I feel sort of obligated to comment on this, since there are few harsher critics of SLS than Your Truly (I even raised money to fight it).
The main benefit of using an HLV is that fewer individual launches are needed to get the same amount of mass into space – with fewer launches of larger payloads, a lower launch cost per unit mass is realized.
A lot of people say this, including Mike Griffin, but they never actually show their work. I’m sure I’ve written this before, but the underlying assumption here is that large vehicles have economies of scale. Well, that might be generically true, all things being equal, but all things are not equal, and in terms of economies of scale, flight rate is a much more important factor than vehicle size. In the real world, we know that each SLS flight will cost billions initially, and even with the generous assumption of two flights per year, it will still be well over a billion dollars a flight.
A few larger pieces are more easily assembled in space than are a multitude of smaller ones. The cost buy down is mitigated somewhat by the assumption of more risk, as the loss of a single HLV will more greatly impact the mission campaign than the loss of a single smaller vehicle. But the benefits of fewer launches overall and less complex on-orbit operations are usually judged to outweigh these drawbacks.
Judged by whom? The only actual analysis I’ve ever seen, performed by S&MA at JSC five years ago, indicated just the opposite, partly because (again) the higher flight rate offers reliability improvement that SLS will never see in this century. And if we fear the “complexity” of orbital operations, we might as well give up on being a space-faring nation.
He goes on to bash Falcon Heavy:
No existing commercial launch vehicle (nor any anticipated in the near future) has the launch capacity of the SLS.
Note that the need for the launch capacity of SLS has never been described or generated; there is no Design Reference Mission for it, other than (as stated in the 2010 NASA authorization) to deliver money to Huntsville, Promontory, and other places.
The largest extant commercial LV is the Delta-IV Heavy, which can put a bit less than 30 metric tons into LEO, less than half the capacity of the core SLS. Critics of SLS claim that the advent of SpaceX’s “Falcon Heavy” vehicle will render SLS unnecessary, but that launch vehicle was announced in 2011 and we have yet to see even a structural test article of it. It is stated that this vehicle will be able to put about 53 metric tons into LEO, significantly less than the 70 ton payload of the SLS core. The acceptance of this lower performance by its advocates is predicated on a proclaimed vastly lower cost, but as no Falcon Heavy has yet to fly, we have no idea of what its cost would be.
First, his numbers are out of date. The 53 MT number is from 2011, before the performance improvements to the Falcon core. In expendable mode, I’ve been told by sources at SpaceX that the performance of a densified stretched version (which is the only kind that will be flying) is more like 60 MT. As for its “cost,” no, know one knows what it will be except SpaceX. Moreover, no one cares, because we don’t pay its cost. We pay its price, which SpaceX lists at its web site. The current list price is $90M, but I suspect that’s for a reusable flight. Double the price for an expendable, and it’s still a small fraction of the cost of an SLS flight. Two of them will deliver almost the same tonnage as the 130 MT version of SLS (and NASA still has no idea how they’re going to get there), and still be a small fraction of the cost. As for the fact that “no structural test article exists of it,” why would it? What would one be “structurally” testing with such a thing? I expect the first FH we will see will be the one they plan to launch, on the pad, currently scheduled for half a year from now. It gets sillier from there.
Moreover, there are good reasons to question the technical viability of the Falcon Heavy. Released design details show that it consists of 3 Falcon 9 rockets, strapped together and burning simultaneously. Such a configuration would consist of 27 engines, all of which must burn for the same duration and thrust level. The Soviet Union once had a launch vehicle (the N-1) that had 30 rocket engines; it flew four times, each flight ending in a catastrophic fireball, largely as a result destabilizations following an engine-out condition.
Remind me, how many times did a nine-engine version of the N1 fly?
Oh, that’s right. Never.
