Ichor is an early stage propulsion study for a pressure fed, bipropellant liquid rocket engine targeting 3.5 kN sea level thrust, with hydrogen peroxide as oxidiser and kerosene as fuel.
Before any hardware is drawn, two numbers fix most of the engine: the oxidiser to fuel ratio and the chamber pressure. This page maps how specific impulse, chamber temperature, characteristic velocity and thrust coefficient respond to both, to find which variable earns its cost.
Thermochemical equilibrium calculations with RPA1 and NASA CEA2, post processed in MATLAB. The sweep spans O/F 5 to 8 and chamber pressure 1 to 4 MPa, with the nozzle expansion ratio as a free parameter. Each point in the maps below is one converged equilibrium state.
The states are chemical equilibrium compositions at each O/F and Pc pair, expanded through an ideal nozzle. Shifting equilibrium is assumed through the expansion. The two tools were run on the same sweep and post processed together.
Rocket Propulsion Analysis, one independent implementation of the equilibrium problem.
Gordon and McBride, the second implementation.
Common units, sweep assembly, the maps of Figures 1 to 3 and the design point selection.
RPA against NASA CEA over the full sweep
the two tools agree, and nothing more is claimedno closed form exists for these mixtures
none was runA 4 by 13 grid at minimum over O/F and chamber pressure, run through both tools and post processed to common units.
O/F 6.4 and Pc 3.5 MPa against a 3.5 kN sea level target, chosen for temperature margin against peak Isp. It feeds the stat cards under Finding 3.
Isp peaks near O/F 6.4 at every chamber pressure, and above about 2 MPa more pressure buys almost no Isp. The ★ marks the global maximum in each space.
Where Isp ignores chamber pressure, the thrust coefficient does not. Pressure decisions live in the nozzle, not in the chemistry.
The sweep shows that chamber temperature keeps rising past the Isp optimum. The design point was set at O/F 6.4 and Pc 3.5 MPa, which maximises specific impulse while keeping chamber temperature within structural material limits.
The two variables are not symmetric. Mixture ratio moves specific impulse and chamber temperature together, so the design point is a trade along one axis, peak performance against material margin, and O/F 6.4 buys that margin for a small Isp loss.
Chamber pressure is bought, not free. It costs tank mass and feed pressure in a pressure fed system, and above about 2 MPa the chemistry returns almost nothing for it. The 3.5 MPa point is set by the nozzle through the thrust coefficient, not by the chemistry.
One measured characteristic velocity from a firing closes the gap between equilibrium chemistry and a real chamber, the combustion efficiency this page assumes to be 1.
The feed system this page ignores. One measured drop across a candidate injector converts the chamber pressure choice from a chemistry statement into a system one.
Equilibrium only. No injector model. No combustion efficiency. No wall heat transfer. No feed system. Ideal expansion assumed. No hardware exists.
The connection
The same modelling discipline pointed at a fuel the literature cannot yet size: Melt Layer Thermoacoustics →