Explained, by Jeff Greason (it’s buried in the comments, so I thought I’d post it up front here):
A little disappointed in the debate above.
I’m going to try, one more time, to explain flexible path. It isn’t hard. You just have to read what we said rather than try to do Kremlinology on what you think we must have meant.
I’ll boil it down the same way that I explained it to policy makers.
* We want to go to Mars.
* We can’t reasonably go to Mars without more experience with long-duration missions.
* Long-duration missions can be done to Lagrange points, NEO’s, and Phobos/Deimos and they are all worthwhile missions in their own right.
* We can’t reasonably go to Mars without updating our experience doing manned planetary exploration.
* Manned planetary exploration would be done on the Moon, which is a worthwhile mission in its own right, and could be a source of propellant for exploration.
* The Moon vs. Mars vs. NEO’s is therefore a FALSE CHOICE; the only choice we have is what sequence we do them in.
* Therefore, the only reasonable way to proceed is to accept that we MUST plan to do all of these things and plan accordingly.
* Since the spacecraft, lander, and boosters/EDS’s are the expensive part, constrained budget says develop 1 or at most 2 of them first.Now, the version of this in the Augustine report was:
* Do the boosters/EDS’s and spacecraft first
* Do buildup flights in LEO, Lagrange, Cislunar, NEO’s
* Do Lunar landings
* Do Mars
(whether Phobos came before or after Lunar landings really wasn’t clear, it depends on how the technologies shake out).Look at the mission timeline in the report, under flexible path, and you see Lunar landings, NEO visits, and Phobos visits before Mars. Construing that as “abandoning the moon” or “don’t touch” requires one to either refuse to read the report, to assume we only meant part of what we said, or to be dishonest.
Today, as it seems the NASA budget may not support doing 2 elements at once, I would suggest we do one at a time:
* spacecraft
* then boosters
* then landersBecause that way we can begin the exploration sequence with spacecraft on existing boosters and build the (relatively modest) upgraded boosters we need for more agressive missions as we go.
Makes sense to me. But the “look but don’t touch” morons will continue to be confused. I’m sure that we’ll be discussing this this evening, on a panel on which Jeff and I will be on, at the conference.
If flexible path is the goal, then eliminated anything that is a specific path would further that goal.
A general purpose spacecraft (GPS) would be flexible path. A lander could be, but tends toward a specific path. It can come later. Anything that improves orbital access is flexible path assuming transfer to the GPS. The engineering goal is low cost and reliable. You shakedown the GPS, starting from short missions and going to longer ones. Orbital refueling happens in parallel.
I can’t fathom why the future of humanity is on a dry frozen rock that makes Antarctica look like a tropical paradise in comparison.
If a rich second Earth planet existed in this solar system would that be a goal? Some would argue, even then, stay off planets and create colonies in space. I believe we will do both and discover that a different culture will occur in both types of colonies. In the near and mid future I believe space colonies will tend to stagnate. Long term they have well known advantages. A planetary colony will allow greater individual initiative sooner especially if property rights and free market principles apply.
If we can’t live on that frozen rock we really should stay home and forget about space.
If a rich second Earth planet existed in this solar system would that be a goal?
You’d at least have a better argument that it was the “future of humanity”. If we had people backed cheek-to-jowl in Antarctica, the Gobi Desert, under the Greenland ice cap, and across the surface of the ocean, then I might be able to accept the argument that “we need space to grow.”
A couple of weeks ago I flew from Dallas to San Jose. As I flew across New Mexico, I marvelled that for hundreds of miles I saw no evidence whatsoever of human existence on this planet below me. I might as well have been looking at Mars. And that’s right in the continental United States!
If we can’t live on that frozen rock we really should stay home and forget about space.
Even in your rosiest scenarios, that will be what happens for 99.9999% of humanity.
Ferris,
So lets give it a specific mission forces itself to move in the sane direction. Lets give NASA 20 years to focus, not on a particular rocket, or to go to a particular destination, but to solve the killer application problem. That is, NASA has 20 years to figure out how to build a thriving space faring industrial sector, that isn’t solely dependent on NASA for funding.
