‘Shuttlyndra’ and the Smoking Rocket
The Spaceref web site has uncovered an internal NASA document that completely undermines the rationale for Shuttlyndra, or the Senate Launch System — Congress’s pork rocket to nowhere:
On 26 September 2011, Rep. Dana Rohrabacher (R-CA) issued a press release regarding fuel depots. This included a letter to former Administrator Mike Griffin who had dismissed the notion of fuel depots and commercial launch vehicles as being a viable alternative to the Space Launch System (SLS) during Congressional testimony.
Rohrabacher noted: “When NASA proposed on-orbit fuel depots in this Administration’s original plan for human space exploration, they said this game-changing technology could make the difference between exploring space and falling short. Then the depots dropped out of the conversation, and NASA has yet to provide any supporting documents explaining the change.”
Well, despite what NASA may or may not have been telling Rep. Rohrabacher about its internal evaluations regarding the merits of alternate architectures that did not use the SLS (and those that incorporated fuel depots), the agency had actually been rather busy studying those very topics.
And guess what: the conclusions that NASA arrived at during these studies are in direct contrast to what the agency had been telling Congress, the media, and anyone else who would listen.
For the uninitiated, propellant (not fuel — one needs an oxidizer as well) depots are storage facilities on orbit that allow the accumulation of the propellant needed for deep-space missions, which is most of the payload. When the depot has enough propellant delivered to support the mission, the propellant is transferred into the earth-departure stage, and the astronauts are sent on their way. Because the propellant can go up in arbitrarily sized quantities, it enables doing lunar missions, or asteroid visits, or even missions to Mars, without having to build a large Saturn-V-like rocket (most of the payload of the Saturn V for Apollo was mission propellant).
The internal NASA study shows that tens of billions of dollars can be saved with such a mission architecture, because that is how much it will cost to develop the new launch system that Congress insists that NASA build. In addition, missions can be mounted much earlier, because the money can instead be devoted to the actual mission hardware, launched on existing or soon-to-be existing commercial rockets. The NASA study team identified several alternate architectures to the heavy-lift baseline (which doesn’t do an actual lunar or asteroid mission until almost the end of the next decade), and all of them were faster and cheaper, and what NASA would be doing if its job were to actually explore space, as opposed to provide jobs in Alabama, Florida, and Utah.
This article does not accurately report the basis of the NASA study.
The NASA study reports a comparison of a combined SLS/SEP mission architecture to one based on propellant depots. This burdened the SEP mission with solar electric propulsion (SEP), which is stupid. So of course it came out worse.
An asteroid mission using SEP requires solar panels 25 tomes the size of those on the space station (which based on the ISS solar array cost of $300 million, would cost $7.5 billion for the solar array alone), and then need to spend about a year spiraling our from LEO through the radiation belts to attain Earth escape. It is a ridiculous mission plan, and even dumber if used as a basis for Lunar or Mars missions.
The right way is to just use a hydrogen oxygen upper stage on the heavy lift booster to directly send the mission to the asteroid (or Moon, or Mars) just as was done during the (real) Apollo program and every (real) robotic planetary mission to date.
This is not to say that there are not major problems with the SLS program. The heavy lift booster needs to be procured as part of a coherent mission architecture, which also develops the other flight elements needed to do the mission. An HLV with out the rest of the flight systems needed to do a mission is nearly as useless as a lunar ascent vehicle without a lunar lander to deliver it.
Also, the SLS program is being done not as a procurement for a piece of hardware, but as an “activity” to keep people busy for an indefinite duration. Thus its costs are out of sight. The right way to get an HLV is simply to put out an RFP for a fixed price contract to develop such a system for $5 billion. All the players in the industry would bid.
But that said, we need an HLV if we are going to send humans beyond LEO. Alternative mission architectures, including those involving propellant depots, are severely defective.
OTSCHW would engender considerable efficiencies.
OTSCHW: Off The Shelf Commercial HardWare
In this case, a Can of Campbell’s Alphabet Soup.
The argument presented is obscured by the alphabetic jargon.
