Neutron tank dome beside an Electron tank dome with a Buzz Lightyear for scale

What is Rocket Lab's Neutron Rocket? How is development getting along?

Rocket Lab's Neutron rocket is a marvel of engineering, that's for sure. But how's the development of the vehicle getting along? This article will include a report on the development status as well as an advanced guide on Neutron and how it operates.

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Matthew B.

Matthew B.

Thu Dec 22 2022Written by Matthew B.

At the time of writing, it's been 661 days since the public announcement of Rocket Lab's upcoming, reusable, medium-lift Neutron launch vehicle. This might sound like a long time but Neutron's expected inaugural launch date is still, and has always been NET 2024. And Rocket Lab appears to be ahead of schedule. So let's get updated on the progress they're making, as well as a general guide to the complete Neutron vehicle and their Archimedes engines below the progress update!

An update on Neutron's progress

A mostly complete guide on what Neutron is and how it works is below. If you have any misunderstandings or want to know more about Rocket Lab's new in-development rocket, please see the below sections. But let's get up to date on where they currently are, and how well they're progressing towards their 2024 launch date!

The most recent update we have regarding Neutron's development progress and it's journey towards launch is an tweet from Peter Beck, on the 22th December 2022, which is the day of writing. The tweet, which can be originally found here, says "Neutron tank dome beside an Electron Tank dome with a Buzz Lightyear for scale..."

This image really shows the progress Rocket Lab has been making towards the first flight of Neutron, but most importantly the scale of the Neutron launcher. If it wasn't obvious, the tank in the back is Neutron's, and the tank in front is Electron's, with a surprise guest making an appearance in Electron's dome. The Neutron dome is most likely the bottom dome of the top fuel tank in the second stage. If you look at the image below showing a wireframe image of Neutron, it is most likely the middle dome on the first stage.

On the 4th November this year, Rocket Lab opened their Archimedes engine test stand at Stennis Space Center in Mississippi. The new site will be home to all testing of Rocket Lab's Archimedes engine, and is slated to begin in 2023 by using their existing A-3 test stand, and developing other existing infrastructure. The Archimedes test complex is located across a 1 million square foot area and will be able to create dozens of new jobs. Rocket Lab have exclusive use of the land for 10 years, with an option to add another 10 years on-top of that.

On the 22nd September 2022, Peter Beck founder and CEO held an Investors Day and Neutron Update discussion, along with other members of the executive team. They went through a detail-rich presentation which included lots of new facts about Neutron and it's development, as well as existing systems and programs on Electron. During this update, they confirmed that they are pouring concrete and beginning construction on the first Neutron Production Complex. It was slated to be stood up before the end of the year, we are unsure if this has been completed, and we will confirm with Rocket Lab soon. This site will also serve as a development area for tank testing, allowing for rapid build and testing iteration.

During the same update, we got the information we all wanted to hear, that the Neutron program was on track. Keep in mind this was 3 months ago and might've changed, but they seem to still be rapidly smashing their goals towards launch. Many milestones are expected to be achieved by the end of 2023, a few of which being: engine pre-burner testing, construction at Launch Complex 3 for Neutron, Stage 1 and 2 tested, full engine testing and avionics hardware and software being operational.

With the recent updates and milestones being quickly achieved on Neutron, it seems full-steam ahead with building and testing at the moment. All we can do is hope that the testing program is clean and swift, and there are no significant delays! Best of luck Rocket Lab with developing and manufacturing this amazing rocket!

What is Neutron?

First of all, let’s develop an understanding of Neutron. Neutron is Rocket Lab’s up-and-coming launch vehicle. It can lift 13,000kg of payload to Low Earth Orbit when the first stage is reused, 8,000kg for an RTLS (Return To Launch Site) landing, and 15,000kg when expended. It is suited for Low Earth Orbit (LEO), Medium Earth Orbit (MEO), GEO (Geostationary Orbit) as well as interplanetary missions, it can take 1,500kg of payload to Mars or Venus. Neutron is 40m in height - it has a base diameter of 7m, however it has a unique diameter design - the diameter decreases as the height of the rocket increases. This design helps decrease the pressure along the vehicle, so when Neutron re-enters, there are no shock waves attached to the vehicle. This design also limits thermal loads on re-entry.

