Interorbital successfully test flies its upper-stage engine


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Capitalism in space: The smallsat rocket company Interorbital Systems successfully test flew the upper-stage engine for its rocket last week.

Video of the test below the fold. This company had appeared to be moving towards test flights in 2014, than nothing seemed to happen until earlier this year. The four year gap made me suspect they were in trouble. It now appears they are moving forward towards their first flight, though when that will happen remains unclear.

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7 comments

  • Col Beausabre

    1) The shots from aboard the rocket reminded of similar views from early launches at White Sands

    https://www.bing.com/videos/search?q=white+sands+v2&&view=detail&mid=C6A91F8921BEB231C986C6A91F8921BEB231C986&&FORM=VRDGAR

    https://www.bing.com/videos/search?q=white+sands+v2&&view=detail&mid=C8E169F0EF01FABC60C6C8E169F0EF01FABC60C6&&FORM=VDRVRV

    2) I know it works (obviously). but Nitric Acid and…..TURPENTINE?! Somebody got the deal of the century on paint thinner?
    What’s the specific impulse and how does it compare with other mixtures?

  • John E Bowen

    “What’s the specific impulse and how does it compare with other mixtures?”

    I think the answer is: not as good as the best choices, but . . .

    . . . followed by the explanation of why they, like other small launch companies, choose another path. For small operators, white fuming nitric acid may sound exotic but is simpler to deal with than the amount of engineering that goes into using cryogenics like liquid hydrogen. I’m not deriving this from first principles on my own, just recalling what Rand & Rhonda Milliron said on The Space Show.

    If I can stretch the comparison to pressurization, my layman’s understanding is that turbopumps yield the highest efficiency, so medium to big stages from medium to big companies pursue turbopumps, but smaller firms rely on gravity fed or pressure from gradually warming liquid helium (autogenous?).

    Whether they, or any of the other “smaller players” survive economically is another story, but they’re definitely serious.

  • John E Bowen

    I have a question of my own. From the video, it looks like the stage was spinning around, very fast.

    Is it what they call “spin-stabilized?”

    If so, has anyone launched a small payload into orbit with the whole craft, multiple stages, spinning like this? Or how about even a sounding rocket for research into the upper atmosphere, for instance?

    Maybe I’m overthinking it. Maybe they don’t have their complete guidance, navigation, and control system, or they don’t want to risk the (expensive) module on this sort of flight test when they could just spin instead.

  • John, I was wondering the same thing. It would seem to me that, at some point, one needs to stop spinning and control the trajectory such as a trajectory that minimizes gravity losses.

  • Col Beausabre

    “If so, has anyone launched a small payload into orbit with the whole craft, multiple stages, spinning like this? Or how about even a sounding rocket for research into the upper atmosphere, for instance?”

    Not the whole vehicle but Explorer I back in the dark ages had a bunch of small solid fuel rockets in a “tub” as an upper stage with another – tipped with the actual instruments – on top. The tub was spun up prior to launch

    https://www.bing.com/videos/search?q=explorer+1&&view=detail&mid=3A7842E0F5244544EC7D3A7842E0F5244544EC7D&&FORM=VRDGAR

    https://www.bing.com/videos/search?q=explorer+1&&view=detail&mid=CCE26D048D6C01EDF590CCE26D048D6C01EDF590&&FORM=VDRVRV

    https://www.bing.com/videos/search?q=explorer+1&&view=detail&mid=BDD65C32190644EBFBA2BDD65C32190644EBFBA2&&FORM=VDRVRV

    The X-8 (part of the Aerobee family) sounding rockets were spin stabilized

    https://en.wikipedia.org/wiki/Aerojet_General_X-8

  • Col Beausabre

    Anyway, nitric acid is no surprise, but WHY turpentine? Alcohol is cheap when bought in industrial quantities, you could use kerosene (JP-5), etc. Enquiring minds want to know!

  • Edward

    John E Bowen asked: “From the video, it looks like the stage was spinning around, very fast. Is it what they call ‘spin-stabilized?’ If so, has anyone launched a small payload into orbit with the whole craft, multiple stages, spinning like this? Or how about even a sounding rocket for research into the upper atmosphere, for instance?

    Since this was a test of the Interorbital engine, rather than a test of a rocket system, the engineers probably did not need to worry about spin, and being a sounding rocket, spin was unlikely a problem.

    Going to orbit, however, requires that the rocket turn from vertical to horizontal over the course of the launch. Spin would make that more difficult, since the turn direction would continuously change from the Y axis to the Z axis to the -Y axis, etc.

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