OK, Jon has guilted me (Darn you, Goff, darn you to heck) into putting my presentation at Space Access on line.
I’ll try to annotate them tomorrow…
27 thoughts on “My Propellant Depot Slides”
Comments are closed.
OK, Jon has guilted me (Darn you, Goff, darn you to heck) into putting my presentation at Space Access on line.
I’ll try to annotate them tomorrow…
Comments are closed.
Rand,
As a side note, Tugs rarely tow ships unless they are disabled. What they do is help large ships maneuver in the tight confines of harbors. That is why modern Cruise ships have been able to eliminate the use of tugs with bow thrusters.
I think the term you are searching for in Slide 3 is LASH (lighter Aboard Ship). Lash is used in many river port system in which tugs tow lighters downstream to the delta where the water is deeper so they are able to be placed aboard a ship for the transocean crossing.
There are many kinds of transportation that use tugs or tug-like entities. In other words, there are many examples of an “engine module” that can be connected or disconnected from “cargo module(s)”, traveling without cargo modules when needed, for example to return to pick up more cargo modules when there is no load to be carried in the other direction.
* Tow and tug boats for barges.
* Tractor units in tractor-trailer trucks.
* Engines pulling or pushing trains.
It makes great sense to me, once we are using ISRU propellants, to do this in for example the LEO to GEO haul: have a “tractor unit” dock with satellite(s) in LEO, transport them to GEO, then return to LEO for another go.
One thing not mentioned in the slides (maybe it will come up in the notes) is the hybrid craft capable of aerocapture. Maybe the need for such a technology will fade as on-orbit propellants become plentiful, but the trades I’ve seen make it pretty useful.
Given that this presentation was about Propellant Depots in orbit this comment may be a little off topic.
All the presentations I see seem to trivialize the difficulties associated with the first two hundred miles. Until or unless we have reasonably permanent human habitation in space then all LEO transfers will intersect with the Earth’s surface. Robotic re-fuelling would be OK too but it really is a long reach.
Until we have conquered the first two hundred miles safely and reliably and have constructed an infra-structure in space to support our endeavours we are going to have problems. Constructing such an infra-structure will require a Heavy Lift Vehicle, probably the heavier the better. However, such a vehicle cannot come along until it is needed. Yes, the ISS was extruded through a small hole and look how expensive that was. Could it have been done differently? Probably but we’ll never know. The same argument applies to Fuel Depots: are they needed? If so, then when? If so, then how are they going to be made to work? How much fuel will be stored or manufactured on site? What are the criteria for success both technically and economically?
The very fact that people are considering Fuel Depots in space is an implicit admission that they are building an infra-structure to support their plans – they are just missing a large part of what that infra-structure must be in order for their part to function properly and hopefully profitably.
So, how about widening the discussion to include that which all of us with plans for the use of space need – an infrastructure that functions?
You assume that ISS was expensive because it was extruded through a (not that small) hole. There were many reasons that ISS was expensive. Yes, we have to get cheaper access to orbit, but the way to do that is frequent flights of lower-cost vehicles. Propellant is an excellent payload for such systems.
Rand, I agree with you but you have to be able to do something with it when you have it on orbit.
I believe that the best way to build the infra-structure is to have a dedicated HLV that does just one job well, launch a lot of stuff but not men. That “stuff” can be propellants, stores, spacecraft – in kit form so they don’t have to be designed to survive launch shock etc. – habitat components for any exploration mission. Only criteria are to do it often and do it cheaply. If we go this way then third stages can become raw material for other projects in space, effectively increasing the usable payload mass. Economy of scale in manufacturing is another potential gain if the launch numbers are high enough.
The Manned vehicle can be some small, stiff vehicle that does just one job too; transport people from the surface to space and back. After that the ships of space, built in space, can take folk anywhere else they want to go.
We don’t need, and can’t afford, heavy lift. We need cheap lift.
Rand, I agree with you but you have to be able to do something with it when you have it on orbit.
Hmm, what could we do with propellant in orbit? Maybe, you know, propel something? A spacecraft maybe, manned or even unmanned. If it is refuelable we don’t even need a dedicated depot. We could do that today and we could have done it much earlier.
And even if we decided we wanted full depots anyway (as we would eventually) we wouldn’t need an HLV to launch them, although by that time we would probably have one in the form of EELV Phase 1.
