Virgin Galactic Misled Ticket Holders, Public on Complexity of Engine Change

RocketMotorTwo firing. (Credit: Virgin Galactic)
RocketMotorTwo firing. (Credit: Virgin Galactic)

When Virgin Galactic announced it was switching from the nitrous oxide/rubber rocket engine they had flown on SpaceShipTwo three times to one powered by nitrous oxide and nylon, company officials told ticket holders and the public the change involved only minor modifications to Richard Branson’s space tourism vehicle.

A document released last week by the National Transportation Safety Board directly contradicts that claim. In  it, a Federal Aviation Administration (FAA) safety expert describing his concern over “major modifications” that had been made in the suborbital space plane to accommodate the new engine.

When the engine change was announced last May, Virgin Galactic CEO George Whitesides told Space News:

The vehicle’s hybrid engine, manufactured by Sierra Nevada Corp., will need to undergo what Whitesides called “minor tweaking” to accommodate the plastic propellant.

“We just need to tweak the plumbing line in the motor to go with the plastic, which is sort of a minor mod,” he said.

In a May 23, 2014 email to ticket holders obtained by Parabolic Arc, Virgin Galactic Commercial Director Stephen Attenborough wrote:

Both fuels were designed to be interchangeable with the hybrid motor, with only minor plumbing modifications, meaning that we have been able to remain objective and unbiased in our assessment of the alternative fuel choices. Both have also been tested extensively.

As we have entered the qualification phase of the commercial hybrid motor in preparation for the final series of powered test flights, it has been critical to finalize the fuel that we’ll use for this and into the start of commercial operations.

Having made this decision, we will now be working hard to make the minor modifications to the spaceship systems in order to continue powered flights with the chosen fuel type as soon as safely possible.

At a press conference four hours after the crash of SpaceShipTwo on Oct. 31, 2014, Scaled President Kevin Mickey described the change of engines as a “minor nuance”. He also correctly stated that the engine was not the cause of the fatal accident that killed co-pilot Mike Alsbury.

NTSB documents released last week as part of its crash investigation show the engine change was anything but minor or nuanced. The switchover involved much more than using a different  fuel grain and slightly modifying the plumbing.

So says Tom Martin, the lead technical system safety engineer at the FAA Office of Commercial Space Transportation (FAA AST) who reviewed the modifications last year as part of the renewal of Scaled Composites experimental permit to test SpaceShipTwo.

“They’ve made some major modifications,” Martin told NTSB investigators examining SpaceShipTwo’s crash. “They’ve shortened the engine. They’ve changed the fuel, the shape, and they’ve added [redacted] – [redacted] plumbing and tanks, [redacted] psi tanks in the wings and changed the structure of that.”

Sources have told Parabolic Arc the nylon engine uses helium and methane in addition to the nitrous oxide to burn the nylon fuel. SpaceShipTwo flew with this configuration on its fatal flight last October. The first three powered flights in 2013 and 2014 used nitrous oxide and rubber without wing tanks or additional gases.

The engine was not implicated in NTSB’s investigation of the crash. The accident was caused after Alsbury unlocked the ship’s feather mechanism too early in powered flight. The twin tail booms deployed, resulting in aerodynamic forces tearing the ship apart.

The engine change added complexity and additional failure modes to the propulsion system, which was originally touted as being simple, safe and benign. The modifications also altered the way air flowed over the spacecraft in flight.

Martin said he was concerned enough about how the changes might affect how SpaceShipTwo flew that he unsuccessfully argued for Scaled Composites to submit additional data about the ship’s structure.

“You know, we at least ought to get [Scaled Composites] to update the structures [analysis],” Martin told his bosses. “And to their credit, you know, we had the discussions — you know, Scaled was willing to do that, but my management didn’t feel it was necessary.”

