STCAEM Cryogenic Aerobrake TMIS

American space tug. Study 1991. The Trans-Mars Injection Stage (TMIS) consisted of a core unit with four advanced space engines (ASE), avionics and cryogenic propellant tanks, and provision for up to four "strap-on" propellant tank sets.

This configuration allowed propellant cross-feeding in the case of engine-out, and modular accommodation of the entire stage's performance according to the mission opportunity requirements.

Keeping the engines close together on the core stage allowed tracking the center of mass (CM) during an engine-out condition via gimballing. This strategy avoided either opposing-shutoff (leading to long burn times and greater gravity losses), or a requirement for extra structure (a 125m truss) between the propellant tanks and engines to allow CM tracking. The TMIS accounted for about 75 % of the total initial mass in low earth orbit (IMLEO), a substantial pre-mission resupply.

The TMIS had dry mass of 54,560 kg and a propellant load of 490,950 kg, for a total mass of 545,510 kg.