Rockets of Today

ELECTRON — New Zealand, 2018

These guys are making a success of the tiny rocket business, as they cut the cost per launch to $6 million despite having no reusability yet. One market is “cubesats” — tiny orbital devices consisting of one or more cubical sections with a standardized size (10 cm) and strictly limited mass per cube (1.3 kg). This rocket could launch a hundred or more of them at a time. They aim to schedule such launches very frequently, like once or even twice a week, so that small budget satellite customers won’t have to wait for a berth on a big rocket, which can take months or even years, and might make you settle for a less than ideal orbit. The company is called Rocket Lab, and one of the seed investors is actually named Mark Rocket, though he is not a founder. They moved the company to Los Angeles, but the launchpad is still in New Zealand, on a cliff at the end of a peninsula, making it the prettiest launchpad in the business, as well as (they hope) being capable of really fast turnaround for frequent launches.

For 2020 they built a new launchpad at Mid-Atlantic Regional Spaceport on Wallops Island, Virginia. This will be more suitable for equatorial orbits. They didn’t launch from it until early 2023.

This little carbon fiber missile is a two stage kerosene burner based on a very compact and inexpensive engine they call the Rutherford, after the famous New Zealand-born physicist. It’s small enough for one person to easily pick up, and can be made very quickly with 3D printing. It was the first rocket engine to use electric motors to pump the fuel — hence the rocket’s name. (I do not know if the name was also chosen to complement Russia’s big Proton.) This electric motor makes the engine much more efficient, with the tradeoff that the rocket has to lift a big pack of lithium batteries. Each engine has two soda-can-sized brushless DC motors of 37 kilowatts each, or 50 horsepower.

Like a quarter-scale Falcon, the Electron’s booster uses nine Rutherfords, and the second stage uses a single Rutherford with a vacuum bell. Their first flight attempt came up just short of reaching orbit, and their second delivered a payload. They’ve also got a tiny third stage, or “kick stage” as they call it, available for tasks such as raising or circularizing orbits. It doesn’t extend the rocket stack, it just fits inside the fairing. It has a little engine called the Curie which consumes monopropellant. It doesn’t use hydrazine — they’ve got some “green” alternative. I don’t know what it’s made of, but it might be based on hydroxylammonium nitrate (NH3OHNO3) liquified in a solvent. The miniscule thrust allows orbital insertions to be extremely precise.

They went on to evolve this kick stage into a general-purpose satellite bus onto which customer devices could be mounted, so you can just build the instruments you want and not the complete satellite. They call this the Photon. It can be had in various sizes, with monopropellant or bipropellant. A basic Photon takes up around 100 kg of your payload allowance. They have a stretch version of it which is intended to send a tiny payload to the moon, and a customer who wants to use two electrons for a “Moon Express” mission. (That launch was supposed to happen in 2019, but has been delayed and delayed.) This version is getting an upgraded “Curie 2” or “HyperCurie” engine which has electric pumps where the original was pressure-fed, and is still not much bigger than your hand, aside from the flare of the bell. It has higher specific impulse than most kick-stage engines... but they aren’t saying what its fuel is. The Photon has solar cells on the back, around the Curie nozzle, like a Starliner service module, and on the sides.

They are currently a long way from getting their launch cadence to a weekly pace, but they are still looking like the most successful of the new batch of smallsat launch companies so far. With just four launches in 2018 and six in 2019, they hope to get to a fortnightly pace soon, if they can streamline and automate enough manufacturing steps. They’re only hoping for a monthly pace in 2021, and haven’t gotten there yet. But even the minimal pace they’ve got so far is enough to position them solidly as the leading brand among new small-launch companies.