Government funded exploration is not being held back by lack of launch vehicles or by lack of technology. Large scale commercial activity in space on the other hand is being held back by the lack of the sort of launch vehicles that would give us cheap and reliable access to space and perhaps even by a lack of technology, although I doubt it. Technology development is also being held back by spending NASA’s money on unneeded and redundant launch vehicles.
This points us at the means to break the deadlock: do exploration with current technology and freely competing commercial launch vehicles of unrestricted sizes, thus pumping lots of money into the launch sector at no additional cost, invest in new technologies and rely on the market to develop RLVs or other vehicles that will give us cheap and reliable access to space. After that nothing NASA does will matter anymore. Once we have CRATS, then cryogenic depots, large SEP tugs, ISRU etc will follow, built by the private sector.
Two points.
1.Heavy lift can and will be cheap lift if done correctly.
2. Right now we probably have the lift capability we need and it is in things like the big Atlas, the Delta IV Heavy, Ariane, the Russian stuff and maybe Falcon 9.
I’m not trying to make a case for heavy lift but it will become necessary at some time in the future.
The real question right now is this; ” If we had a need for heavy lift, would we build it or cobble together some half-baked response that goes nowhere”? We probably won’t build an HLV until we need it but will it then be to late? Chicken and egg to some extent unfortunately.
If we had a need for heavy lift, would we build it or cobble together some half-baked response that goes nowhere
If NASA is involved, the latter, otherwise the former.
We probably won’t build an HLV until we need it but will it then be to late?
Why would it be too late? Atlas and Delta could evolve into EELV Phase 1, which is an HLV, though conveniently one that reaches down to commercial levels and allows for single stick no solids configurations for payloads that now require either multiples cores and/or solids. After that you could grow further to Phases 2 and 3, although I don’t think that would be terribly useful. It would more likely be harmful, especially Phase 3.
Martijn,
How, exactly would we refuel spacecraft in orbit. If the assumption is robots that’s fine but which part manoeuvres where and how is it controlled? There would need to be truly common interfaces. The problems are there, they are not insoluble but you cannot get away from the fact that in order for the idea to work properly you need a reasonably stable infra-structure which implies that the fuel depots themselves have to be serviced at some point – unless of course they are considered disposable when something goes wrong.
Other than that I agree with your comments on the effect of government.
The problems are not just soluble, they have been mostly solved. In fact some of them were solved as long ago as the late seventies. The spacecraft and later depots could be serviced in space, like the ISS or they could be disposed of after a couple of years. You can read Jon Goff’s site for the details of what kind of tugs you would need.
We will not need large ISS-scale depots until there is large scale commercial traffic beyond LEO, maybe not even then. You can fit a lot of propellant inside a depot that will fit inside an EELV fairing. And EELV fairings can be huge, the last I heard was 7.2mx32m. LEO to L1/L2 is perfectly feasible with such “small” depots, even with truly massive payloads, and L1/L2 to moon/beyond is even more feasible.
In fact, though this is not a popular point of view in New Space circles, we don’t need full depots at all in the near to medium term. Paraphrasing Rand, we “need” cheap access to space, not depots, and we “need” it fast. Having commercial propellant flights is of course one of a very few keys to that, but that doesn’t require full depots, just propellant transfer and, presumably, something to do with that propellant.
Amen to that! the problem with the solutions of the 70’s is that the current crop of people are no longer interested in history. They have shown an alarming propensity to re-invent the wheel.
I guess that with respect to Propellant Depots my attitude is this.
We don’t really need them at the moment although they could well be the enabler for building a real manned infra-structure. Americans don’t build infra-structure though; if they did our bridges and inter-state highways would be in much better condition and we might even have a good mass transit system too! Infra-structure ain’t sexy so why bother?
There is one other thing that upsets me about the people with grandiose plans for space exploration and that is that they depend on someone else to get them to LEO. Someone else has to spend that money and it is often cloaked in vague phrases like “national security” or we are “ceding the high ground etc. to Russia or China. Good god; Reds under the bed and reds over our heads, how can we sleep at night?
Before any of this can happen though we really do NEED cheap and reliable access to LEO. Rand is absolutely right about that.
They have shown an alarming propensity to re-invent the wheel.
Not unique to the aerospace business I’m afraid, many technical disciplines suffer from that. After all, inventing stuff is fun, especially if someone else is paying you for it. And in addition to reinventing the wheel there is a tendency to invent too far ahead. As a few wise men said many years ago: do the simplest thing that could possibly work. Infrastructure up front: you ain’t gonna need it. The point was not that infrastructure is unnecessary, it is in fact crucial in the long term, just that it isn’t needed up front, since it can be grown incrementally.
