Quick thought that I haven't seen anyone mention. When ISS visiting vehicles are opened up, the crew wear masks to avoid floating debris - and this is after the loading crews make efforts to avoid contamination. For a crew that are living out of MCT on the surface, or even just making occasional visits, ISTM they will trek in a lot more debris than the CRS vehicles suffer. How would this be mitigated? Crew wear masks and the ventilation turned to max to filter the air as quickly as possible? Cheers, Martin
The reason they wear facemasks when opening CRS vehicles is because in zero-gee, stuff floats around and you could inhale it...
Quote from: Robotbeat on 10/31/2015 04:59 pmThe reason they wear facemasks when opening CRS vehicles is because in zero-gee, stuff floats around and you could inhale it... Yup, that was exactly what I was discussing. Human occupation of the MCT on Mars' surface will create a debris problem once it's launched back to LMO. Cheers, Martin
...The size of boulders that would pose a problem for an MCT landing would be faaar to large to handle with a small rover. And boulders are only part of the issue, dust blasting may be more of a problem, and that certainly cannot be addressed by a small rover....
15 years ago I had a bobcat working around my house. I fail to see how you get that into the and out of the Dragon 2.
Quote from: Hauerg on 10/31/2015 05:28 pm15 years ago I had a bobcat working around my house. I fail to see how you get that into the and out of the Dragon 2.Yeah, Red Dragon is a good idea for getting some experiments to Mars without having to design a custom lander, but something like a small robotic bulldozer will need a custom lander.
Quote from: Lars-J on 10/30/2015 03:52 am...The size of boulders that would pose a problem for an MCT landing would be faaar to large to handle with a small rover. And boulders are only part of the issue, dust blasting may be more of a problem, and that certainly cannot be addressed by a small rover....Boulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.
It seems like SpaceX went to some pain to eliminate hydrazine RCS from Falcon 9, replacing it with compressed nitrogen at a much poorer performance level.What exactly would be used for high-frequency, low-latency thrust in an MCT? One of the ideas I'm tossing around is supplementing the massive methalox tanks & Raptor engines with a moderate amount of hydrazine + NTO, and using SuperDracos. This fulfills the need for RCS (which I don't think raptors are suited for), does not introduce any new engines (which SpaceX have specified: they're only working on one) and gives some thermal benefits relative to methalox alternatives.An alternative might be one of the upcoming green propellant blends.
Quote from: Robotbeat on 10/31/2015 05:25 pmQuote from: Lars-J on 10/30/2015 03:52 am...The size of boulders that would pose a problem for an MCT landing would be faaar to large to handle with a small rover. And boulders are only part of the issue, dust blasting may be more of a problem, and that certainly cannot be addressed by a small rover....Boulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.1) MRO can resolve objects of "about a meter across"...
I am quite sure they will use pressure fed methalox thrusters for RCS. The pressurized tanks can be small and get refilled from the main tanks when needed. The morpheus moon lander testbed has not only the main engine but methalox thrusters too. I would not see this as a contradiction to working on one engine only. Thrusters are not engines in that sense.
If your backing off to a hohmann transfer speed direct from mars that would indeed be ~6 km/s and comes in at a dry mass fraction of 20%, considerably more reasonable and well below the mass fraction of SSTO vehicles of any propellant, if you were to include an efficient aerocapture system like magneto-plasma I could even see this vehicle being possible all be it optimistic. But the transit time is now no good for passengers, only cargo.
Quote from: Burninate on 10/31/2015 09:26 pmQuote from: Robotbeat on 10/31/2015 05:25 pmQuote from: Lars-J on 10/30/2015 03:52 am...The size of boulders that would pose a problem for an MCT landing would be faaar to large to handle with a small rover. And boulders are only part of the issue, dust blasting may be more of a problem, and that certainly cannot be addressed by a small rover....Boulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.1) MRO can resolve objects of "about a meter across"...MRO has a resolution of ~30cm per pixel. Multiple exposures of the same site from different angles and ESPECIALLY with the Sun at high angles (thus casting long shadows) can identify hazards.
Quote from: Robotbeat on 10/31/2015 10:59 pmQuote from: Burninate on 10/31/2015 09:26 pmQuote from: Robotbeat on 10/31/2015 05:25 pmBoulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.1) MRO can resolve objects of "about a meter across"...MRO has a resolution of ~30cm per pixel. Multiple exposures of the same site from different angles and ESPECIALLY with the Sun at high angles (thus casting long shadows) can identify hazards.Perhaps, but that kind of coverage does not exist. Yes. And even when it does, it tells you nothing about the relative strength of the surface. It could be the Martian equivalent of quicksand for all we know.But it is still irrelevant. MCT will need to be able to land on unprepared terrain, it will be necessary to allow of off-nominal EDL and abort scenarios. So it will need a sturdy gear, and you seem reluctant for some reason to admit that.
Quote from: Burninate on 10/31/2015 09:26 pmQuote from: Robotbeat on 10/31/2015 05:25 pmBoulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.1) MRO can resolve objects of "about a meter across"...MRO has a resolution of ~30cm per pixel. Multiple exposures of the same site from different angles and ESPECIALLY with the Sun at high angles (thus casting long shadows) can identify hazards.
Quote from: Robotbeat on 10/31/2015 05:25 pmBoulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.1) MRO can resolve objects of "about a meter across"...
Boulders big enough to cause problems for MCT landing are easily spotted using MRO. You can just avoid them in the planning stages.