The problem with that suggestion is the same as with Flexible Path (as NASA is implementing it) — it is in essence a license for the agency to do nothing. Money will be spent on technology research, but no end product or activity is specified. So you don’t know which technologies are useful and which are irrelevant. In the particular path you suggest, what are your metrics for success? How do you know when your “thriving industrial sector” has been brought into realization? A billion-dollar a year market? Ten billion a year?
I certainly agree with you that a spaceflight killer app is highly desirable. I just don’t think NASA is the entity to find and develop it.
Martijn,
It should be re-born in its original, pre-ESAS incarnation.
You mean with Steidle’s spirals?
I do not. I mean the pre-Steidle VSE implementation first articulated in an internal study by the Office of Spaceflight in early 2004 and elaborated on by several others since then. It called for a Shuttle side-mount; two launches can put over 120 mT into LEO (there is no real reason not to launch crew on the Shuttle side-mount; arguments about the higher safety of inline versions are specious). We do extensive robotic preparation and pre-emplacement of assets at the lunar outpost site prior to human arrival. It is at the poles to take advantage of permanent sunlight and water deposits. The surface mission is staged from Earth-Moon L1; lander is small (LM-scale, not LSAM), cryo-based and reusable. Goals are demonstration production of lunar water, then consumables for outpost, propellant for the LM taxi, and finally propellant for export. All of these activities are affordable under the existing run-out budget; the VSE calls for time, rather than money, to be the free variable in program implementation.
Martijn,
And what do you make of the Huntress et al plan for the ‘Next Steps in Exploring Deep Space’?
Sorry – I forgot that you asked me about this. Another solution for maximum entropy.
So what’s the main sticking point? Is it that the moon has to be the first destination beyond LEO? Any specific reason the lander has to be cryogenic? Do you want the SDLV yourself or are you just willing to accept one if it is politically necessary?
Trent, you wrote:
Karl, which is entirely my point. Kirk asked what the national need is, your answer is about cost, that can’t be an answer to Kirk’s question.
Doesn’t look like that to me. As I see it, he’s asking, if it costs hundreds of billions of dollars to put an astronaut on Mars, then how do you justify it? Answer: you can’t justify it, if it costs that much. You have to reduce costs. As it turns out, I don’t see an inherent obstacle in the technology or the mission that requires it to cost hundreds of billions of dollars.
Kirk, you wrote:
As I flew across New Mexico, I marvelled that for hundreds of miles I saw no evidence whatsoever of human existence on this planet below me.
That just means you couldn’t see it. I’ve flown across New Mexico many times before, and the road network usually can be seen even from 35,000 feet in the air. There isn’t a spot in New Mexico with hundreds of miles without roads.
Even in your rosiest scenarios, that will be what happens for 99.9999% of humanity.
That is doubtful. You’re claiming that there never will be more than one in a million people leaving Earth for space. I think that’s irrationally pessimistic though obviously there’s a lot of development of technology and infrastructure required to get from here to there.
Martijn,
Is it that the moon has to be the first destination beyond LEO?
I believe the Moon to be the logical next destination as it has the materials and energy we need close by and easily accessible to create permanent space faring infrastructure. So why avoid it?
Any specific reason the lander has to be cryogenic?
So that it can use the propellant we make on the Moon.
Do you want the SDLV yourself or are you just willing to accept one if it is politically necessary?
The latter. It is the easiest, cheapest way to get back to the Moon.
I believe the Moon to be the logical next destination as it has the materials and energy we need close by and easily accessible to create permanent space faring infrastructure. So why avoid it?
I wouldn’t want to avoid it, but I would like to see precursor missions first. The idea would be to make sure there are manned missions beyond LEO within five years. The moon may be too ambitious a target for that. Moon and Earth Lagrange points, LLO and NEOs are easier targets that can be reached with a subset of the systems that are required for moon missions. Robotic precursor missions to the moon itself can happen concurrently.
After that some people would like to go to Phobos/Deimos/Ceres first. I could live with that, but I would prefer doing the moon first. The moon would certainly have to come before Mars. I would like to see moon missions within ten to fifteen years from now.
So that it can use the propellant we make on the Moon.
You don’t need cryogenics for that. You do need propellant transfer. You may be able to do that exclusively on the surface which wouldn’t require new technology even for cryogenics, but it looks iffy unless you had ISRU right from the beginning. Would you advocate starting with purely robotic missions until ISRU was operational?
