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Space Transportation Build Technology

Rocket Lab Unveils "Electric" Rocket Engine 75

Posted by timothy from the partially-electric-is-still-cool dept.
New submitter Adrian Harvey writes The New Zealand based commercial space company Rocket Lab has unveiled their new rocket engine which the media is describing as battery-powered. It still uses rocket fuel, of course, but has an entirely new propulsion cycle which uses electric motors to drive its turbopumps.

To add to the interest over the design, it uses 3D printing for all its primary components. First launch is expected this year, with commercial operations commencing in 2016.
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Rocket Lab Unveils "Electric" Rocket Engine More

Rocket Lab Unveils "Electric" Rocket Engine

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  • Hype pain (Score:5, Insightful)

    by SuricouRaven ( 1897204 ) on Saturday April 18, 2015 @11:33AM (#49500483)

    It's a rocket engine with 'turbopumps!' And 3D printing!

    Ok, de-hyped version: Rocket engines consume huge amounts of fuel. Getting fuel from tanks to engines needs pumps, which usually need their own mini-engines. This design uses electric pumps, saving weight and complexity. They are using 3D printed parts, including titanium, because it lets them iterate through design refinements quickly. The engines themselves still burn fuel as normal, they just weigh less.

    • Re: (Score:3)

      by DarkOx ( 621550 )

      The engines themselves still burn fuel as normal, they just weigh less.

      Hype or no hype that last clause is a pretty big deal when it comes to anything related to rocketry.

    • It's a rocket engine with 'turbopumps!' And 3D printing!

      If it were only connected via the internet of space things and solar powered, it would be the perfect /. story.

    • Re: (Score:1)

      by linearZ ( 710002 )

      The pumps may be lighter, but where do they get the electricity to run them?

      I wouldn't expect the energy required to run electric pumps to be any different than the previous methods, and that probably wasn't trivial to start with. So does the electricity come from batteries (heavy), or are they doing something tricky like generating current off the massive amount of waste heat using some undisclosed thermal junction technology. A scenario like the latter would be interesting. But if they are using batter

      • At 3g, it took the shuttle 8.5 minutes to get to Low Earth Orbit. This rocket is going at 30g. If things scale, then it will take less than a minute to reach orbit. Even if it took 5 minutes, there are three stages on this rocket. The batteries need to run for two minutes, max. In other words, you don't need big heavy batteries. Small, lightweight batteries will do just fine.

        • The minimum amount of energy required to pump a given quantity of propellant against a given chamber pressure is fixed, and not low. Doing it in a shorter period of time only makes the *power* requirements *higher*. You also need enough batteries to supply your power demands with the batteries partially discharged, so the effective energy density is reduced.

          For a rough, BOTE calculation: they claim a thrust of 4600 lbf and specific impulse (vacuum, presumably) of 327 s. Mass flow rate is something like 6 kg

    • Still, I'm disappointed that they could fit "cloud computing" and Node.js into the design. That would be a truely awsome rocket

    • You are one of the few commenters that are making any sense. The several trolls criticizing their electric pump methodology sound like the thousands of critics of Tesla Motors... even years after achieving glowing success, dingbats such as Eric [ig] Noble have been making fools of themselves, proclaiming Tesla and EVs a dead end, failure, noncompetitive, etc. This Kiwi company reminds me of Musk, Tesla, and SpaceX in many ways, including the very aggressive use of 3D printing in the SpaceX rockets and oth

    • Re: (Score:2)

      by delt0r ( 999393 )
      The power rating of turbo pumps is in MW and even GW. Batteries are not going to cut it on anything that not a toy.

  • Meh. (Score:4, Interesting)

    by Rei ( 128717 ) on Saturday April 18, 2015 @11:45AM (#49500531) Homepage

    About 10 years ago I worked on simulating a rocket with electric turbopumps for fun. The concept was the exact same as theirs - minimize the number of parts that have to operate in harsh environments to reduce cost, maintenance and risk of failure. You don't even need any penetrations of the propellant lines, the rotor of the electric motor is the compressor itself.

    I have no clue whether the design will actually be practical. But it's certainly not new. I'm sure I'm not the first person that this concept occurred to.

    • Re: (Score:2)

      by Twinbee ( 767046 )
      You're probably a good candidate for answering this. Why doesn't a decent Ragone chart exists for rocket propulsion? I looked for ages in Google, an only found a few [reddit.com] diagrams. It'd be amazing to see where new propulsion technologies fit on a single unified graph.

      • There are quite a few for propulsion. A few for space propulsion. But the whole field is just too new.

      • Re: (Score:3, Informative)

        by Anonymous Coward

        Because you're asking the wrong question. Aerospace engineers don't plot energy density vs. power density: they plot specific impulse (or equivalently exhaust velocity) vs. acceleration (or thrust). Which gives the same answers in the form of variables more directly useful for rocket equations.

        You can get such plots in any good propulsion or mission planning text. E.g. Rocket Propulsion Elements by Sutton & Biblarz (8th ed). has one on p. 42; Space Mission Engineering: The New SMAD* by Wertz et al. has

        • Re: (Score:2)

          by Twinbee ( 767046 )
          Yes I meant specific impulse vs thrust.

