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2 Responses to “Interview With Jim Dunstan”
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.
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.