As opposed to twenty-something for the Falcon 9. The Falcon Heavy isn’t a new vehicle sprung from the head of Zeus, as the N1 was. It is simply taking three rockets with a demonstrated flight history, and flying them simultaneously. The Falcon 9 has demonstrated engine-out capability, so there is no reason that three of them together won’t (there is plenty of gimbal authority to compensate for small loss of thrust on one of the side cores). The only problem with that number of engines is not reliability per se (it should be quite high) but schedule reliability if they maintain a rule of pad abort with an engine anomaly, because obviously the chances of that will increase with more engines. But they will work through this by a) continuously improving engine reliability with experience and b) changing flight rules and performance margin to allow a lift-off with engine out.
Given that there has in fact been no demonstration of actual technical need (that is, no payload or mission has been identified that can only be performed by a vehicle with the technical specification of SLS), yes, sorry Paul, but it is a jobs program, pure and simple. Or pure and complicated. But it is a roadblock to Mars or the moon, not a road to those places.
[Update a while later]
I missed this straw man the first time through:
A few larger pieces are more easily assembled in space than are a multitude of smaller ones.
This reminds me of a few years ago when I asked Mike Griffin what payload demanded an SLS and he yelled at me from the podium something like “We can’t take up every part and fastener on individual launches.”
Note the word choice: “a few” versus “multitudes.” In reality, if using a FH instead of SLS, it’s “a couple” versus four or five. Even with Vulcan, it would be “a couple” versus half a dozen at most. And of course we have no idea what Blue Origin has in mind. Even with smaller vehicles, it might be a dozen or so. Hardly “multitudes.”
[Update a couple minutes later]
OK, one more point. The same question to Paul I ask all other SLS supporters. If we can’t get beyond LEO without a rocket in this payload class, then why don’t we need two? After all, the Shuttle was down twice during its life for almost three years each, during which we had no (American) way to get astronauts to space. Why should we bet that the same thing won’t happen to this (Shuttle-derived) vehicle? If you don’t think that redundancy is important for this capability, it’s the same as thinking that getting beyond LEO isn’t important. The commercial alternatives give us resiliency; NASA-only solutions tend to be fragile. But that’s OK, because apparently the only thing that’s really important is maintaining the work force, which we can do whether we fly or not.
[OK, maybe one more point, I really should address this, because I don’t very often]
the Congress (who had twice voted their overwhelming support for the goals of lunar return, in two different authorization bills) mandated the construction of SLS, largely because NASA was dragging its feet on doing anything about it. Congress was concerned that an important national resource – the industrial and technical infrastructure (including its human resources) to build and fly HLV rockets – was being lost through neglect and attrition. They asked the agency to come up with a specific design for an HLV system but received no cooperation. So, they consulted external technical experts to derive the specifications of a general purpose HLV and mandated this design in the authorization. Its purpose was to make sure that the vehicle would be built and to assure that our national capability in this area would not be lost.
Let’s be clear what we’re talking about here. The capability to “build and fly” HLVs was not being lost, all that was being lost was the capability to do it with legacy Shuttle hardware, and its associated work force. That was the requirement that Congress built into the law. Moreover, it wasn’t being “lost” because, at least in terms of development (if that’s what one means by “build”) the capability had been lost decades before. Marshall Space Flight Center had not developed a heavy rocket since the 1970s, despite many failed attempts. Mike Griffin himself said that one of the purposes of Ares I was as a “training rocket,” so that they could learn how to develop rockets again, before they took on Ares V. If SpaceX flies FH in the next year (increasingly likely), they will have demonstrated their own capability to build a heavy rocket. There is no national need to maintain the ability to build SSMEs, Shuttle ETs and Shuttle SRBs and other obsolete hardware from forty years ago. There is only the need to maintain jobs in certain zip codes, which uncoincidentally generally exist in or near congressional districts or states of congressmen or senators on the space committees on the Hill.
Yes, Paul, it is a jobs program.
[Late-evening update]
Keith Cowing has weighed in as well, with lots of commenters.
Honestly, Paul is a smart guy. I cannot imagine what he is thinking, unless he is simply in the thrall of Apolloism.
