2 thoughts on “Interview With Jim Dunstan”

  1. I read an AIAA paper a few months ago about MEMs technology applied to rocketry. They spoke of turning rockets into a usable commodity. Microthruster arrays like those built by TRW can rival larger engines at far lower mass and far higher reliability – achieving 1000 to 1 thrust to weight ratios and astronomical reliabilities – when built on the scale of pixels on a HDTV screen – forming what I call a ‘propulsive surface’ of millions of thrust elements to ‘paint’ ‘thrust effects’ across the surface – the same way real time pictures are painted by tiny spots of glowing plasma on a HDTV screen. Micro UAVs are one application, on a larger scale though, such surfaces can become as common as wheels and as easy to use in a wide variety of aerospace applications – incuding major launcher applications.


  2. Comments about MEMs propulsive surfaces

    Area scales as the square of dimension, weight scales as the cube. So, smaller engines have higher thrust to weight. Engines on a MEMs scale achieve 1,000 to 1 thrust to weight as a result. This is 10 to 20 times better than macroscopic engines.

    MEMs processing costs about $1 per square inch. MEMs rockets produce 50 pounds per square inch. So, we’re talking about $0.02 per pound of thrust.

    So, a 3 million pound thrust engine – enough to loft a fully loaded ET off the pad at nearly 2 gees – would cost only $60,000 !! and cover 60,000 sq inches – 416.7 sq ft – a disk 23 ft in diameter – 4.6 ft less than the diameter of the ET itself.

    With 1,000 to 1 thrust to weight, the 3 milion pound thrust engine masses only 3,000 pounds. Added to the 58,500 pound tank we have an empty mass of 61,500 pounds and a full-up wieght of 1,683,000 pounds.

    Adding a 7,000 pound section to the intertank region for a payload, and a 25,000 pound payload – we have a full up weight of 1,715,000 pounds at lift-off and 108,500 pound empty weight. With an exhaust velocity of 14,650 fps this system has an ideal velocity of;

    Vf = 14650 * LN(1715000/108500) = 40,440 fps

    Which exceeds escape velocity.

    If the ET costs $50 million – this is $2,000 per pound – which is remarkable.

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