- Parabolic Arc
- March 30, 2023
Virgin Galactic Spins Its Way Back to Rubber Engine for SpaceShipTwo
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)
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.
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.
- 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?
- 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?
- Is Virgin test firing the polymide? Or are you doing rubber engine firings and comparing it to past polymide results that Scaled obtained?
- What is Scaled’s role, if any, in SpaceShipTwo’s development?
- 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?
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.
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.