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Honda conducts successful launch and landing of experimental reusable rocket

(global.honda)
1355 points LorenDB | 3 comments | 17 Jun 25 15:02 UTC | HN request time: 0.521s | source
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whatever1 ◴[17 Jun 25 16:02 UTC] No.44300677[source]▶
Question why is it so easy today to build reusable rockets? Is it because the onboard cpu speed of the chips can solve more granular control problems with low latency?
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roshdodd ◴[17 Jun 25 16:41 UTC] No.44301068[source]▶
As someone who actively works in the field, it was a culmination of:

- Advances in rocket engine design & tech to enable deep throttling

- Control algorithms for propulsive landing maturing (Google "Lars Blackmore", "GFOLD", "Mars Landing", and work through the references)

- Forward thinking and risk-taking by SpaceX to further develop tech demonstrated by earlier efforts (DC-X, Mars Landing, etc.)

Modern simulation and sensor capabilities helped, but were not the major enabling factors.

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bumby ◴[17 Jun 25 16:50 UTC] No.44301152[source]▶
Can you elaborate on the advances in deep throttling?
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1. 93po ◴[17 Jun 25 17:17 UTC] No.44301416[source]▶
Also didnt spacex do reuse without throttling and only having on/off?
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2. timschmidt ◴[17 Jun 25 18:48 UTC] No.44302471[source]▶
No. SpaceX's Merlin engines use a single https://en.wikipedia.org/wiki/Pintle_injector which has excellent throttling capabilities.
3. Tuna-Fish ◴[17 Jun 25 19:02 UTC] No.44302641[source]▶
They do throttle, and quite low compared to other comparable engines, but they still cannot throttle an engine below 1 TWR when the stage is near empty. Meaning that they cannot hover a stage, either the engine is on and the stage is accelerating upwards, or it's off and it's accelerating downwards. (And you cannot rapidly turn engines on and off.)

So they need to "hoverslam", that is, arrive at the landing pad rapidly decelerating so that their altitude hits zero just as their speed hits zero. This was thought to be very hard, but I don't think SpaceX has lost a stage due to estimation failure there. It helps that there is significant throttle range and fairly rapid throttle response on the engines, so they can have some slack. (Plan to decelerate at 2.5g for the last ~20s or so, with the ability to do anything between ~1.5g to 4g, so you can adjust throttle based on measured landing speed.)

Their Superheavy has more engines, allowing them to bring the TWR below 1, enabling hovering.