Before any of this can happen though we really do NEED cheap and reliable access to LEO. Rand is absolutely right about that.
Actually, I believe part of the argument is that it is only needed first for commercial activities, not for government activities. For commercial activities it would be the other way round: propellant transfer needs to come first so that the large demand for launch services needed for exploration can be channeled through the market and thus lead to cheap and commercial access to space as a side-effect. Governments can already afford space, commerce by and large cannot yet, at least not manned orbital spaceflight.
One point I like to emphasise is that that only requires propellant transfer (refuelable spacecraft), not full depots. The only infrastructure that would be needed up front is the commercial launch infrastructure we have today.
. Until or unless we have reasonably permanent human habitation in space then all LEO transfers will intersect with the Earth’s surface.
WTF is this supposed to mean? The vast majority of stuff launched, including all real commercial cargo, doesn’t return to earth, if that was supposed to be the connotation. But I guess as usual real commerce doesn’t count, it’s only our precious heavenly pilgrims that are the focus of voodoo space development.
Reinventing the wheel can be very profitable, especially if you have the government paying for it. Commercial companies (i.e. those that rely on profits) are a little more reliant on the technology at hand, or at least very near-term.
I agree with the view that cheap access to space enables lots of things. For HLLV, I think the need for it has to be because the lack of it is stopping us from doing something – it shouldn’t be a small pain, but a big one. Those also tend to be the point that commercial companies are willing to step into a market, when they know there is a known/large demand for it.
We have lots of 5m building blocks whose designs have already been paid for (i.e. ISS), and would be the cheapest way to start doing stuff in space. Instead of designing the optimal solution (which costs $B & time), we should be making do with what we have, and incrementally improving upon them. Typically this is going to be at the cost of fuel, since they are going to be far heavier than optimized systems, but with frequent launches, fuel becomes a commodity item.
BTW, I am quite happy to see Jon’s small RLV proposal which is quite a bit better fitted to real markets than the larger proposals. It’s a big improvement assuming the components can be scaled down proportionately. I am however highly skeptical of the idea that the needed low development costs can be achieved for a system including an RLV and a refuelable upper stage. But there are ways to overcome most such skepticism for investors who are willing to gamble a fraction of the total development costs on the early stages: give them “options to cancel”, i.e. to get the rest of their money back, when milestones happen over budget.
I agree with googaw that “tractor” is a better name than “tug” – the function performed is much closer to the function of a semi or a farm tractor than that of a tugboat.
“…you have to be able to do something with it when you have it on orbit.”
The first thing that comes to mind is the refueling of the big GEO comsats. Orbital Sciences (IIRC) had an orbital refueling vehicle plan which would work much better if propellant depots were available, as they wouldn’t have to be the ones launching the fuel to orbit, but would instead be a customer for propellant stored at the depot. They in turn would sell a refueling service to (most likely) the insurance companies that underwrite these large orbital assets.
If OSC is serious, they are in a good position to do satellite servicing because they also make satellites, including quite a bit of real commerce. Which means they need to overcome mostly just internal rather than external skepticism to the idea. Much of which skepticism is, BTW, well warranted. Traditionally the benefits over the costs of such servicing have been greatly overhyped by astronaut fans. But that doesn’t automatically mean Orbital can’t figure out a way to do some kinds of teleoperated servicing economically. I hope they succeed.
What are fuel depots?
I would say that if fuel depots are not related being a market, they will be useless.
My kitchen isn’t a market. My kitchen isn’t a restaurant. I could decide to make it a restaurant [though I would need to jump thru numerous hoops to do so legally].
A restaurant is a market. If there is someplace that food is only sold to people with three feet and four heads, it’s not a market.
As a general rule markets aren’t places in which one need to send in request forms to be signed off.
Govt dispensaries are not markets.
A fuel pump at a military base or in my backyard is not a market.
A Shell gas station is generally a market [unless it’s contracted by say the military and does similar things as it would in a free market.]
Could there be any advantage of having a NASA dispensary of rocket fuel in space?
I suppose it’s theoretically possible, but the actual track record indicates it’s not. It’s not reasonable to assume there should any advantage of doing this- and it’s more likely to merely “add up” to be a waste of tax payer money.