The latter. It is the easiest, cheapest way to get back to the Moon
I don’t think that is true. EELV mediums are good enough if you use LM-sized landers with a separate crasher stage, even without any propellant transfer. If you want reuse you’ll obviously need propellant transfer. It may be true that an SDLV is the only way to get a program beyond Earth orbit funded (not completely convinced, but it might be). In that case I would choose not having a beyond Earth orbit program at all, because commercial development of space would be my priority. I can see how people who care more about exploration or planetary science might reasonably feel differently.
Karl, don’t miss the forest for the trees here. What I’m saying is is that there is no lack of open space, even in the continental US, for human expansion, every square inch of it infinitely more inhabitable than anywhere in space. And that even if space is “colonized” (which I highly doubt) a tiny, tiny sliver of humanity will be affected by this fact.
There’s no space equivalent of North America out there, with wide open spaces of temperature fertile land, largely uninhabited. Although most of North America is still fairly uninhabited.
And that even if space is “colonized” (which I highly doubt) a tiny, tiny sliver of humanity will be affected by this fact.
Are you talking about in our lifetime, or do you doubt it will ever happen?
I doubt it will ever happen. The circumstances that would have to take place to make living on this planet LESS attractive than living anywhere in space are difficult to conceive. I’m even throwing asteroid strikes into this consideration as well.
“he and the rest of the committee members agreed that permanent human presence on and colonizing Mars is the future of humanity.”
And they are all wrong. Neither Mars nor any other planet should have any sort of priority, with the exception of the Moon – and even there, any settlement will probably end up as nothing more than a mine.
To settle Mars in any sort of meaningful way it has to be terraformed, which will take probably centuries and will need us to be able to do things like dropping comets on it to give it air and water. Which in turn means being able to get around the solar system fairly easily. And even then, because Mars has no magnetic field to speak of, the radiation levels would be huge. Unless everyone lives underground.
Building a space settlement could take as little as a couple of decades, if we put our minds to it. And the environment inside it would be comfortable from the word go. And once built, building more would get easier – quite rapidly. Go to Mars when it isn’t much more difficult than a school trip.
The circumstances that would have to take place to make living on this planet LESS attractive than living anywhere in space are difficult to conceive.
Here’s some simple examples to the contrary:
1) Political or economic freedom – as I understand it, most people move for economic reasons followed by political ones. If space offers a better paying job, or the ability to live outside of burdensome restrictions on Earth, then that will be a draw for a lot of people even if the environment is less pleasant than that of Earth.
2) Space may more attractive than Earth. A good O’neill cylinder could result in a far more comfortable living environment than a run down city on Earth.
3) Engineering projects are less restricted. Gravity helps in a lot of ways. But one hindrance is in the scale of building construction. You simply can’t build stable structures on the scale of a large (tens of miles long) O’Neill colony. And you can’t build structures larger than the scale of Earth. If I want to build an interferometer with a base larger than about 8,000 miles, I have to have at least part of it in space. If I want to build a solar collector or sail larger than Earth, it has to be in space.
4) Space has a lot more stuff. Energy, space, and matter are all far more plentiful in the Solar System, than they are on Earth.
O’Neill cylinders are dynamically unstable. They rotate about their minor axes.
Matter is more common on the Earth than in space. Nuclear energy is far more common on the Earth than in space. Solar energy is just as diffuse.
99.9999% of humanity [will stay on the Earth]
Controlling our environment is what humans do (unless controlling other people is what they attempt to do.) Both of these facts will push some out into space. 0.0001 x 6 billion is what? 600,000. I’ll take it. That’s a good start on a colony or half a dozen.
The Earth has the best environment for human life. Yes, but even here it requires modification of the environment. Otherwise, you’d freeze in the Dakotas or dry up to dust in the southwest. That’s the temperate continental United States! It’s worse where other people live.
How many billion can live on the Earth without war? Only someone with an extreme view might claim 100 billion. Now if I have a dozen colonies of 50k people anywhere, they are going to grow. They are going to do what humans do. Expand and tame their environment. Assume a 2% growth per year. How many years will it take those colonies to pass Earth’s 100 billion (or choose your own) limit? And that’s just the beginning. Thank you Kirk, you’ve given us the stars. Now I’ve got to go figure out the formula so I don’t have to continually add that 2% individually to find the result. I’m so ignorant.
