Scaled Conducts Additional Tests of RM2 Engines

RocketMotorTwo kicks up some dust during a hot fire on March 30, 2013. (Credit: Virgin Galactic)
RocketMotorTwo kicks up some dust during a hot fire on March 30, 2013. (Credit: Virgin Galactic)

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 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.

Fire: 32
Date: 06 Sep 13

Objectives:
Thirty-second 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.

Fire: 31
Date: 22 Aug 13

Objectives:
Thirty-first 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.

Fire: 30
Date: 06 Aug 13

Objectives:
Thirtieth 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.

  • joy kirkwood

    The smoke from 1st powered flight was black but the smoke from the rocketmotor was white during 2 nd test. Apparently they used tire rubber on 1st flight
    Anyone know anything about this as i am unable to find any info.

  • Michael Vaicaitis

    Virgin Galactic website says “a rubber compound”; Wikipedia identifies this as “hydroxl-terminated polybutadiene (HTBP)”,…so “rubber compound” then.

    They justify the hybrid motor as safe and simple, but I’m not convinced about the simple part. Even if the motor can be run simply, “refuelling” is surely not so simple. I presume they must remove the motor from the airframe and install a new (or refurbished) unit from SNC.

    XCOR, by contrast, seem to have a robust rocket motor solution, which they claim to be good for 5000 flights and 40 flights between maintenance cycles. But their Lynx vehicle seems a bit “small” to fully appreciate the zero gravity experience.

    It’ll be interesting to see what the customers/critics say once these vehicles are flying. Roll on 2014.

  • Hug Doug

    the form of rubber that Virgin Galactic is using is called Hydroxyl Terminated Poly-Butadiene (HTPB), and they use Nitrous Oxide as the oxidizer for their hybrid rocket. the exact blend of HTPB that they use, i’m unsure of. there has been speculation that they have blended some solid oxidizer in with the HTPB. part of the reason for years of delay is that Virgin Galactic has had lots of trouble perfecting their hybrid rocket system.

  • Tonya

    Regarding XCOR, it may be smaller but which seat would you prefer, one back in the passenger compartment or one up front next to the pilot?

  • therealdmt

    Up front, for sure! As a long time flight instructor, I’d feel like I was actually in command (except for very beginning students, instructors are in command, from the right seat, while rarely touching the controls).

    Still, floating around in a big cabin would be cool too.

    It comes down to the view vs. the zero-g experience. Tough choice!

  • Michael Vaicaitis

    After thinking some more, I suppose you could do the floaty thing in a vomit comet, and I guess the view is the main attraction (and perhaps the thrill of the ride.

    But your comment brings up a good point which has me somewhat perplexed. What is the pilot for?. And SS2 has two pilots!, why?, ballast at the front end?
    And if that’s not scary enough, I see that SNC are building a simulator for Dreamchaser pilots. Why are these vehicles designed for human pilots?

    I have a feeling some people hereabouts may find this point of view controversial, but I am quite serious. A hand-holder can perhaps be justified for suborbital roller-coaster rides, but how can the added risk and added complexity of a human pilot be justified for a vehicle like Dreamchaser?.

  • Carolynne Campbell

    The answer to the fuel-grain question is in the Scaled test report. ‘ Formulation and geometry of fuel’. If it’s pure HTPB, there’s nothing to ‘formulate’. They’re up against a tough problem. Historically it has proven difficult to scale these things up. Others in the field have abandoned HTPB and gone on to paraffins and kerosene. Was Spaceship One the upper limit? It’s claimed Specific Impulse was 250 secs at altitude. They do appear to be struggling to get near that.

  • Nickolai

    My response will be very generic, as I don’t believe I have any specific data to contribute to this, but here goes:

    It takes a lot of development effort to develop a full autopilot. Take a look at the Soviet Union’s Buran shuttle, which flew automatically. They had to modify a Tu-154 plane to serve as a testbed for the automated technologies, then they built some Buran replica’s with jet engines to test the system. It also required a lot of ground infrastructure. Point being: significant development time.

    Another point: it’s not always perfect. When making a turn near the end of its one and only flight, Buran chose to go left whereas the pilots of the chase planes expected it to go right. This very nearly led to a midair collision between Buran and one of its chase planes. I think later analysis showed that technically Buran made the “right” decision based on available parameters, but still, it’s unnerving when your aircraft doesn’t do what you expected

    Final point: Computers have to be programmed. People don’t. You can come up with a finite number of scenarios and make a pretty good autopilot, a really good one in fact, but unless you test it in every one of those scenarios you’ll never know how it will perform when up to a challenge. You can have confidence in a pilot’s skills based upon a wide range of previous experience, but it’s harder, IMHO, to trust a computer, even one that has passed simulations.

    Mostly though, I think it’s just the significant development time as well as the Scaled Composites philosophy that they prefer stick-and-rudder style craft. That’s why they have the feathering system and why SS1 didn’t have a flight computer (and I imagine SS2 doesn’t have one either)

  • Robert Gishubl

    Still no information on the duration is disappointing. Until they do a full duration burn paying passengers are a long way off. You may end up getting a Dragon to orbit before VG gets passengers at this rate.

  • Tonya

    That’s actually a very good question, even though my first reaction to the idea is that it sounds quite mad! But you’re absolutely right, when you think it through the pilot is replaceable, either through an advanced autopilot or remote operation similar to UAV control.

    However, I suspect for most people having a pilot on board increases the perception of safety even if it makes little difference in reality. At the end of the day, both companies are in the business of selling tickets to civilians.

    I wonder what the regulatory position would be?

  • Tonya

    As you’re a pilot, I think I can guess which you’d choose if you had to pick one.

    I have wondered what percentage of those buying tickets hold some level of pilot’s license. I suspect it’s quite high.

  • Michael Vaicaitis

    I kinda made the assumption that the suborbital outfits might be short on budget to develop an autopilot. I confess that “human error in the loop” is one of my pet peeves, so I generally take any chance to whinge.
    I can’t see that SNC have any excuse for exluding an autopilot on Dreamchaser.

    As for not trusting humans over GNC computers. Every fly-by-wire multi-hundred seat passenger jet in the world has a computer supervising and assisting the pilot. Not to mention fighter jets that intrinsically cannot be flown without a computer. Admittedly they do have a gazillion dollar budgets, so I can forgive these fledgling suborbital outfits this little indiscretion.
    Given the choice though, when it comes to complex flying machines, especially those with rocket motors, I’d rather trust a machine.

  • Aerospike

    As far as I know, Dream Chaser is supposed to be able to fly fully autonomous. So we could say the pilot is “optional”. đŸ˜‰

  • Michael Vaicaitis

    Good to know, thanks for the heads up.

  • Douglas Messier

    Virgin Galactic has said that the engine needs to fire for over a minute, but they’re not specific about it. There’s nothing in the engine test logs to indicate that they’ve reached that point. The closest thing is November 2011 hot fire that was split into separate 10 and 58 second burns.

    I have a hard time believing that if they had achieved a full-duration, full-thrust burn on the ground, VG would have trumpeted that with a press release and a full length video.