Virgin Galactic Spins Its Way Back to Rubber Engine for SpaceShipTwo

SpaceShipTwo in powered flight. (Credit: Virgin Galactic)
SpaceShipTwo in powered flight. (Credit: Virgin Galactic)

Despite Richard Branson’s increasingly dire pronouncements (The Time for Climate Action is Now) about how rising global temperatures and sea levels threaten the planet (and his private island home), it looks as if Virgin Galactic will go back to using a carbon spewing rubber hybrid rocket engine to power SpaceShipTwo.

That’s the word from Virgin Galactic officials in Mojave, who say that the rubber/nitrous oxide engine they previously abandoned is now performing better than the supposedly superior nylon/nitrous oxide engine they abandoned it for in May 2014. It’s not entirely certain, but it looks that way.

Branson won’t lose any sleep over this further expansion of his carbon footprint. He never has. Anyone who can passionately advocate for the climate while flying around the world in a private jet, expanding his fuel-gulping airlines, launching three new massive cruise ships, and burning rubber in the upper atmosphere is clearly untroubled by irony or contradictions. Here’s a guy who urges billions in new public spending on climate change while living as a tax exile in the British Virgin Islands.

Whatever Branson lacks in consistency, he more than makes up for in spinability. He’s a master at glossing over contradictions and obscuring unpleasant realities, even when what he’s saying is at odds with reality. (Branson’s Jaw Dropping Press Conference in Mojave)

Richard Branson speaks to the press at the Mojave Air and Space Port about the crash off SpaceShipTwo. (Credit: Douglas Messier)
Richard Branson speaks to the press at the Mojave Air and Space Port about the crash off SpaceShipTwo. (Credit: Douglas Messier)

And that brings us back to Virgin Galactic, a company that has clearly absorbed its founder’s talents in this area. This is certainly true with SpaceShipTwo’s long-troubled engine program, which has been going along just fine for many years now without producing very much.

So, why is the rubber engine now superior to the one they abandoned last year? Nobody’s really saying. As usual, the latest engine pronouncements arrive without any details about enhancements, overall performance, payload capability, etc. In other words, the kind of basic information that ULA, SpaceX and other space companies routinely provide.

Back in May, Vice President of Special Projects Will Pomerantz stated the company had an “internal horse race” going between the nylon and rubber engines to see which performed better. This raised an interesting question. Virgin Galactic is developing the rubber engine. However, the nylon motor was a Scaled Composites project. And word around Mojave was that Scaled was no longer involved in the SpaceShipTwo program.

Nitrous nylon engine test on Jan. 16, 2014. (Credit: Ken Brown)
Nitrous nylon engine test on Jan. 16, 2014. (Credit: Ken Brown)

So, is there actually a race going on? Was Scaled’s reported withdrawal from the program a factor in switching back to the rubber motor? Was the nylon engine ever really an improvement? Or was something else behind the change?

In an effort to clarify some of these matters, I sent the following questions to Pomerantz last week. Because Pomerantz was out on leave, they were forwarded to Richard DalBello, vice president of Business Development and Government Affairs. I used the word polymide instead of nylon in the email.

  1. As of May 2014, the polymide engine had better performance than the rubber one. Can you describe why the rubber motor now has superior performance? Details on changes made, etc?
  2. The polymide engine was a Scaled Composites engine. Are they test firing it for Virgin? Or have you brought the polymide test firing work in-house?
  3. Is Virgin test firing the polymide? Or are you doing rubber engine firings and comparing it to past polymide results that Scaled obtained?
  4. What is Scaled’s role, if any, in SpaceShipTwo’s development?
  5. If the rubber engine wins the race, what sort of performance would it give SpaceShipTwo? Specifically, for a full tourist flight with two pilots, how many passengers could it carry in the cabin and what maximum altitude could it reach?
Rich DalBello (Credit: Virgin Galactic)
Rich DalBello (Credit: Virgin Galactic)

DalBello’s response was unhelpful, but apolegetic.

I poked the team and they said, “We’ll do another update about the hybrid propulsion system a bit later in the year. We will give you a heads up.“

Sorry – that is all I have.

