ISS Habitat has MMOD shielding. Not sure how a presumably single layer of carbon fiber structure on ITS would compare to shielded ISS habitat.Also, trying to quantify MMOD risk in LEO and deep space. Found this document which specifies baseline risk = 0.5% or 1 in 200 over 14-day mission in LEO:https://ston.jsc.nasa.gov/collections/TRS/_techrep/TM-2009-214785.pdf
Quote from: flyright on 06/19/2017 04:27 amISS Habitat has MMOD shielding. Not sure how a presumably single layer of carbon fiber structure on ITS would compare to shielded ISS habitat.Also, trying to quantify MMOD risk in LEO and deep space. Found this document which specifies baseline risk = 0.5% or 1 in 200 over 14-day mission in LEO:https://ston.jsc.nasa.gov/collections/TRS/_techrep/TM-2009-214785.pdf??ITS will be extensively covered in TPS with margin to last probably dozens of entries/reentries (one on each end, 12-15 cycles). Not just carbon fiber.
Has any ISS habitat been punctured? I think not. Likelihood in interplanetary space is a lot smaller than that. I don't think puncturing the tank or habitable volume is a big risk with 4cm of carbon composite walls.Any exposed systems, like the solar panels or the heat rejection system may be more at risk.
ISS deals with this by having Soyuz lifeboats on permanent standby in case of a danger to life. ITS will need to use a different strategy, unless there are multiple ships flying in convoy. Cheers, Martin
Edit: and even then, loss of the cargo in an ITS could be life critical for the crew for the rest of the flight and on the ground, or for people already on the ground.
ITS will need to use a different strategy, unless there are multiple ships flying in convoy.
Quote from: MP99 on 06/19/2017 07:31 amISS deals with this by having Soyuz lifeboats on permanent standby in case of a danger to life. ITS will need to use a different strategy, unless there are multiple ships flying in convoy. Cheers, MartinI am well aware of the life boats. But the risk in interplanetary space is much smaller and my point was, that even in its long lifetime, the main pressure vessels were never punctured. So the risk would be very small, to the point of being acceptable. Punctures in the passenger compartment can be fixed. The landing propellant is in separate inner tanks, so even a puncture would not compromise that propellant, further reducing that risk. Quote from: MP99 on 06/19/2017 07:31 amEdit: and even then, loss of the cargo in an ITS could be life critical for the crew for the rest of the flight and on the ground, or for people already on the ground.How so for the crew? How can cargo be lost and the crew in danger by that?Loss of a single cargo must never be allowed to be life threatening to the colony. Stores must be adequate, just like they are on the ISS.
Quote from: guckyfan on 06/19/2017 07:43 amQuote from: MP99 on 06/19/2017 07:31 amISS deals with this by having Soyuz lifeboats on permanent standby in case of a danger to life. ITS will need to use a different strategy, unless there are multiple ships flying in convoy. Cheers, MartinI am well aware of the life boats. But the risk in interplanetary space is much smaller and my point was, that even in its long lifetime, the main pressure vessels were never punctured. So the risk would be very small, to the point of being acceptable. Punctures in the passenger compartment can be fixed. The landing propellant is in separate inner tanks, so even a puncture would not compromise that propellant, further reducing that risk. Quote from: MP99 on 06/19/2017 07:31 amEdit: and even then, loss of the cargo in an ITS could be life critical for the crew for the rest of the flight and on the ground, or for people already on the ground.How so for the crew? How can cargo be lost and the crew in danger by that?Loss of a single cargo must never be allowed to be life threatening to the colony. Stores must be adequate, just like they are on the ISS....added bold to quote...The ITS will also spend time in LEO. Shuttle required detailed inspection of the TPS prior to being cleared for reentry. This after just a couple weeks in orbit.TPS for ITS may not be fragile as shuttle tiles, or may not cover as many critical structures.I think it is likely that ITS will need to have, at the very least, a means of detecting and inspecting if impact damage has occurred. This could be implemented on the non-TPS areas using a thin film piezoelectric “strike detector”, possibly as part of an MLI blanket. TPS areas may need an equivalent of the Shuttle’s Orbital Boom Sensor System, for inspection. I think this might be easier implemented as a small vehicle rather than a boom.
Good point, but wouldn't the TPS also be susceptible to micrometeroid or orbital debris damage that could endanger the vehicle? I'm thinking that having a device to do inspection and repair of the TPS might be a good idea, but trying first to understand the risk. Possibly the ITS TPS is not near as fragile as shuttle TPS?
With a bunch of ITS rockets flying together, then could they inspect each other? Could you have some specialization in roles among the various ships comprising this caravan?Would it be useful to have the bunch of ships flying in formation, where they could all keep their TPS facing the inside of the formation(ie."belly in") to minimize TPS exposure to potential damage?What if they could do more than just fly in formation - what if they could be linked together at common hardpoints? They could then fly together as a cluster, and then detach prior to Mars arrival.
The inspection device I was thinking of would be a sphere with compressed gas RCS and a camera.Such devices have been flown previously on shuttle and they would also be similar to the SPHERES devices frequently flown inside the ISS.Here is a link to a good document on the subject and the NSF thread I found it in. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120002583.pdfhttps://forum.nasaspaceflight.com/index.php?topic=42484.0If used for actually doing minor repairs, I don't think it would need to anchor to the surface being repaired. It could have an applicator sticking out with a sticky patch on the end of it. It would line up and bump against the spot to be repaired in order to apply the patch/plug/liquid (whatever works for the situation).This would be similar to how the OSIRIS-Rex spacecraft take a sample from an asteroid with negligible gravitational attraction.