Whitesides Responds to Bower’s Allegation About SpaceShipTwo’s Engine

branson_behind_the_maskVirgin Galactic CEO George Whitesides has responded to Tom Bower’s new book, “Branson: Behind the Mask.” The author makes a series of claims about the performance and safety of the nitrous oxide-rubber engine that is scheduled to send SpaceShipTwo on a suborbital flight later this year.

Whitesides wrote a letter to The Sunday Times, which began serializing the biography a week ago. The response, published on Feb. 2, is reproduced below:

Dear Sir:

Tom Bower’s claims in extracts from his new book on Richard Branson that Virgin Galactic has “no licence” and “no rocket” to go to space (“Lost in space” and “The sun lizard fading into exile”, News Review, last week) misrepresent the facts and use old information to create a story. Indeed the recent progress of the Galactic programme, including the latest rocket powered flight, renders Bower’s main claims false.

The company’s rocket motor has burned for the full duration and thrust multiple times, and the company released video footage of one such test in December. Bower also fails to note that the team has an experimental permit from the Federal Aviation Administration for the test flight programme phase.

The company applied for a commercial licence in 2013 as planned and to coincide with the latter stages of the test flight programme. It expects to receive that licence well in advance of commercial service later in 2014.

Most seriously, Bower attempts to cast doubt on Virgin Galactic’s absolute commitment to safety, particularly by suggesting that any potential lessons that could have been learnt by the tragic 2007 industrial accident at Scaled Composites were somehow brushed under the carpet. The opposite is true. The company supported the full independent enquiry and accepted all the resulting recommendations in terms of system re-design along with their costs and time implications. The end result is a system that will be significantly safer.

Bower also claims that Richard no longer owns any of the principal Virgin businesses and that the company has ceased to innovate. Among others, Virgin Galactic is majority owned by Richard Branson and it certainly innovates. Richard’s empire has not shrunk and his work, through his foundation and companies, is creating a real impact.

Yours sincerely

George Whitesides
CEO, Virgin Galactic

Let’s look at the response more closely.

Engine Claims

Bower’s claim is specific: he says that Virgin Galactic lacks an engine powerful enough to get SpaceShipTwo with two pilots and six passengers above the 100 km (62.1 mile) boundary of space (aka, the Karman Line). This is what the company has been promising to ticket holders for the past nine years.

Whitesides’ response doesn’t specifically address that claim. It references  several developments that show significant progress in the air and on the ground. However, the letter doesn’t say, ‘SpaceShipTwo can reach 100 km with a full load of crew and passengers with the RocketMotorTwo engine we have. Bower’s claim is false.’

The letter points to the recent third powered test of SpaceShipTwo, which fired its engine for 20 seconds, reached Mach 1.4, and flew to a new record altitude of 71,000 feet.  The test was similar to one performed in September, although the ship went 2,000 feet higher.

My sources tell me that they have gone as far as they can with that version of the hybrid nitrous oxide-rubber engine. It has serious vibration and oscillation problems that engineers have been attempting to solve.

The letter references a video of a 55-second hot fire of RocketMotorTwo. The test looked good, but Virgin Galactic has  released no details about it, including thrust, when it was conducted, or whether this is the final version of what will fly on SpaceShipTwo. Without those specifics, it’s impossible to evaluate whether the engine is powerful enough to lift SpaceShipTwo to 100 km and thus disprove Bower’s claim.

Assuming the test was conducted recently, then it would have been part of an ongoing series of ground hot fires that Virgin Galactic Vice President Will Pomerantz told NBC News Science Editor Alan Boyle about recently.

“We and our contractors at Scaled Composites and Sierra Nevada are continuing to develop ways to improve the motor design by making them easier to manufacture and install, or by further improving their handling characteristics and performance,” Pomerantz wrote in an email to Boyle.