SpaceShipTwo lights its engine as WhiteKnightTwo flies overhead on Jan. 10, 2014. (Credit: Ken Brown)
SpaceShipTwo lights its engine as WhiteKnightTwo flies overhead on Jan. 10, 2014. (Credit: Ken Brown)

Martin’s first hint of significant changes to SpaceShipTwo came after the spacecraft’s third powered flight on Jan. 10, 2014. He and other FAA officials noted flutter in the aft tail wing during powered ascent. Flutter is defined as an “unstable oscillation which can lead to destruction. Flutter can occur on fixed surfaces, such as the wing or the stabilizer, as well as on control surfaces such as the aileron or the elevator for instance.”

Subsequent investigation indicated that Scaled Composites had made some changes to the wings before the flight in anticipation of installing helium tanks in them. The modifications had caused a change in the way air flowed over the ship, resulting in the flutter.

The helium was needed to compensate for instability in the hybrid rubber-nitrous oxide motor that caused vibrations and oscillations to SpaceShipTwo. The company had not informed FAA AST in advance of the changes before the flight test.

Martin, who had helped investigate the crash of the space shuttle Columbia, said he was very concerned about the wing modifications. With Columbia, a piece of foam from the external tank had punctured a hole in a wing of the space plane during launch. The shuttle burned up during re-entry when super hot gases entered the ship through the hole.

“The aerodynamics and analysis that we did during our investigation of that showed that that breach ended up tripping the flow differently than what it was designed for and actually impeded the leeward side of the shuttle cargo bay,” Martin explained. “And more importantly, it produced a shock — a supersonic shockwave on the vertical tail, and we saw loads pretty much near their limit. And the only reason the tail didn’t fall off is because the wing ended up falling off and it disintegrated. So I used that as an analogy to my management and said, look, you know, I’m concerned with this.”

His bosses were not nearly as worried.

“My management got comfortable with it because Scaled Composites came back and said they had done a lot of C and D and drop testing with it, and they had a lot of information to correlate the data,” Martin told investigators. “So the next round in the experimental permit, we didn’t see any updates to their hazard analysis. So I did not get involved other than to say no hazard analysis was seen or provided; therefore, you know, I didn’t have any evaluation or comments to the regulation, and the permit was issued or reissued.”

After Virgin Galactic decided to change to the nylon engine, Scaled returned to FAA AST with a revised permit renewal application that incorporated data about the modifications required for the new motor.

Given the extensive nature of the changes, Martin wanted to see updates to the hazard analysis as well as the structural analysis for SpaceShipTwo. At that point, he had the opportunity to examine the entire application for the first time and made a surprising discovery.

“I noted to my management that they did not identify structures as safety critical, and they didn’t provide us with any type of hazard analysis associated with that,” Martin said. “My management’s technical response was that they didn’t believe structures was safety critical at the time.”

NTSB’s investigation has shown SpaceShipTwo’s nylon engine performed as expected and the ship flew normally during 12 seconds of powered flight last October. A 38-second engine burn was planned for the test, but the ship broke up before that goal could be reached.

NTSB found that “the probable cause of this accident was Scaled Composites’ failure to consider and protect against the possibility that a single human error could result in a catastrophic hazard to the SpaceShipTwo vehicle. This failure set the stage for the copilot’s premature unlocking of the feather system as a result of time pressure and vibration and loads that he had not recently experienced, which led to uncommanded feather extension and the subsequent aerodynamic overload and in-flight breakup of the vehicle.”

Co-pilot Alsbury, who unlocked the feather early, died in the crash. Pilot Pete Siebold survived with serious injuries.

During an appearance at the Space Access 2015 conference in April, Virgin Galactic Vice President Will Pomerantz said the company is still testing both rubber and nylon engines. His best guess was that they would go back to using the rubber engine, whose performance has been improved. Pomerantz also characterized the engine switch as a change in the fuel grain.

  • redneck

    The modifications also altered the way air flowed over the spacecraft in flight.

    This makes me wonder if the engine change affected the feather unlock nature. Speculating, it seems possible that the original engine/airframe configuration may have been more forgiving of an early unlock. Is there any information about the unlock timing during flights with the original engine?

