A-HA! SpaceShipTwo’s Parallel Engine Program Revealed

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Doug Messier
on July 20, 2012, at 4:05 pm
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23 Comments


By Douglas Messier
Parabolic Arc Managing Editor

There have been stories floating around Mojave for some time that there is a liquid-fuel rocket being developed for Virgin Galactic’s SpaceShipTwo in parallel with the troubled hybrid RocketMotorTwo program. And, what do you know? The stories are true, according to Aviation Week:

LauncherOne will be powered by a two-stage, liquid-fueled rocket, now in initial development by Virgin Galactic. The same rocket also is intended to ultimately replace the non-reusable RM2 hybrid motor that will power the SS2 to suborbit, Virgin says….

Initial LauncherOne flights are due to start in 2015, with commercial flights getting under way by 2016…

So, it seems that SpaceShipTwo flights with liquid propulsion are about four years away. In the meantime, the RM2 engine will suffice:

The RM2 is in the final stages of development by Sierra Nevada Space Systems and “all major components have now been qualified for powered flight,” according to Virgin Galactic CEO George Whitesides. The RM2 is the major pacing item to the start of rocket-powered flight tests of SS2, which are expected to start by year’s end. Assuming tests go as planned, Virgin hopes to start initial suborbital passenger flights by the end of 2013.

And what happens if tests don’t go well and the hybrid motor isn’t a good interim solution? Well, then Virgin Galactic’s 500 plus millionauts are going to have quite a wait on their hands. And some of them are already pretty restless.

It will be very interesting to see how all this all plays out.

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  • Carolynne

    I do hope that they are purchasing a proven rocket motor system and not repeating the mistake of thinking developing a new rocket motor from scratch is a simple matter.

    I, for one, am much happier that these relative beginners are now proposing to launch non-human payloads. The odd blow-up small satellite will doubtless be more acceptable than the odd blown-up millionaut.

    One hopes that they are capable of learning lessons from the past (their past and that of others).

  • Rob Coppinger

    Its not correct. In an article yet to be published by Space.com I asked Richard Branson and George Whitesides directly about the new liquid propulsion system and they said it wasn’t for SS2

  • http://exoscientist.blogspot.com Robert Clark

    Thanks for that. The author of the article Guy Norris says the info that the hybrid will be replaced by a liquid-fueled engine comes from Virgin.
    It is true that Virgin Galactic could get a suborbital vehicle from just SpaceShipTwo alone, without WhiteKnightTwo, if it used the new hydrogen-fueled Vinci engine:

    SpaceShipTwo could be single stage to suborbit says ESA firm.
    By Rob Coppinger on April 29, 2010 4:24 PM
    http://www.flightglobal.com/blogs/hyperbola/2010/04/spaceshiptwo-could-be-single-s.html

    Reusable Space Plane Idea Intrigues Europeans.
    Rob Coppinger, SPACE.com Contributor
    Date: 01 May 2012 Time: 04:30 PM ET
    http://www.space.com/15494-vinci-space-plane-suborbital-flight-idea.html

    More important than this though is the fact if you scaled up such a perhaps by a factor of 2 you get a fully orbital single stage vehicle. This is because scaling your rocket up actually improves your mass ratio.

    Bob Clark

  • Ratliff

    Single stage to orbit requires a fuel fraction (by weight) of 92%. That leaves just 8% for EVERYTHING else. SSTO with current materials and technology is not happening.

  • http://exoscientist.blogspot.com Robert Clark

    SpaceX has achieved a mass ratio of 20 to 1 on the Falcon 9 first stage which corresponds to a fuel fraction of 95%:

    SPACEX ACHIEVES ORBITAL BULLSEYE WITH INAUGURAL FLIGHT OF FALCON 9 ROCKET.
    “The Merlin engine is one of only two orbit class rocket engines developed in the United States in the last decade (SpaceX’s Kestrel is the other), and is the highest efficiency American hydrocarbon engine ever built. The Falcon 9 first stage, with a fully fueled to dry weight ratio of over 20, has the world’s best structural efficiency, despite being designed to higher human rated factors of safety.”
    http://www.spacex.com/press.php?page=20100607

    They expect the side boosters on the Falcon Heavy to have a mass ratio of 30 to 1 using the lighter Merlin 1D engines, which corresponds to a fuel fraction of 97%.

    Bob Clark

  • Paul451

    “SpaceX has achieved a mass ratio of 20 to 1 on the Falcon 9 first stage which corresponds to a fuel fraction of 95%”

    Figures given for the F9 first stage are launch mass 258 tonnes, burn-out mass 19.25 tonnes. That’s about 13:1. The figures for F9.1 first stage are 429t at launch, 28t burn-out, about 15:1.

    http://www.spacelaunchreport.com/falcon9.html

    I’m not sure what SpaceX is referring to with their “ratio of over 20″.

  • Marcus Zottl

    Paul451, spacelaunchreport has only some “estimated” numbers and with a quick glance over the site I can’t find an information how they came up with those numbers. Unless spaceX is blatantly lying about their mass ratios, those values can’t be true.

