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Comment Re:"flight proven"? hahah (Score 1) 111

You are mistaken in thinking that dense fuel is something nobody else wanted to try. USSR did that in the 1970ies, they have even developed a special high density fuel (syntin) but stopped using it in the 1990ies due to high cost of it.

Sorry, I should have known that most readers would not be up to speed on what SpaceX has done, and I should have explained densification as they've done it. While the Soviets used a chemically denser hydrocarbon, SpaceX has made conventional LOX and kerosene denser by cooling them to a lower temperature than is necessary just to liquify them. LOX gets almost 10% more dense and kerosene about 2% more dense, and they have changed the size of the LOX and kerosene tanks relative to each other so that the ratio required for combustion remains the same. This is just through refrigeration, rather than the more expensive process of molecular synthesis employed by the Soviets.

Comment Re:"flight proven"? hahah (Score 1) 111

Agreed. But besides the metallurgy, SpaceX accepted a bunch of challenges that nobody else wanted to do, to get as far as they have so far.

Nobody else thought fuel densification was worth it. It complicates the launch window because densified fuel has to be unloaded and cooled off if you don't launch in time, and SpaceX had a few technical hiccups to resolve when they started using it. But it gives them more fuel to work with.

We've been able to land rockets on their tail manually since the terrestrial LEM simulator (which almost killed Neil Armstrongr one day) and with computers since DC-X, but SpaceX was the first to try to recover a booster that way.

And the automated barge landing is something nobody ever tried before, but saves a ton of recovery fuel.

No doubt there are a lot of other additions to the list of firsts that were required to get a SpaceX booster recovered.

Comment Re:On its way (Score 2, Interesting) 406

Yes, but given the number of folks who set out to disprove and ended up with thrust they can't explain, we're far from ready to say "no".

If you live in a Newtonian world, you're not going to accept that this could ever work. If you admit to the possibility that momentum could be quantized, you can't rule it out yet.

Comment Re: Still higher than a Soyuz launch (Score 1) 111

That should say perigee at 151 km. Oops. The point is that to the extent that the lifter can deliver the satellite to GTO, the on-board fuel of the satellite is saved for other activities. So, for this the payload is not the maximum the rocket can lift to LEO, and the remaining second-stage fuel is used for a second, in-orbit burn for going from LEO to the geostationary transfer orbit. The Falcon 9 first stage had enough remaining fuel to land successfully after this. They could have given it a bit higher kick if they'd operated the first stage as expendable.

Comment Re: Still higher than a Soyuz launch (Score 1) 111

The last Falcon launch brought JCSAT-16 to a supersynchronous orbit, very definitely not LEO, with the apogee at 36183 km and the apogee 151 km, and about 20 degrees inclination off of equatorial. The apogee was a bit higher than geostationary. The remaining load for on-board propulsion is to change the inclination (which is most economical to do with a burn at apogee) and to circularize the orbit (raise the perigee).

By giving the satellite a kick to high orbit, the Falcon 9 saves fuel on the satellite that will be used to maintain the orbit longer than would otherwise be possible.

Comment Re:Still higher than a Soyuz launch (Score 2) 111

I have always been highly skeptical of are their launch costs. I simply don't believe them.

If you are concerned about the "shear violence", I suggest you go to 1 Rocket Rd, Hawthorne, CA, cross-street is Crenshaw. Stand in front of the building. SpaceX has left a rocket right on the front lawn for you to look at, a first stage that returned from lifting the Dragon capsule to ISS. It got to 1/5 orbital velocity (the second stage does the rest), burned its rockets for about 2.5 minutes, was in the air for less than 10 minutes overall.

Regarding the economics, I think the main point is that there was not an incentive to lower cost until now. The USA had a single-source contract and the two former competitors formed a joint venture so that there would be no competition. Also, there was more subcontracting: for example most companies didn't make their own avionics and these came with tremendous markups, space-qualified fasteners were quoted at $10/screw in the '90's and are probably more now.

So, a vendor who actually tries to reduce prices can probably reduce them a great deal, simply because nobody else has tried very hard before. There would be a lot of low-hanging fruit.

Comment Re:Seat? Same cost, Falcon 2.5X capacity (Score 1) 111

I agree that Elon is way too self-indulgent. Forget about the simulation remark, hyperloop is either cynical in nature (meant to divert funds from real trains) or wildly underestimating the costs and safety issues.

However, I think you're wrong about the space junk issue. One of the problems right now is the lack of any way to economically de-orbit legacy space hardware in high orbits. You don't get that without economical access to space.

Comment Re:The engineering is the expensive bit (Score 1) 111

The reason that you spent that much money building the cargo has comparatively little to do with the cost of the launch and everything to do with the fact that you really don't get multiple chances to get it right

I think you need to go back to your initial assumption, which might not be true any longer. With lower $/kg to your selected orbit, replacing a satellite is economically possible and building a satellite with a much shorter projected lifetime is probably optimal because the alternative is for the operator to be stuck with 20-year-old technology in orbit (given 15-year design lifetimes and a 5-year design-to-launch cycle, which might be optimistic).

If you really run that sort of company, you need to be looking about what could happen if your assumptions are wrong. And not advertising the fact that you aren't doing that.

Comment Re:Still higher than a Soyuz launch (Score 1) 111

Remember when Rogozin said the U.S. should get its astronauts to ISS with a trampoline? He's singing a different tune now. SpaceX is currently operating at a very significantly lower cost than Russian rockets in terms of $/kg to the specified orbit. And that's in the expendable configuration. Given successful reuse by SpaceX, Russia probably won't have a place in the market.

Comment Re: Weirdly specific statement (Score 1) 55

What is the limiting factor? Buildup of CO2?

People need a certain amount of oxygen for their metabolism, you need to carry that much. CO2 effects the blood pH: too little and the body is too alkaline, too much and it's too acidic. So, you need to maintain a precise amount of CO2 and remove the rest. The scrubbers in the space shuttle were able to regenerate the CO2-absorbent material after use, so there was use of power but material wasn't consumed.

Beyond this, you need to control temperature and humidity. The other requirements than atmosphere for crew survival are that you water, feed and shelter the crew, maintain orientation, and maintain a G-force envelope that doesn't injure the crew.

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