Comparing sizes again:Also excluding panorama window, shuttle orbiter have bigger individual windows than ITS.
I would assume for the propellant refrigeration system?
I was wondering, given that the spaceship can just about make LEO on it's own, without the booster, would it be conceivable to launch an early prototype into LEO, stripped down to the bare essentials, and then refuel it using repeated FH tanker flights? That would allow shake down cruise in earth orbit or further out, maybe cis-lunar, and EDL. If it has life support, a Dragon 2 could even bring crew up, and take them down again, before the autonomous landing of the BFS. Anybody done the numbers?
Quote from: Nathan2go on 09/30/2016 03:46 am I would assume for the propellant refrigeration system?What propellant refrigeration system?
Quote from: nacnud on 09/29/2016 06:25 pmQuestion: Why launch the spaceship first, then the tankers.I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one. Thoughts?Launching the spacecraft first requires the least number of vehicles; booster, spacecraft, and tanker.If there was a fuel depot, then the tanker flights could fill up the depot first and the spacecraft could be the last launch, but that would require a depot or second tanker. With these vehicles costing hundreds of millions of dollars, that's a big jump in cost.
Question: Why launch the spaceship first, then the tankers.I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one. Thoughts?
I was impressed with robustness and redundancy of the engine configuration on the BFS. I have been imagining how the ship would fare if engines were lost and doing some rough calculations. I think it could probably land on Mars with any 2 engines out and land on Earth with perhaps 3 out (as long as they are not all Sea Level Raptors).This 6-3 engine set-up seems optimized to be a minimum engine configuration to get a maximum redundancy level. But I really don't know how to quantify it.
A 600 t BFS landing on Mars would have a weight of 3.8 x 600 = 2,280 kN. Raptor SL engines have a max. thrust of 3,050 kN, so any or all of them could be used to land.And yes, gimballing the engines outwards while landing on an unprepared site seems like it would help reduce blowback.
Quote from: Snake on 09/30/2016 07:06 amA 600 t BFS landing on Mars would have a weight of 3.8 x 600 = 2,280 kN. Raptor SL engines have a max. thrust of 3,050 kN, so any or all of them could be used to land.And yes, gimballing the engines outwards while landing on an unprepared site seems like it would help reduce blowback.SL Raptors on Mars surface have more than 3050 kN of thrust. If we assume that they use the same 40:1 nozzle area ratio with the BFR Raptors, then the derived thrust according to the available information should be somewhere between 3,285 kN and 3,333 kN (138 MN / 42 engines or 31MN - 6x3,500kn) /3 engines), or a little less.
Tim Urban has a new article about the ITS up. The title contains an easily guessable "F" word, so I won't be writing it here.He had a discussion about it with Elon Musk several months ago, and kept quiet about it until today.
From the attached maybe it can do so
Quote from: TheTraveller on 09/30/2016 09:11 amFrom the attached maybe it can do so Musk said it cannot.
For those who still have a hard time visualizing how to unload cargo from so far up, here is what Elon tweeted:https://twitter.com/elonmusk/status/781206685553528833Quote@BArtusio:@elonmusk How will occupants descend from the spacecraft?At 162 ft., appears too tall to utilize ladder w/ spacesuit. Especially repeatedly@elonmusk:@BArtusio Three cable elevator on a crane. Wind force on Mars is low, so don't need to worry about being blown around.So basically slightly fancier version of this classic Tin-Tin crane.
@BArtusio:@elonmusk How will occupants descend from the spacecraft?At 162 ft., appears too tall to utilize ladder w/ spacesuit. Especially repeatedly@elonmusk:@BArtusio Three cable elevator on a crane. Wind force on Mars is low, so don't need to worry about being blown around.
So I guess people on Mars would have to embark/disembark in a basket held by the crane? Is that the fastest, safest, most efficient form of ingress/egress? What if someone has a leak in their spacesuit? Hopefully the winch won't break down. For frequent ingress/egress it might be nicer to have one of those scissor-lift things:They could even support vehicles easily:
Quote from: Jim on 09/30/2016 03:48 amQuote from: Nathan2go on 09/30/2016 03:46 am I would assume for the propellant refrigeration system?What propellant refrigeration system?Elon seemed to say that they relied on subcooled prop to avoid various issues, including cavitation. Is it possible for prop to remain sub-cooled over a multi month Mars transit? ISTM the alternative is to let the prop reach boiling point, then manage boiloff? Cheers, Martin
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.