I believe the $90M cost for a FH flight is for 1/2 of a GTO mission, making a full flight at least $180M. According to the website, it’s $90M for an 8 mT payload to GTO, but the FH can carry 22 mT to GTO according to this (probably old data, but on the order of 1/2):
http://www.spacex.com/about/capabilities
I have never liked SLS, but I think we should fly SLS as soon as possible.
And generally we should regard it as experimental exercise.
And the first payload it delivers should not be expensive- so a water payload. And whatever than think would be safe for expensive payload to launched in the being, they should increase the first payload size by 10% or more than test flight with an expensive payload. Then if successful launch the test flight with expensive payload [10% less payload].
And after this assess, the program costs and make recommendation about future use of SLS.
Under current plans, that third test flight would occur about eight years and many billion dollars from now.
I wouldn’t number the test flights sequentially until they stabilize the design. For a while they’re going to have a string of first test flights.
Yes. The current plan is that the SLS will only fly once every four years. Such a low flight rate will cause costs to balloon.
Frankly, my opinion is by the time of that 3rd flight of the SLS, it will be obsolete by lowered costs due to reusability.
Bob Clark
Thank you for a fine fisking.
The Soviet Union once had a launch vehicle (the R-7) that had 5 cores and 20 rocket engines; it flew many times, launching Sputnik, Vostok, Voskhod, and Soyuz. It is still used to carry passengers and cargo to the ISS. Not bad for a 60-year-old concept.
I suppose all this just slipped Paul’s mind. If the Soviets (!) could do this in 1957, then why can’t Elon Musk do it today?
Excuse me. I’m trying VERY hard not to be…imtemperate.
I don’t recall where they built a structural test article for the Space Shuttle after all the components had made 20 flights.
A structural test article isn’t going to tell you anything because the unknowns would all be aerodynamic, involving boosters attached to a core, something that’s only been tried on… *looks up references* not every last launch vehicle.
It’s hard to take such claims seriously coming from the agency that declared solids okay for manned space flight, built a vehicle with no launch escape system at all, and launched it with a human crew without a single unmanned test flight. The rule book is whatever they say it is.
I share your disagreement with Spudis’s comparison of Falcon Heavy with the N-1. First stages of the R-7 family, though, might be more accurately described as having just five engines: each has four combustion chambers and four nozzles, but just one set turbomachinery. And it’s the turbomachinery that tends to be the most troublesome.
Spudis made some glaring factual errors that show he knows little about Falcon Heavy. For example, his claim that all three cores burn for the same amount of time (not true even without cross-feed).
There are so many things in Spudis’s article that bother me, but the one that stood out the most was his dismissal of Falcon Heavy due to not yet existing, while at the same time accepting SLS Block II as if it existed (current plans call for block II by 2036, IIRC).
Thanks for the fine fisking, Rand.
Insanity has been defined as doing the same thing over and over again, each time expecting a different outcome.
How is that different to the people who continually expect the next big NASA rocket to be the one that finally gets us beyond LEO?
After 40 years of NASA fails they still expect the same organizational system to suddenly start to work.
They’re nuts and not worth wasting time on.
“They’re nuts and not worth wasting time on.”
Yeah, but a billion here, a billion there, pretty soon you’re talking real money.
As a general rule, the cost of aerospace hardware scales with the dry weight to roughly the .85 power. That implies that bigger is cheaper, all else being equal.
But all else is not equal. If you build smaller, you will need more flights and more vehicles to accomplish the same number of missions. Flying more often and building more often means you will work further down the learning curve on cost.
Put these two factors together, and the result is pretty much a wash. What’s undeniable, however, is that the initial capital cost is greater for the larger vehicle, and there’s always a limit to how much money will be available. If you run out of money before you finish the big vehicle, it doesn’t matter how cheap it might have been.
You also need to consider the cost of money — interest on what you need to “borrow” to build the vehicle. That can be a killer. The Sea Dragon is something of a legend in the space community. Space advocates love to talk about how cheap it would have been. Unfortunately, if you go back and look at the original NASA study, you find that it failed to consider the cost of money. If you redo the figures, taking the cost of money into account, you find that Sea Dragon costs are not fantastically cheap after all but in line with other large boosters. That should not be surprising, really.