Questions for Mr Zubrin:
Above you state that “we need an HLV if we are going to send humans beyond LEO”, what is the minimum launch capacity you consider for a launch vehicle to be an “HLV”? Does Falcon Heavy qualify?
Given that you have already put forth a manned Mars mission architecture based on 3 Falcon Heavy launches, what sort of manned Mars mission architecture, using FH, do you believe could be developed for the $10-$30 billion it is estimated the SLS will cost to develop? Would that be a better option than spending that amount on SLS or not?
> But that said, we need an HLV if we are going to send humans beyond LEO. Alternative mission architectures, including those involving propellant depots, are severely defective.
Not true. I suggest that Robert Zubrin read a book called “The Case for Mars.”
In Chapter 4 of that book, the author says, “Maybe the [manned Mars] mission could be done without a heavy-lift vehicle at all.” He then goes on to outline a way of conducting such missions using Single Stage To Orbit vehicles (such as the proposed Delta Clipper) and orbital propellant depots.
In Chapter 10, the author discusses what he calls “The Gingrich Approach.” This approach calls for the US government to put up a $20 billion prize for a manned Mars mission.
According to the author, such a prize could be won by US aerospace companies using orbital assembly and “existing US boosters such as Titan’s, Atlas’s, or Delta’s.” He estimates “a total program cost of less than $5 billion.”
By coincidence, “The Case for Mars” was written by an author named “Robert Zubrin,” but that was obviously a very different Robert Zubrin from the one who says innovation approaches like fuel depots are impossible, big government is the answer to every problem, and NASA must never attempt anything that wasn’t tried in the Apollo days.
Perhaps the two Zubrins will someday show up at a Mars Society Conference together and debate one another.
It is so sad that we are blind to the future. Heavy lift will happen on it’s own schedule with no need to force it. It will come sooner if we just ignore it for now and use what we have to make progress. We should have two objectives.
1) Put a general purpose ship in orbit today. For about $300m we could have a six passenger ship base on a BA330 and F9 upper stage. Using kerosene 300s engines we then have a market for ten times its mass giving it enough delta V for any inner system targets. Collapsible bags of fuel and oxidizer should work. This not only doesn’t require heavy lift but gets us to points heavy lift alone can not. It’s scaleable as well. Send two to mars tethered together and you have both redundancy for safety and artificial gravity for health. It also puts twelve ISRU researchers on mars to speed that process which is needed for colonization.
2) Make loans available to anyone secured by the resale of developed for habitation from half a sq. km. land claim. This provides at least 800% profit to the bank making the loan. Pays whatever the cost of travel to the martian surface of a colonist and supplies. Provides the colonist with a lifetime of income to purchase any supplies they discover they need or want. Ensuring individual ownership provides the drive for future ambitions.
To be clear. Allow a one sq. km. claim to individuals and they have all the assets they need to pay for any level of colonization at any cost. Only half of that claim is needed to secure a loan and they retain the other half for whatever they see fit to do with it.
The cost of land is based on it’s development cost. A single square kilometer is made up of 100 hectares. So break even is resale of each hectare at 1% over cost whatever the cost which includes todays cost whatever that might be. Meaning, cost is not the limiting factor everyone dreams it to be.
Once that lightbulb gets lit, all the other mythical limitation fall away as well.
Technology and cost are not what keeps us from moving forward. It’s our own blockheadedness that keeps us from moving forward. Provide loans and a ship and the volunteers will be overwhelming.
Zubrin: But that said, we need an HLV if we are going to send humans beyond LEO. Alternative mission architectures, including those involving propellant depots, are severely defective.
Why? If we are going to exploit and live in space (as opposed to simply living on the planets) we need to learn how to work there. Once we are comfortable with living and working in space, as we should be by now, after 20 years with the ISS, there is no particular reason for requiring heavy launch vehicles for any mission whatsoever. Missions of any size can simply be assembled and fueled in orbit.
