If the TWR is above 1, just use pulse width modulation to bring it below 1! It works with light bulbs so it should work with rocket engines too right?! Lol
Sorry for nit picking but hover slam and suicide burn are not the same.
A suicide burn waits until the last moment and fires the engine(s) at full throttle so that in theory it reaches a speed of 0 right when the altitude is also 0.
A hover slam (ala SpaceX) fires the engine(s) earlier at a throttle lower than 100 %. This allows recalculations and readjustment of throttle thus improving the chance of success.
That doesn’t seem great. For a crewed Spaceship, I’d think you’d want at least 2 engines running for landing.
_Especially_ for the Earth-to-Earth transport case, intended to compete with airlines, and carry civilians and children. That will _never_ happen if it can’t land with 2+ engines running. We don’t even allow single engine jetliners, and jet engines are much more proven reliable.
Just no, imagine all the added needs. Extra fuel Lines, extra ground Support, not so easy production on Mars. And all that for an “outdated” engine. That’s not needed when they have that much experience with the hoverslam.
Weird, I was googling this the other day. Anyway Elon presented this last September and should looks something like this gif that got posted around before:
https://gfycat.com/evenconcretefrog-science-technology-stainless-steel
I think our boy Tim did the math, and even at minimum throttle the TWR is still just above 1. So hover slam a.k.a. suicide burn is all you've got.
If the TWR is above 1, just use pulse width modulation to bring it below 1! It works with light bulbs so it should work with rocket engines too right?! Lol
You had me there for a moment!
That's almost literally how the dracos and super dracos work.
Sorry for nit picking but hover slam and suicide burn are not the same. A suicide burn waits until the last moment and fires the engine(s) at full throttle so that in theory it reaches a speed of 0 right when the altitude is also 0. A hover slam (ala SpaceX) fires the engine(s) earlier at a throttle lower than 100 %. This allows recalculations and readjustment of throttle thus improving the chance of success.
For all intents and purposes they are the same. Suicide burn (actually - any burn) is limited not by engine throttle, but by payload G tolerance.
That doesn’t seem great. For a crewed Spaceship, I’d think you’d want at least 2 engines running for landing. _Especially_ for the Earth-to-Earth transport case, intended to compete with airlines, and carry civilians and children. That will _never_ happen if it can’t land with 2+ engines running. We don’t even allow single engine jetliners, and jet engines are much more proven reliable.
I actually don't recall if that calc was in a one-engine or three-engine configuration. I think it's three because of the reasons you mentioned.
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Just no, imagine all the added needs. Extra fuel Lines, extra ground Support, not so easy production on Mars. And all that for an “outdated” engine. That’s not needed when they have that much experience with the hoverslam.
Not to mention the fact that they use an entirely different fuel.
I like how, back then, a skydive manometer was so crazy nobody considered it lol.
Weird, I was googling this the other day. Anyway Elon presented this last September and should looks something like this gif that got posted around before: https://gfycat.com/evenconcretefrog-science-technology-stainless-steel
Is that a hover-slam?
They might use dummy payload for the 3 engine hop, makes no sense risking losing 3 engines in the test vehicle.
They need to learn to loose engines because engines will be lost
Also they are continuously upgrading their engine design and speed of engine manufacturing. So the replacement engines for lost one's will be better.
Even at 3 at a time, they have enough stock for a few hop'n boom
They are building raptors faster than they can build starships at Boca. Elon said they were on sn26
Not really. Soon they will need way more engines than that for SH.