Having said that, the question is moot in the real world. NASA is going to continue to build what they have been trying to build for the last 40 years, and Congress is going to continue to fund what Congress wants. There are better uses for our time than trying to change that. I almost had Ted Cruz persuaded to oppose SLS, before Rick Tumlinson opened his big yap and saved it, but it becomes harder and harder to change NASA’s course with each passing year. And the opportunity costs of lobbying efforts are very high.
The opportunity of lobbying costs are trivial, compared to the costs of what one is lobbying against.
Trump could kill the SLS like it was Jeb!
“SpaceX can launch the same payload for $180 million that is going to cost NASA $1.5 billion, easy. Are we stupid? The SLS is a bad deal. They’re going to fly what, ten people a decade? You can’t stay in business that way. You can buy your own Boeing for less than their cost per seat – per flight! Believe me, I bought my own Boeing. Nice plane. Very nice.
I have great respect for NASA, truly brilliant people, but what they’re building is crazy. Congress told them they have to build it. Do they want to build it? I don’t know. But I know we don’t need it. They don’t even have a payload for it! It’s all just crazy.
If you’re going to ship something, go with the cheapest shipper with the best record. It’s a no-brainer. And the cheapest shipper we got is about a tenth of what the SLS will be. They’re focused. They’re making money at it. Lots of money. They’re flying what, every couple weeks? Just outstanding. And made in America. They saw a market and went for it. That’s what we need to be doing, instead of all this craziness from people who make bad decisions.
And this will free up so much money for NASA. So much money. It’s eating their budget. They’ve killed so many programs to pay for this thing, and they don’t even need it. They’re only building it because a bunch of lawyers in Congress told them they have to build it. How do you motivate people that way? They just start punching a clock.
We keep shooting ourselves in the foot. Why do we keep doing that? We need to stop doing that. I look at the numbers on this thing, and I can’t justify it. It’s a bad deal. A horrible deal. Possibly the worst deal in the history of deals.
They say it’s crucial for exploring “beyond Earth orbit”, but it’s not useful for getting beyond enough to go anywhere else. It’s not going to land anyone on the moon. It’s not going to land anyone on Mars There just going to roam around for a week in the middle of no place, come back and ask for a check. Why would we pay someone to go to nowhere and come back? I can understand paying a homeless guy twenty dollars to go away, but this is just nonsense. I am not going to pay anyone a couple billion dollars to go away for a week or two.
If we’re going someplace out there, I want to see a plan for how we get there, what we do there, and how much it will cost for me to build a hotel. Maybe a casino. I’ll have Ivanka evaluate the bids. She’s really good at that, or I’d have fired her long ago. She is ruthless with numbers, and oh so gorgeous.
Believe me, we’ll get our space program moving again. Moving faster than it’s ever moved. We’ll be actually going places. We’re going to put hotels in space. We’re going to the moon. We’re going to Mars. But to get there we have to make good deals. We have to be smart. And throwing tons of money at a crazy rocket that’s built out of parts that belong in a museum isn’t smart.
And when I’ve got sunk costs in a disaster like this, I bail. I do.
It’s the smart thing to do. I bailed on Atlantic City as soon as I saw the market shift. Well, the launch market is shifting, and shifting fast. SpaceX is landing their rockets instead of throwing them away, and these rockets cost many millions of dollars. NASA’s rocket costs a billion and they’re not even planning to have planning meeting about trying to discuss landing and reusing it! They’re just throwing money away because they were told to throw money away.
No, we’re not going to do that anymore. We have to be smarter than that. We have to start winning. And we are going to win, by freeing up so much money for NASA, and going with SpaceX and Blue Origin and so many others who know business. We’re going to change course, because the current one makes no sense. No sense at all.”
Trump could kill the SLS like it was Jeb!
Suddenly I’m warming to Trump.
