Rocket Plane Build Aims For High Speed Flight

[James Whomsley] likes flying, and likes flying fast. After reaching a speed of 114 miles an hour with an RC plane, he wanted to go further and break that record. To do so, he looked towards rocket power, and started a new build.

The design consists of a combination of 3D printed parts, laser-cut plywood bulkheads, and foamboard flight surfaces, with a few carbon fiber stiffeners thrown in here and there. For this early prototype, power is solely from hobby rocket motors, providing thrust for 1.6 seconds, meaning flight times are necessarily short. The craft is launched from an aluminium profile rail thanks to a 3D printed sliding guide pin.

Initial tests with two rocket motors were promising, leading to a second trial with a full six motors fitted. The thrust line was a little low, however, and a major pitch-up just after launch meant the plane only reached around 62 miles an hour. [James] still has a ways to go to beat his previous record, so intends to explore adding ducted fan propulsion to get the plane in the air before using the rockets as a speed booster in steady flight.

Of course, if you can’t lay your hands on rocket engines, you could always consider spinning up your own. (Or ditch the engine entirely.) Video after the break.

19 thoughts on “Rocket Plane Build Aims For High Speed Flight

  1. If it was my project knowing I intended to give it sustained powered flight too I’d put the EDF in the body or make it a tail pusher (move the rockets around a little in both cases to accommodate airflow/motors etc). With the EDF in body approach can even shut the air intake for better airflow when the rocket fires. I think I’d also go for making my own grain for the rocket so it is shaped and sized to be as large as possible inside the airframe – longer for a greater sustained burn with less COG change and probably oval in profile so it can be wider (fitting in a bit like a Vulcan bombers air intakes at the join of the body and wing).

    That said its a good build, and fun project I look forward to seeing the continuation of. Also trying to do all of the above in the first version is bound to be catastrophic – much more complex and many more steps to screw up in your own hands.

      1. Hmm that should work – but its equally something in the airpath creating more drag the rest of the time.. Which will likely make it harder to fly when the rocket isn’t active and possibly slower overall – why I was favouring the close the EDF inlet for that super smooth air cutting profile – removing all the drag of the EDF and mounting stuff in the air path..

    1. Yeah, NASA did the calculations a long time ago.
      An EDF acts as an giant air brake as soon as the speed increases above the speed with only EDF.
      Another option is a longer start ramp with a rocket powered sled to accelerate the plane from zero, and a delayed start of the onboard rockets

      1. Not to mention the extra forces of the fins can cause the blades to explode etc.. Its not an easy thing to take a few G extra and the massive wind load as rapidly as the rocket gives it for such a thin bit of plastic – assuming that is that the EDF is exposed to the airflow when the rocket fires I’d be surprised if the fan survives or it goes much faster.. Close the air intake and it becomes much more believable it will survive.

        I like the rocket sled idea, steam cannon, anything to get it going with gusto before ignition.. Could also just drop it from a rather large height I suppose..

  2. Rocket planes need to work like a semiautomatic shotgun. When the motor burns out, use the staging charge to eject it and rack in the next. Igniters wired to rings on the casing, and a servo channel to ignite, so you only ignite each motor when you need it.. Maybe a larger motor for the initial launch.

  3. My very first thought was is this going to hit the COCOM Limits.
    It is a limit placed on GPS tracking devices that disables tracking when the device calculates that it is moving faster than 1,000 knots (1,900 km/h; 1,200 mph) at an altitude higher than 18,000 m (59,000 ft).

    Some manufacturers apply this limit only when both speed and altitude limits are reached, while other manufacturers disable tracking when either limit is reached.

    And then I watched the video, 59km/h (Mach 0.05), and then 101km/h (0.08) and he said that his maximum velocity so far was 114km/h (Mach 0.09). So there is lots of headroom to 1,000 knots (1,900 km/h; 1,200 mph) which is about Mach 1.5. I do not think that he needs to worry about his GPS turning off, at least not yet.

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