Suicide Burn with a single, big, slow engine

Awesome job

@AnotherFireFox
it's hard to grasp at first glance, this is impossible and yes as you replied to someone here, it takes tiny fractions to screw everything up , i dropped my rocket from 35,000 m hoping the vertical speed would scare it off and ignite but air drag worked faster than the engines and i got back to square zero with little time that's consumed for engine waking up. i would put another up-vote if i could

@crowxe yes, even with the great TWR engines, if you can throttle down your engine enough you eventually have low TWR. In this video I sustained 70%-ish throttle to the end and then just cut the engine off without further throttling.

@AnotherFireFox
yes now i get you and i tested 6 TWR from 1~2 Km , the thing slammed into the ground and crashed before the engine could produce any significant thrust, so yeah it's impossible from that height. but maybe it works from much greater heights where the required time is longer and allow drag time to help. and oh, i don't know much about real engines minimum thrust, it seems to be an issue ?

@crowxe Yeah, sure. If you can throttle down to get low TWR, you have much larger room to compensate and maneuver, so your suicide burn would be much safer and much robust. The best case is you can reduce your TWR as low as 1.0 so that you can hover before touchdown. However if you can't throttle down too much so you have to do a suicide burn with high acceleration, such as this video which was 5G, it's really hard.
Furthermore, in this video the engine is slow to throttle so have to cut off the engine way before touchdown. You can check the video that the engine cutoff was higher than 60m from ground.

@AnotherFireFox
i think it depends on the power demand , i played with it a little but not enough to give complete report. in the burn trigger block i divide "Max thrust" by a value that ensures TWR at sea level is somewhere between 1.5 and 2 , that triggers the burn earlier and gradually reduces thrust (because of the drag assistance and mass loss) by the time the legs are about to touch the ground , the thrust is virtually at 1 TWR , so the engine will be at zero when "grounded" block works before the rocket bounces (i fool the rocket to think the ground is 0.25~0.5 m further to avoid hover)

@TestRunner But this is a matter of physics itself. Due to the law of physics this algorithm is super fragile. If you measure your height 0.001m wrong, you crash. If you measure your engine spooling time 0.01s wrong, you crash. Nature is such hard to please :(

Rocket engines are not able to do a deep throttle, or even a shallow throttle. Suicide burn with high thrust, slow spooling engine is really hard. That's why modern reusable rockets are equipped with a few of small engines: With this configuration, you can cut some engines off to reduce your TWR.

However, is it really impossible to do a suicide burn with a single, big, slow engine? Let's try. Target TWR was 6 but throttled down to compensate drag and to maintain constant acceleration.