Ken, I’ll leave it to you to realize how absurd it is to take my simple number and turn it into an argument for galactic conquest. Just don’t ask me to donate any money (through my taxes) to your nutty fantasy.
Proxmire was right back in the 1970s after all…and to think I used to write him letters trying to change his mind.
Ok, looks like 50k(1.02)^years.
100 years… 362k
200… 2,624k
500… about a billion
Proxmire? I admire you Kirk. Don’t ruin that by bringing up Proxmire.
I’ll leave it to you to realize how absurd it is to take my simple number and turn it into an argument for galactic conquest.
Is it absurd to apply a formula that applies to almost everything that grows?
Don’t admire me Ken…please.
Sorry, as long as you make reasonable arguments and stick to your guns I’m going to admire you. Live with it.
acronyms reduce giggle factor, otherwise we could just call it space mining.
That may be the saddest thing I’ve read in a long time. It’s disingenuous in practice. It’s true.
Ferris,
[[[So lets give it a specific mission forces itself to move in the sane direction. Lets give NASA 20 years to focus, not on a particular rocket, or to go to a particular destination, but to solve the killer application problem.]]]
Because under President’s Obama’s program there may not be a NASA in 20 years.
First to go will be the HLV funding, slowly cut starting next year since there is no rush (deadline) to go any where with them. NEOs and LaGrange points may wait – their are ‘better” uses for the money elsewhere.
Then the funding for “flagship” technology demonstrators will be picked off one by one as they slip their schedule or just because the money is needed elsewhere. Since the are not vital to any agency wide program, since there isn’t any, they will be easy targets to pick off in budget cuts.
If a new President is elected in 2012 you may as well say good-bye to the funds for monitoring Earth for climate change. Hope the people building those systems get them flown by early 2013 or they will join the “GoreSat” in storage.
The commercial crew funding will be hacked away at using the excluse of schedule slips or any “launch anomalies” to end fixed price milestone contracts with “winners”. I really, really hope all of the Falcon 9/Dragon flights go perfect or Elon Musk will learn from experience what the majors already know about the drawbacks of fixed price contracts as he tries to radically cut his burn rate to survive after COTS is pulled out from under him.
And of course I also hope there are no major problems with ISS. Just one big “anomaly” that requires it to be abandoned will pull the rug out from under commercial crew. No ISS, no place for them to fly to.
That is the fragile future of NASA under Flexible Path and President’s Obama’s new policy. Anyone of a number of single point failures could end funding for human spaceflight or any of the technology goals under his new policy.
And without the large Shuttle workforce in Texas, Florida, Utah and Alabama you will also see Congressional support for space spending, and willingness to fight for NASA’s budget disappear. Note the silence from California on the new plan now that their space workforce is almost gone? President’s Johnson and Kennedy understood well the need to create Congressional self-interest to keep Apollo going. The entire purpose of JSC was to bring Texas into the fold. Same with Florida given a location on a U.S. island near the equator would have made much more sense then Florida for the lunar missions.
You see Ferris, that is why opposition to the President’s plan is so strong, because the people that really understand NASA, Congress and space policy see this as the slow destruction of NASA. And no, the money from the destruction of NASA will not go to other space funding, it will just disappear.
I also would not expect private investors to pick up the slack as new space advocates believe. None will want to compete with the “winners” NASA selects for commercial crew. And a firm fails to create commercial crew under NASA funding no investors will be crazy enough to put money into them.
Kirk Sorensen 8:21 am
Solar energy is just as diffuse.
While that’s certainly true if you’re focused on photoelectric effects, the key issue changes if you’re more interested in running Rankine or Brayton cycle generation as the crucial pieces are maximum delta T and outgoing heat flux.
Beyond straight power cycles – where there’s bit a tiny bit of exploration – there hasn’t been much examination of the possibilities in the wider field of chemical engineering. It keeps running into the fundamental wall of the price of lift. But a whole lot of effort in a chemical plant is devoted to keeping some spots hot, other spots cold, preventing heat transfer between two widgets, and otherwise fighting entropy at every step. This would still be a serious job in space. But it would run into the limitations in a fundamentally different fashion. Meaning there should be a variety of process pathways that are implausible here on Earth.
