For decades, rocket propellants with a significant environmental impact have been used. The research carried out so far in the field, underlines its own partiality, but nevertheless reveals disconcerting data.
Among the propellants used for space launches from Russia (Proton) and China (Long March) there is the UDMH, Unsymmetrical Dimethylhydrazine. This fuel, dubbed devil’s poison by Soviet scientists, is responsible for the transformation of a large area of a Kazakh steppe. The ecological disaster was noted in a report from the United Nations Development Program. Russia said in 2018 that it would discontinue Proton production and replace the launcher with a new rocket called Angara, which uses Rocket Propellent 1 (RP-1), a refined version of aviation fuel kerosene.
“Sooty” space travel.
These are small tourist trips organized by Virgin Galactic with the SpaceShipTwo suborbital space planes. These, as scientists explain, function like spark plugs, releasing a lot of soot into the environment, although they are hybrid rocket engines that burn solid fuel with liquid or gaseous oxidizer. Another example similar to this is that of RP-1 powered rockets which also produce soot. RP-1 powered the first stages of NASA’s famous Apollo-era Saturn V. Today he pushes the SpaceX Falcon 9.
An environmentalist-proof solution. But weak.
From an environmental point of view, nothing beats liquid oxygen / liquid hydrogen (LOx / LH2). The discharge of this fuel consists almost entirely of water vapor, the effects of which in the atmosphere have been extensively studied. Zero impact. The only dilemma is that lifting a rocket off the ground using only LOx / LH2 would require huge fuel tanks. That’s why large rockets like ESA’s Ariane 5 and 6 and NASA’s SLS have additional solid boosters to overcome the initial pull of Earth’s gravity.
Is the future running on methane?
Methane-based rocket propellant is an upcoming technology that could eliminate the more polluting SRMs. Methane is a powerful greenhouse gas. But it burns cleaner than RP-1 and delivers more energy than LOx / LH2. Despite being a very potent greenhouse gas, methane as a rocket fuel also appears to be quite environmentally friendly due to its combustion efficiency.
Some studies, however, point out that methane, often transported in the form of gas, could leak into the atmosphere from gas pipes. Rockets testing methane include SpaceX’s super-heavy Starship rocket and an experimental engine called Prometheus, which is currently under development by the European Space Agency.
Start-up in the testing phase.
Several rocket start-ups are experimenting with sustainable alternatives to RP-1 based on waste products or biomass. British company Orbex building a 3D printed Prime micro-launcher that runs on biopropane recently commissioned a study that found the technology could produce 86% fewer emissions than a similarly sized RP-1 powered rocket. But it’s all in the testing phase.
ADN, cheaper in human lives.
The RHEFORM project examined the ADN-based LMP-103S propellant used by a Swedish space company called ECAPS. This research focuses on a compound known as ammonium dinitramide (ADN). When heated it only decomposes into nitrogen, oxygen and water. The problem is that ADN is a salt, so it is solid. While it can be dissolved in other fuels such as methanol or ammonia, it takes a high temperature – more than 1500 ° C – to ignite it. Even if the propellant is a little more expensive, the total cost of living may be lower.
The US space agency NASA, which was not involved in the project, agrees that there is a need for greener rocket fuels and is also working on a safer propulsion system to operate.