    Robert Clark, please stop using that stupid news about the “study” from the UK that SS2 could be single stage to suborbit with a liquid engine. The news only talks about reaching a laughable 50k ft altitude. Unless you have access to the actual study and the values there make more sense, I would refrain from using this news as a pro SST(S)O argument.

  • Rob Coppinger

    Bob,

    I know Guy and he has got that from Branson’s Farnborough speech where he said the liquid propulsion would be important to the ‘future of the SS2 program’. But when I asked Branson directly about it the answer was no it wasn’t for SS2.

    Yes I am aware of the stories I wrote. It’s an interesting idea but Virgin has to pay off the hybrid engine development first. ;-)

    Rob.

  • Paul451

    Marcus,
    The total mass at launch is well publicised, so is the maximum payload, and the Isp of the engines. So unless the entire first stage, rockets, thrust-frame, tankage, etc, weighs just a couple of tonnes, I can’t see the 20:1 and especially 30:1 figures being related to launch-mass/burn-out-mass.

    Additionally, if Musk effectively already had an SSTO in his first stage, why would he be bothering to develop anything else?

  • http://exoscientist.blogspot.com Robert Clark

    Paul451, those numbers on the Ed Kyle’s SpaceLaunchReport site are only estimates as he acknowledges since SpaceX has not released those numbers, only the gross mass.

    Bob Clark

  • http://exoscientist.blogspot.com Robert Clark

    Marcus Zottl, no reasonable interpretation of that news story could take it to mean only 50 thousand feet as that is not suborbital. The altitude mentioned is only referring to the altitude the WhiteKnight reaches, an altitude subsonic jets can reach easily, as WhiteKnight itself is. It would be worthless to use a high performance cryogenic engine such as the Vinci to take a vehicle to that height.
    Also in the Space.com story the second design graphic with the caption “A design drawing of the Vinci suborbital space plane Concept 2 under review by the European Space Agency” shows the craft with a length of 60 feet, the same as that of SpaceShipTwo.

    Bob Clark

  • http://exoscientist.blogspot.com Robert Clark

    Paul451, unless you know the breakdown between the first and second stages, you still can’t get what the individual masses are from the gross mass, payload and engine Isp’s without further information.
    GW Johnson a former rocket engineer made some estimates using different assumptions than Ed Kyle and got numbers quite close to a 20 to 1 mass ratio for the Falcon 9 first stage:

    WEDNESDAY, DECEMBER 14, 2011
    Reusability in Launch Rockets.
    http://exrocketman.blogspot.com/2011/12/reusability-in-launch-rockets.html

    Bob Clark

  • Ratliff
  • Ratliff

    http://www.spacedaily.com/news/oped-05zy.html Why SSTO is not happening with known technology

  • Paul451

    Robert,
    Someone (you?) posted a comment on that article linking back to this one. So hopefully Gary will add some details.

    My point remains: If Musk already has a 30:1 ship, he can SSTO the first stage. In that case, why would he bother building a multi-stage expendable? He’s already “won”. Unless the 20:1 & 30:1 figures aren’t referring to gross-lift-off-mass vs burn-out-mass, but to something more obscure.

    “and got numbers quite close to a 20 to 1 mass ratio for the Falcon 9 first stage:”

    Actually it looks like Gary used 20:1 to back-calculate the dry & prop masses.

  • Dave Klingler

    Ratliff: You do *not* want to use Jeff Bell for a reference. Jeff rarely gets his facts straight. In this case, he’s convoluting SSTO and reusable, which are separate issues. And “former space scientist” means he’s a former astrophysicist, with just barely enough physics knowledge to be dangerous but absolutely no experience in rocketry.

    Paul451: Just because the first stage might fly on its own to orbit doesn’t mean that Musk wouldn’t want to take a little more payload along with it. It’s not reusable, and there’s no reason to waste the cost of a first stage on relatively little payload.

    SSTO isn’t that hard. SSTO reusable is hard, although nowhere near as hard as Jeff Bell makes it out to be. Bell alleges that all rocket engineers who work up SSTO designs are either lying or not as smart as he is. That’s why Bell is constantly incorrect.

  • Robert Clark

    Paul451, that was not me who posted a comment about the source for the numbers on the http://exrocketman.blogspot.com/2011/12/reusability-in-launch-rockets.html blog post.
    Perhaps GW Johnson reversed engineered those numbers; I’ll ask him.
    In any case, here are some other clues you can use:

    I found this reference after doing a web search on the Falcon 9 mass:

    Appendix A
    ELV Specifications and Descriptions.
    “Falcon 9
    The Falcon 9 is a medium class launch vehicle with a gross lift-off weight of approximately 315,000 kg (693,000 lbs) and an overall length of 54 meters (178 feet). The Falcon 9 uses LOX
    and RP-1 to carry payloads into orbit and is basically a scaled-up version of the Falcon 1 vehicle.
    First and Second Stages.
    The first stage of the Falcon 9 is approximately 3.6 meters (12 feet) by 30.5 meters (100 feet), and includes 9 Merlin engines, the same engine used on the first stage of the Falcon 1. The second stage is approximately 3.6 meters (12 feet) by 12.5 meters (41 feet), not including the fairing and payload, and uses one or two Merlin engines. The fairing is 5.2
    meters (17 feet) by 15.2 meters (50 feet), and a smaller version may also be used. The first stage consists of LOX and kerosene tanks that hold 146,000 liters (38,672 gallons) of LOX and 94,000 liters (24,840 gallons) of kerosene. The second stage consists of 27,600 liters (7300 gallons) of LOX and 17,400 liters (4600 gallons) of kerosene in tanks with a common bulkhead.”
    http://sites.wff.nasa.gov/code250/docs/expansion_ea/Appendix_A_MARS_Final_EA.pdf

