Interorbital Test Fires Rocket in Mojave

Interorbital Systems engine firing in Mojave. (Credit: IOS)
MOJAVE, Oct. 28, 2012 (IOS PR) —On a calm clear high-desert October evening, Interorbital Systems’ NEPTUNE rocket series’ main engine roared to life in its first hot-firing test.

The engine, the IOS GPRE 7.5KNTA (General Purpose Rocket Engine; 7,500lb-thrust; Nitric Acid; Turpentine; Ablative cooling), blasted a 22-foot (6.71-meter) plume of fire across Interorbital’s Mojave Spaceport test area, scorching the sand an additional 50 feet (15.24 meters) beyond the plume end.

The 7.5K-pound (33,362-newton) thrust engine is the largest rocket engine in the world utilizing high-density, storable nitric acid and turpentine. These hypergolic propellants provide almost instantaneous chemical ignition. 

This static firing marks a major milestone in the evolution of the company’s NEPTUNE Modular Orbital Launch Vehicle series. Refining the engine operation paves the way for the first flight test of the CPM—Common Propulsion Module—the stand-alone rocket that is the primary construction element of various bundled configurations that yield launch vehicles specially designed to meet specific mission requirements.

IOS’ first orbital launcher is a seven-module rocket designated the NEPTUNE 7 (N7)—powered by seven of the GPRE 7.5KNTA engines—and purposed to lift a mixed-manifest of some 24 TubeSats and CubeSats on each launch. Interorbital recently completed a NASA Phase I SBIR contract, awarded to further the development of the NEPTUNE Modular Rocket series.

  • No opinion Doug? Just repeat the press release?

    I think this deserves a word or two.

    Interorbital has been claiming they’re going to launch payloads *to orbit* for a few decades now. Actually testing an engine is a pretty good sign that they might start flying something soon.

    That’s how people tend to treat Virgin Galactic’s various rocket tests.

  • Anon

    I feel like it goes without saying, actually. Anyone happen to know the ISP of nitric acid and turpentine?

  • Jason

    I calculated Isp to be 196 from this example:

  • Nothing to say really. Everyone in Mojave is kind of stunned speechless that Interorbital test fired something. I don’t think that’s happened in the entire year I’ve been living out here in the desert.

    Been rather preoccupied with a few other crises over the last 24 hours. Trying to figure out what this test actually means has been a low priority.

  • Tom

    I heard through the grape vine they were going to do an engine test, good to see that it was not just words and has actually happened!

  • A correction for Jason: actually, the specific impulse of Interorbital’s nitric/turpentine engines is 235 seconds (sea level). Due to the high density of these propellants, the Density Specific Impulse is 310 seconds, which allows the use of smaller and lighter propellant tanks than are required for other lower-density propellants. The low Isp of the Veronique engine you referenced is the result of that rocket engine’s inefficient injector and combustion chamber design. Try using NASA’s ODE propellant program for your calcualtions. You’ll see that the theoretical maximum specific impulse for a sea level expansion ratio for an engine using nitric acid and turpetine is near 246 seconds. Also: mixture ratio plays a major role in the performance of the propellants.