Rakaydos

Actually, my point was that if the booster really can be reused 100+ times, the fuel cost (relative to the booster cost) just went up by 2 orders of magnatude. It's not that the fuel isnt cheap, it's that the rocket is cheap too and goes through a LOT of fuel over it;s lifetime.

Also, methane is cheap. Fuel might be pennies to the dollar for current rockets, but it's also the 1 price he cant reduce with fast cadence reusability, so the cheaper the rocket, the more the fuel costs matter.

Problem is that apparently mars has a lot more Calcium Perclorate and Magnesium Perchlorate than sodium or alunimum perchlorate. " Unexpected though was the presence of ~0.6% by weight perchlorate (ClO− 4), most likely as a mixture of 60% Ca(ClO4)2 and 40% Mg(ClO4)2 "

It's not the best option, but it is an option. Elon Musk is ideologically driven. He currently believes that simply making the rocket will lead to expansion happening, but if that fails, he's still got a slowly building fortune, and the same ideology. If the rocket doesnt solve the problem he wants solved, he'll start work on the next bottleneck, and the next, until he dies, changes his mind, goes unexpectedly bankrupt or has his mars colony.

Great, now how do we turn a chem-lab process into an industrial one? For PVC, lets go down your steps... Step 0: separating the perchlortes from the soil and other nutrients. Washing it out is easy, but how do you purify the perchlorates? Electrolysis of a dissolved base, what kind of equipment is needed for this, and to capture and separate chlorine and oxygen? (cant be too hard, I saw a documentary saying that this was how potasium was discovered, shortly after the battery was invented) "Burning" chlorine and (water-electrolized) hydrogen. Likely to be violently exothermic, so design may bemore complicated than first glance suggests. Acetylene production- looks to be straightforeward with the right equipment Mercuric Cloride catalyst- is the quantity small enough that it's worth bringing from earth, or is it easier to make on site? "Initiator"- Need the final special sauce. Presumably you should also have extrusion equipment to make useful stuff from the PVC.

You dismiss SpaceX as a free enterprise without goverment backing on it's goals. https://www.bustle.com/articles/109479-elon-musks-net-worth-is-more-than-the-gdp-of-nicaragua-54-other-countries After a certian point, a sufficently rich backer with a goal in mind can effectively BE the "goverment" backing it. He who has the Gold makes the Rules. Usually this is far more selfish than what Elon has planned, but there's no reson it has to be.

The advantage is you can refill the tanks on your transfer ship (without needing to empty equally large tanks on your lander) if your transfer ship is your lander and you fill up on the ground. You lose the same amount of payload lofting the extra fuel, whether its a tanker/lander refueling a mothership or a single ship. And a mothership needs enough fuel to orbit, whereas the singleship can do direct entry.

That's the beauty of Musk's plan. every step except the last one is economically justifiable, but it all moves toward his ideological goal, bringing it closer to fruition. If noone else steps foreward to put research stations on mars, then with a few years profit from earth based endevores like this and the BFR UHLV, he can send his own corporate enclave out of his own pocket.

It looks like that article ignores orbital refueling, unless I'm missing something. It also rejects the capsule shape based on lack of balistic coefficent, when other sources call for retroprupusive drag enhancement. (that is, even just the bloom of your angled rockets increase your aerodynamic drag, even without any propulsion from those rockets)

From an nterview with Iain M Banks: Somebody once told me that the ships Very Little Gravitas Indeed and Zero Gravitas were a response to a scathing review. Is this true? Yes. But it was a scathing review of Culture ship-naming policy delivered by another Involved civilisation. They suggested that such enormously powerful and intellectually refined entities ought to have names with a little more gravitas, to reflect their near-god-like status; the immediate and sustained reaction of one of the Culture's ship manufacturies was to name all its subsequent vessels things like: Stood Far Back When The Gravitas Was Handed Out; Gravitas, What Gravitas?; Gravitas... Gravitas... No, Don't Help Me, I'll Get It In A Moment...; Gravitas Free Zone; Low Gravitas Warning Signal, etc etc (including the Zen-like Absolutely No You-No-What). I am so sad I have a separate list of the Gravitas ships at home. It currently runs to about 20, I think.

So names like "Has Anyone Found My Gravatas?"

So there's some indications that Ron Howard's Mars MAY include spoilers for Elons big mars plans http://www.popsci.com/watch-trailer-for-ron-howards-mars

I wouldn't want to be the guy who's little mistake killed Zuckenburg's plan of global domination. Such a person may be able to hide behind his own evil mastermind, but... it's facebook. They know EVERYTHING about you.

Why are WE building the fantasies of science fiction authors? Nuclear submarines, geosynchronus satelites, even smartphones were predicted at least once by the wild mass guessing that is science fiction.

IIRC, CRS7 actually relied on telemetry from vibration sensors to identify the pressure bottle breaking loose, then impacting the forward bulkhead, triggering the event.

It only has to be signal detectable above the noise. in 40 years we can build a big enough telescope to detect the probe we already sent.

Probably even longer, but the flipside is that instead of efficntly focusing the laser through ort cloud and beyond, you can build more lasers as the probe gets furthur away and brute force it to maintain acceleration.

I'm not sure where the "in 5 minutes" bit is coming from. My understanding was that even a fraction of a g of acceleration, applied until the probe is out of range, would get the probe up to an appreciable fraction of lightspeed. Simplifying the flight path to an eliptic escape trajectory, and assuming you wanted to keep the earth "behind" the probe(s) for the entire boost period... Launch on the far side of the sun from alpha centauri, on a trajectory for a venus slingshot flyby at periapse. Combine launch laser with solar sail propulsion for continuous acceleration. As the sail gets furthur from earth (and sun), build more lasers to maintain acceleration. Off the eliptic, same idea, but plan the Venus slingshot to throw you into the proper inclination. Once it's out of range, stop building lasers, staart building a bigger telescope, so we can read the probe's signals when it gets there.

Project Starshot, with an electrotether-powered gas laser expanded in flight. Moving at .2c, an electrotheter moving through a stellar magnetic field is going to produce a heck of a lot of current, even soe distance away. this lets you put most of the mass into using the power, instead of generating it.

It will be called Beta Colony or Beta site. As the first site we would be capable of colonizing outside our own solar system

The question is, then, can Raptor get a higher massfraction to orbit than Merlin?

I cannot parse the bolded line (Mainly the last bit about supplies). Can you please clarify? I havnt seen the Mars DRAs, but I strongly suspect they ran numbers based on monoprop or hypergolic propellants. Methane engines are a new field, ISRU is theoretically sound but untested, so they would have stuck to the less efficent but storable propellant types that require every bit of fuel be carried both ways. If the dry mass of the ship is cut even 70%, combined with the more efficent engines, they should be able to at least get on a hoffman return without martian orbit refueling. ------------------------------------------------------------------------------------------------- Mirroring from (the non-pay forums at) NASAspaceflight.com:

If you're bringing enough supplies to keep people alive to the next synod, presumably you arn going to be bringing those supplies home. That's got to be some pretty significant mass. Drop the entire cargo comparment to save on dry mass, and it may actually approach the 90% figure.

Same order of magnitude.

18 mil in payroll, sure. Probably a few million more for pad rental, and workshop rental, and material costs. So call it 30 million profit per launch. Plus any research and development contracts they can snag on the way, like the airforce "Raptor upper stage" contract. do you really think that, if spaceX builds a BFR, Nasa and the like wont pay to fly on it? Even with simlar markup?