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By Mark Mackay and Iain Finer

Peter Beck, CEO of Rocket Lab stands with an early test article of the Electron rocket
 

Rocket Lab today has announced some juicy new details about its forthcoming Electron rocket, and especially the Rutherford engine that powers it. Making the announcement at the National Space Symposium underway in Colorado, USA, the company declared their new launch system as the first “battery-powered rocket.” The tagline conjures dreams of being able to simply replace the batteries and fly again, but the reality is more subtle. We dig a little deeper in the announcement and the innovations may give Rocket Lab an edge in the competitive space-launch sector.

Electric Rutherford Engine

According to their press release:

 “Unlike traditional propulsion cycles based on complex and expensive gas generators, the 4,600 lbf Rutherford adopts an entirely new electric propulsion cycle, making use of high-performance brushless DC electric motors and lithium polymer batteries to drive its turbopumps.”


Promo video for the new Rutherford engine, with electric turbopumps.

Turbopumps help get the propellant into the rocket’s main chamber and keep it at the right pressure for efficient and stable combustion. In most modern rockets these are gas-powered, using some of the rocket propellant to power themselves while they pump the fuel and oxidiser into the main combustion chamber. Thus such rocket engines have two sets of combustion going on at same time, although one is much less explosive and more like a jet engine. However this greatly adds to the complexity of the system, which adds additional materials and hence weight. Weight is the enemy of any rocket, and so reducing this means you are able to fly bigger payloads, faster and higher.

So how does switching to electric turbopumps help?

Firstly, this must be far simpler to manage than all the additional plumbing, control systems, and moving parts that come with traditional systems. Switching to an electric motor that turns on with the flick of a switch seems like a no-brainer. And with nine engines in its tail, this will substantially simplify the intricate web of cables and hoses.

Electric pumps should also provide a great deal of control over how the propellant is injected into the engine. Electron utilises liquid oxygen and rocket-grade kerosene as propellants, and like most engines - the mixture needs to be delicately controlled to match various power levels. We would imagine that it is possible to shut down and then restart the engine mid-flight. Electric pumps may also provide improved dynamic control over fuel flow rates, allowing for fine-grained tuning of the mixture and even greater efficiency and throttle-range.

Rocket Lab's new Rutherford engine, powered by two electric turbopumps (one visible, in red). Pneumatic actuators (blue) allow the engine to be steered.

Compared with SpaceX's Merlin 1c engine - Rocket lab doesn't need the turbine exhaust and should require far less plumbing. (Note: the two engines are vastly different sizes in real life)

 

A big question is whether the electric turbopump will save weight. Batteries are heavy, but the turbopump itself would likely be lighter than its gas-fed equivalent, and all of the rocket’s propellant would be used to get the vehicle to orbit (not spin pumps). We need some more specifications from Rocket Lab to answer this question, but we’d gamble that it's more efficient, or the simplicity trade-off was worth it.

Moving away from gas-turbines was also likely driven by size constraints. SpaceX’s Falcon 9 rocket is 3.66m in diameter, whereas Electron is only 1m. This makes the engine no larger than the average kitchen rubbish bin.

Test fire of the Rutherford engine – Nine of these will work together to get Electron and its payload off the launch pad.
UPDATES (18 April 2015)

KiwiSpace unfortunately wasn't present at the Space Symposium, but other media coverage has revealed additional information and confirmed some of our analysis:

  • The battery-powered pump, (Peter Beck) said, can be easily changed with software, making it far easier to modify. “It takes a really complex thermodynamic problem and turns it into software that’s infinitely tweakable,” (Source
    – This supports our suggestion that Rocket Lab will have finer-grained control over the propellant mix and make it easier to optimise the engine performance.
  • Additive manufacturing allows the company to build a rocket engine in three days, versus a month for traditional approaches. (Source)
    – We would also imagine that if the process becomes optimised so you just hit "print", then you can horizontally scale a large part of the production just by having multiple 3D printers. Certainly a 3-day turnaround on building a rocket engine is impressive.
  • The approach, says CEO Peter Beck, eliminates the complex valves and other plumbing required to use hot gas to turn turbomachinery, boosting efficiency from 50% for a typical gas generator cycle to 95%. (Source)
  • Each Rutherford engine has two electric motors the size of a soda can, Beck says, one for each propellant. The small motors generate 50 hp while spinning at 40,000 rpm, “not a trivial problem,” (Peter Beck) says. (Source)

 

What’s in a name?

The announcement also puts greater heritage in Rocket Lab’s choice of nomenclature for their rocket systems. Founder Peter Beck has previously announced that the engines were named after New Zealand scientist Ernest Rutherford. The choice to name the vehicle “Electron” was perhaps dismissively thought to relate to the scientist’s nuclear physics work, but may be more to do with the battery-powered rockets within.

Printing your own Rocket Engine

Rocket Lab is following a similar approach to most newspace companies and is adopting 3D printing for as many systems as possible:

 “Rutherford is the first oxygen/hydrocarbon engine to use 3D printing for all primary components including its engine chamber, injector, pumps and main propellant valves. Using this process, Rocket Lab’s engineers have created complex, yet lightweight, structures previously unattainable through traditional techniques, reducing the build time from months to days and increasing affordability.”

3D-printed rocket components and engines have been successfully tested but if Rocket Lab achieves their target to launch by the end of 2015, they may be the first to achieve orbit using one.

