Hydrogen Peroxide (HTP) (H₂O₂) is a storable oxidizer / monopropellant propellant used as a oxidizer (or monopropellant). Storable but slowly decomposes; requires passivated containers. Typical ISP: 150–170 s (monopropellant), 250–300 s (bipropellant with kerosene) seconds.
Hydrogen peroxide is the same chemical sold in brown bottles at the pharmacy, but rockets use a far stronger version. At high concentration it can power an engine all on its own, simply by being poured over the right metal.
Quick facts
- What it is: highly concentrated hydrogen peroxide (H2O2) dissolved in water, called high-test peroxide, or HTP.
- Strength used in rockets: typically 85-98% H2O2 by weight; common grades are 70%, 85%, 90%, and 98%. The 98% grade is known as rocket-grade hydrogen peroxide (RGHP).
- Three jobs: a monopropellant (works alone), an oxidizer paired with a fuel, and a gas generator to spin pumps.
- Exhaust: only steam and oxygen, both non-toxic.
- Performance alone: a specific impulse (a measure of fuel efficiency) of about 160-161 seconds at 90%, with roughly 10-20 seconds more at 98%.
- Temperature: decomposition runs about 600-740 C for 90% HTP (around 1,015 K).
What it is and how it works
HTP looks like water but is restless: it wants to break apart into ordinary water and oxygen. A catalyst (a material that triggers a reaction without being used up) makes this happen almost instantly. Engineers feed the liquid over a bed of silver or platinum screens, often silver-plated nickel for the 90% grade. Iron, copper, and manganese also set it off.
The reaction is exothermic, meaning it releases heat. Above about 67% concentration there is enough heat to flash all the water into steam, producing a hot, fast jet of steam and oxygen. Push that through a nozzle, the funnel-shaped opening that turns hot gas into thrust, and you have a rocket. Think of a kettle that boils itself the instant the lid touches the right metal.
As a bipropellant (an oxidizer plus a separate fuel), the hot, oxygen-rich gas burns an injected fuel such as kerosene, giving much higher performance. As a gas generator, that same steam-and-oxygen flow spins a turbine that drives the pumps feeding a rocket’s main propellants. A standout advantage: it needs no separate igniter, it stores as a liquid, and its exhaust is essentially harmless.
Why it matters
HTP is a storable, comparatively safe, non-toxic “green” alternative to hydrazine, and it needs no super-cold (cryogenic) handling. Because it decomposes on contact with a catalyst, it is ideal for simple, restartable thrusters used to steer spacecraft, and for spinning turbopumps without separate gas-generator chemistry.
The trade-offs are real. Used alone, its efficiency is low compared with modern bipropellants. And concentrated peroxide is a strong oxidizer that demands scrupulously clean, compatible materials. It is hazardous: at 35% or higher it appears on the US Department of Homeland Security’s Chemicals of Interest list, it causes immediate skin whitening and burns and can blind on eye contact, and contamination by iron or copper can trigger a runaway reaction. Spills are flooded with water, and emergency showers are standard at HTP sites.
Where it is used and notable examples
- Messerschmitt Me 163 Komet (WWII): the Walter HWK 509 engine used 80% HTP, code-named “T-Stoff,” as the oxidizer.
- V-2 rocket: HTP decomposition drove the turbopump feeding the main alcohol and liquid-oxygen propellants.
- Black Arrow (UK, 1971): Bristol Siddeley Gamma engines burned kerosene with 85% HTP and launched the Prospero X-3 satellite.
- Soyuz: several metric tons of concentrated H2O2 (around 82%) per vehicle drive the first- and second-stage turbopumps that feed the kerosene and liquid-oxygen propellants; HTP also feeds Soyuz spacecraft attitude thrusters.
- Modern and research: Skyrora’s HTP/kerosene engines, Blue Origin’s early BE-1 and BE-2 engines, Armadillo Aerospace, the ILR-33 AMBER/Nucleus suborbital rockets, X-15 reaction-control thrusters, and the Bell Rocket Belt.
Green-propellant programs at the European Space Agency and commercial startups have revived HTP, including Skyrora’s HTP/kerosene staged-combustion engine work, keeping a wartime idea alive in modern spaceflight.
Used in the V-2 Walter turbine, Black Arrow, Mercury spacecraft, and early British rockets. Seeing renewed interest for green propulsion.
Storable, non-toxic exhaust, can serve as monopropellant, catalytic decomposition
Moderate Isp, slow decomposition in storage, material compatibility issues, can detonate
