Liquid Methane:  The Fuel of Rocket Lab’s Neutron

Rocket Lab’s Neutron rocket runs on liquid methane (CH₄) and liquid oxygen (LOX), which work together to burn fuel. This mix, called methalox, is used in both stages of the Neutron launch vehicle. Rocket Lab’s Archimedes engines, which power the rocket, use this methalox as a fuel.

More and more people are realizing that liquid oxygen (LOX) and liquid methane (LCH4) could be useful cryogenic propellants for current rocket propulsion systems. Using them together has many benefits, especially for space applications. They have a higher specific impulse, less carbon buildup, and can be stored better than traditional propellants like Liquid Hydrogen (LH2) (Ricci et al., 2023; Xu et al., 2023; Taya et al., 2014).

The chemical makeup of LOX and methane is a big part of why they work so well as propellants. LOX is a good oxidizer because it has a high density and specific energy. Methane, on the other hand, is a gas that has a higher boiling point and can be stored better at room temperature than LH2 (Xu et al., 2023; Taya et al., 2014). The way methane burns also makes less smoke, which is important for keeping engines running well and lasting a long time (Hurlbert et al., 2016; Taya et al., 2014). Using methane also lets you use resources that are already there on planets like Mars, where methane might be able to be made from nearby materials, which makes missions last longer (Hurlbert et al., 2016; Marshall et al., 2017).

When it comes to efficiency, LOX/methane propulsion systems have a lot of benefits. Their high efficiency comes from having good specific impulse values, which are important for making launch vehicles lighter and able to carry more payload (Hurlbert et al., 2016; Taya et al., 2014; Marshall et al., 2017). LOX/methane engines are also made to be used again and again, which is a key way to lower the total cost of going into space. According to Taya et al. (2014) and Kose (2023), the regenerative cooling systems in these engines make them safer and more efficient by handling heat loads well.

Moreover, the storability of LOX and methane is superior to that of LH2, as methane can be kept at higher temperatures and pressures, simplifying ground handling and launch operations (Xu et al., 2023; Taya et al., 2014; Kose, 2023). This trait is especially helpful for reusable launch vehicles (RLVs), which need to be able to be used again quickly (Xu et al., 2023; Hurlbert et al., 2016). The use of LOX/methane systems in future space missions will help reach the goal of lessening the damage that space exploration does to the atmosphere, since methane is less harmful and corrosive than other common propellants (Hurlbert et al., 2016; Marshall et al., 2017).

Finally, using both LOX and methane together as cryogenic propellants makes a strong case for using them in future space flights. LOX/methane systems are a key technology for advancing space travel and lowering the costs involved because they have good chemical and physical properties and are more efficient, can be stored, and can be used again.

References:

Hurlbert, E., Whitley, R., Klem, M., Johnson, W., Alexander, L., D’Aversa, E., … & Asakawa, H. (2016). International space exploration coordination group assessment of technology gaps for lox/methane propulsion systems for the global exploration roadmap.. https://doi.org/10.2514/6.2016-5280

Kose, Y. (2023). Regenerative cooling comparison of lox/lch4 and lox/lc3h8 rocket engines using the one-dimensional regenerative cooling modelling tool odrec. Applied Sciences, 14(1), 71. https://doi.org/10.3390/app14010071

Marshall, W., Osborne, R., & Greene, S. (2017). Development of augmented spark impinging igniter system for methane engines.. https://doi.org/10.2514/6.2017-4665

Ricci, D., Battista, F., Fragiacomo, M., & French, A. (2023). Thermal behaviour of the cooling jacket belonging to a liquid oxygen/liquid methane rocket engine demonstrator in the operation box. Aerospace, 10(7), 607. https://doi.org/10.3390/aerospace10070607

Taya, K., Ishikawa, Y., Kimoto, K., & Ishizaki, S. (2014). Development status of lox/lch4 rocket engine.. https://doi.org/10.2514/6.2014-3480

Xu, J., Wu, Y., Zhu, Q., Jin, P., Wang, J., & Cai, G. (2023). Transient study on filling characteristics of lox dome. Journal of Physics Conference Series, 2472(1), 012036. https://doi.org/10.1088/1742-6596/2472/1/012036