The US Federal Aviation Authority has assessed SpaceX’s coming plans for Falcon 9 and Falcon Heavy launches over the next few years:
Draft Environmental Assessment for SpaceX Falcon Launches at Kennedy Space Center and Cape Canaveral Air Force Station
SpaceX is usually fairly vague about numbers for the Falcon design specifications, but this analysis of environmental impacts has the following:
| FALCON 9 | |
|---|---|
| Propellant | RP-1/LOX |
| Mass (lb) | 1,135,925 |
| Thrust (lb.f) | 190,000 |
| Total Thrust (lb.f) | 1,710,000 |
Falcon 9 is essentially the core of a Falcon Heavy, thus the Second Stage of the Falcon Heavy applies to the Falcon 9, while the Falcon Heavy boosters are essentially first stages of the Falcon 9.
| Falcon Heavy | LOX (lb) | RP-1 (lb) | Total Propellant (lb) |
|---|---|---|---|
| Stage 1 | 1,898,000 | 807,000 | 2,705,000 |
| Stage 2 | 168,000 | 64,950 | 232,950 |
Presently the Starship is in development, promising 380 seconds of Specific Impulse. The question is: what the next technological leap required to store liquid methane and liquid oxygen for extended periods of time in orbit and beyond?
Thus I’ve been pondering “Space Storable” propellants – oxidisers and fuels which don’t require regenerative cooling systems to remain liquid for months at a time. One combination which is “Green” and has received significant research is using hydrogen peroxide to burn kerosene. Kerosene (as RP-1) has twice the density of liquid methane, which means smaller tankage. Hydrogen peroxide (H2O2) has a reputation of being a difficult oxidiser, but it’s non-toxic compared to the legacy option of nitrogen tetroxide (N2O4) and thus is sufficiently attractive for rocket propulsion developers to investigate further. “Apollo”, for comparison, used a combination of hydrazine (a specific formulation of) and N2O4 – a combination which gives similar performance to RP-1 + H2O2. Another advantage of hydrogen peroxide is that it can be made from lunar water, thus there’s potential to resupply deep space missions from the Moon.
Of course, if you’re going to all the trouble of building fuel depots in Lunar Orbit, keeping cryogenic fuels, like LCH4 + LOX, isn’t a huge cooling burden. Solar powered cryocoolers can do the job.
The rationale behind using methane/oxygen for the Starship is in-situ resource utilization on the Moon and Mars. Oxygen is available either by reducing regolith or by processing carbon dioxide, providing 80% of the propellant mass. 75% of the mass of the methane is carbon, requiring only the addition of 25% hydrogen by weight. Also, for the Starship large tankage is a feature not a bug since it increases the surface area to weight ratio which helps reduce heating on atmospheric reentry.
Hi Michael,
Indeed. Carbon isn’t as available as oxygen on the Moon as Mars, of course, but it is present. There has been work on CH4/H2O2 propellant mixes as well, which reduces the total hydrogen mass a bit. If a good carbon source is found on the Moon, then CH4/O2 is still a front runner for SpaceX Starships.