Could there be any advantage of having a NASA dispensary of rocket fuel in space?
What is being proposed is that NASA should buy propellant in orbit, not sell it, and only to the degree it was going to launch that propellant itself to go and explore. If you think NASA shouldn’t be spending money on manned spaceflight, then argue against government funded manned spaceflight. If it is going to do it anyway, then it is perfectly legitimate for companies to try and sell their services. Propellant transfer is a way to make this possible.
And it so happens that propellant is an ideal payload for small RLVs: cheap, useful and easily divisible so you could make do with a very small RLV which would be cheaper to develop and which would have an easier time getting the needed flight rate than a larger one. And conveniently such small RLVs could eventually also be used to launch people, a very promising market once you get costs down by an order of magnitude as RLVs might.
“What is being proposed is that NASA should buy propellant in orbit, not sell it, and only to the degree it was going to launch that propellant itself to go and explore. ”
My point was that the sole importance of a fuel depot in space is to encourage access to space- and that this is the case if there is a market for rocket fuel.
“If you think NASA shouldn’t be spending money on manned spaceflight, then argue against government funded manned spaceflight. If it is going to do it anyway, then it is perfectly legitimate for companies to try and sell their services. Propellant transfer is a way to make this possible.”
I think NASA’s job is to do things that could cause there to be markets in space- and that includes exploration.
And the whole manned vs robot debate is mostly nonsense- as it’s based on misunderstanding of the nature of govt programs in general and NASA specifically.
And the US spends far too little on Space. And that’s including NASA and DARPA spending- if you simply compare it to other types of govt spending. I mean it’s obvious that NASA doesn’t actually do enough of anything of importance and giving them more money doesn’t mean there would be significant improvement in that score. But I mean as far simply sums of money in comparison with other sums of money and the potential public benefit in comparison.
Of course with say the State Dept, one doesn’t expect much, other say holding down the fort and not causing too much trouble, whereas NASA actually needs do things, and therefore needs be more intelligent.
“And it so happens that propellant is an ideal payload for small RLVs: cheap, useful and easily divisible so you could make do with a very small RLV which would be cheaper to develop and which would have an easier time getting the needed flight rate than a larger one. And conveniently such small RLVs could eventually also be used to launch people, a very promising market once you get costs down by an order of magnitude as RLVs might.”
I don’t know if propellant is ideal for small RLV. I do know that what has been mostly brought into space [in terms of tonnage] is rocket fuel and it makes sense to specialize in delivery of rocket fuel.
But even this isn’t as significant as creating demand for rocket fuel- creating market for the commodity: rocket fuel in space.
With a market for rocket fuel, it significantly lowers the threshold to start other markets in space- such as making rocket fuel in space. By being able to know the price and have the valid expectation of being able to sell it to that existing market.
So fuel depot is mostly significant because it is the most obvious market to start and has the expectation of additional markets resulting.
I’m seeing a consensus here…
1) propellant transfer; this needs to become routine.
2) full depots; a free enterprise engine that increases…
3) flight rates; which lowers cost.
4) heavy lift; when and if it makes economic sense.
5) NASA becomes a smaller part of the picture as markets take over.
I’m seeing a consensus here…
So what? Why does this matter? If it makes sense for real markets to do they don’t need a consensus, or even a majority.
“5) NASA becomes a smaller part of the picture as markets take over.”
Hmm.
NASA may appear smaller, but it would grow as a bureaucracy.
Space will become more important, therefore NASA would get more funding.
Not that I am a big fan of enlarging bureaucracies, but it’s what can be expected.
NASA could easily become as big as say the Dept of Agriculture within a relatively short time. And within decades to a century dwarf all of them- including even the military.
Why does this matter?
Does it matter what people focus on?
they don’t need a consensus, or even a majority
I agree. However, saying they don’t need it is not the same as saying having a coherent vision doesn’t matter. Does it matter if people pull in one direction or work against each other? I think it might.
I think if you make propellant transfer routine, the next step to depots is much easier. Once you have depots, the idea that free markets can support them can get a foothold. I strongly suspect that economic opportunity can increase flight rates. Then when we argue about heavy lift it will be a new category altogether.
NASA may appear smaller, but it would grow as a bureaucracy
This is possible of course, but it doesn’t have to be. It’s also possible that so much can be going on that most of it is divorced from anything NASA does. Smaller government would include NASA if we swing in that direction… which is the hope of many.