    From already known densities of LOX and rocket grade kerosene (RP-1) you can get an estimate of the propellant weights for each stage. I calculate an estimate of 240 mT to 250 mT total propellant load for the first stage depending on which source I use for these densities. These densities do change with temperature.

    Two videos of SpaceX tours also give some info on the Falcon 9 mass. This one gives the all up dry mass including the Dragon as payload as 30 “tons”. And it gives the first stage dry mass as 32,000 lbs., 14,500 kg:

    SpaceX.
    http://www.youtube.com/watch?v=F-nwPnNQIWM&feature=player_detailpage#t=266s

    This one also gives the all up dry mass as 30 “tons”:

    A tour of Space Launch Complex 40 – SpacePod 2011.05.23.
    http://www.youtube.com/watch?v=JaGHbXOBcWc&feature=player_detailpage#t=44s

    By “tons”, from the informal, non-technical manner in which it is spoken, I’m inclined to believe they mean english tons, i.e., short tons, not metric tons. If so, that would be 27,270 kg for the all up weight.

    A problem though is that first stage dry mass at 32,000 lbs, 14,500 kg. This creates a problem for a 20 to 1 first stage mass ratio if the propellant load for the first stage is in the 240 mT to 250 mT range. This might be resolved if the 32,000 lbs, 14,500 kg, first stage dry weight they’re referring to in that first video includes an interstage.
    The interstage is frequently included with the first stage weight since it drops away along with the first stage with staging. You would also expect it to be attached if they were working on the first stage. A rocket this size very well could have an interstage in the 1,000 kg to 2,000 kg size range.

    Bob Clark

  • http://www.parabolicarc.com Doug Messier

    I just had an email exchange with Guy Norris. This is what he told me:

    He stands by his story and says that information did not come from Branson’s speech. He said that another high-ranking Virgin Galactic official volunteered that information to him during a conversation after the main event at Farnsborough. Virgin Galactic has made no request that the information be corrected, which it would normally do if this report was inaccurate.

    Norris is standing by his story. I stand by this post unless I hear otherwise.

  • http://www.parabolicarc.com Doug Messier

    Rob:

    Is this the denial you’re citing?

    SPACE.com. Will we see LauncherOne’s liquid propulsion system developed into something for Virgin’s spaceliner SpaceShipTwo, or a future version of SpaceShipTwo?

    George Whitesides: I think we’ll have to see how things go. Clearly, having a highly reusable engine is a great thing, but at the same time we think the right application is LauncherOne.

    “I think we’ll have to see how things go” is what they call a non-denial denial. Having a highly reusable engine is a great thing because they will need to replace the SS2 hybrid engine after every flight. It’s time consuming and adds the possibility of something being damaged in the process. It’s also extremely expensive. The whole architecture leads to relatively low flight rates, high operating costs, and the need to build additional vehicles.

    If they’re going to spend the next four years developing LauncherOne and they’re not using that as the basis of a low-cost, reusable engine for SS2, then I would really question their business smarts. It’s the only way to really lower SS2′s operating costs and bring down the cost of spaceflight.

  • jazzfiend

    I think I saw something a few weeks back that Dreamchaser was also supposed to use a hybrid engine. I also was under the impression that the engine for both SS2 and Dreamchaser were being developed by the same people. If that is correct, what is the status of the engine for Dreamchaser?

  • http://www.parabolicarc.com Doug Messier

    The Dream Chaser hybrid engine is similar to the one Sierra Nevada is developing for SpaceShipTwo. However, it is smaller. I’m not sure where it is in terms of development.

  • Ratliff

    If SSTO is not reuseable, then what’s the point? However, it’s a moot point because a vehicle that’s BOTH reuseable and SSTO is not happening with known technology.

    Whether it’s Virgin Galactic or one of the other private suborbital spaceplanes, the lack of escape systems assures that the Challenger and Columbia disasters will soon be repeated on a smaller scale.

    Whoever starts flying first will probably lose a plane before they make “enough” flights to “certify” it “safe” for carrying passengers.

    That’s assuming Virgin Galactic ever makes powered flights, because so far their engine development program has been a complete disaster.

    Although the suit worn by Felix Baumgartner greatly expands the envelope in which escapes are feasible, to assure escapes in all phases of the flight regime requires an encapsulated ejection seat such as developed over fifty years ago for the B-58 supersonic bomber.

  • richard_schumacher

    What’s the point? No staging, and no air-starts, for two. Both big wins for reliability, and potential big wins for system operating costs.