          Thanks, I saw the plot in the former book you mentioned, though the diagram is still pretty coarse (not giving specific techs), and it doesn't unfortunately extend the chart to future or theoretical technologies.

          This kind of diagram summarizes perfectly why we can't (yet) create a brilliant, compact, and efficient rocket, so I expected a few more about.

          • Re: (Score:1)

            by Anonymous Coward

            I recomend you check out Progress in Astronautics and Aeronautics Volume 223: Advanced Propulsion Systems and Technologies, Today to 2020 by Lu et al. It doesn't have the exact plot you want (the matter is a little more complex and subject to further development) but you'll get a good understanding.

    • Re: (Score:2)

      by wjcofkc ( 964165 )
      I think the idea here is that we have only recently achieved the energy density needed from lithium ion batteries for this to be practical. This could not have been accomplished in 1999 - or at least it would have been a lot more heavy.
  • In terms of rockets. there's a trade off between fuel efficiency per kg and thrust per kg (similar to power versus energy for batteries).

    So where does the technology fit on this Ragone chart [nasa.gov]?

    • Nowhere, because this is just a different mechanism to run the pumps in a normal liquid-fueled conventional rocket.

      • Not true. Measures of rocket efficiency almost always count losses to the pumps.

        That's why gas-generator-pumped rockets (like the F-1, at 263s, or the Merlin 1D at 310s) are listed as less efficient than staged-combustion rockets (like the NK-33, at 331s). The rockets are measured as a full system, not at just the combustion chamber and nozzle.

        This one, I would expect, has higher fuel efficiency per kg and lower thrust per kg. Not having to burn any fuel for non-propulsive purposes will undoubtedly help its

        • Some of that mass cost might be made up for by simplified pipes and valves, though. Not sure how much you'll really save here, as you're probably still routing stuff around the bell for cooling.

    • Higher ISP than a regular chemical engine and worse thrust and thrust-to-weight-ratio I bet.

  • Cheap because of size, not engines (Score:3, Interesting)

    by gman003 ( 1693318 ) on Saturday April 18, 2015 @12:00PM (#49500609)

    Big rocket engines use big propellant pumps. The pump on the F-1 (used on the Saturn V) ran about 55,000 horsepower.

    Electric motors won't do that cheaper. And they'll sap the weight of the rocket, since even a dead battery is heavy. Fundamentally, a big rocket will be better served by a gas-generator or staged-combustion cycle.

    That's fine for this rocket because it's so small. The payload is 110kg. For comparable rockets, turn to Iran's unflown Simorgh, Israel's Shavit, or North Korea's Unha, all in the 100-160kg range.

    To put those numbers in comparison, let's look at SpaceX. The single-engined Falcon 1 put 670kg into orbit. A Falcon 9 runs 10,000-13,000kg. And the Falcon Heavy is supposed to lift 53,000kg.

    Or for an older comparison, Sputnik 1 weighed 80kg, and Sputnik 2 weighed 500kg. So they're building a rocket that couldn't even lift the second satellite to ever fly. I'm not particularly impressed.

    Maybe there's a niche for small payloads like this, but in all honesty, I expect you could fly several such payloads on one bigger rocket, or just hitchhike on the spare capacity on a big satellite launch. Still, worth a shot. Just don't pretend to be playing in the big leagues.

    • Maybe there's a niche for small payloads like this

      For when an Amazon drone just isn't fast enough.

    • It can be used for Cubesats. You can do a useable satellite smaller than a Sputnik today because the electronics are better. Yes it is mostly used for universities or things like that. There are also some people doing "space burials" so I guess this could be used for that as well.

    • Maybe there's a niche for small payloads like this, but in all honesty, I expect you could fly several such payloads on one bigger rocket, or just hitchhike on the spare capacity on a big satellite launch. Still, worth a shot. Just don't pretend to be playing in the big leagues.

      Where did they claim to be playing in the big leagues? And yes, there is a niche for microsatellite launch services. Your unnecessarily grumpy comments are largely correct, but you've missed the whole point of the operation, which is cost. Virgin's LauncherOne is aiming for $10m per launch, these guys are claiming half that price.

  • Questionable engineering decisions. (Score:3)