Hey George, I can’t find what you’re quoting, got a link?
I just made that all up. I do that from time to time.
I could probably do a Ted Cruz version about how SLS is God’s plan for America.
I should have known.
That from Trump? Impossible!
That from you? Typical!
Crushed.
Trump could kill the SLS like it was Jeb!
Sure, George. Shouldn’t you be preparing another crackpot lawsuit against Ted Cruz for assassinating JFK?
Well, here’s an interesting letter regarding that.
That was a sent by Lee Harvey Oswald to the Dallas office of the INS in June, 1962. It turns out that children born or adopted abroad to US parents are aliens until the parent files form N-600, has it approved, and receives a certificate of citizenship, making the child a naturalized citizen.
If Oswald had explained that to Rafael Cruz then the 2016 race would have been so much simpler.
Odd fact. If children born abroad to US parents really are natural born citizens, then it passes by descent outside of laws passed by Congress for the naturalization of aliens. This would mean Prince William and Prince George are natural born US citizens because Princess Diana’s ancestry traces back to a socialite born in New York City in 1857.
Apuzzo and William’s cases still proceed, and perhaps now that Cruz is not longer an actual candidate a judge will rule on the “settled law” so that we don’t have a million foreigners like Prince William filing suit, demanding US citizenship by citing the Ted Cruz rulings.
Using reason George? When are ya gonna learn?
BTW, it’s the media narrative that Cruz’s father was part of the JFK plot. All Trump is saying (and there is photo evidence) is they passed out pro Cuba flyers together.
It turns out that children born or adopted abroad to US parents are aliens
Not aliens, hybrids! Without Majestic 12, your theory is incomplete. But keep going, the truth is out there!
Dang, you’re good. I can hear Trump’s voice as I’m reading that.
You also need to consider the cost of money
Why? Money has no cost in a government program. And there is no way for a government agency like NASA to pay back the treasury with interest.
interest on what you need to “borrow” to build the vehicle.
Interest is only on the deficit as a whole, not tied to any specific program or agency.
The time value of money doesn’t matter either because the money in question wont be earning anything no matter how it is spent. Same goes with IRR. You can’t even create a list of alternatives because they are all ideological expenditures not intended to make profits.
Maybe you weren’t talking about a government program but I just wanted to harp on government spending being an ideological one not one of economic/fiscal/business/whatever.
And the opportunity costs of lobbying efforts are very high.
But opportunity costs are the most convincing, IMO, for convincing people to change their thinking on SLS. That didn’t used to be the case but it is now. The biggest roadblocks are looking at sunk costs the wrong way and a genuine, nonpork, concern for the welfare of workers who will lose their jobs.
Money has no cost in a government program. And there is no way for a government agency like NASA to pay back the treasury with interest.
False. DoD accounting rules require all program costing to include the cost of money, from the time initial development begins. To the best of my knowledge, NASA does not do that, which means all of NASA costing is invalid. Not to mention all the space-cadet comparisons between NASA and DoD programs.
False. DoD accounting rules require all program costing to include the cost of money,
It is an extraneous requirement. Money has no cost for any individual government program or agency. But there are always people who claim defense spending is the cause of deficits rather than whatever program or agency they support.
Sure, if you just make up your own accounting rules, you can show results as low as you like. I don’t know what your point is.
Outside of government, we call that sort of creativity “accounting fraud.”
But opportunity costs are the most convincing, IMO, for convincing people to change their thinking on SLS.
I don’t think you understand what opportunity costs mean.
With all the time and effort that’s gone into trying to fix SLS, we could have saved Centennial Challenges, CRuSR, the FAA’s $20M CATS prize… etc.
I’ll note that space-advocacy groups have spent as much time trying to fund/save SLS (under all its various names and incarnations) as they have trying to kill it. In many cases, the same people worked to save it *and* kill it, at different times.