Well, that was disappointing. These are the types of questions that Virgin Galactic should be able to answer in about five minutes. Especially after 11 years of development, four years of flight testing, 34 SpaceShipTwo flights, numerous engine firings, and more than $600 million spent.

When they switched to the nylon engine back in May 2014, Virgin officials referred to it as a change in fuel grain. Scaled President Kevin Mickey called the engine change a “minor nuance” after SpaceShipTwo crashed last year. None of that was true. (Virgin Galactic Misled Ticket Holders, Public on Complexity of Engine Change“Minor Nuance” in SpaceShipTwo’s Propulsion System Was Neither)

The nylon engine actually featured a new fuel injection system that required major changes in SpaceShipTwo. I wrote about it at the time. The full truth was revealed in the 9-month NTSB investigation that resulted from the loss of SpaceShipTwo and the death of Mike Alsbury.

Now that the earlier claims have been officially proven false, Virgin Galactic officials are now embracing the complexity of the nylon engine to spotlight the superior simplicity of the new and improved rubber motor. CEO George Whitesides explained it all to Aviation Week:

According to Whitesides, the change not only provides adequate power but also results in a lighter and simpler installation. The switch to a polyamide-based grain involved changes to the pressurization system that feeds liquid nitrous oxide into the solid fuel of the rocket motor. Those changes included additional piping to improve initial combustion, as well as adding helium to stabilize the motor toward the end of the burn.

It’s a nice bit of spin. And effective, as long as no one remembers what you said before.

Now, why would Virgin and Scaled have obscured the changes? For proprietary reasons? That would be a good rationale. More likely, they wanted to hide the fact that the new nylon engine introduced additional risks, complexity and failure modes to the propulsion system.

Then there was the flight test schedule. They planned to fly a handful of flight tests with the new engine before beginning commercial service. Virgin and Scaled were hoping to fly SpaceShipTwo to a maximum altitude by the end of 2014, and then fly Branson and his son, Sam, on the first commercial flight by the end of March 2015. At least that was the plan at the time.

SpaceShipTwo right boom. (Credit: NTSB)
SpaceShipTwo right boom. (Credit: NTSB)

It was a risky schedule made riskier by the engine change. They pursued it even as they assured everyone that safety was the North Star of their operation. Ultimately, it wasn’t the engine that brought down SpaceShipTwo, but the vehicle’s feather system that was designed to keep the ship and its occupants safe. No one saw it coming.

The first anniversary of that sad Halloween accident is coming up in less than two weeks. Virgin Galactic has already started spotlighting the progress it has made since then. Maybe we’ll learn more about the new and improved old rubber engine by the end of the month.

  • redneck

    It has been said many times that switching to a liquid engine wouldn’t work as SS2 is built around the hybrid and there structural and aerodynamic problems with a switch. I have never understood why it would be that difficult relative to their ongoing problems and under-performance of hybrids to date. XCOR put rockets in a LongEZ to make the EZRocket. XCOR and Armadillo put rockets in a Velocity for the rocket racer concept. Both of those planes had heavy piston engines originally.

    IMO, they could have a Kero/LOX engine to their specs in a few months by writing a check to any of several suppliers. The increased engine performance would compensate for structural changes necessary to accommodate that engine while keeping the aerodynamics and COG in place for the vehicle.

  • Hemingway

    Will this switcheroo cause more delays?

  • stoffer

    I have read somewhere that the N2O tank is a structural element, so new tanks would mean a significant airframe redesign.

  • Hug Doug

    Bingo, stoffer. Yes, the N2O tank is a structural element and is integrated into the SS2 design. Removing it means redesigning the entire airframe.

    It would require years more delay, but frankly I think it would be safer and more reliable in the end. Then again, I always thought it should have been liquid fueled from the beginning.

  • Douglas Messier

    Probably not.

  • Douglas Messier

    NewtonThree is sized for SpaceShipTwo. The plan was to modified the third SS2 to use it. That idea was shelved. Perhaps with NewtonThree now under development for LauncherTwo, they will revive that idea for future versions.

