SpaceX Tuesday...
Discussion
Flooble said:
Just out of interest, are all the probes using hypergolic fuels and pressure fed engines? Possibly that is a slightly simpler engineering problem.
They seem to like hydrazine monopropellant quite a lot. E.g. the two Viking mars missions in the 70s. Even the sky crane element of the upcoming Mars 2020 mission has several little hydrazine fuelled engines to control final descent and hover.Flooble said:
Just out of interest, are all the probes using hypergolic fuels and pressure fed engines? Possibly that is a slightly simpler engineering problem.
I can't say for the others but Perseverance lands on Mars (or, tries to) in 3 days.The Skycrane rockets are monopropellant hydrazine. That's passed over a catalyst and decomposes, producing a lot of heat/thrust depending on the structure of the catalyst.
Brother D said:
Thats the first miss in a long time. I did get worried when it lost comms @ 21k.
Video showed flames but not near the ship.
Last failures were 11 and 12 months ago respectively. They've come so far it makes the news when they have a booster landing failure.Video showed flames but not near the ship.
Re-entry burn starts here https://youtu.be/L0dkyV09Zso?t=1579
After shutdown is called, there's still a lot of illumination from the hot end.
It appears to be travelling sideways-on to the direction of travel rather than hot-end-down and being steered with the grid fins. Might just be the cold gas thrusters though.
Telemetry cuts out when it's at 21.3km (70000ft) and 5241km/h (roughly Mach 4.9 at that height and speed).
I still wonder if it came in sideways and potentially/partially broke up rather than falling hot-end down.
rxe said:
I don’t see how they will be able to land safely on an unprepared surface, maybe they’ll land a load of unmanned ships to get supplies down, and then land humans in a more conventional disposable capsule. The humans then get the concrete mixer out.
Has to be this. Equipment pre-supply drops can go in at much bumpier speeds than manned flights. As a corollary, a manned capsule that doesn't need also to be carrying equipment means less mass to manage down to the surface. Humans won't even get off the sofa until multiple successful flights have landed with all the necessary equipment. Some of that equipment will be a bulldozery-thing, which will be remotely operable allowing a bit of ground pre-prep ahead of the advance team's arrival.rxe said:
Eric Mc said:
How big and heavy would you think this "bull-dozery thing" would need to be?
Assuming they pick somewhere flat, you probably don’t even need much of a bull dozery thing. Scaff board shuttering, a bit of mesh, and some sort of concrete that works in a near vacuum. The landing weight might be (assuming zero fuel, and 20 tons of gubbins) in the region of 160 tons, which is equivalent to 60 tons on Earth -- so even on initial landing there will need to be something capable of dealing with those forces.
On the way back up it's much harder.
Given the lack of gravity/pressure on Mars, I think Starship will be SSTO from the Martian surface so lets ignore the booster. Lets take 1.4 million kg as the takeoff mass. Martian gravity is about 38% that of Earth, so that 1.4Mkg will exert a force equivalent to 532 tons on Earth.
Mesh won't do; a trampoline won't work; what I'm saying is, the launch platform is going to have to be solid.
Tough problem. Do they have dry lakes on Mars?
*yes I know.
edited to add: I know the target is 100 tons to Mars surface. I don't see that being what happens with the first landing though!
Edited by CraigyMc on Tuesday 16th February 14:50
^ Yeah that’s on the Blue Origin thread too.
They’re relaying a large section of the Starship landing/crash pad currently, so I can’t see SN10 launching soon.
Texas has been suffering a severe wintery snap (for Texas at least) which has driven power demands way up. The grid has struggled to cope, so they’ve had rolling power cuts state wide. Boca Chica had no mains power until this morning apparently.
This is Tesla’s under-construction gigafactory in Austin, Texas:
They’re relaying a large section of the Starship landing/crash pad currently, so I can’t see SN10 launching soon.
Texas has been suffering a severe wintery snap (for Texas at least) which has driven power demands way up. The grid has struggled to cope, so they’ve had rolling power cuts state wide. Boca Chica had no mains power until this morning apparently.
This is Tesla’s under-construction gigafactory in Austin, Texas:
Edited by Beati Dogu on Tuesday 16th February 17:27
CraigyMc said:
The landing weight might be (assuming zero fuel, and 20 tons of gubbins) in the region of 160 tons, which is equivalent to 60 tons on Earth -- so even on initial landing there will need to be something capable of dealing with those forces.
Well the InSight lander's 'mole' has shown just how hard the subsurface is, so maybe a simple wide pad on the end of each landing leg will suffice. If they use the same landing engine system they're looking at for Lunar missions, with engines in the upper section being used for the actual landing to avoid ground erosion & debris, then maybe not much will be needed
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