    by mpoulton ( 689851 ) on Saturday April 18, 2015 @01:24PM (#49500953)
    Ever since their first widespread implementations in the mid 20th century, turbopumps have been powered by rocket propellants - either the same stuff they are pumping (F1 engine in the Saturn V), or a separate propellant dedicated to powering the pumps (Space Shuttle Main Engines). There are excellent reasons for this, and not many good reasons to use batteries and motors instead. Rocket propellant pumps require truly massive amounts of power to move thousands of gallons per minute of propellants at thousands of PSI pressure. The SSME turbopumps require over 70,000 horsepower per engine. Like all other rocket hardware, size and weight are extreme concerns. Power-to-weight ratio is the single most critical design goal. Rocket engines themselves burn the propellants they do specifically because those chemical combinations are the absolute best we have for producing the maximum amount of thermo-mechanical energy from the least mass, no-compromise. Using the same types of propellants to drive the turbopumps also provides the maximum achievable power to weight ratio. The SSME turbopumps produce over 100HP per pound, which is insanely high. No known electric motor technology can even reach that order of magnitude in power density, even considering only the actual motor itself! There is no legitimate contest in performance between a gas-driven turbopump and any other technology besides nuclear, and that's that. To make such a large compromise in power to weight ratio by using electric pumps is very odd. Yes, gas-driven turbopumps are really hard. They are the hardest part of building a large liquid rocket engine. But those challenges were first solved over 60 years ago, and avoiding a tough engineering exercise is no excuse for making a giant compromise in performance. The extra mass of that electric drive system could be replaced with propellant or cargo.

    • Re:Questionable engineering decisions. (Score:4, Informative)

      by gman003 ( 1693318 ) on Saturday April 18, 2015 @01:52PM (#49501053)

      Uh, the SSME engines ran off the same propellant as the rocket - LH2 and LOX. It's a staged-combustion rocket - some of the fuel and oxidizer flow was diverted to a preburner, which partially combusted them (the mixture was fuel-rich, limited by oxygen), ran the fuel-rich exhaust through turbines for the fuel and oxidizer pumps, then exhausted into the main combustion chamber where it was mixed with the remaining oxygen to complete combustion.

      A better example for a separate propellant would have have been the V2 rocket, which burned ethanol and LOX, and had a pump powered by hydrogen peroxide.

      Right on all other points, though.

    • Re: (Score:2)

      by rtb61 ( 674572 )

      You missed the bit where you can also feed the exhaust from the gas driven pump into the rocket engine exhaust and recover some of that energy and mass as thrust. The energy from an electric motor being completely lost. I though rocket patents are really tricky as most countries incorporate legislation to override patent laws and treaties when subject to national interests (patents with regard to military applications are purely voluntary and can be readily over ridden).

    • Re: (Score:2)

      by dbIII ( 701233 )
      On the other hand batteries really sucked in 1962.

  • vs. a Falcon 9 (Score:1)

    by Anonymous Coward

    They can carry about 110kg to LEO, compared to the Falcon 9's 13150kg. That's 0.84% of the payload capacity. A launch is estimated to cost $4 900 000, compared to the Falcon 9's $61 200 000. That's 8.01%. That means cost per mass to orbit is nearly an order of magnitude worse.

    Surely if you need a small payload to orbit, it would be much cheaper to piggy-back on another mission, either paying for space on someone else's satellite or somehow launching multiple satellites in one launch? SpaceX is planning to l

    • They can carry about 110kg to LEO, compared to the Falcon 9's 13150kg. That's 0.84% of the payload capacity. A launch is estimated to cost $4 900 000, compared to the Falcon 9's $61 200 000. That's 8.01%. That means cost per mass to orbit is nearly an order of magnitude worse.

      Yes, this is a really small rocket. If you are a government or some other entity that needs to put something small in orbit right away, the USD$5 Million price might not deter you, even though you could potentially launch a lot of smal

      • Re: (Score:2)

        by Guspaz ( 556486 )

        But you can also get on a larger rocket (like the Falcon 9 you mentioned) as a secondary payload pretty cheaply, so there's no cost advantage in the "I only want to launch a small payload" category. There's also, for that matter, no guarantees that these guys would be able to get your payload into orbit any faster than established players, especially by the time some of the new launch infrastructure under construction comes online.

        • They don't have nearly as much to offer if they can't do launches quickly. I'm sure they would make that a feature of their offering.

    • You know, that rocket that isn't flying because there isn't enough of market for its payload category...

  • This *might* be an avenue alternative to ion engines for flights that don't stray too far from the Sun. LEO-Moon, Lagrangian Points, inner planets. And it could be combined with ion and rocket propulsion.

    You can't store all the propellant at extreme pressures simply because the tank needed to contain these pressures would be extremely heavy. There's a fine balance between weight of the tank and savings on storing pressurized fuel (both energy stored as pressure and more fuel fitting in). We're at "state of

  • The technology seems sound. Others here raise concerns but I don't think they are showstoppers. This rocket ought to work. But who will buy it? The Falcon 1 filled a very similar niche and price point to this new rocket, and SpaceX simply couldn't find any customers for it. So why do people keep building these dedicated small satellite launchers? I am guess its because its easy. Your engines can be below the size threshold of various difficult and expensive problems. You don't need such a large launch fac

  • Would not Scotty have said "Ion power" ?

  • Are extremely efficient for their mass and volume. The key issue they must overcome is cooling. If the motor is in the liquid stream, (and this is a likely assumption) cooling is damn near free. As for the power supply, I am fairly sure that the reduced mass, complexity of the pump, plumbing and associated benefits with reducing the volume of the pump system that must survive extreme temperature and pressure, more than make up for the battery mass.

    Those that doubt the tech will scale up to larger designs

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