Yeah, Joe's stuff is actually pretty cool to watch, but it's not very practical.
I wonder if you could use the Krushnic effect to throttle the solid fuel retro
motor by moving it up in the tube to throttle it down. That would be an
interesting exercise... and if you could pull it off it would probably work
better than intentionally vectoring the motor back and forth.
Eggtimer Cris
________________________________
From: roc-chat-bounce@xxxxxxxxxxxxx <roc-chat-bounce@xxxxxxxxxxxxx> on behalf
of Evan McCarthy <evan.mccarthy@xxxxxxx>
Sent: Wednesday, November 25, 2020 7:33 AM
To: roc-chat@xxxxxxxxxxxxx <roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Controlled launch and landing of a model rocket using
thrust vectored F class motors
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<mailto:roc-chat-bounce@xxxxxxxxxxxxx>
<roc-chat-bounce@xxxxxxxxxxxxx><mailto:roc-chat-bounce@xxxxxxxxxxxxx> on behalf
of Evan McCarthy <evan.mccarthy@xxxxxxx><mailto:evan.mccarthy@xxxxxxx>
Sent: Wednesday, November 25, 2020 6:52 AM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
<roc-chat@xxxxxxxxxxxxx><mailto: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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DYixmPK26upk&data=04%7C01%7C%7C5b1f3f569180451b65bd08d891576dcb%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637419151968019231%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=bVoDqDM6UB2ueiITsbQbcg70y6iNrHD7l8JF65al3lQ%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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