For example: The SFF, which initially supported Ares I and V, later changed its mind and recommended that NASA cancel Ares I and use the money to accelerate development of Ares V for BEO missions. Which is basically what NASA did. A short time later, SFF changed its mind again and began to call for cancellation of Ares V. (And you wonder why Congress is so reluctant to take activists seriously?)
And then, of course, there was Rick Tumlinson telling Ted Cruz it was politically impossible to cancel SLS so he should just make sure NASA had enough to fund both SLS and COTS/CCDev.
That was probably the best way to go.
I don’t think you understand what opportunity costs mean.
You were talking about your opportunity costs but I was talking about the opportunity costs of SLS over the alternatives. I was just referencing the concept.
Opportunity cost is much more persuasive argument on SLS than the cost of money or the time value of money, both of which have tangential relationship to government budgets at best. Interest is especially bad because NASA programs are not intended to return a profit or the funds for them repaid to the treasury.
Taking what is spent yearly on SLS/Orion, adding it all up for the estimated years to completion, and dividing by F9 or FH launches is very compelling in terms of money and payload either yearly or in total. You could even go backward and do the same for the sunk costs but that wouldn’t be a good way to make a decision, even if it’s very persuasive.
This used to be an exercise of paper rockets but it isn’t any more.
You’re assuming that NASA would buy the F9 or FH launches you want, if SLS were canceled. That would be true if you or Rand were King of NASA and did not have to answer to Congress or the White House. The probability that cost savings would be transferred over to programs *you* want is actually quite small. More likely, the program would be used for some new program which you wouldn’t like any better than SLS.
But even if you were King of NASA, how many Falcon 9 launches do you think NASA might buy? How does that compare to the new industries that might have been created if Congress had passed Dana Rohrabacher’s Zero G Zero Tax bill, for example? Or other legislative incentives which NewSpace ignored because because of the single-minded focus on NASA programs?
The idea that “Needs two launches” is equivalent to “Requires complex and fiddly on orbit assembly” always seems to be lurking in the implications and thus needs thrashing IMNSHO.
The simplest “multi launch” missions should require nothing fancier than docking. Even “Transferring fuel over” isn’t a -needed- step. But I’d like to think the implausibility of “ship empty to orbit, fill there” is the next silly objection to get trumped by demonstrated reality.
I’d like to think that we can figure out how to attach a couple tubes together from the inside as opposed to from the outside as well. But even just a two-lift mission is portrayed as Herculean.
What a silly suggestion ! We never needed to do any docking tricks for Apollo .. oh .. wait .. i’m being told docked all the time .. on lunar orbit, to boot.
You make an excellent point. The infeasibility of assembly and/or docking and/or refueling is not at all an argument for SLS.
There are several existence proofs that show that things can be brought together in orbit successfully:
* ISS: Assembled mostly with docking, from multiple different launchers in chunks of about 10K kgs
* ISS: resupply missions
* Skylab repair
* Gemini / Agena
* Soyuz + Soyuz
* Mir
* Salyut
* Hubble repair missions
Even rendezvous on the surface of the Moon: Apollo 12 and surveyor.
Also, Bigger is cheaper is a heuristic which doesn’t work at all scales. With SLS, it is simply counterfactual.
Also, the Chinese doing autonomous rendezvous with their space station modules. Everyone keeps saying how far behind us they are so if they can do it, so can we.
You could cite some other obvious counter examples involving the cost of shipping completed rocket stages to NASA or shipping Space Shuttles to museums. Small rocket parts are cheap to ship. You call up Freightliner, Schneider, or J.B. Hunt. Big rocket parts are extremely expensive to ship.
The same applies to shipping any cargo that’s bigger than our usual carriers are set up to handle. To justify the cost of upgrading the infrastructure or building a special purpose heavy hauler, you have to look at the amount of traffic in the new market (the anticipated launch rate) to see if the investment will be worth the cost compared to shipping the same cargo as parts using existing, high-volume carriers.
The idea that method A is cheaper than method B comes from comparing the bottom line figures from two possibilities and noting which one is cheapest. You can’t say that bigger is cheaper in all cases if you’re staring at a detailed financial spreadsheet that says otherwise.
