign savings.