Because under President’s Obama’s program there may not be a NASA in 20 years.
And little of value was lost.
But perhaps this can be inspirational for other government programs. “If we can shut down the space program, why can’t we shut down…?”
Paul,
Having read through this, and some of your other statements, I see serious problems, that I hope you can address.
1. Everything you describe in your response to Martijn involves substantial R&D, and I would argue, much of it is beyond the funding capabilities of NASA, as it is currently funded. Not only are you going to have to develop the Sidemount concept, but all of the associated tech you mention (LM, ISRU, and so forth). I don’t see how you can get that without either a massive funding increase to NASA, or else a massive cultural change at NASA.
2. You ask about a metric – we can develop a metric for measuring the industry. There are a number of options – you gave one example about how much the industry should be worth. Bill White has suggested another – the first completely private space station is another. We can come up with a number of metrics – how low the cost of human spaceflight to a particular destination is another possibility. we can come up with a metric, that is easily understandable.
3. You seem to think there isn’t much point in trying to reform NASA, and that it can’t be the enabler for the killer application problem (before I go on, I will state that I don’t think NASA can solve this problem, per se – it can, however IMHO, be the major enabler of it). If that is truly the case, then we should be in the streets calling for the ending of NASA, because the question that needs to be asked then, is what is it for? The science can be given to the NSF, or something along those lines. The commercial part can be given to the Office of Space Commercialization.
At the end of the day, if it can’t be reformed, and can’t serve a meaningful purpose, lets just kill it. I don’t believe thats the case, but that seems to be the logical conclusion to what you are saying
Because under President’s Obama’s program there may not be a NASA in 20 years.
You say that like it’s a bad thing. I’m coming to the conclusion that NASA long ago outlived its usefulness as an agency. Perhaps it’s time to reevaluate how American wants to do space and form a new organization along the lines of NASA’s predecessor, NACA. What we have now and have had for the last few decades isn’t working very well.
Ferris,
[By the way, there is another “Paul” on this thread, but it is not me — I always use both my names when I post here.]
I see serious problems
So do I, but those exist for any direction in which we proceed. In any event, to address your specific points….
1. I simply do not agree with you that what I described requires a significant increase to the agency budget. This graphic:
http://blogs.airspacemag.com/moon/files/2010/03/SDHLLV-costs.jpg
was prepared as part of John Shannon’s Shuttle side-mount study and makes very conservative cost assumptions. It is certainly just as credible (and in my opinion, more so) than any of the cost estimates done for Augustine by the Aerospace Corp. All of the robotic components are simple re-builds and extensions of existing flight and mission hardware. The only new pieces are the EDS and LM, both of which have high heritage from Apollo (the LM propulsion system excepted.) ISRU is experimental at first, but we know a lot more now about the presence and state of water on the Moon than we did when the VSE was announced and it will likely be much easier to harvest and use than we originally thought. I agree that everything we need is not all in hand at the moment, but the parts that we need soonest are.
2. Fine with me — go for it. Aiming for low cost is great, but how low is “low”? For commercial activity in space, it is arguably “low” enough right now, in that a thriving commercial satellite industry already exists.
3. I didn’t say that we shouldn’t TRY to reform NASA — I am just saying that the agency seems to very adept at resisting reformation. I am also saying that their track record of accomplishment is much better when they are given specific direction and a well defined mission than it is when they are not. Flexible Path is too nebulous for them; it will likely turn into a viewgraph-making exercise.
If you want to kill NASA, we don’t have to make any special effort towards it. The current direction should do that job just fine.
O’Neill cylinders are dynamically unstable. They rotate about their minor axes.
They just need a control system capable of generating more torque that they pick up from precession. Then they become dynamically stable.
There are also passive methods like linking two or more cylinders rotating in opposite directions so that there is no collective angular momentum in the system.
Matter is more common on the Earth than in space. Nuclear energy is far more common on the Earth than in space. Solar energy is just as diffuse.
“Common” means nothing since matter is as common on any other body in the Solar System.