Keeping in mind the recent SpaceX declaration for developing a fully-reusable launch vehicle (www.spacex.com/assets/video/spacex-rtls-green.mp4, something that NASA should have been working on for the past 30 years) there is absolutely no further reason to be developing very heavy launch vehicles, especially non-reusable ones. Harry Stine made this case very well 15 years ago with “Halfway to Anywhere: Achieving America’s Destiny In Space” (and I will never forgive NASA for wrecking the DC-X prototype and not continuing the program). What NASA should be doing is what Stine proposed and what SpaceX and Virgin Galactic (and others) are doing: putting travel to space on a par with commercial air travel.
I’m no engineer but I go with ordinary, everyday, economy-size cans of Campbell’s Alphabet Soup like Rick Z says. Leapfrog our way into the far reaches of space where man has never gone before like in the old black and white sci-fi movies.
Easy as leapfrogging across the pacific to Japan during the last Big One. Push comes to shove, as we get further and further from home, we may have to develop a brand-spanking-new and explosive form of energy just like we had to in order to reach Tokyo and squat for a while until the Japanese became civilized and rejoined the brotherhood of man.
But why do that today when we have plenty of Campbell’s-soup-technology sitting on the shelf, canned and all ready to heat up? Let’s use what we have in the house on the shelf before we go out to the market and buy some kind of half-baked, non-hydrogen or carbon or nuclear based alphabet soup product developed in a pure, green, environmentally safe laboratory environment for a pure, green, environmentally safe and very, very, very far in the future America.
Ref : orbital fuel depots
One of the big problems in returning from orbit is shedding orbital velocity, which has heretofore been done by atmospheric braking.
This is a lot of wear and tear on the ship, and requires those ceramic tiles all over the bottom of the ship. If the tiles fail, as happened with shuttle Colombia, the ship will be lost.
If propellant were available in orbit, then a future shuttle could refule there and shed orbital velocity with a controlled burn, then return to earth with a simple parachute, or by gliding.
This would significantly reduce the size and complexity of the shuttle, making the whole launch package simpler and cheaper.
… or so it seems to me. Can anyone tell me if I am talking nonsense ?
First of all not all thermal protection systems are as frail as the Shuttle tiles were. Secondly using atmospheric drag to reduce orbital velocity is free (after the initial retro burn to cause the spacecraft to dip into the upper fringes of atmosphere), whereas lofting propellants to orbit to then be used to reduce velocity is not.
Freddy
The problem with your idea is that for a shuttle type craft to loose enough speed for a safe reentry without a heat shield would require as much fuel that it took to put the craft into orbit in the first place. The idea of refueling in orbit has been with us for a long time. I believe that Clarke and or Von Braun suggested this concept way back in the “50′s. In fact this was suppose to be one of the main purposes for a manned space station. Well, we have the station, so let’s use it as a refueling depot for deep space craft, as it was orginally intended.
“… we need an HLV if we are going to send humans beyond LEO.”
You say this like you believe it, but you fail to supply any support. After so carefully trashing the NASA study, I would expect you to take some pains to prove this far more important point – probably because there is no possible justification.
In other words, you are just another Franken-rocket lover. Sorry Bob but I had thought better of you than this.
Sorry this was supposed to be a reply to Robert Zubrin’s comment #1 above.
There’s an old religious song titled “Give me that old time religion” that contains the lyric “it was good enough for Grandpa and it’s good enough for me.”
It seems that’s the thinking of some people when it comes to the need for a heavy lift rocket. “It was good enough for Apollo and it’s good enough for me.”
If anything useful has come from the ISS experience, it’s the knowledge of how to design modular spacecraft and assemble the pieces in orbit. It makes no sense at all to spend tens of billions of dollars building the SLS when there not only isn’t an identified payload but no money left over to build any possible payload for it. If they do build it from Shuttle legacy components, it’ll require a large standing army of infrastructure (people and facilities) that will continue to consume large parts of the NASA budget whether the SLS flies or not. To the politicians, that’s a feature, not a bug. They likely don’t care if the SLS ever flies a useful mission so long as it keeps the money flowing to their districts.
