As for SLS, Obama started this mess… As far as I can see, he signed the bill so he owns it.

I bow to your prosaic art — you got all three useless holy places of the astronaut cult into one sentence. And managed to include not a single place in space where the natural market and military with their profane unmanned satellites is actually operating (presuming by LEO you mean ISS, per contemporary cult-speak).

And it seems there are schisms among the sects about which heavenly destination is holiest. What a shame.

It’s actually a good thing that the holy and the useful are completely distinct. Keeping the astronaut cult away from useful space development is fine by me — I don’t want the astro-nuts to screw it up.

Again, this is nonsense. There is nothing “vague” about the plans for commercial crew — the plan is to have multiple providers no later than 2017 (it would have been earlier, if Congress had funded it according to the request, and it may still be).

SLS, which I don’t think you can actually call it anything but an unintended Obama legacy, is a big albatross waiting for a mission. (Aside: Does that say something about how much support and understanding there is for going to an asteroid????)

SLS is not part of “the Obama plan.” That is a misshapen child of the Senate.

Again, there was nothing VAGUE, or even vague about that. To claim that it was is tantamount to claiming that you didn’t even bother to read the technology plans.

“But sadly there isn’t that clarity of thinking going on at the highest levels of NASA or our government…. Much less in Congress.”

And I think that really gets back to the “need” for doing anything in space. Right now Congress is OK with the science part, and I include the ISS in that.

But human exploration has historically been a very expensive endeavor, and there is no clear consensus inside and outside of the space community on where to go next. I don’t blame Congress or the President for that, as the lines in the sand for Mars or the Moon are very big, and their advocates very vocal. There is even a huge debate over how we’ll leave LEO – capability based or mission based.

Until a consensus is reached within the space community, our politicians are just making guesses what will resonant and get supported.

It is debatable, and has been debated, whether the Obama “plan” actually sustains and extends the bounds of human exploration. SpaceX’s recent success is nothing more than a delayed milestone defined back in 2006 with the COTS program. Commercial Crew is but a chalkboard idea at present with very vague targets for when it will come to reality. SLS, which I don’t think you can actually call it anything but an unintended Obama legacy, is a big albatross waiting for a mission. (Aside: Does that say something about how much support and understanding there is for going to an asteroid????)

Coastal, your assessment makes as much sense as any I’ve read in a long time. But sadly there isn’t that clarity of thinking going on at the highest levels of NASA or our government…. Much less in Congress.

No, I’m not advocating new government spending, I’m advocating redirecting existing spending, principally SLS / Orion, but most everything else is fair game too, including ISS. And I’d be perfectly happy if the spending were cut altogether, as long as it also includes canceling SLS / Orion.

I agree the private sector shows no signs of launching vast quantities of propellant, although there are signs they are considering launching small quantities. And of noncryogenic propellant, just as I’m proposing.

I.e., for NASA to buy bulk propellant, launched when and where they don’t need it,

No, not when and where they don’t need it, always in support of existing exploration plans, either manned or unmanned. Manned exploration is inherently propellant-intensive (even with ISRU, that just changes where the propellant comes from), barring some breakthrough in ultra-high Isp propulsion.

rather than doing what both they and commercial entities do now, which is get it launched when and where they actually need it, on the spacecraft themselves.

You can’t do that for manned exploration, unless you have a preposterously large and expensive HLV for which there are no commercial customers. So you could either abandon manned exploration (fine with me), or you could use propellant transfer. Using propellant transfer allows that propellant to be launched on existing launchers, and could finance competitive development of cheap lift, which would make manned spaceflight commercially viable.

Maybe that’s something you don’t want your government to spend your hard-earned money on. That’s fine with me, I’m not saying governments should fund manned spaceflight. As soon as the goal of exploration is abandoned, the case for the propellant market evaporates – at least until some time in the distant future when it will become commercially viable.

I’m not saying NASA should create such a market ex-nihilo, all I’m saying is that if they are planning to do exploration (and they are), they should do it in a way that seeks the maximal synergy with commercial spaceflight, both manned and unmanned.

you have been and are vociferously lobbying for new NASA spending on new programs to achieve economic goals outside the private market. You are blatantly violating the principles you claim to stand for.

Again, not true. I’m sure you sincerely believe that’s what I’ve done, but if you look at my past postings you’ll see that they’ve always been in the context of redirecting existing spending, not increasing total spending. I’ve argued against SLS and Orion, not in favour of commercial crew or propellant launches as a goal in itself, but always in the context of exploration plans. And I haven’t even advocated exploration itself, it just so happens that there has been a budget for it for many years. In fact I’ve said many times that I know of no compelling justification for government funded manned spaceflight, exciting though it is.

As if that is any different from the SLS / Orion plans which don’t have enough money left to develop a spacecraft and actually do something useful. At least the technology development program could have led to raising the TRL level of some important technologies. It would likely not have amounted to much (what the hell is the point of an ARD when we have Soyuz, ATV, HTV, Dragon and soon Cygnus to tell us it can be done and why do we need to demonstrate storable propellant transfer which has seen operational use since 1978?), but it would have had some limited value.

Let’s say in ten years someone can find a lower cost way to send propellant to the depot. If NASA owned the rocket, you are stuck with whatever costs it has. If instead it contracts filling the depot out, then it becomes possible for the price to send propellant into space to decline. As for new technology, at the moment there is no fuel depot in orbit.
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“And electronic propulsion??? Perhaps for long-term deep-space missions, but hardly the stuff that is going to enable the efficiency and speed that is going to “change the game” of human spaceflight.”

Ah, electric propusion can indeed increase the speed of spaceflight. An electrically propelled spacecraft could thrust all the way from earth to mars gaining more and more delta v in the process. Where it bites is if you attempt to go into orbit, then the low thrust becomes a curse, but then again there are ways to deal with that(i.e. Land on mars before going into Orbit or use aero capture).

It also enables efficiency, an electrically propelled spacecraft might take say 3-6 months to reach the moon, but it could make round trips between LEO and say l1/L2. That would make it possible to supply a lunar base or a cis lunar space station with smaller cheaper rockets. Electric propulsion gets more mass to the destination per mass of propellant. Imagine being able to supply a moon base with say a Falcon 9 or Atlas instead of at least a Delta Heavy. You could also do the same to Mars

It also enables reuse. An electrically propelled NEO, Venus, or Mars mission could return to earth orbit given enough time. Again the crew could depart early via direct reentry if needed.

Even when electric propulsion is not the main propulsion, say you still want chemical to mars. You can use electric propulsion to reduce the amount of mass of propellant needed for the mission. Let your mars ship spiral out unmanned into a high earth orbit over say months or even a year which in turn reduces the amount of mass the chemical propulsion system needs.

“And aero-braking??? Again, like propellant depots, not much of a technological leap, just a new application with known physical principles.”
Aero braking at the scale of a manned mission would be a leap. Aero capture even more so of one.

“All the “game-changers” are viable concepts, but what Holdren and Garver ignored is how they will be applied???”

Oh there are lots of applications of these ideas. Heck Von Braun would know about all these technologies. It is just when NASA valued shuttle operations over technological advance did manned spaceflight suffer. If it were the late 19th century, it would be as if NASA were tasked with operating an horse stable(and frankly not a good one at that–as competing stables are cheaper), instead of working on things like better technology for trains, automobiles, better telegraph/telephone systems, and radio heck even better horse carriages.