    Someone who works for them once told me they end up zigging and zagging a lot because they’re not sure where they want to go. You can see that in the engine development and LauncherOne program.

  • Hemingway

    The dangers of rocket propulsion are well-known. Maybe the hybrid rocket motor should reject the usual rubbery polymer and use ordinary paraffin wax. Yes, wax. Here is an excellent article on the subject.

  • savuporo

    So dont remove it. N2O and Propane make a fine biprop. Also, NOFBX maybe

  • Hug Doug

    I’m not sure it can be designed around, but maybe it can. I’m not sure there will be enough propellant to get it up to the Karman Line though. VG has lots of issues to work through.

  • TimR

    You think the bloom is now off the rose for VG and SS2? These ticket holders have been waiting so long that I imagine most just want to have the confidence to step into SS2, experience nearly the edge of space and then return safely to Earth. They’ll get their zero-G experience. Whether its 3 minutes or 4 won’t matter because in such unique experiences people lose track of time; either span will seem too short. Furthermore, whether its 60 miles high or 70 or whatever the numbers bounced around are, the customers won’t know the difference. Having never seen nearly “the edge of space”, it will look high enough. Pardon the cynicism but I think there is some degree of such thinking among VG executives. Use the rubber fuel, give the kid passengers rubber-duckies and the old men rubbers made from the fuel base as a gag gift.

  • Scott

    Now you are on to something.
    That is the same “big change”, “big idea” that was going to revolutionize the hotel industry in the world which Branson (once again) promised when he started Virgin Hotels which were specifically designed for women executives, who according to Branson had been mistreated by too many chauvanistic male jerks in the hotel business who just did not know what women wanted and needed in a hotel room. The big deal was that they would design the hotel rooms for traveling women executives and the their special needs which clearly Branson is an expert on by making the closets bigger and supplying rubbers, oils and vibrators.
    I am not kidding.
    Look it up.

  • TimR

    Yes, I’ll have to look that one up! whew.

  • Hug Doug
  • Douglas Messier

    What sources indicated about the rubber to nylon engine switch was this:

    Sierra Nevada had figured out a way of dampening out the vibrations and oscillations that involved using helium. There was an engine test in December 2013 that Virgin published a video of showing a full-duration burn on the stand.

    Scaled flew a third powered flight with the unimproved rubber engine on Jan. 10, 2014. It was another 20 second burn like on the second flight test. A week later, they flew a glide flight and then took SpaceShipTwo out of service for modifications. Those included some tanks in the wings for the helium and other changes.

    As far as SNC knew, things were moving ahead with the modified engine. However, the SNC engine could get the ship up to like 50 miles with four passengers. That was a significant cut in revenue. The other problem was that SNC’s agreement was costing Virgin a lot of money. And Whitesides was under pressure to both cut expenses and get Branson into space by the end of the year.

    Meanwhile, Scaled had developed a nylon engine that was viable. And Scaled was already doing a fair amount of the work relating to the rubber motor. So, Virgin could cut costs by switching to the nylon motor. And Scaled would get more income.

    So, Virgin announces this big change on a Friday going into Memorial Day weekend in the U.S. and bank holiday in the UK. (A good time to dump news you don’t want a lot of questions on.) SNC was totally, completely blindsided by all this. Had no idea it was coming. People there reading my blog and Alan Boyle’s story on NBC News online to try to figure out what the hell was going on.

    The nylon engine wasn’t necessarily better performing, but it was an affordable interim solution that would work so they could finish up the flight test program and begin some initial commercial operations. They wee under some real pressure from investors (read: Aabar) to show some results real soon. They were trying to get Branson flying by the end of 2014; that was later extended to first quarter 2015.

    The nylon engine would involves some significant changes to the ship, including a fuel injection system using the wing tanks that reportedly contained methane. The changes to the ship were quite substantial from the much simpler propulsion system that had flown for the first three powered flights.

    So, the plan was to use the nylon engine in the interim but to eventually pick up internally where SNC left off on the rubber motor and try to improve the performance even more. And that seems to have been what they have done. How much of that work was done between dumping SNC and the SS2 crash is unclear. Certainly there has been a lot of work done on it since the accident.