Instead of building a honking big rocket and then wondering what we can do with it if we find any additional funding, it makes more sense to design mission architectures for different destinations and then determine what’s the most massive/largest indivisible component. Once you’ve done that, you know what your lift requirements are and can then evolve/develop boosters with that capacity. Instead of spending an estimated $40 billion to develop the SLS, allocate perhaps $10 billion to purchasing lift capacity and the rest to developing the payloads that will be launched. Simply proceeding with the SLS and hoping that money will magically appear for payloads is patently stupid.
The first post on this thread makes me happy I never belonged to the Cult of Saint Zubrin.
We’re not going to Mars anytime soon. We’re broke, for one; the other reason is that Mars is not what space settlement is all about; building a viable, efficient space infrastructure is. What is the use of “going to Mars” if that venture is unsustainable without systems in place in free space and elsewhere to make “going to Mars” or anywhere both viable and sustainable?
“Shuttleyndra” is cute, but this avid fan of SpaceX is very concerned that Elon Musk may face a “Solyndra Moment” with Tesla Motors, his other major venture that is decidedly NOT a free-market approach to business; it is heavily sustained by very large “green stimulus” loans.
How will a possible collapse of Tesla affect SpaceX?
“How will a possible collapse of Tesla affect SpaceX?”
Tesla is a publicly traded company, whereas SpaceX is privately held and is not supported by government loans. Other than Musk being distracted (he’s CEO of both companies), I don’t see any potential connections.
Odd how Zubrin thinks he can use inflated and unsubstantiated cost numbers for heavy, high voltage solar panels (designed nearly 30 years ago and manufactured more than 20 years ago) as the basis for projecting the cost of new solar arrays that could be made years from now using much cheaper/more efficient designs. But Bob is full of contradictions these days – as The Corrector has already noted.
In answer to the posts made above:
1. I support heavy lift development. I do not support the SLS program as currently proposed. This is made very clear in my first posting, above, which says:
“…the SLS program is being done not as a procurement for a piece of hardware, but as an “activity” to keep people busy for an indefinite duration. Thus its costs are out of sight. The right way to get an HLV is simply to put out an RFP for a fixed price contract to develop such a system for $5 billion. All the players in the industry would bid.>
In other words, it should be done as an open competition for a fixed price hardware contract, not as a sole-source entitlement.
This, I believe, is also precisely what SpaceX wants. I believe this because:
a) It would be strongly in their interests, and
b) They have said so.
2. In The Case for Mars,I examined alternative architectures, but clearly came to the conclusion that heavy lift was the best way to go. My position on this has never changed. There is a new edition of the book out, by the way, just updated through 2011. Pick it up!
3. I strongly support Falcon Heavy, and was quick to point out the possibilities it could offer for near-term human Mars exploration. At 53 tonnes to LEO, it promises 2.5 times the lift capability of any booster now flying, and so would make many things possible that are currently impossible. That said, at just 53 tonnes to orbit, it is suboptimal. A booster that could do 100 tonnes to orbit would be much better. Furthermore, Falcon Heavy does not yet exist, and its successful operation has yet to be demonstrated. Therefore, it would be unsound to base all of our hopes for human exploration beyond LEO on it.
4. As to the issue of the problem with orbital depots, this was addressed in my PJ media debate with Rand Simberg, published May 22, 2011. I reprint the relevant passage below:
Do we need orbital propellant depots to go to the Moon? Clearly not, as we went there in the past without them. Furthermore, the Apollo approach of employing a Saturn-V class heavy lift booster with a hydrogen-oxygen upper stage could also be used with equal effectiveness to directly throw the ~40-tonne payloads needed for human missions to Mars or near Earth asteroids as well.
But, if not necessary, would it at least be preferable to fly such missions using multitudes of small lifter payloads to assemble and refuel interplanetary spaceships on orbit? Certainly not. The per-pound cost of space launch decreases as launch vehicle capacity increases, so by shunning heavy lift for orbital refueling, the depot approach will increase the cost of interplanetary ventures. Worse yet, it will greatly increase the mission risk, since the more launches that are needed to mount a mission, the greater the chance that one will fail. In addition, the costs and risks associated with the construction and operation of the orbital depot itself must also be included.