  • Hemingway

    From Ricochet blog in 2014:

    “The pilot that day, Brian Binnie, is no longer with Scaled Composites, who built the spacecraft, and has gone to work next door for XCOR Aerospace, who is developing their own suborbital vehicle, the two-person Lynx. I stopped by XCOR on Saturday morning before the event to see how it was coming along, and it looks like they have all the major components (cockpit, wings) that have been holding them up, and appear to be on track for flying the first prototype in the next few months. In any event, apparently, Brian now feels free to discuss the issues of the program:

    “The delay in SpaceShipTwo has not been the development of either of the vehicles,” Binnie says. “But the rocket motor has just been problematic from the get-go.”
    Those problems start with scale. Binnie says the company’s original plan was simply to scale up the design of SpaceShipOne’s motor to fit the larger SpaceShipTwo. “That sounded good to us. Our name was Scaled,” Binnie says. “Basically an airframe was built betting that the propulsion system would meet the demands that the requirements [for SpaceShipTwo] offered.”
    Scaled Composites lost the bet. Binnie says every part of the original motor design has had to be revised from the ground up. Take the nitrous oxide tank, which had to be bigger while maintaining a high internal pressure, with the additional requirement that it hold up over the course of the many flights expected during commercial operations. In 2007, a version of the tank exploded during a ground test, killing three Scaled employees. The tank has since been completely redesigned.”

  • Dave Salt

    Yet more evidence that VG’s senior managers are either completely ignorant of the engineering issues or, more likely, they’re being ‘economic with the truth’.

    Either way, it speaks volumes about their professional competence.

  • Scott

    I must say, without Doug Messier and Parabolic Arc reporting the real news on Virgin Galactic and their escapades all we would know would be what Sir Richard did at his latest party on Necker Island and other celebrity hogwash.
    Not only has the FAA failed in its duties, but the entire journalistic community has acted like star struck school boys and girls.
    Our Founding Fathers got it right when they recognized that it was newspapers and journalists that were our defense against “big shots, billionaires, and the like manipulating the process and government for their own personal benefits and profit without proper concern for honesty, truth and full disclosure.
    I hereby nominate Doug Messier and Parabolic Arc for a Pulitzer Prize for his reporting, honesty and truth and dedication in being a real journalist in the face of many hardships and suspicious attacks by those hoping to dissuade him from digging deeper and sticking to it.
    This is a one person operation with no outside big money sponsors or partners.
    Some have criticized Doug for his relentless reporting on VG and his attention to seemingly obscure details and now all the world can see that Doug was on target all along and doing his job as a journalist with honesty, integrity and truth.

  • Douglas Messier

    Good question. There is some information in the documents about previous flights. I’ll have to look for it.

    One concern I’ve heard involves the vibration environment with the new engine. Could the pilots see the instruments clearly? What sort of a ride would this give the passengers?

  • Douglas Messier

    There’s been a lot of attention focused on engine problems. But, it took a long time before they could figure out how to build and install a nitrous oxide tank. I don’t think it was installed until about six months before the first powered flight at the end of April 2013.

  • Douglas Messier

    Thank you Scott.

  • Michael Clark

    I second the nomination. Thank you for all your hard work Doug.

  • twizell

    The additional complexity of switching to the new nylon based engine and the systems needed to support it has been discussed on here a number of times.

    I wonder… does the pilot manually control any of these transitions from methane start to main burn to helium injection? If so then this is additional load on the pilot. I note the various NTSB statements about the time pressure that the pilot and co-pilot had to deal with and wonder if this more complex propulsion system was a contributing factor to that load?

    I’m afraid the more we find out the more we see the nature of VG as secretive and manipulative. It’s essentially part of a conglomerate that specialises in PR. The wrong company culture to be doing cutting edge engineering.

  • Hemingway

    I third the nomination:) Great investigative reporting.

  • Kirk

    Unlock timing during the powered flights was discussed during last week’s NTSB meeting. (Corrected transcript and video here.)

    The feather was not unlocked on PF-01 due the the short burn. It was unlocked on time at 1.2 Mach on PF-02 and at 1.3 Mach on PF-03, and was scheduled to be unlocked at 1.4 Mach on PF-04.