There is a lot more matter in the Solar System than on Earth. If we assume that the entire surface area of the Earth’s land is available for exploitation down to a depth of 4 miles, that turns out to be roughly 250 million cubic miles of material. On Ceres, one could go down almost to the core (about 25 miles away from the center of a body that is almost 290 miles in diamete, if my crude calculations are correct) to get a similar gravity potential difference to that depth on Earth. That volume is roughly 40% of the accessible volume on Earth.
So the largest asteroid alone has almost half the volume underlying the land on Earth to a depth of four miles. As matter, it also is pretty good quality. There’s supposed to be more water on Ceres than fresh water (which is roughly 1% of the total terrestrial water) on Earth. IIRC, Ceres has roughly a third of the entire mass of the asteroid belt which means that the asteroid belt (especially given the high iron-nickel content) probably weighs more than the volume of Earth i described above.
Second, given that many of the asteroids mentioned are exposed pieces of core material from a planetoid (for example, Vesta, Eros), they have a lot of valuable heavy elements (iron-nickel plus a bunch of other stuff like PGMs) and probably have a lot more fissionable material accessible than the bit of crust I mentioned above. I would consider fissionable materials to be both more in mass and more prevalent per unit mass in the asteroid belt (though perhaps more difficult to get, energy-wise), than on Earth.
Finally, solar energy is not equally diffuse everywhere. For example, on the surface of Mercury, solar intensity ranges from 4 to 10 times (due to the relatively high eccentricity of Mercury’s orbit) as intense as in Earth orbit and Mercury doesn’t have an atmosphere. Even at minimum intensity, Mercury gets well over half the solar radiation that the Earth receives. At closest distance from the Sun, it’s more like double the solar radiation that Earth receives.
And you can get a lot closer than that. This “diffuse source” can get quite intense.
I think I’ve made convincing rebuttals to all of your claims.
Oh Karl, there’s nothing passive about a 10km cylinder rotating around its minor axis. O’Neill should have been embarrassed for ever proposing such a thing in the first place, or some competent spacecraft attitude control engineer should have alerted him to his fatal and fundamental flaw. That’s one of the reasons that I suspect the Ames Summer Study proposed a Stanford Torus (which is dynamically stable) instead of the O’Neill cylinder.
“Common” means nothing since matter is as common on any other body in the Solar System.
Precisely. So what is the point of trying to get the same stuff in space that’s already here?
There’s no lack of fertile nuclear materials on Earth to justify space development. So now I think I’ve made convincing rebuttals to all of your convincing rebuttals to my claims. But deep down I don’t think I’ve changed your mind, because you, like I once did, REALLY want space to be the “answer”.
Humanity needs to be space “competent” in much the same way it needs to be “agriculturally” competent, “ocean faring” competent, “technology” competent, “scientifically” competent, etc. Because being “life” incompetent leads to a great deal of unhappiness.
Considering Paul’s original point that NASA can only do destinations and not space competency, and therefore the flexible path will not work – the goal of developing space competency is not really negotiable, NASA is. Hence if NASA can not develop economically sustainable space capability, then it needs to be replaced by something that can.
The task is space, not NASA. The flexible path is far more important than NASA is.
There are many branches of the federal government that are already “space-competent” and using space to meet key national needs. They don’t utilize human spaceflight so they seem to get ignored by the space enthusiast community.
[By the way, there is another “Paul” on this thread, but it is not me — I always use both my names when I post here.]
Yes. Please do NOT confuse me with Paul Spudis, we are two different and unrelated persons.
I will change the name I post under in the future to avoid confusion from quotations.
Hi All,
So if this new policy marks the end of NASA what do you plan to replace it with? And do you really expect the money NASA is getting to continue to be spent on space?
Tom
Kirk wrote: There are many branches of the federal government that are already “space-competent” and using space to meet key national needs. They don’t utilize human spaceflight so they seem to get ignored by the space enthusiast community.
No more than an ant who has learned to swim has gained mastery of the ocean.
Space is perhaps the greatest of natural environments, and yet one in which we are completely out of our depth.
>Hi All,
So if this new policy marks the end of NASA what do you plan to replace it with? And do you really expect the money NASA is getting to continue to be spent on space?