Furthermore, an orbital depot will need to be in a stable circular long-duration orbit, at least as high as the 220 nautical mile altitude Space Station, and launch vehicle delivery capabilities to such orbits are considerably less than that required if all the booster has to do is lift the interplanetary payload to the 80 mile perigee temporary orbits that can be employed by direct-throw missions. Moreover, an orbital depot needs to be in an orbit at a particular inclination to the Earth’s equator. If a high inclination orbit, like that of the Space Station, is used, this will further reduce the payload that can be delivered to it by any booster. If a low inclination orbit is used instead, access to the depot will be restricted.
In addition, propellant delivered to an orbital depot will have to be stored in heavy thickly-insulated tanks, which are a waste of launch capacity and so disadvantageous for use on an interplanetary mission that duplicate lightweight flight tanks will also have to be launched, thereby running up mission mass and costs still further.
However beyond all that, the rest of the Obama administration’s space program portfolio assumes that interplanetary missions will be accomplished not by chemical rockets, but by gigantic nuclear electric spaceships. These will have to operate from nuclear-safe orbits at least 600 miles up, an altitude to which booster delivery is fatally reduced. So, shall we then have two orbital depots, one at 220 miles and one at 600 miles, with ferry services running in between? The scheme is quite fantastical, and not to put too fine a point on it, utterly crazy, since everything such an elaborate futuristic mission architecture proposes to achieve can be accomplished at much lower cost, risk, and schedule simply by developing a competent heavy lift booster..
Rand and Robert talk past each other about depots and other topics here:
http://pajamasmedia.com/blog/the-great-pj-media-space-debate/?singlepage=true
Mr. Zubrin, thank you for taking time to answer and clarify your viewpoint.
One point, you state that “Falcon Heavy does not yet exist”, and this is true. It is my understanding however that FH is under construction, right now. Given that FH is in essence simply F9 cores used in a different manner the hardware exists and has been flight tested in a simpler configuration. This is much more than can be said for SLS or anything else even remotely approaching the capacity of FH. FH will, if all goes well, be flying many years before SLS or any other heavy lift vehicle. In my opinion the time and money spent on SLS, or other HLV projects, would be better spent designing and building payloads for FH.
Dr. Zubrin, I very much enjoyed ‘the case for mars’ when it came out and plan to get your new edition. I’m an enthusiastic supporter of much that you’ve proposed and pioneered.
the depot approach will increase the cost of interplanetary ventures.
NASA has an internal study that contradicts this. The reason heavy lift doesn’t provide the cost benefits they would be able to provide in time is that it ignores current market realities. Heavy lift will happen in time from market pressures. At the right time, it will reduce costs. Now however, isn’t the right time, precisely because it doesn’t reduce costs. Timing is everything.
Why is a Falcon Heavy “sub-optimal”? Why do you want to put all your eggs in one basket? The key is and always will be Cheap Access To Space. Modular construction works great, that’s how we build all our major refineries and gas plants today, because it’s cheaper and faster. Lots of relatively small inexpensive rockets, each carrying parts of the whole, nothing irreplaceable … versus all-in on a single flight. It’s the smart thing to do.
Sorry but I’m not forking out hard-earned cash for your book when I can already see big problems with your arguments.
Space Launch System Backers: “Hey, we’re going on a long trip! Let’s spend a lot of money on a BIG truck towing a BIG trailer of fuel!”
On-orbit Fuel Depot Backers: “Hey, we’re going on a long trip? Where’s the best place to get fuel along the way?”
Now, I realize I’m not NASA, but no matter how I try, I’ve yet to convince my wife we need a Kenworth and 9000 gallon gas trailer for our next trip to Disneyland…
Why are we so sure that the best way to explore space is leave from Earth EVERY time? We can build in space, station shows that. Let someone build us a hanger. Then build a SPACECRAFT and leave from station. Why fight gravity? what is needed for travel,(not getting out of the gravity well) is much, much different than what is needed to leave EARTH.
Canada’s arm works because it was made for where and what it is to do. So should space craft for Exploration.
