It’s always a pleasure to build rocket motors with @VirginGalactic. We’ll never get tired of working on projects like this. pic.twitter.com/hnB4pMVsaJ — TheSpaceshipCompany (@TheSpaceshipCo) November 14, 2018
Video Caption: The creation of a hybrid rocket motor system for SpaceShipTwo represented a significant engineering challenge. We are particularly proud that we designed and now test and manufacture this world class motor in house. Come meet the team behind the burn…the Rocket Guys.
One of the most interesting aspects of the National Transportation Safety Board (NTSB) investigation into the SpaceShipTwo accident is the ability to find out what was actually going on behind the scenes during the vehicle’s development and testing. Reality is at times at sharp variance from what was being said publicly at the time.
Parabolic Arc Flashback: One year ago, Virgin Galactic announced it changing SpaceShipTwo’s propulsion system from a rubber hybrid to a nylon hybrid engine due to demonstrated better performance. The news was announced on a Friday at the start of long holiday weekends in the U.S. and Britain, a perfect time to dump news when neither reporters nor the public are paying much attention. Sierra Nevada, by the way, was blindsided that their rubber engine was being dropped and their lucrative agreement was going away.
Today, the nylon engine decision is being re-evaluated due to performance. The company recently revealed it is testing both hybid engines again, and it might go back to using the rubber one. That means the company still doesn’t know how its going to power its spacecraft despite being nearly 11 years into the SpaceShipTwo program. That explains why it is taking as long as it is.
MOJAVE, Calif., May 23, 2014 (Virgin Galactic PR) – Virgin Galactic, the world’s first commercial spaceline which is owned by Sir Richard Branson’s Virgin Group and Abu Dhabi’s aabar Investments PJS, has selected a polyamide-based fuel grain to power its hybrid rocket motor for the remainder of the test flight program and start of commercial operations. This decision follows numerous ground test firings and is supported by data collected over an extensive development program.

Richard Branson speaks to the press at the Mojave Air and Space Port about the crash off SpaceShipTwo. (Credit: Douglas Messier)
The Wall Street Journal has a good piece on all the problems Scaled Composites and Virgin Galactic have had with SpaceShipTwo and WhiteKnightTwo over the years. It pretty confirms everything I’ve been writing for the last few years, adding some interesting details but getting a few of them wrong.
There were a number of interesting elements here:
The article claims that Sierra Nevada Corporation was brought in by Scaled Composites to develop SpaceShipTwo’s engine in 2009. That’s not accurate.
Video Caption: Footage from Virgin Galactic’s recent Hybrid Rocket Motor Test Editor’s Note: I saw this test while I was driving into Mojave. Managed to pull off the highway and catch the ending of it. You’ll notice the video fades out prior to shutdown, and there’s a reason for that. The shutdown didn’t seem to go that well. The best I can describe it as is the engine seemed to […]
MOJAVE, Calif., May 23, 2014 (Virgin Galactic PR) – Virgin Galactic, the world’s first commercial spaceline which is owned by Sir Richard Branson’s Virgin Group and Abu Dhabi’s aabar Investments PJS, has selected a polyamide-based fuel grain to power its hybrid rocket motor for the remainder of the test flight program and start of commercial operations. This decision follows numerous ground test firings and is supported by data collected over an extensive development program.
UPDATE 1: Video of a SpaceShipTwo engine test conducted at the Mojave Air and Space Port on Thursday, Jan. 16. Scaled Composites conducted this test of a nitrous oxide/nylon engine to power Sir Richard Branson’s suborbital space plane, which is scheduled to begin operations later this year. The nitrous oxide/nylon engine is being tested as an alternative to the nitrous oxide/rubber engine that SpaceShipTwo has used for three powered flights […]
Engineers have been busy over the last three months conducting 9 ground tests of SpaceShipTwo’s hybrid engines. At least one of these tests was of an alternative to rubber/nitrous oxide engine design that SpaceShipTwo has been using to conduct powered test flights.
RocketMotorTwo Hot-Fire Test Summaries
Via Scaled Composites
Fire: | 37 | ||
Date: | 07 Nov 13 |
Objectives:
Thirty-seventh full scale flight design RM2 hot-fire. Continued evaluation of all systems and components:
– Pressurization
– Valve/Injector
– Fuel formulation and geometry
– Nozzle
– Structure
– Performance
Results:
All objectives completed.
Scaled has conducted four hot fires of the RM2 engine over the past month, including the powered flight of the SpaceShipTwo on Sept. 6. The log entries are of limited value because three of them lack details about the lengths of the hot fires. The powered flight had an engine burn of 20 seconds. RocketMotorTwo Hot-Fire Test Summaries Via Scaled Composites Fire: 33 Date: 06 Sep 13 Objectives: Thirty-third full […]