Quote from: MikeAtkinson on 10/29/2016 08:57 amQuote from: guckyfan on 10/29/2016 06:17 amQuote from: Robotbeat on 10/28/2016 02:37 pmIf you refuel more often, you can STILL send 450 tons on a fast trajectory.Where would you see those other refuelling positions?L1/L2 is the obvious option. But there are at least two others.I find it very doubtful they can do efficient aerobraking with such a heavy payload and very fast entry. Maybe with aerobraking into orbit first.
Quote from: guckyfan on 10/29/2016 06:17 amQuote from: Robotbeat on 10/28/2016 02:37 pmIf you refuel more often, you can STILL send 450 tons on a fast trajectory.Where would you see those other refuelling positions?L1/L2 is the obvious option. But there are at least two others.
Quote from: Robotbeat on 10/28/2016 02:37 pmIf you refuel more often, you can STILL send 450 tons on a fast trajectory.Where would you see those other refuelling positions?
If you refuel more often, you can STILL send 450 tons on a fast trajectory.
Note the presentation is carefully worded to say "Cargo to Mars", not cargo landed on Mars. It is talking about the Spaceship transfer capacity in terms of delta-v, not the landing capacity.
Their is a great irony involved in mars return trajectories, a trajectory that allows the vehicle to make one round trip every synod will involve a VERY long duration is space or nearly 1.3 years for the return leg. This is clearly unacceptable for human flight being longer then any human has ever spent in space in one stretch and that was in LEO which is far milder.
Quote from: guckyfan on 10/29/2016 09:08 amQuote from: MikeAtkinson on 10/29/2016 08:57 amQuote from: guckyfan on 10/29/2016 06:17 amQuote from: Robotbeat on 10/28/2016 02:37 pmIf you refuel more often, you can STILL send 450 tons on a fast trajectory.Where would you see those other refuelling positions?L1/L2 is the obvious option. But there are at least two others.I find it very doubtful they can do efficient aerobraking with such a heavy payload and very fast entry. Maybe with aerobraking into orbit first.So do I, 300 tonnes is probably pushing it initially.Note the presentation is carefully worded to say "Cargo to Mars", not cargo landed on Mars. It is talking about the Spaceship transfer capacity in terms of delta-v, not the landing capacity.
Quote from: Impaler on 10/29/2016 03:40 amTheir is a great irony involved in mars return trajectories, a trajectory that allows the vehicle to make one round trip every synod will involve a VERY long duration is space or nearly 1.3 years for the return leg. This is clearly unacceptable for human flight being longer then any human has ever spent in space in one stretch and that was in LEO which is far milder. 'Clearly unacceptable' to whom? To current NASA, sure, but probably not to private efforts ~10 years from now.It is only marginally longer than the longest Mir stay (over 14 months). Sure that was in LEO, but zero-gravity is the same there, and the radiation isn't that bad. (Higher than NASA accepted astronaut doses, sure, but those are very conservative.)
There is another issue I thougt about. They will want a fast transfer for crew. I think they will also want to test Mars entry of a ship with a similar speed and similar mass before they send people. That would limit the mass of the first cargo ship. They could send two in 2022, one fast and one on a slow trajectory with 300t. But that may stretch their resources so early in the development. Maybe 1 cargo with 150t fast in 2022. 1 crew fast in 2024 plus one cargo 300t in 2024. Distribution of cargo in a way that it would not endanger the crew if they lose the big cargo ship.
Quote from: Vultur on 10/30/2016 12:16 amQuote from: Impaler on 10/29/2016 03:40 amTheir is a great irony involved in mars return trajectories, a trajectory that allows the vehicle to make one round trip every synod will involve a VERY long duration is space or nearly 1.3 years for the return leg. This is clearly unacceptable for human flight being longer then any human has ever spent in space in one stretch and that was in LEO which is far milder. 'Clearly unacceptable' to whom? To current NASA, sure, but probably not to private efforts ~10 years from now.It is only marginally longer than the longest Mir stay (over 14 months). Sure that was in LEO, but zero-gravity is the same there, and the radiation isn't that bad. (Higher than NASA accepted astronaut doses, sure, but those are very conservative.)Musk has all but admitted it himself with his emphasis on a fast transit time to mars to outrun the health issues inherent in deep space, to speak nothing of the human factors of confinement for that length of time. The radiation dosages are not just higher then NASA acceptable dosages they are significantly higher, your looking at an extra year in which dosages are not reduced by shielding on mars and more time for solar flares to occur which even if shielded add to cumulative dosage. Lastly the fact that a vehicle and it's mission might be private in no way negates NASA or the FFA's regulatory power or responsibility to see that the trip is up to safety standards, if it doesn't meet their standards their astronauts won't use it, and they will never let civilians fly on something that they won't put their own people on.