Take it up in pieces,build and launch in it’s environment. It can be as long and wide as necessary. An atomic engine on a five mile line if needed. Take the taxi to station, board and leave. Even Captain Kirk figured that one out.
Just becuase we did it before, does not mean it should be done this time that way.
Forget about exploration for a moment. Think about commerce. How do you get a piece of heavy equipment into orbit without heavy lift?
Bill, the quickest way to do that is to design the heavy equipment so it can be modularized, and sent up in pieces of 50 tons or less size. Then send it up in a Falcon Heavy. The re-design will cost *far* less than the $100 Billion + that would be wasted on the SLS. A cheaper way to do that is to redesign whatever process you will use that heavy equipment in so that it can be done with lighter initial equipment, and its majority of mass be provided from the Iron, Nickel, Aluminum, Titanium, etc, to be found in the lunar regolith.
As an example, many illustrations of building a lunar base show bulldozers scraping away at the lunar regolith, piling up dirt for various tasks. A bulldozer of the size often shown would mass, at minimum several 10s of tons. Instead, when you want to move lots of dirt, put 3 posts in the ground in a triangular formation around where the dirt is, and use a “mucker” drag bucket to move the regolith where you want it to go.
That might well be to an electrolytic pot, or even an electrolytic pit, which can get you Iron from the regolith, …or, with a bit more energy input, it can get you Aluminum. If you are in a place where you can get some of the ilmenite sampled on the lunar surface, the new FFC electrolytic process can get you Titanium,…you even have lots of Calcium around for the Calcium Chloride needed for the electrolysis solution.
Each of these metals can be powdered in fairly small equipment, and used in 3-d printers to build a *very* large number of items useful to a lunar development. The total mass of the equipment needed to get those resources is *less* than a single 53 tons orbital payload of the Falcon Heavy. Reload propellant at the propellant depots in orbit, and head for the Moon.
Even *less* expensive is to begin experimenting with sintered designs using powdered basalt, which is what the lunar mare are made of. A surprisingly large amount of stuff that would otherwise have to come from Earth could be made out of the fines of lunar dirt!
Well, this is not an ISRU thread, but a depot thread. So, if we are willing to use depots to make propellant launch a *lot* cheaper, and if we are really willing to develop *settlement*technology*, as opposed to “extended campout” technology, things get a lot more doable, fast.
Forget about exploration for a moment. Think about commerce. How do you get a piece of heavy equipment into orbit without heavy lift?
Design the equipment to fit existing lift capacity or near-term available lift capacity.
Consider the following analogy:
The military has a lot of equipment – some of it very heavy – that it needs to move around. For mass transfers, they use ships. For fast movements, they use cargo planes. Whenever they design a new piece of equipment that may require fast transport, they design it to fit the existing planes (C-130, C-17, C-5, etc). They don’t force the design of ever bigger planes every time they want a new piece of equipment because developing the new plane costs many billion dollars.
What Congrss has mandated is exactly opposite of the military example. They’re mandating spending tens of billions of dollars to develop a heavy lift booster (micromanaging it to the point of specifying the payload capacity) but nothing for any payload other than the Orion capsule. They’re mandating use of very expensive Shuttle-legacy hardware to protect jobs in various congressional districts. Should they spend the money to develop the SLS, what will it carry? How much will each mission cost (likely billions)? Why would anyone in their right mind think that building a very expensive rocket with no payload makes any sense?
Missing in most all the commentary here are notions of the budget scenarios ahead. Mr. Zubrin makes some points about using Saturn-V class boosters, or about how a 100 tonne booster would be better.
If everyone would read that leaked HAT/Depot study carefully, you would see that the concepts explored are trying to fit into not just some flat overall agency budget scenarios, but also scenarios where Human Spaceflight in particular gets a smaller portion of that total flat budget. Although the HAT/depot study began in early 2011, before that exploration budget profile had matured, it’s turned out to be right on the mark. The original budget portion that Exploration assumed would be assigned to them is now seen to be optimistic (compare the “black-lines” in the report).