Neutron uses 9 Archimedes sea-level engines for the first stage, designed and manufactured by Rocket Lab. It uses 1, Archimedes vacuum engine for the second stage. Both engines use Liquid Oxygen and Methane as propellants. The sea-level variant has a thrust of 734kN per engine, and the vacuum engine has a thrust of 890kN in the vacuum of space. Both variants of the Archimedes engine are Oxidizer Rich Closed Cycles. The definition of this and more information on the Archimedes engine will be below in the What is the Archimedes Engine? section.

Neutron is designed to be reusable, and has one of the most unique approaches to keeping as much as possible reused per flight. Neutron’s first stage, like some other rockets, lands using engine propulsion back at a landing pad close to the launch site, which saves manufacturing costs, as the first stage structure and 9 Archimedes engines can be used again for another flight, and they don’t need to be produced anew each flight.

The second stage and fairings are where Neutron’s unique yet brilliant engineering really shows. Instead of separating the stages like traditional rockets, the second stage is hung from the payload separation plane. Its fairings remain attached to the first stage - they open to release the second stage and payload by the use of mechanical latches, and close again in preparation for re-entry. This unique fairing design allows for rapid launch capabilities; once Neutron’s 1st stage has landed, in theory, the only task needed to launch again is to lift a new second stage into the payload area, and launch again.

Neutron utilises a Carbon Composite structure which helps to reduce mass while keeping a robust shape and support. As mentioned earlier, a tapered profile is used to minimise the load on re-entry and completely remove the opportunity for sonic booms to occur. To guide the vehicle upon landing, canards at the tip of the rocket are used to provide aerodynamic control. They can be seen in the image above, they poke out of the rocket just underneath the fairings. Neutron has 4 landing legs structures on the base of the vehicle which have deployable interior bumpers to soften the load on landing and touchdown without damaging the bottom of the vehicle.

As the same with Rocket Lab's smaller, currently sole launch vehicle Electron, Neutron will use 3D printing and robots to help manufacture a launch portion of the launch vehicle. Rocket Lab use an advanced composite manufacturing technique to construct complex and lightweight structures with a very high strength level. Complete, carbon composite tanks can be manufactured in just days. An advantage of using robots to create carbon composite tanks instead of metallic structures is that minimal human labour is required, less material is used and not as much waste is produced in manufacturing. It also costs a lot less.

What is the Archimedes engine?

This section will be a continuation of the explanation included in the section above. If you didn't read the part above, I highly recommend doing that before reading this, as crucial information is included above. Archimedes is an Oxidizer Rich Closed Cycle, which means the two propellants are mixed in a small combustion chamber inside the engine, known as a preburner. This provides a fast, oxygen rich gas which can be passed over turbopumps to spin them faster. The faster the turbopumps spin, the higher the propellant pressure and faster the flow of propellant into the main combustion chamber and nozzle. However, we can't just have a closed loop of gas without it going anywhere - the typical response to this is to create an outlet that takes the excess hot gas and dumps it into the atmosphere. This is called a gas generator engine. Archimedes is a closed cycle, meaning that instead of dumping this excess hot oxidizer gas into the atmosphere, the pipe containing the oxidizer-rich gas is rerouted into the main combustion chamber. A diagram of both an open cycle rocket engine and an oxidizer rich closed cycle rocket engine are provided below by Rocket Lab.

The Archimedes stage 1 engine has a vacuum Specific Impulse (ISP) of 329s, and the stage 2 engine has a vacuum Specific Impulse of 367s. The higher the specific impulse, the more efficient the engine is, and the more performance it can deliver.

The definition of Specific Impulse is "a measure of how efficiently a reaction mass engine creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is exactly proportional to the effective exhaust gas velocity."

Image: An Archimedes engine next to an Electron, Rutherford engine. Check out the size difference! Credit: Peter Beck on Twitter

Progress report as well as both What is Neutron? and What is the Archimedes engine? sections were composed by Orbitly.