The goal of that hot fire might well have been to test a method to dampen out the oscillations in the nitrous oxide-rubber hybrid. Did the engineers achieve this goal? What modifications did they make to do so? And what impact, if any, would those modifications have on the ability to SpaceShipTwo to reach 100 km?

The letter provides no answers. In sharp contrast with Virgin Galactic’s chattiness about the Newton engines it is developing for LauncherOne, the company has been extremely reluctant to release details about RocketMotorTwo.

The engine hot fire test logs on partner Scaled Composites’ website are so lacking in specifics that it’s very difficult to glean very much useful information from them. The entries tell you when a test took place, what parameters were tested, and that all results were inevitably achieved. Beyond that, there’s not much there.

It’s not even possible to tell what type of engine they tested on any given day. Scaled conducted a hot fire test of an alternative engine design that uses nylon and nitrous oxide on Jan. 16. The hot fire, which sources say is part of a series of engine tests using nylon, ended up on the Scaled’s log page along with entries about rubber hybrid tests.

It has long been public knowledge that SpaceShipTwo might go through flight tests with a nitrous oxide-nylon engine instead of one that burns rubber. This was clearly indicated in the FAA’s Final Environmental Assessment for the Launch and Reentry of SpaceShipTwo Reusable Suborbital Rockets at the Mojave Air and Space Port  published in May 2012.

The assessment, which was required for the experimental flight test permit that Whiteside mentioned in his letter, includes emissions calculations for both nitrous oxide-rubber and nitrous oxide-nylon engines.

The evidence shows that even as Virgin Galactic is promising to start commercial service this year, engineers are still working on perfecting the engine it will use to do so. The company has provided no evidence to specifically knock down Bower’s claim about SpaceShipTwo’s performance issues, i.e., can the ship reach 100 km with a full load of crew and passengers.

Commercial License

Whitesides is likely correct in saying Virgin Galactic will receive a commercial license to fly passengers well in advance of doing so. There has been some confusion on this issue, which I inadvertently contributed to with some recent ill-informed speculation about the FAA’s licensing process.

I had earlier believed that the FAA would need to see some evidence that SpaceShipTwo was capable of performing its principle mission — flying into space — before it issued a license. Jeff Foust and others say that I’m wrong, and I believe they are correct in their judgment.

In commercial aviation, it’s up to an aircraft’s builder to prove to the FAA that the vehicle is safe to fly passengers under a strict certification regime. That system has worked well in producing reliable aircraft, although the problems Boeing experienced with the 787’s batteries show it’s not perfect.

With suborbital commercial spaceflight, the company must only prove to itself that the vehicle is safe enough to fly passengers. There is no certification regime and no requirements for extensive flights tests prior to the granting of a license.

Virgin Galactic and other spaceflight companies are operating under an informed consent regime. As long as customers are informed that the activity is dangerous and they could die, and they sign a waiver acknowledging these realities, they can fly on these vehicles.

The FAA’s main concern is the safety of the uninvolved public.  The agency uses a similar standard in licensing commercial satellite launches. The FAA doesn’t care if a Falcon 9 launch vehicle fails, it just doesn’t want the rocket killing anyone at Cape Canaveral or crashing into Cocoa Beach.

Safety of Hybrids

Whitesides says that the hybrid motor will be “significantly safer” as a result of what engineers learned from that tragic accident that killed three engineers in Mojave nearly seven years ago. That is almost certainly true.

Bower’s book raises more specific questions. One is the issue of whether nitrous oxide is safe enough to use in human spaceflight. There are engineers who have worked with nitrous oxide who are quite passionate in saying that it is not safe enough to use.

The second issue Bower raises is the accuracy of Virgin Galactic’s claims about the safe, benign nature of its hybrid rocket system and nitrous oxide. The company makes very strong claims on the safety page of its website, including the assertion that hybrids are superior to both liquid and solid-fuel engines.