And now, after CEO Peter Beck saying they would never pursue reusability, Beck has officially eaten his hat (shredded with a blender) and started a reuse project. The plan is to put a para-wing in the interstage, and as a drogue, a small balloon which will add drag at high altitudes during reentry. (Beck says they might also look at air brakes on the bottom of the stage.) They will not burn any fuel to slow down the booster — they’ve got none to spare. They will have some tiny cold-gas thrusters to keep it straight, but these are only needed at subsonic speeds. Before that, surviving the reentry heat is going to be quite a challenge, but they already had a lot of heat shielding on the bottom just to protect the parts from the rocket flame. After some early tests, they also found benefit in adding shiny foil to the sides of the booster, to reduce the heat intake of the underlying black finish.

The last step of the reentry is to pluck the para-wing out of the air with a helicopter, which is a fairly well-understood technique that the Air Force was doing fifty years ago. Beck says helicopters are way cheaper to operate than ships. In 2022, on the first attempt to catch a booster from a real launch, the chopper did indeed catch it, but then the pilot felt it doing something nasty to his stability, and cut it loose again. The chute reopened and it splashed down softly, perhaps still refurbishable.

Though chutes and balloons are lightweight, with a rocket so small that weight becomes significant, so even the lightest possible approach does take a bite out of their payload capacity. Fortunately, weight on the first stage imposes only a fraction of the cost that second stage weight does, because it applies to only part of the flight, so from what Beck says, the capacity penalty of the chutes may be well under thirty kilograms.

They originally said that the whole purpose of reuse was not to launch cheaper, but to launch more often — without reuse, their manufacturing process was keeping them stuck at a cadence of at most one launch a month. But this is not an issue anymore, as a pace of one launch every six weeks or so is the most they’re finding buyers for, and they now have manufacturing capacity going underused. At this point it is about saving money. And after a couple of failed helicopter catches where they had to hoist the booster out of the drink, they found that it was coming out in such good shape that with a little more waterproofing, they might just be able to forget the helicopter and let it splash down every time, which would be cheaper and safer.

In early versions the total payload capacity was only 150 kilograms, but soon they raised it to 225, and in 2020 they got it up to 300 by improving some components and lightening the batteries.

Another thing Beck said they wouldn’t do is develop a larger rocket. But in 2021 they announced the forthcoming Neutron, which will have an eight ton capacity with reuse of the booster... and be human rated. The idea is to use an ultralight upper stage, enclosed in a five meter fairing which is part of the booster and gets reused. Normally, a significant part of the dry weight of a second stage is a sturdy outer wall to support everything stacked above it, but on the Neutron that wall goes back down with the first stage, so the second is basically just bare tanks, hanging suspended from the support platform that the payload rides on. The main stage would use fixed fins as legs — an idea SpaceX pursued for a time but then dropped. They chose this because it was less trouble than having legs with hinges. It will have upper steering fins for use during landing.

Despite the human rating, Beck says the Neutron will be mainly intended for launching swarms. Their customers are still people with small satellites, but some of them want to launch them in batches. The Neutron’s first stage will do vertical landings like a Falcon, back at the launch site (no sea landings because ships are expensive). Its short thick body will be carbon fiber — even the outer heat-protection layer is just another type of graphite composite, and they say it’s good enough to not need a re-entry burn. The engines for it are not developed at all yet, and will burn methane in a conventional gas generator cycle, as the electric pumps in the Rutherford don’t scale up to that size nearly as well as turbines do. Beck wants this engine to be “boring”. There will be seven of them in the first stage (they originally said four), and they’ll be dubbed Archimedes. They won’t launch the Neutron from New Zealand, but only from a site in the USA, maybe Virginia. Their goal is to fly it cheaper than a Falcon 9, which is probably doable.

Recently Beck was accused of abusive management. As the company grows and matures, he still expects people to work tons of overtime as if it were still a little startup, promising big rewards later for “key contributors”. Words like “culture of fear” and “toxic” were used. Some of the pressure may be because the company is still losing money every year.

Electron: mass 12.5 t (early ones were lighter), diam 1.2 m, thrust 224 kN, imp 3.4 km/s, electric pump (kerosene), payload 0.3 t (2.4%), cost $20M/t, record 30/1/2 through January 2023.