SpaceX Tuesday...
Discussion
Eric Mc said:
That's why I see a combination of both as being maybe the best solution - as already practiced on Mars.
On Mars the atmosphere is so thin parachutes alone would never slow the lander down sufficiently to avoid damage on impact.
On earth, up to certain sizes, parachutes can work. But a combination of parachutes and rockets can be used for earth landings too.
Just look at Soyuz.
But why bother with parachutes if you can solve it without? On Mars the atmosphere is so thin parachutes alone would never slow the lander down sufficiently to avoid damage on impact.
On earth, up to certain sizes, parachutes can work. But a combination of parachutes and rockets can be used for earth landings too.
Just look at Soyuz.
RobDickinson said:
It used a parachute but that wasnt enough to slow it down fully so then we had rocket crane to lower it..?
I assume larger heavier items will need more effective braking - chutes will still be part of the solution but couldnt ever be the whole one, not on Mars, not when you have to get back off Mars.
The crane was used to give the landing more precision, stop the lander getting stuck on top of a boulder, upside down etc.I assume larger heavier items will need more effective braking - chutes will still be part of the solution but couldnt ever be the whole one, not on Mars, not when you have to get back off Mars.
London424 said:
But why bother with parachutes if you can solve it without?
IF is the operative word.Nobody's managed it yet.
I'm not saying they won't do it. And if they do, it will be a great achievement. But it ain't going to be easy. I think SpaceX themselves expect quite a few failures before they get it to work. After that, they need to show that it works reliably.
annodomini2 said:
The crane was used to give the landing more precision, stop the lander getting stuck on top of a boulder, upside down etc.
It also allowed them to use the wheels of the lander as the actual landing undercarriage. This meant they didn't need a landing platform with legs, saving a lot of weight. Separate landing platforms had been used for every automated rover (both lunar or Mars) up to then.Eric Mc said:
It also allowed them to use the wheels of the lander as the actual landing undercarriage. This meant they didn't need a landing platform with legs, saving a lot of weight. Separate landing platforms had been used for every automated rover (both lunar or Mars) up to then.
Yep, and as they'd removed the need for any kind separate landing pod to put the rover in they then had concerns about the landing rockets kicking dust and rocks around and damaging the rover so the skycrane was also solution to keeping the thrust away from where the rover was sitting on the ground.Eric Mc said:
London424 said:
But why bother with parachutes if you can solve it without?
IF is the operative word.Nobody's managed it yet.
I'm not saying they won't do it. And if they do, it will be a great achievement. But it ain't going to be easy. I think SpaceX themselves expect quite a few failures before they get it to work. After that, they need to show that it works reliably.
Grasshopper showed a remarkable level of fine control, and the barge crash proves they can deliver a booster from a real trajectory to a precise location and down to a landing speed. It seems like the things they need to pull it off are already demonstrated. Tweaks to hydraulic fluid levels & other stuff they've learned from the last one and I think there is a pretty good chance we'll see the next one touch down as intended.
I wonder how much adding all the reuse systems is costing in terms of payload to orbit?
Probably not as much as it would have years ago. I'm pretty sure the legs are composite - which makes them much lighter than older metal legs would have.
Back in the 90s McDonnell Douglas tried out hovering and landing a tall rocket stage (the DCX) and it sort of worked - until one of the landing legs collapsed and the rocket toppled over, exploding.
Back in the 90s McDonnell Douglas tried out hovering and landing a tall rocket stage (the DCX) and it sort of worked - until one of the landing legs collapsed and the rocket toppled over, exploding.
Yeah I was surprised at that, the whole first stage is less than 20t dry so it's a significant proportion. I guess they need a lot of strength in those legs to handle the bump and potentially a bit of wobbling about when one or two legs might be briefly carrying nearly the whole load.
That's interesting. So they have to carry the weight of those engines into orbit - and they have to protect the rocket motors from the heat and stresses of re-entry.
The Russians, of course, use rockets on their Soyuz to cushion the landing and these need to be protected during re-entry too but they are obviously much less powerful than rockets that would be needed to pull the whole capsule off the rocket during an abort.
Again, SpaceX are showing a different approach.
The Russians, of course, use rockets on their Soyuz to cushion the landing and these need to be protected during re-entry too but they are obviously much less powerful than rockets that would be needed to pull the whole capsule off the rocket during an abort.
Again, SpaceX are showing a different approach.
SpaceX were touting the fact their LES provides protection for the complete mission rather than just early stages of launch. With 4 pairs of engines it can apparently cope with multiple engine outages and still perform as LES, or eventually, landing function for which they have chutes as backup too.
LOL, didn't think of it like that
I suppose one might take it as given that the Launch Escape System was designed to work in the case of a launch escape scenerio (failure / loss of Merlin 1D main launch engines).For clarity, the LES comprising 8 Super Draco engines within the Dragon2 capsule has redundancy and can still perform it's LES / landing duties in degraded form with a couple of the Dracos out.
The LES (whatever system is used) should be designed to safely extract the crew module from the rocket from a position of sitting motionless on the pad right through to the point in the lift off where the capsule could safely detach and parachute back without needing to fire the LES.
That would usually mean that it will be required to work from a state of Zero Altitude and Zero Velocity to around Mach 4 and an altitude of around 20 to 30 miles.
That would usually mean that it will be required to work from a state of Zero Altitude and Zero Velocity to around Mach 4 and an altitude of around 20 to 30 miles.
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