    An hour into the hearing, Chairman Hart asked about brief feather movement during a previous flight. John O’Callaghan (Vehicle Performance Group Chairman) replied: That’s correct. That occurred on powered flight two. The vehicle goes through the transonic region two times, once while it’s accelerating with the rocket motor on, and then when the rocket motor shuts off, it decelerates back through the transonic region. And in terms of moment coefficients, you have the same high coefficients wanting to move the feather up. On powered flight two, the deceleration through this region occurred at a relatively lower altitude and a deliberately tested point to explore the limits of the feather operating envelope. So it was deliberately flown very close to the edge of the ability of the actuators to keep the feather down, and in fact they got a slight movement of about 0.8 degrees for less than half a second.

  • ThomasLMatula

    I fourth it 🙂

  • ThomasLMatula

    You have to wonder if/when Scaled Composite’s owner, Northrup-Grumman will step in. Although they purchased Scaled Composite for its creativity, and have kept hands off, they are ultimately responsible as their owner. It will be interesting to see if they take a more active role in the future.

  • ThomasLMatula

    If I read this right, Tom Martin is basically speculating that even if the feathering mechanism had not been unlock there could have been an accident due to structural failure from the engine modifications. If so it seems that have a lot of work to do before it flies again.

  • Stu

    It must be quite difficult for VG/Scaled, in that they trying to make a flawed design work because it is too expensive to chuck it all away if their is the faintest hope they can salvage something. VG were sold a turd and they should have identified this and given up on their chosen path a long time ago. Once you have thrown half a billion dollars (and in this case a decade) at a problem, it is hard to turn around and throw it away, so the BS increases, investors are tapped for more money and the cycle continues, with the goal never getting much closer. I very much doubt SS2 will ever pay its way (even if it manages to eventually do what it is supposed to).

  • Snofru Chufu

    Is not the non-sufficient pneumatic feather actuation system the main problem, which seems not able to held the feather in a neutral position under a range of loads, and not the unlocking procedure (which is secondary)? May be the feather actuation system it is not “stiff” enough under external loads?

  • Aerospike

    In a vehicle where weight is more important than anything else, you can’t simply use arbitrary powerful pneumatic actuators. More powerful systems tend to be heavier and also larger (and space is also in limited supply).

    That’s why they have the additional “feather lock”, because (I’m making assumptions here) that was “cheaper” (in terms of weight and space, not money) to implement. The downside is an additional failure mode and the requirement of strict procedures on how and when exactly to operate the system(s).

    It’s a tradeoff between simplicity and efficiency and in a system that uses chemical propulsion to go to space, simplicity is not always an option.

  • Aerospike

    I support the nomination as well.

  • MachineAgeChronicle

    I also do the nomination thing.

  • Paul451

    You can’t “nominate” anyone for a Pulitzer. Only the Columbia University Jury can do that.

    You can, however, enter Parabolic Arc and Doug himself for the various Journalism categories. (Such as Criticism, Breaking News Photography/Reporting, Investigative Reporting (series), and even Local Reporting. Along with Public Service (which is the Gold Medal award.))

    However, entries for this year are closed. You’ll have to wait until the December-2015 to January-2016 window for the next public entry window.

  • LA Julian

    Read up on the sordid details of the Virgin Rail problems with the sewage on their trains in the UK and you’ll find that your statement doesn’t just apply to the aerospace wing…

  • LA Julian

    Sunk cost fallacy, is the technical term for this.

    I’m also getting flashes of the Mary Rose and Vasa scenarios, although those were military vessels built for governments. But the same attitude that “we can just scale up our old, tested designs!” without considering the differences in weight, flow of air and water, balance, etc. that this brings with it. Architects have learned the hard way that this doesn’t work for buildings either, in the past.

  • Snofru Chufu

    You misunderstood me to some degree. I see the additional lock-mechanism also as a need, however without relaxing my question to feather actuator design as such. I learned that SS2 uses a “pneumatic” system (what is the operating pressure?), but a hydraulic or electromechanical system might better suited due to its higher stiffness.

  • Interesting news that they will go back to the rubber fuel. I think they should investigate using liquid-fuel. Several studies have shown with liquid fuel you can get a suborbital craft with that one single stage, no WhiteKnightTwo needed.

    Bob Clark