It had 3 massive heat exchangers positioned along the inlet. Solid methane (kept at 20K) flow through them, freezing oxygen and nitrogen. In static mode, electric powered fans create airflow. The frozen oxygen will then meet with the methane, now gaseous due to heat exchange and the two will combust. They and other air will exhaust through an aerospike. Some oxygen will not be combusted but to be used to fill the lost weight of used methane. They come into play when there is no air left to catch. 15/35 tonnes. 20 tonne methane storage. Stage 1 consists of burning 16000kg of methane and replacing the mass with collected oxygen. Assuming an average VE of 35000m/s and the burn rate of 10KG/S, you will get 350000N, or 350KN of thrust. This thrust allows the craft to accelerate at 10m/s2 for the entirety of the stage. 16000kg burned at this speed will only suffice for 1600s of burn, thus the math shows 16000m/s Delta V. (Note that 40kg/s of oxygen scooped up from air was also used but doesn't count) After this stage the remaining 4 tonne of M and 16 tonnes of scooped up LOX will be perfect for the combustion ratio
needing 47.3 for Methane. 47.5cubed meters fuel tanks, 67.5 cubed meters total usable interior space. Inlet area: 3 Sq.meter. Assuming V of 7000m/s at 0.01kg/cube meter air density, The mass of air entering every second is 210KG which only 20% is oxygen. Thus we have 42KG of oxygen entering the inlets every second at this velocity. Any speed higher will be performed via the second stage that close the cycle and rely on interior stored fuels. Same setup (0.01kg/m3, 7000m/s) with assumed drag coefficient of 0.05 and frontal area of 7m3, 85.75KN drag.
