I wanted to take some time to explain what I believe to be Rocket Lab's biggest challenge with their upcoming Neutron rocket: the engines.
Rocket Lab has stated that the Neutron will be ready in 2024, but details have been very light. Specifically, we know very little about what engines the Neutron will be using.
There are two main issues at hand here:
1. Rocket Lab's Rutherford engine design is not scalable to the requirements of NeutronRocket Lab's electric pump fed Rutherford engine design will not scale up to the kind of larger engine needed for the Neutron. The turbopumps needed to power rocket engines need to be extremely powerful. For a tiny engine the size of the Rutherford, which is so small that you can
hold it in your hands, the power requirements of the turbopump is relatively small. But for a
much larger engine like the Falcon 9 Merlin, the power requirements are very high. Too high, in fact, for an electric pump fed engine--an electric pump that powerful would be too heavy as it would require massive batteries.
Electric pump fed engines like the Rutherford are thought to have an upper limit for thrust of about 22,000 - 25,000 lbs (the Rutherford has about
5,600 lbs of thrust). In comparison, the Falcon 9 Merlin engine produces about
200,000 lbs of thrust,
ten times the theoretical maximum of an electric pump fed engine design. A more detailed discussion of this topic can be found
here.
2. A new rocket engine takes about five years to develop, and it is unclear how much progress Rocket Lab has made on this frontRocket Lab claims that the Neutron will be ready in 2024, only three years from now. However, as per the previous point, Rocket Lab's existing Rutherford design will not scale to the Neutron. This necessitates the development of a brand-new engine which uses a traditional turbopump design. The problem is that these types of engines are very complex and take considerable time to develop. For example, SpaceX's Merlin engine took about
five years to develop, SpaceX's Raptor engine took about
six years, and Blue Origin's BE-4 engine has been in development for
ten years and
still isn't completed.
Unfortunately, Rocket Lab seems to still be in the hiring phase for their new engine, and their
open job posting for the Director of Neutron Propulsion Development states: "As the Director of Neutron Propulsion, you are responsible for developing a liquid rocket engine (LOx /LNG) from a clean sheet. This is a key role in supporting the development of the Neutron launch vehicle where you will build a high performing team under your direction."
It seems that they still haven't
hired the team needed to build their new engine, which will be extremely difficult to build and could take as long as five years to develop. In other words, Rocket Lab appears to be in quite the pickle.
Considering the above, it is critical to be on the lookout for any details about the engines when Rocket Lab releases their much-anticipated announcement about the Neutron. Perhaps Rocket Lab has made more progress on the engines than it seems. Perhaps they will go the route of Astra and give up on trying to develop an in-house engine for their new rocket and
license somebody else's engine instead. I'm not surprised that Astra went this route--they faced the exact same problem as Rocket Lab in that their Delphin engine was also an electric pump fed engine design that wouldn't scale up for their new rocket.
Some clues can be found
here, Rocket Lab executive Lars Hoffman is quoted as saying that Rocket Lab has looked at partnering with other propulsion developers for Neutron, and believes that Rocket Lab has found "
a solution that is a perfect fit for us".
In any case, if Rocket Lab gives their Neutron update and doesn't present a clear path to having a viable engine, that is a huge red flag for the future of the Neutron program.
The silver lining is that Rocket Lab is diversifying away from the launch business. In the future, Rocket Lab will hopefully make more money from Space Systems and Space Services than Launch, and they won't necessarily need to launch everything on their own rockets. However, if Rocket Lab wants to maximize their competitiveness in Space Services, they probably need the capability of efficiently launching their own satellite constellations, for which the Neutron is instrumental. Otherwise they will be at the mercy of another launch provider, who will force Rocket Lab to adhere to their launch schedule and their cost structure.
What do you think Rocket Lab's plan for the Neutron's engines is?