Quote from: Lobo on 10/15/2015 07:43 pmSo, how often have liquid boosters went "boom" in the US?How important is it to protect against that one failure mode?Antares, October 28, 2014.Falcon 9, June 28, 2015.That's two in the past 12 months.At least launching from Earth, it's pretty important. As you mentioned, for early MCT missions with a small crew, send the crew up on a Dragon 2.
So, how often have liquid boosters went "boom" in the US?How important is it to protect against that one failure mode?
You say that a six month transfer to Mars is intolerable for passengers, so you guys are proposing that we go to these great lengths to avoid it. And the identical six month transfer back from Mars is... more tolerable?
Dragon survived the Falcon 9 second stage failure, that was not a "boom".
Quote from: Burninate on 10/16/2015 04:14 amYou say that a six month transfer to Mars is intolerable for passengers, so you guys are proposing that we go to these great lengths to avoid it. And the identical six month transfer back from Mars is... more tolerable?100 people out, mostly colonists, 15-20 back, mostly crew. Different rules.
Great work, but could you please break out your math a bit more rather than listing totals? For example, what dV do you assume for Mars Ascent leg?
Also: 300 tons of propellant in Mars orbit is not a very high amount, given that you can use SEP all the way and the gear ratio is excellent on that; If you want a short transit you have to send more launches worth of propellant to deep elliptical earth orbit for the outbound leg than to LMO for the inbound leg (using your SEP propellant tug idea), which in turn is far fewer than if you avoided DEO rendezvous altogether and stuck to LEO rendezvous only.
Impaler: I don't think Musk mentioned 100 day trajectory on the return trip, just on the way there. Also, exactly 100 is a little bit of, um, spurious precision. 102 days is essentially the same thing. (I know you know this, just want to point it out.)Not sure SpaceX would start at LEO. A high orbit seems more realistic, as it allows you to leverage SEP without actually including SEP on MCT directly. SEP would be just used to haul up propellant from LEO. This helps reduce IMLEO a LOT.But yeah, I still think MCT will start on the surface of Mars and go straight to Earth, with a much-longer-than-100-day trajectory.
and yet people here easily accept that MCT is going to land dozens of people and/or dozens of tons of cargo?
Quote from: Pipcard on 10/16/2015 04:59 pmand yet people here easily accept that MCT is going to land dozens of people and/or dozens of tons of cargo?Because of his successes, Musk's statements, even his off the cuff remarks, receive far more credibility than they might otherwise.If Interorbital Systems were proposing the MCT it would be greeted with snorts of derision. But Musk has succeeded so often in the past, and is saying something we all fervently want to be so, that we sometimes forget that Musk is only human after all.
Quote from: Jim Davis on 10/16/2015 05:11 pmQuote from: Pipcard on 10/16/2015 04:59 pmand yet people here easily accept that MCT is going to land dozens of people and/or dozens of tons of cargo?Because of his successes, Musk's statements, even his off the cuff remarks, receive far more credibility than they might otherwise.If Interorbital Systems were proposing the MCT it would be greeted with snorts of derision. But Musk has succeeded so often in the past, and is saying something we all fervently want to be so, that we sometimes forget that Musk is only human after all.SpaceX having succeeded in launching resupply missions to the ISS as well as satellites to LEO and GTO doesn't make statements about "Mars colonization plans" (which are vastly more ambitious and difficult) any more credible.
SpaceX having succeeded in launching resupply missions to the ISS as well as satellites to LEO and GTO doesn't make statements about "Mars colonization plans" (which are vastly more ambitious and difficult) any more credible.
NASA has already landed several rovers on Mars. SpaceX still hasn't even landed their own demonstration payload there yet.
Quote from: Lobo on 10/15/2015 07:12 pm[Dragon's trunk] It is 2/3 of the way to a lifeboat on a biconic MCT.It really, really isn't.
[Dragon's trunk] It is 2/3 of the way to a lifeboat on a biconic MCT.
NASA has already landed several rovers on Mars, so they have at least some experience with Mars missions. SpaceX still hasn't even landed their own demonstration payload there yet.
An innovative partnership between NASA and SpaceX is giving the U.S. space agency an early look at what it would take to land multi-ton habitats and supply caches on Mars for human explorers, while providing sophisticated infrared (IR) imagery to help the spacecraft company develop a reusable launch vehicle
...Agreed, and I do not think this issue can be brushed away by claiming that their are few (or no) return passengers. All trips to mars will come with FREE return according to Musk, and I fully expect all personnel to rotate in and out at a rate that is so close to 1:1 that it might as well be that....
...I don't think we will actually see 100 day transits mainly do to capture g-force limitations...
I find the whole 'NASA risk aversion' myth so annoying and dumb. People seem to forget all the failed NASA missions and development efforts that were so crazy ambitious. Dose anyone remember the X-33 which was in all likelihood a less ambitious vehicle/mission profile then MCT? NASA isn't caviler with astronaut lives and neither is SpaceX nor will they ever be if they want to actually sell tickets to normal people.
NASA is not monolithic. Nor is NASA unchanging through time. Some elements of current NASA are not risk averse, but other elements are. But risk aversion is not bad by itself, unless it is taken to the extreme. (Human spaceflight being part of that - Witness Orion/SLS, the "Apollo revived with Shuttle parts" mixture, designed to be as conservative as possible)A side note: Your X-33 example would carry more weight if it actually flew.