So in comparing which way we might explore space, any conversation that starts with some assumptions about the largest rocket, and not wanting to do in-orbit assembly, or some notions about how to get the cheapest cost per pound, have to backtrack to what any of that will mean in that total YEARLY budget, and across time. It’s of no use to get the cheaper dollar per pound marginally, on the 2nd or 3rd launch, when you don’t have the money for the yearly fixed costs in the first place. Think about how many car buyers would love the mileage of a Prius or a Volt, but can’t afford more than a 2002 Civic. Sure, the numbers look great on the former, but reality is the later.
There are some considerations here that come from the budget realities. Assume that Exploration beyond Earth orbit remains on NASA’s plate. Well, we still have an ISS in orbit. And we still have to get cargo and crew to the ISS. On top of that we want a reinvigorated R&D base, decimated during the operational years of Shuttle, and the construction years of ISS. NASA’s plate has been added to functionally, without a matching budget increase. Sure, we have ended the Shuttle program, but look at the budget numbers and the additional costs for science on the ISS, and for cargo and crew, will easily make most of the freed up Shuttle money unavailable to any new exploration initiative. That’s why the Cx program planning was decimated when their assumption of a 2015 de-orbit of the ISS was shown to be a woefully incorrect. The correct assumption would have been no de-orbit, and no money freed up or added for Constellation.
So bring all this commentary back to reality. Budget reality.
The HAT/depot concept is about trying to address a basic strategic reality about sustainability. The agency will not go forward into ever more ambitious content on a budget that does not rise to match, unless previous steps in the exploration framework get much cheaper. One step is getting to low Earth orbit. That’s one way to make increasing content match flat budgets. Something HAS TO GET CHEAPER YEARLY.
Now a saving grace in the HAT/depot concept is to have the budget margin (see the un-used funds in those cost charts) to place more resources into in-space elements. You also want to fly more often as regards missions (not propellant). Otherwise, without these two factors you’ll never get the test-fail/fix cycles on in-space elements necessary if you want to go beyond Earth orbit for lengthy durations. The SLS based architectures do the opposite. They fly fewer missions, and the resource pressure will be working against making the in-space elements better, at those lower production rates (of Landers or habitats for example). Funds favor the rocket to LEO. So any SLS based architectures reliability as it evolves will assure a vicious cycle of more inspection, more delay, less assurance a long duration mission is doable as regards risk or reliability.
No long duration mission, no mission beyond Earth orbit, is going anywhere without addressing the elements that make up most of the risk, the in-space elements. Place more money there, less for the rest. That’s the reality. It’s a reality the HAT/Depot tries to address.
That all said, back to sustainability. ANY desire to go beyond Earth orbit for the agency is an ambition exponentially more difficult than the previous mandates under Shuttle and Station. But it’s an exponentially more challenging content with a budget that is arguably to be flat – at best. Well one answer is the steps along the way to the new content are sustainable if previous steps, like getting to LEO, can be made significantly more affordable (PER YEAR). That’s the real crux of the matter here in what the HAT/Depot team is trying to get at. It’s one option. But any options must address this ultimately.
Consider the Webb/Hubble analogy. Why didn’t our astronomy community come together around a better, newer Hubble? Because our ambition says we did that already, so let’s try to go farther. So Webb is bigger, farther away at L1, etc. The problem? No added budget for all that additional ambition.
The Human Spaceflight community has a sense of this I think. Talk about additional SLS flights at some attractive cost per pound and what people are really hearing is “they will come after MY money (in ISS, commercial, R&D, etc)”. This will be why SLS like architectures, or in general low-mission rate systems with high fixed costs, are not engendering friends and stakeholders in Human Spaceflight. Because today’s little gorilla becomes tomorrows 800-lb gorilla that will come steal your lunch money. At a gut level, many in the agency with other plans (like supporting ISS, or doing R&D, or encouraging industry, and strategies for long term, more routine access to space) see any SLS phrases about costs per pound, read into it more flights, and realize –“hey, that extra flight means they are coming after my money!” Why? Because of the Constellation experience that bore this out.
It’s a zero sum game – until leadership makes the game one of many functions in complement, and in balance, and some of those having to cost much less than in the past.