“However, there is a third type of rocket propulsion known as a hybrid motor. Here the fuel is in solid form and the oxidizer is a liquid. The passage of the oxidizer over the fuel is controlled by a valve which allows the motor to be throttled or shut down as required.

“Hybrid motors offer both simplicity and safety. This is the type of motor that SpaceShipTwo will employ and that was used by SpaceShipOne. It means that the pilots will be able to shut down the SpaceShipTwo rocket motor at any time during its operation and glide safely back to the runway. The oxidizer is Nitrous Oxide and the fuel a rubber compound; both benign, stable as well as containing none of the toxins found in solid rocket motors.”

Again, there are very strong counter opinions about just how safe hybrids are, and whether they offer any real advantages over liquid and solid-fuel systems. That’s an engineering debate I’m not going to wade into.


The letter addresses more general concerns than the specific ones that Bower has raised in his book. Something more specific will need to be released to put the concerns about performance. Even then, only test flights above 100 km will finally put the issue to rest.

As for safety, that question can only be resolved after SpaceShipTwo flies many times using the nitrous engine. It’s the only way to prove the reliability of any rocket engine.

  • Hemingway

    With all the uncertainties and lack of information about SpaceShip Two, nobody could get me to fly in that space contraption.

  • Guest

    Dogs, monkeys and mice have been there but I guess we’ll just have to wait a bit longer for the first chicken in space.


  • patb2009

    For anyone interested in a mid sized engine, they may enjoy this.


  • therealdmt

    I believe you had a typo in the following sentence (should have been “year”, instead of “month”):

    “The evidence shows that even as Virgin Galactic is promising to start commercial service this month, engineers are still working on perfecting the engine it will use to do so”

  • Good analysis and reporting here. Yours is one of the very few blogs that offer analysis on space issues and not just copies of press releases.
    Because of the serious concerns with nitrous by those in the know I think VG’s continuing focus on using it is misguided. Those concerns will be aired more publicly when they attempt to carry passengers, informed consent or not.
    Then all that time and all that expense trying to get the hybrids to work will have been wasted. They will have to turn to liquids anyway. A decision they could have made years ago, and one that would have allowed them to be flying years ago.

    Bob Clark

  • Carolynne Campbell

    “Hybrid motors offer both simplicity and safety… The oxidizer is Nitrous
    Oxide and the fuel a rubber compound; both benign, stable as well as
    containing none of the toxins found in solid rocket motors.”

    There’s a lot in those two sentences.

    Let’s start with simplicity. Saturn V was certainly not simple. It took ten years from concept to repeated flights and a man on the moon. Scaled has been working for that long on what appears to be a ‘simple motor’, they’re still ground testing. Simple is as simple does.

    Safety: They destroyed their test facility in 2007. This was a cold-flow test, without engine ignition. Having no range safety protocols in place they allowed an un-policed gaggle of spectators to stand close by and we all know the result. Scaled appointed a Board of Inquiry (is this the ‘Independent Inquiry’ Whitesides refers to?). So lessons must have been learned, and I’m sure many were, such as not allowing unprotected spectators. That inquiry must have looked into the root cause of the accident. Scaled have never published what the cause was. They did make changes. I’ve been told that they lined the composite tank with Inconel, to prevent hydrocarbon contamination, they added massive burst-plates to protect against over-pressure and they probably did some re-design of the valve/injector assembly. Problem solved, right? Well, no.

    If that massive burst plate should ever actually depart the tank, it’s departure would probably result in a BLEVE (Boiling Liquid Vapor Explosion), which would destroy the aircraft. In May last year (2013) a test managed, again, to completely obliterate their Mojave test facility. Lessons have been learned. Nobody was hurt. Scaled claim that they had deliberately introduced ‘Anomalies’ into the fuel-grain. Maybe they did, maybe they didn’t. I’ve never heard of any operation deliberately conducting a test that would destroy the entire facility. Reports state that those present (in a nice safe bunker), were visibly shocked and surprised. This was not a cold-flow, but a live-fire test. Lessons had undoubtedly been learnt from the first accident, but (after a further seven years of testing) Scaled got another nasty surprise from Nitrous Oxide. What other nasty surprises still lurk out there?

