RP-1

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RP-1
other names

Kerosene

Brief description Highly refined middle distillate from petroleum for the operation of rocket engines
properties
Physical state liquid
density

0.81-1.02 kg / l

Hypergol with

highly concentrated hydrogen peroxide

Flash point

43 ° C

safety instructions
GHS labeling of hazardous substances
no classification available
H and P phrases H: see above
P: see above
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

RP-1 (abbreviation for Rocket Propellant 1, originally Refined Petroleum 1 ) is a kerosene-like liquid hydrocarbon mixture for the operation of rocket engines . RP-1 was developed in the United States .

history

RP-1 was developed from the aviation fuel JP-4 by distilling it again in order to obtain the highest-boiling, least aggressive components with the highest calorific value as rocket fuel.

features

The substance, which is liquid at room temperature, consists mainly of branched and polycyclic hydrocarbons with small proportions of alkenes , aromatics and linear alkanes , which can polymerize on the one hand during long storage and on the other hand at the temperatures reached close to the engine. The desired and partially synthetic molecules contain approximately twelve carbon atoms. These molecules mean that the fuel has a high flash point as well as good lubricating properties of engine components and can be stored for a long time.

In the manufacture of the fuel, care is taken to keep the sulfur content extremely low, since combustion residues containing sulfur in rocket engine combustion chambers would lead to premature wear and tear and failure of the drive. In addition, sulfur compounds would support the polymerisation of fuel constituents and unduly increase the risk of failure of the engines that are manufactured with very low mechanical tolerances. Due to the very low content of aromatics and alkenes, the substance is significantly less toxic than gasoline, for example, and also has a significantly lower carcinogenic potential than hydrazine .

This fuel can be produced on the basis of crude oil from theoretically any source; in practice, however, only a few high quality varieties are used. This and the low demand result in a significantly higher price compared to conventional aviation fuels or other oil product users. RP-1 is standardized in US military standard "MIL-DTL-25576D".

Comparison with other rocket fuels

Compared to the fuel combination of liquid oxygen and liquid hydrogen (LOX-H 2 ) , the combination of RP-1 with oxygen cannot generate as much thrust in relation to its mass, so its specific impulse is lower. On the other hand there are the advantages of the much higher density of RP-1, so that in relation to the volume the combination with RP-1 can deliver more thrust. The comparatively lower specific impulse is due to the fact that the combustion products of RP-1 such as carbon dioxide (CO 2 ), carbon monoxide (CO), water (H 2 O) and unconverted hydrocarbons are heavier on average than the gases produced during the reaction a rich mixture of hydrogen with oxygen (H 2 O and H 2 ). More energy from the combustion of RP-1, which is lost for thrust generation, goes into the structural oscillations of the unburned hydrocarbons.

RP-1 is easier to handle than liquid hydrogen, since no cooling is required, even if in the Soviet and later Russian space flight the fuel is partially cooled to further increase the density using the already existing hydrogen infrastructure.

Compared to the fuel combination hydrazine derivative - nitrogen tetroxide , RP-1 is significantly less toxic, cheaper and offers a slightly higher specific impulse with the oxidizer oxygen. Instead, the density of the hydrazine derivatives with nitrogen tetroxide is somewhat higher.

Similar fuels

Similar hydrocarbon-based fuels have also been developed outside of the United States. In the Soviet Union / Russia there were and still are several petroleum-based rocket fuels, and even a synthetic rocket fuel, Syntin, for a slightly higher performance in the 1980s .

application

Launch of a Falcon 9 (2017)

These fuels are usually burned together with liquid oxygen (LOX) in the engines. RP-1 was and will be a. used in the rocket types Atlas , Delta I-III , Saturn , Titan I and the Falcon 9 . The Energija , Soyuz and Zenit missiles use similar fuels according to Russian standards. In the Black Arrow , an unspecified kerosene with 85 percent hydrogen peroxide was used as an oxidizer. This combination has a worse specific impulse than RP-1 / LOX, but is hypergolic .

The fuel is fed into the combustion chamber from the pressurized tank by means of turbo pumps ; the pressure must be generated by a separate pressure system that works with helium or nitrogen , for example .

Some boundary conditions must be observed in the context of engine operation. Liquid rocket engines are designed for multiple ignitions (e.g. on test stands and later in flight), which can lead to problems if fuel residues left in lines polymerize or coke as a result of the heat . These effects are counteracted by the careful synthesis of fuel and cooling of the delivery system. On the other hand, fine soot or graphite deposits in the combustion chamber and nozzle are not necessarily undesirable, as they form a thermal insulation layer and can thus reduce the heat flow into the engine material by a factor of around 2.

Web links

Individual evidence

  1. ↑ a b NASA: Rocket Propellant 1 Specifications & DOT Shipping Information ( Memento from July 12, 2010 in the Internet Archive ), October 5, 2006, accessed on March 13, 2012 (PDF; 84 kB).
  2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  3. ↑ a b Bernd Leitenberger: The Atlas launch vehicle. Accessed: January 23, 2012.
  4. ↑ Lox / Kerosene in the Encyclopedia Astronautica, accessed on March 13, 2012 (English).