I sure hope US government has no power to decide how people can or cannot risk their own lives. (Risking other people's lives is another matter).
Quote from: MikeAtkinson on 10/29/2016 09:16 amNote the presentation is carefully worded to say "Cargo to Mars", not cargo landed on Mars. It is talking about the Spaceship transfer capacity in terms of delta-v, not the landing capacity.Why then would the presentation explicitly show the amount of delta-v reserved for landing 450 tonnes of payload?
Quote from: MikeAtkinson on 10/29/2016 09:16 amSo do I, 300 tonnes is probably pushing it initially.Note the presentation is carefully worded to say "Cargo to Mars", not cargo landed on Mars. It is talking about the Spaceship transfer capacity in terms of delta-v, not the landing capacity.Disagree.Again, you can use some propellant for slowing down and only aerocapture into Mars orbit (perhaps elliptical), then refuel again.From the presentation, it seemed clear to me the 450tons was for payload to the ground. It would take much fuller tanks to enable that (hence more refueling in multiple places), but it's most certainly possible. Supersonic retropropulsion is uniquely scalable. If you have enough propellant, you can land a lot.
So do I, 300 tonnes is probably pushing it initially.Note the presentation is carefully worded to say "Cargo to Mars", not cargo landed on Mars. It is talking about the Spaceship transfer capacity in terms of delta-v, not the landing capacity.
Musk has all but admitted it himself with his emphasis on a fast transit time to mars to outrun the health issues inherent in deep space, to speak nothing of the human factors of confinement for that length of time.
Lastly the fact that a vehicle and it's mission might be private in no way negates NASA or the FFA's regulatory power or responsibility to see that the trip is up to safety standards,
Quote from: Impaler on 10/30/2016 03:00 amMusk has all but admitted it himself with his emphasis on a fast transit time to mars to outrun the health issues inherent in deep space, to speak nothing of the human factors of confinement for that length of time.By the nature of a colonization vehicle, return passengers will be much fewer than outbound, and the vehicle is big.Also, people over-state the confinement issues IMO; people are greatly variable in this regard, and Mars colonists will be heavily self-selected for not being bothered by confinement. Plenty of people I know already spend the great majority of their waking hours in a chair staring at a screen...(And consider the Antarctic winter quarters in the 1900s and 10s, over a dozen people in a small hut for months...)QuoteLastly the fact that a vehicle and it's mission might be private in no way negates NASA or the FFA's regulatory power or responsibility to see that the trip is up to safety standards,NASA has no regulatory power, and currently the FAA has very little authority over the commercial space industry due to a Congressional moratorium. This was extended to 2023... I see no reason to expect it necessarily won't be extended again (and again). 2023 is late enough to see if Musk's plans look likely to pan out... if they do, I think there will be enough public enthusiasm to make "government interference" look unpopular and therefore unlikely.Anyway, this is a colonization vehicle; coming back to Earth is an edge case EDIT: incomplete sentence
Quote from: Vultur on 10/30/2016 07:30 amQuote from: Impaler on 10/30/2016 03:00 amMusk has all but admitted it himself with his emphasis on a fast transit time to mars to outrun the health issues inherent in deep space, to speak nothing of the human factors of confinement for that length of time.By the nature of a colonization vehicle, return passengers will be much fewer than outbound, and the vehicle is big.Also, people over-state the confinement issues IMO; people are greatly variable in this regard, and Mars colonists will be heavily self-selected for not being bothered by confinement. Plenty of people I know already spend the great majority of their waking hours in a chair staring at a screen...(And consider the Antarctic winter quarters in the 1900s and 10s, over a dozen people in a small hut for months...)QuoteLastly the fact that a vehicle and it's mission might be private in no way negates NASA or the FFA's regulatory power or responsibility to see that the trip is up to safety standards,NASA has no regulatory power, and currently the FAA has very little authority over the commercial space industry due to a Congressional moratorium. This was extended to 2023... I see no reason to expect it necessarily won't be extended again (and again). 2023 is late enough to see if Musk's plans look likely to pan out... if they do, I think there will be enough public enthusiasm to make "government interference" look unpopular and therefore unlikely.Anyway, this is a colonization vehicle; coming back to Earth is an edge case EDIT: incomplete sentenceThe congressional moratorium is not going to be extended indefinitely and would never be a basis for unregulated wild-west colonization of mars, that is pure fantasy as is the notion that public opinion will be behind the colonization to such a degree that it will be free from any safety or regulatory standards.