Tom>>
Replace it with patience enough to wait for an honest free market approach to spaceflight. No, the money will not be spent on space. If it is not going to be done more effectively than much of the agencies history suggests, then it will be a small loss.
Some of the competant true believers in the agency will find productive gigs in the industry while the spear carriers move on to greener pastures. I believe there is a huge amount of frustrated talent in the agency, some of which will find it’s way to a more appreciative setting.
I believe that human expansion into the solar system will happen. I don’t believe I have the right to use your tax money to support that belief.
I believe that human expansion into the solar system will happen. I don’t believe I have the right to use your tax money to support that belief.
Well said, John.
> I believe that human expansion into the solar system will happen. I don’t believe I have the right to use your tax money to support that belief.
Hear, hear. Given our budgetary woes, NASA is a luxury. I still want to keep ISS flying, though, given our sunk costs.
Yours,
Tom
Tom,
[[[Hear, hear. Given our budgetary woes, NASA is a luxury. I still want to keep ISS flying, though, given our sunk costs.]]]
Never fear, ISS will continue beyond any decisions NASA makes. The international partners will see to that 🙂
Thomas
“I believe that human expansion into the solar system will happen. I don’t believe I have the right to use your tax money to support that belief.”
John,
Even if you did believe in using tax money to do it, tax money would ultimately fail in that mission. Humanity is not going to be able to expand into space in any meaningful way on the tax payer’s dime. There isn’t enough of a justification for the use of public funds for a large scale move into space.
Very well said John.
If NASA does not reform it may be a long time dying.
I would further add that NASA funding and talent is somewhat fungible. The death of NASA will likely see a significant increase in far more effective private funding and talent that will quite possibly increase the pace of space development – a net win for space.
Also, if this commercial shift ultimately helps result in a dramatic reduction in costs the economics may change and government funding further become irrelevant. This was always an economic problem, not the type of problem that NASA was ever really capable of solving itself.
Oh Karl, there’s nothing passive about a 10km cylinder rotating around its minor axis.
Two connected cylinders rotating in opposite directions cancels out any any precession torquing from tidal forces. And to be honest, an active torque control system seems more than capable of stabilizing an O’neill colony.
Given that, I found that the stability problem seems not so bad. For example, if I have a huge 100 km long, 1km radius colony (which would be the most extreme aspect, I think). To generate an apparent force of 1 gee (9.8 m/s^2), would require a rotation rate of almost one revolution per minute (57 seconds per revolution).
At thermodynamic equilibrium, the three modes of rotation (two degrees of freedom are end over end and one is the minor rotation around the central axis) should have near equal energy (equipartition of energy). Wikipedia says the The moment of inertia for these two modes is 1/12*m*(3*r^3+h^2) while the moment of inertia for rotation around the axis is 1/2*m*r^2. That means the moment of inertia for end over end rotation is roughly 2,500 times larger than the moment of inertia for the rotation around the axis (looking up the moment of inertia tensor for cylinders). The energy of that mode will be I*w^2 where I is the moment of inertia and w is the angular velocity, so w^2 will be 2,500 less than for rotation around the axis, implying w will be 50 times less.
That means that the habitat will be rotating end over end at roughly once every 47-48 minutes (50 times slower than for the rotation around the axis of the cylinder). That generates an apparent acceleration of 2.5*10^-2 gee at the ends (it may be 5*10^2 gee because I have two orthogonal end over end rotation modes and they might shorten the end over end rotation period by a square root of 2). It’s a pain for docking since traditionally docking ports are at the ends of the O’neill cylinder, but not significant to people inside the habitat. I’m really not seeing the problem with an “unstable” tumbling O’neill habitat here.
So let’s look at what’s perturbing the habitat. The key problem is tidal forces. One end of this long cylinder will be pulled more than the other. That generates a significant end over end torque. Something this big is not going to be in LEO just due to its size, so we’re looking at rather slow perturbations on the time order of the period of the orbit of the habitat. Even if the habitat is stationary at one of the Earth-Moon Lagrange points, it’ll be perturbed by the significant tidal force from the Sun.
As long as we have a passive system that mixes the modes of rotation (say a gentle sloshing lake), the energy contained in the end over end rotation shouldn’t grow too large.