    For a company who has this direct in-house experience of how tricky Nitrous Oxide can be, to persist with the “Safe stable and Benign”message, makes one wonder just what it is they’re smoking. They don’t need the expert opinions of the many engineers worldwide who have worked with the stuff, (most of whom consider it pretty nasty and unpredictable). They have their own catastrophic experience.

    As for the rubber compound, a big lump of synthetic rubber (HTPB in this
    case) is about as safe as a thing could be. That is, of course, if the fuel-grain is simply that; pure synthetic rubber. How about “Containing non of the toxins found in solid rocket motors”?

    When one reads the less-than-informative test reports issued by Scaled, one comes to the line ‘Fuel formulation and geometry’. If the fuel grain is indeed pure HTPB, what is there to formulate? ‘Formulation’ implies some kind of more complex ‘formula’. Have other substances been added to the HTPB to improve ignition and performance? We do know that other engineers working with big hybrids have found it’s really hard to get big fuel grains to ignite and burn evenly. The solution has been to add solid oxidisers and powdered metals to overcome the problem. The oxidiser of choice has generally been ammonium perchlorate (AP).

    One wag observed that the Spaceship Two flying under power looked like “A flying tire fire”. An awful lot of soot and black smoke was being emitted. This indicates partial combustion on some scale. We don’t know the by-products of partially combusted butadienes (the ‘B’ in HTPB) but we do know that butadienes are regarded as possibly carcinogenic. If a chlorate has been added, then the combustion by-products may well include well known poisons and carcinogens such as PCBs and Dioxin. Partial combustion is a strange chemical environment where all kinds of unforeseen reactions can take place, resulting in unexpected by-products.

    Is the fuel-grain non-toxic? We only have VG and Scaled’s word for that. Perhaps they would like to inform the world exactly what is in there? Perhaps not….

  • Carolynne, I know Knights Arrow is also using nitrous for their rocket powered car, despite their own safety concerns. So it must have some advantages over using LOX. What are they?

    Bob Clark

  • Guest

    This is a great question. WHy is Knight’s Arrow a good use of hybrid rockets, but Virgin Galactic isn’t?

  • Carolynne Campbell

    For a small budget operation, the ease of handling an oxidiser we can use at ambient temperatures (provided it’s not too hot) is the main thing. We simply lack the resources required to handle and use a cryogenic oxidiser. The driver is protected from all that explosive power by a serious ballistic shield, and we have developed our own methods to avoid dealing with nitrous is its gas phase. Having said that, the car is an experimental vehicle designed for private high-risk adventure. Is it scary? Of course it is! Is it safe? No it isn’t. As one of the few people who has actually piloted a rocket-powered vehicle with a serious load of nitrous on board, you’d probably expect me to be an enthusiast for the stuff. I’m not.

  • Douglas Messier

    I can add some details about the test in May. Scaled Composites conducted a hot fire of a nitrous-nylon engine. They had introduced flaws into the engine to see what would happen. What they got was unexpected, and they were quite shocked by it. The fuel grain was, as Scaled later admitted, “tested to destruction.” The engine nozzle and fuel container ended up on the desert floor some distance from the test rig. The test stand was destroyed. The nitrous oxide tank was breached and leaked fuel for some period of time. It was no longer usable.

  • Douglas Messier

    Not being an engineer and not knowing exactly what they’ve done to make the engine safer, I can’t really wade into this debate. However, I can give you some anecdotal information based on discussions I’ve had with engineers other than Carolynne who have experience working with nitrous oxide.

    Several I’ve talked to worked with nitrous oxide previously, but they stopped doing so because of safety concerns. They believed that it would have only been a matter of time before they had a serious accident. They would never use it in a human space vehicle.

