Cooper Union Mars Ascent Vehicle

• Propulsion System

  The MAV utilizes a unique hybrid in-situ propulsion system that eliminates the need for complex and heavy cryogenic cooling systems by using paraffin fuel. An in-situ propellant production system will be used to produce the oxidizer for the hybrid system in order to prevent the need for oxidizer to be carried from Earth.

• Trajectory

  The proposed MAV will travel directly to a 1-Sol orbit, therefore limiting the risk involved in multiple docking events and eliminating the need for an expensive taxi vehicle.

• Reduced Weight

  The Cooper Union Mars Ascent Vehicle is a two-person two-stage vehicle with a 3588 kg dry mass. Mass efficiency was the focus for the project, as heavier systems lead to challenges during entry, descent, and landing. All systems on the MAV, including structural, avionic, and power systems, were designed with mass savings in mind.

For our Senior Design project, we designed a Mars Ascent Vehicle for the 2021 NASA RASCAL competition. The Mars Ascent Vehicle was divided into six critical systems:
1. Structures—Focusing on the materials, layout and frame of the MAV
2. Propulsion—Focusing on thrust production
3. Thermal—Focusing on protecting the MAV from external heat
4. Power—Providing electrical power to the vehicle
5. Avionics—The brains that control the MAV flight path
6. Life Support—the systems that keep the astronauts alive

Systems Breakdown

Structures
The MAV structure is comprised of an exterior vehicle frame and permanently fixed interior components including control panels, seats, and environmental control systems. The complete vehicle is divided into three main parts:

1. The cabin that holds all crew and mission necessities and a living space
2. Fuel tanks for both solid and liquid fuel
3. The engines that are part of the propulsive system

Propulsion
The propulsion system for the Mars Ascent Vehicle provides the thrust necessary to propel the MAV from the surface of Mars to a 1-Sol orbit. It was determined that the optimal ∆V for this mission was 5274 m/s, so the fuel requirements were shared around achieving that ∆V. The proposed MAV will use a two-stage hybrid propulsion system with a paraffin based wax as the fuel and liquid oxygen oxidizer collected using an in-situ propulsion system. The system will use three 125kN engines for the first stage, and one for the second stage.

Thermal
During takeoff, the compression of the Mars atmosphere under supersonic speeds will cause the MAV’s exterior to heat up. It therefore is necessary to apply a Thermal Protective layer onto the MAV exterior to prevent any damage to the MAV structure.
The thermal model was conducted using a simplified 1-dimensional heat transfer model of the MAV system. Without the TPS the MAV reaches 475K—the point where the aluminum is at half of its original strength and where the frame will no longer be structurally sound. However, with the TPS it does not reach that point.

Power
The MAV uses a 62 kg 14 kW-hr Ag-Zn battery to power all the electrical components during takeoff and docking. This battery was chosen because of its high energy density and its previous track record in space applications. Although in the past, the Ag-Zn battery has had some issues after many recharging cycles, this should not be a problem since few recharging cycles will be required during the mission.

Trajectory

The Mars mission timeline goes as follows:

1. A MAV will depart from earth to mars on the most energy efficient path which will take 1000 day since it will be using super-efficient yet low thrust ion thrusters to get there. The longtime of flight is not an issue since this vehicle will be unmanned.
2. For the manned flight, 180-day conjunction class trajectory offered the best balance between time of flight, required change in velocity, risk, and readiness level.
3. After the 180-day flight, the rocket will perform an Aerocapture maneuver to enter a 250 km by 33,900 km elliptical orbit –commonly called a 1-Sol orbit. The astronauts will land on mars and perform their mission.
4. Upon completion, the astronauts will board the MAV and initiate their 24-hour trip back to a 1-sol orbit where they will meet up with the vehicle that will bring them back to earth. The 24-hour ascent time was chosen since it was the fastest option with launch opportunities multiple times a month.

Avionics
The mass assessment for avionics is dependent on functional aspects. As a result, the mass estimate was decided to be 407 kg–the same as the four person MAV listed Polsgrove et al. This value also includes the control panel that is inside the crew compartment.
The avionics of the vehicle is located at the upper hemispherical cap. This area is not only easily accessible for the crew, but also saves cabin space, which is designed to be compact for the necessary cargo.

Life Support
Altair and a 4 person MAV concept were used to get a baseline for power requirements. Both of these vehicles provide a conservative estimate for power needs since the estimated power requirements for the 4 person Altair vehicle were driven by the 7 day ’sortie’ mission where astronauts would be living in the ascent vehicle (requiring significant electrical power) and the 4 person MAV has 2 more people (that drive up electrical requirements for life support). Although both concepts use fuel cells for power at some point, the Altair vehicle uses batteries for to power the ascent phase. Which gives a good baseline for the 2 person MAV.

More information on our proposed MAV design can be found through our technical report