I was just amazed at what he was able to pull off from an engineering
perspective in this form factor and with the solid rocket engines.
For the retro rocket braking he goes into some detail later in the
video, he modulates the vertical component of the thrust by making the
rocket swerve from side to side.
He then does a maneuver to cancel out the horizontal velocity component
at the end, just before landing.
He does all of this by knowing the details of the rocket motor thrust
curve and his initial velocity and position above the ground. Once he
detects that the motor is at maximum thrust, he plots a trajectory with
more or less swerve that will get him to the ground with close to zero
vertical velocity.
An interesting solution to not being able to throttle the engine or turn
it off .
Thanks
Evan
On 11/25/2020 7:14 AM, Cris Erving wrote:
Interesting technologies for sure, but limited use in hobby rocketry for several reasons...
1) The TVC to keep the rocket going straight up only stabilizes the rocket if the motor is burning. That means long-burn motors, which have lower average thrust than "normal" motors with a shorter burn time. That constrains the weight significantly, which is a problem considering all of the extra weight required to make it work. All of the TVC's that I've seen have been with relatively small model rocket motors, with a short coast phase. If you look at the video of the TVC in action, it's moving like crazy... that's not what you want to be seeing for a control system. Any R/C flyers out there? You know what I mean...
2) Retro rockets for braking are certainly doable, but if you want to land with one it has to be throttleable... not gonna happen with solid fuel motors. In the video, the rocket stops a few feet short of the ground, starts to lift off again, then ends up on it's a** ass the retro motor burns out. You also need to be able to cut it off right when you hit the ground.
3) Having a lit motor intentionally coming down ballistic probably breaks NAR/TRA rules... it's not explicitly there, but it's certainly not in the spirit of The Code. You'll notice that Joe isn't doing this at a sanctioned launch.
Eggtimer Cris
------------------------------------------------------------------------
*From:* roc-chat-bounce@xxxxxxxxxxxxx <roc-chat-bounce@xxxxxxxxxxxxx> on behalf of Evan McCarthy <evan.mccarthy@xxxxxxx>
*Sent:* Wednesday, November 25, 2020 6:52 AM
*To:* roc-chat@xxxxxxxxxxxxx <roc-chat@xxxxxxxxxxxxx>
*Subject:* [roc-chat] Controlled launch and landing of a model rocket using thrust vectored F class motors
I came across this youtube video of a flight of a model rocket that is fully controlled to do a vertical takeoff and landing using two F class motors and just had to share.
https://www.youtube.com/watch?v=YixmPK26upk <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DYixmPK26upk&data=04%7C01%7C%7C0fc49b4c114a40139a6c08d89151bcb1%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637419127521406454%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=DL2XK9l4D%2FWHKrcg8Rb0q71MocdiszeZgjT7tVgLrZY%3D&reserved=0>
The rocket includes:
* Flight controller with associated sensors
* Reaction wheel
* Thrust vectoring mount for the rocket engines
* 4 high speed cameras on board
* 900 MHz radio data link
* GPS
* Emergency actively deploy-able parachutes
* Actively deployed landing legs
This is my first post to this list, so please let me know if I should not be sharing this sort of content here.
Evan
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