(atmospheric modelling stuff snipped) Using rocket powered rotors for launch makes some sense until after you've reached close to Mach 1. After that, the drag and heating issues are real problems. Not immediately obvious are the sizing and complexity issues with using a rotor. In the case of a SSTO vehicle like we were trying to do at Rotary, the landing weight will be around 5% of the takeoff weight. If you minimum size the rotor for the landing weight, you will only be able to get a 5% boost in required thrust/lift at takeoff from the rotor. Size the rotor for significant help at liftoff, and you end up with a much larger rotor than has been done yet unless your vehicle is really small. As velocity increases during the launch, there quickly becomes a need to be able to aim the rockets at the end of the rotor blades separately from the blade pitch; meaning a complex and heavy mechanism. The small lift benefit combined with the mechanical complexity required and the heating and aerodynamic issues doesn't add up for a SSTO vehicle, and as y'all know, the RRC Roton design didn't use the rotor for launch. Except for the (HUGE) complexity and development effort you'd be signing up to take on, a rocket powered rotor might make sense for a subsonic First stage, except that increasing the effective Isp of the First stage isn't the place to put your efforts for an orbital launcher. Using a rotor for landing is a light-weight solution, but has it's own set of problems if the rotor is deployed during the reentry above Mach 1.
Ken >>It would be nice to airbreath, but that sounds rather too complex and >>lox and tanks are dirt cheap, and you need them above 10km or so anyway. >>Now John Carmack and Gary Hudson had tried a rocket powered rotor; but >>both had abandoned them. And I wasn't entirely clear why that would >>help, what's the theory? >As Gary put it a few years ago, "Rocket engineers have been fighting >the atmosphere since the days of Goddard. We're going to make it work >for us." It was interesting to watch the Roton design develop over >the years. Recently Gary confessed that the rotors were an >opportunistic design he and Bevin came up with. "We wanted to get the >engine out on booms, and spin the booms - instant pump. We had to >fair the booms. We thought, 'Why not use the booms to generate >lift?'" It increases the effective Isp by an order of magnitude, by >using the air as reaction mass. >>Anyway, woke up this morning, and suddenly spotted the theory of why the >>HMX had the rotating rocket tipped wings at takeoff . It reduces the >>effective ISP of the engine. >No, it increases the Isp, by increasing the chamber pressure. Roton >was going to use some obscenely high chamber pressure. I don't >remember how obscene, but something around 5000 psi comes to mind. >>I think HMX abandoned this idea because of weight growth didn't they? >It doesn't scale well. Given current rotor blade technology, there's >a maximum size you can make a Roton. It turns out that's too small to >confidently say you can use the technology to make a commercial SSTO. >Now, if you're flying tourists at a couple hundred pounds per, instead >of cargo at a few thousand pounds per, you might be back in the realm >of feasibility. But I suspect the failure of Rotary Rocket is going >to sour financiers on Rotons for some time to come. >-R >-- _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