Ironically, the squatter the cylinder, the worse the acceleration from end over end motion is. A Stanford torus (something like a bike tire in shape) has as thermodynamic equilibrium, end over end motion that is comparable in rotational speed to rotation around the axis. The difference though is that there’s far, far less (orders of magnitude less) perturbation from tidal forces. It’s not truly dynamically stable, but it won’t get twanged by tidal forces like an O’neill cylinder would.
The 10 km cylinder is in an ugly place. The long axis has a moment of inertia 17 times larger. That implies an end over end rotational rate about 4 times slower than the rotation around the axis. A ten kilometer cylinder rotating end over end at somewhere around one revolution per four minutes, is pretty fast. I get almost 0.2 gee (or almost 0.4 gee, if these two end over end modes add together) of apparent acceleration at the ends of the cylinder. That’s quite a bit. Some sort of control system would be required.
Precisely. So what is the point of trying to get the same stuff in space that’s already here?
Here’s what I came up with: 1) there are some things that have considerable value, fissionables, PGMs, etc and might be worth getting even if they can be had on Earth, 2) Earth is at the bottom of a rather big gravity well which isn’t good if you want that mass elsewhere in the Solar System (say to support one of the other reasons I gave), and 3) you might not be able to get the stuff on Earth even though it is there (due to monopolies, market manipulation, etc).
There’s no lack of fertile nuclear materials on Earth to justify space development. So now I think I’ve made convincing rebuttals to all of your convincing rebuttals to my claims. But deep down I don’t think I’ve changed your mind, because you, like I once did, REALLY want space to be the “answer”.
Is there enough fissionables on Earth to support a Solar System scale civilization?
Karl, you’re following into the same mental trap, where we have to go into space to get the stuff we need…in space. But the dollars are here on earth and no one’s in space, so you need to return something to the surface of the Earth economically that is more cost-effective to get from space than to get from here.
So far there has only been one…commodity…that has fit that bill. Information. Information from geosats, info from remote sensing, info from spysats. I’m asking the HSF booster community to tell me what these expensive people are doing in space that is returning real economic value to the people on the surface that justifies their ruinous expense.
Karl, you’re following into the same mental trap, where we have to go into space to get the stuff we need…in space. But the dollars are here on earth and no one’s in space, so you need to return something to the surface of the Earth economically that is more cost-effective to get from space than to get from here.
What mental trap? Just because you say there’s a mental trap here, doesn’t mean there is one or that I’m in it. For example, any infrastructure to deliver material resources from space will probably be mostly made in space out of resources in space. For example, it may well be feasible to build a huge complex infrastructure to return a relatively paltry amount of PGMs because most of the infrastructure is built in space and hence, the economic inputs from Earth are as paltry as the output.
I wrote out a post on nasaspaceflight.com that outlined a way infrastructure building could occur without a human presence even. All that was required was a) to find a PGM deposit on the Moon of scale similar to the largest ones known on Earth (these happen to be purely of igneous/asteroid origin and hence, can appear on the Moon as well), b) send up a small factory that can make a copy of itself in a year’s time and doesn’t require much in the way of supervision or maintenance, c) build a bunch of copies of the factory, and d) then build the infrastructure needed for the mine (both the mine and the Moon to Earth launch infrastructure. The initial investment is the factory, its trip to the Moon, and resulting supervision can be a very small input compared to a large quantity of gold and other PGMs coming from the Moon.
It doesn’t matter that gold can be had on Earth or that it takes a lot of machinery to get it from the Moon. As long as the Earthside input to the system just has a good ROI, then the business case closes.
So far there has only been one…commodity…that has fit that bill. Information. Information from geosats, info from remote sensing, info from spysats. I’m asking the HSF booster community to tell me what these expensive people are doing in space that is returning real economic value to the people on the surface that justifies their ruinous expense.
Why does their expense have to be “ruinous”? I see here the mental trap of assuming manned spaceflight is expensive. Just because it is expensive now doesn’t mean it’ll stay expensive.
But the dollars are here on earth and no one’s in space, so you need to return something to the surface of the Earth economically that is more cost-effective to get from space than to get from here.
Right and you can. If you have an asset in space and you add to that asset, regardless of the source of materials you have returned value to the title holders on Earth. Once equipment is in place, space may be the most economic source of some materials.