UPDATES (18 April 2015)
  • In another effort to increase efficiency and hold down cost, Rocket Lab is building the regeneratively cooled engine using three-dimensional, additive-manufacturing techniques that include laser and electron-beam sintering, with Inconel and titanium powder as the feed stock. (Source)


Payload Integration

One of the more “why didn’t I think of that” announcements for both authors related to how they plan to get the satellites loaded into the rockets:

 “Electron’s upper stage is designed with the capability to disconnect the payload integration from the main booster assembly. Sealed integrated payloads can then be transported back to Rocket Lab where integration with the main booster can occur in a matter of hours. This approach eliminates the risk of cascading delays and allows customers to regain control of the integration process, using their own preferred facilities and personnel.”


It’s important to remember that Rocket Lab are targeting weekly launches of Electron. Traditionally the launch vehicle operator take a large role in integrating their customer’s satellite into their vehicle. If there are problems, this can be very time-consuming and costly for both parties to resolve. And if you’re trying to manage 52 satellites each year, that’s a lot of logistics to coordinate.

Rocket Lab elegantly solves this by making launch integration the customer’s responsibility. They simply ship (sell?) them the top of the rocket, let them spend as much time as they want getting their satellite to fit and plug in correctly to the module - and then they ship it back to Rocket Lab to launch. When it arrives, it’s given a quick check-out, placed on top, you attach four bolts, connect a few umbilical cables and drive it out to the launch pad. Of course we’re overstating the simplicity, but clearly moving the complicated phase off-site will save Rocket Lab a lot of headache.

And there are other potential benefits too. What do you do if you’re launching each week, and your customer hasn’t dropped their satellite off yet? Simply grab the next integrated satellite from your holding area and launch them instead! Or what if you notice a problem with your rocket while you’re running your pre-flight checks on the launch pad? You simply swap out the rocket base with another one, and continue your countdown.

There are some interesting questions from a legal standpoint. If you’ve made the satellite operator do their own payload integration, and you’ve launched and delivered the rocket to the right orbit -- then presumably it’s their fault if something is wrong with the satellite. But what if the payload fairing fails to separate? The customer integrated the upper module, but it was Rocket Lab’s hardware…

Another interesting angle is sensitive payloads and dealing with countries/organisations that don’t meet normal security requirements for dealing with rocket hardware. Potentially the US government for example could ship Rocket Lab a sealed upper-stage, with “do not open” instructions. And customers without security clearance can still hand-over their integrated satellite at the door to the building, and just not be allowed to see inside.

UPDATES (18 April 2015)
  • “We can integrate them within literally minutes,” he said. “It’s four bolts and we have a payload completely integrated onto the launch vehicle.” (Source)
    — This certainly is an exponential leap over the timelines for other rocket integrations.


--

Overall, today’s announcements by Rocket Lab are very exciting and bode well for them delivering on their planned price-point and rapid launch schedule. All this innovation needs to be flight-tested of course, but in many ways their changes simplify the rocket and reduce risks.

We hope there are more tidbits revealed at the NSS conference this week. And in the coming months we should learn where in New Zealand they’ll be launching from -- and most importantly, when that magical first launch attempt will be.

ADDITIONAL INFORMATION (18 April 2015)

Through discussion with media at NSS, Peter Beck/Rocket Lab also provided some other useful tidbits:

  • There is little aviation and marine traffic that the company would have to work around, and New Zealand’s regulatory system is simple. “For a $400 New Zealand government fee, we can go to orbit,” (Peter Beck) said. (Source)
    — This low cost is certainly a great advantage to Rocket Lab and New Zealand for space-related activities. No doubt New Zealand will develop additional processes and legislation around rocket launch activities, but hopefully they do this in a measured way that support development of industry. Australia unfortunately front-loaded legislation in response to a commercial venture that failed to proceed, and thus launching from Australia carries a very high cost.
  • Rocket Lab currently has about 50 employees, most of whom work in New Zealand. However, Beck says he considers the company an American one, with its headquarters in Los Angeles and plans to obtain a commercial launch license from the U.S. Federal Aviation Administration. “The vehicle flies a U.S. flag. It’s a U.S. launch vehicle,” (Peter Beck) said. (Source)
    — While no doubt fuelled by nationalistic sentiment, we can't help but feel disappointed by this statement. Perhaps it has been said to support the context of the customers they're trying to target at the Space Symposium (dominated by US companies and government), but it's a shame that they aren't embracing their NZ roots. From past reports Rocket Lab is looking to launch from Cape Canaveral at some point in the future, which would give greatly simply approval processes if they are launching US Government payloads. They've also secured several rounds of funding from US-based investors. It will be interesting to see if the rockets launching from New Zealand bear a US-flag though - as this would make the United States one of the "launching states" (as defined by space law) - and undoubtedly introduce a substantial paperwork burden.
  • Beck says the company has about 30 “commitments” from customers. (Source)


 

Electron Fast Facts
  • Lift off mass: 10,500kg
  • Propellant mass: 9,200kg
  • Propellants: Liquid oxygen and kerosene
  • Length: 18m
  • Diameter: 1m
  • Top speed: 27,500kph
  • Maximum engine thrust : 146,000 N (14.8 tonnes)
  • Engine equivalent power: 530,000hp
  • Nominal orbit: 500km circular sun synchronous
  • Nominal payload: 110kg


 

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