    One engineer I know works with nitrous oxide. He knows how dangerous it is and is extremely cautious. He was appalled after reading the Cal-OSHA report on the Scaled accident and the analysis of it produced by Carolynne’s group. He thought there was criminal negligence involved.

    One concern I have with the informed consent arrangement is it places no restrictions on the type of claims that companies can make as to the safety of their systems. The marketing guys who write this stuff don’t necessarily understand the dangers involved.

    The result is that people who signed up for trips based on Virgin’s marketing claims might think that safety waivers they sign are a mere formality. Given the safety assertions VIrgin has made, what could go wrong? Quite a bit, actually.

  • mfck

    Can Chevaliery be revoked?

  • Douglas Messier

    Fixed. Thanks.

  • Carolynne Campbell

    Doug, I share your concerns regarding ‘informed consent’. If customers are relying on the safety claims on the VG website in making their decisions, then perhaps it might me characterised as ‘ill-informed consent. Pray to God, this never has to be tested in a court of law. It’s gratifying to think that some of our work had contributed to the safety of others in the field.

  • Guest

    Carolynne – Bowers interviewed you for this book, right?

  • Guest

    How close are spectators allowed to watch your runs? I can’t imagine it would be much fun to go to the dragstrip but be required to stand 1/2 mile away from the action.

  • Carolynne Campbell

    Yes, I was interviewed.

  • Guest

    Do you know how old the information is in this book? When were you interviewed?

  • Carolynne Campbell

    Now you’re asking questions that need to directed at Tom Bower.

  • Carolynne Campbell

    We don’t run at drag-strips anymore. We couldn’t maintain a safe exclusion zone. Now we run on very long runways with tight controls, big exclusion zones and no ‘spectators’

  • Guest

    Do you mind if I ask what changed your mind about this kind of rocket? How did your opinion change from thinking that a rocket car exhibition racer would be a good idea to thinking that it’s probably best to keep it away from spectators?

    Have you always thought these rockets are dangerous or was there an incident that changed your mind? (Feel free to tell me to buzz off if I’m being too personal).

  • Carolynne Campbell

    Look, as projects progress, ones understanding develops – its called ‘learning’. Now, at the risk of being rude, I feel I have answered enough questions for now.

  • Robert Gishubl

    It is scary that a system designed for regular human flight could fail in a cascading fashion, I would expect design features such as blast walls, non return valves etc to contain the failure to the engine compartment. Even then with the design of the booms an energetic failure could well result in other damage unless any failure is directed to a safe space which would effectively mean armouring the the engine compartment which would be heavy. The SpaceX F9 engine out was an example of controlled failure, although the engine failed in an interesting manner there was no cascading failure and the rocket continued on its mission, that would not have been the case if tanks were ruptured or other engines damaged.

  • Paul451

    Yes. The Queen has the power to do so, on advice of the Forfeiture Committee. Happens every 5-10 years. But I can’t see any circumstances where it would apply to Branson. It took them seven years to strip genocidal Robert Mugabe of his title after Tony Blair referred it to the committee.

  • Nice heraldry knowledge there.

    Bob Clark

  • Tom Colvin

    “Again, there are very strong counter opinions about just how safe
    hybrids are, and whether they offer any real advantages over liquid and
    solid-fuel systems.”

    I’m a graduate student that has worked some with Nytrox/Paraffin and LOX/Paraffin hybrids. I understand the difficulties associated with nitrous handling, but the quoted sentence above makes it sound like there are dangers inherent to the hybrid architecture that are equal to or eclipse the dangers of traditional solid or liquid rockets, which runs counter to my understanding of hybrids. I’m open to new information though. Could you point me to a resource that details these hybrid dangers?

    As a point of clarification, I don’t consider the danger of handling nitrous as a danger *inherent* to the hybrid architecture, so I’m not looking for arguments about why nitrous is dangerous.