# From the Martian Surface to Its Low Orbit in a Reusable Single-Stage Vehicle--[PERSON]
## 3 Results
### Vehicle Subsystems
#### Abort Modes  
Simulations have been carried to determine the feasibility of the abort system on one hand, and to size the abort engines and parachutes on the other. The code of these simulations is publicly available in the abort folder of the GitHub repository [4].  
The first abort mode is between lift-off and Mach 8, as required from the Apollo abort modes [16] (p. 7). At that point, the ascent simulation showed that the capsule will be at a altitude of 38 km, travelling at a velocity of 1.65 km/s. Initiating the abort at Mach 8 will add 225 m/s to this, in 3 s, as required from the Orion abort protocol [17] (p. 15). The altitude and velocity of the capsule from abort at Mach 8 to landing can be seen in Figure 6.  
To decelerate after abort, drogue chutes will deploy at a dynamic pressure of 805 Pa, 106 s after abort. 28 s later, the main chutes will deploy, at a dynamic pressure of 922 Pa. This ensures that the maximum acceleration felt by the crew will be of 6 BEarth. Finally, the abort engines will fire one last time to do a propulsive landing, decelerating the capsule from 95.5 m/s to 0. The abort system is designed to still have an additional 80 m/s available  
Figure 6: Simulated velocity (in red) and altitude (in blue) of the capsule after abort at Mach 8.  
if required. The simulation of the loads and dynamic pressures on the capsule during this abort mode can be seen in Figure 7.  
The second abort mode is from Mach 8 to the phasing orbit. During this flight phase, another simulation showed that the capsule will require 3.47 km/s to get to an orbit at an altitude of 175 km. This orbit being the minimum one from which the capsule can stay 4 days before decaying back into the atmosphere, according to the simulation shown in Figure 8. This would require the abort system to carry an additional 12,450 kg of propellant. This is deemed too high, thus no abort after Mach 8 is possible. This is acceptable, as the need for an abort system after Mach 8 is considerably lowered as the structural load will be considerably decreased, and the engines will have performed nominally for 86 s.  
The third abort mode starts when Charon enters the phasing orbit, and stops when it is 1 km away from the station. In this flight phase, the vehicle will always be pointing away from the station, so that, if need be, the abort engines can instantaneously fire and push the capsule away from the vehicle. To ensure that the station or main spacecraft at  
Figure 8: Simulation of the orbital decay after abort to orbit, showing the capsule velocity (in red) and altitude (in blue) over time.  
Figure 7: Simulated dynamic pressure (in blue) and deceleration (in red) of the capsule after abort at Mach 8.  
500 km altitude orbit does not suffer from any damage caused by a catastrophic failure of the vehicle, the orbit of the LMO node will be increased as soon as the abort has been initiated. Later, another Charon docked to the LMO node would rendezvous with the capsule containing the crew in orbit, and either rescue the crew and land on Mars, or dock to the LMO node.  
The fourth abort mode starts when Charon completes its re-entry burn. If need be, the abort system then needs to get the capsule to an orbital altitude of at least 170 km. This is still possible for the abort system up to 19 min after the reentry burn.  
Finally, the fifth abort mode starts during the end of reentry, when the thermal heating gets below 2 kW/m\({}^{2}\). [PERSON] is required to always point above the horizontal, so that the abort engine can accelerate the capsule away from the vehicle. Then, the parachutes and abort engines will decelerate the capsule, as in the first abort mode.