Anyway, Rand didn’t get vicious on what I thought was the most Fiskable sentences:
Well released design details show that the early block SLS consists of a core stage with two SRBs. “I’m on top of this techno space trivia!”
Honestly, that part made me think he was reciting from index cards being held up by a gun-wielding hostage taker in a NASA hat. Maybe that in part is why he wrote the piece. You should read it more closely for signs of some kind of blink code.
“torture. 8 NASA mgrs making me write this.”
— “8 NASA mgrs making me write this.”
LOL.
Bagdad Bob-esque
“If we can’t get beyond LEO without a rocket in this payload class, then why don’t we need two?”
That’s not much of an anti-SLS argument. From my cursory scan of Spudis’s piece, he’s not so much complaining about FH as he is supporting SLS. Am I missing something here?
He is supporting the need for SLS. My point is that if there is a need for a vehicle with that capability, then there is a need for resiliency (i.e., at least two different vehicle types with that capability). If he doesn’t agree that that’s a need, then I’d like an explanation.
That’s fine, but it doesn’t advance the “SLS is wrong” argument. Arguing that two HLLV systems are necessary implies that SLS is not wrong–if anything, it bolsters the argument that SLS should continue even if FH succeeds.
That’s not the outcome you’d like to see, is it?
No, but it bolsters the argument that maybe SLS isn’t as necessary as its proponents claim.
Good argument but since the private sector has demonstrated the ability to launch payloads into space on a large variety of launch systems, why not open up SHLV services to new entrants and the companies that have been doing launches for NASA and the DoD for decades? The key part being allowing whoever builds a SHLV to have control of the vehicle in order to sell services to non-government entities.
Honestly, Paul is a smart guy. I cannot imagine what he is thinking, unless he is simply in the thrall of Apolloism.
Spudis has been singing this same song for years, reality: People get so tied to their beliefs that the world has to be turned on it head before they can have their epiphany.
Yes, he was a member of the Aldridge Commission which recommended heavy lift as the top priority for BVSE.
That was years before it became anathema in the NewSpace community. A few of us pointed out that it was problematic, but “experts” like Muncy/Miller/Tumlinson said we should confine ourselves to “policy” and never debate us we technical questions. In other words, shut up and go away.
Funny how often, “shut up and go away” is the recourse of a weak argument?
There are three recurrent fallacies that come up in the launch and mission planning area and I regret to say that two are on display in Spudis’ article.
First: there is an economy of scale to larger launchers over smaller launchers, all other things being equal. Most notably, if flight rate and size of production run are equal. The nature of space launch being what it is, not only aren’t those equal, they CANNOT BECOME equal. If you make a bigger launcher, it flies less often and has a shorter production run. Therefore, it is obviously untrue that a larger launcher is, because of engineering scaling, automatically cheaper than a smaller one. Take it to extremes at either end and this can clearly be seen. Is it better to reduce launcher size so we launch individual screws? Obviously not — overall cost would increase. Is it better that we save up all launch demand over twenty years and launch everything as shared payloads on one truly giant rocket? Obviously not, that would be insane — you’d need specialized plant, equipment, and facilities that you would build and maintain for twenty years and the cost would be prohibitive. Therefore, there is an OPTIMUM size of launcher for a given traffic model, and it is neither “as big as we can make” nor “as small as we can conceive”.
The second fallacy is that by saying “assembly is expensive” that this implies the optimum number of launches is one. First, we have never done a deep space mission without assembly — where assembly implies docking pieces together (which is the only ‘assembly’ anyone is seriously contemplating in the near term). Apollo released the CSM from the S-IVB, then docked with the LM and extracted it, then undocked the LM in Lunar orbit, then separated the LM ascent stage from the descent stage, then redocked the LM ascent stage to the CSM for Earth return. So Apollo could not succeed in the mission without two dockings, which is equivalent to assembling three pieces.
Still, accept that there is a cost. Saying “there is a cost” does not eliminate an alternative. What is the cost, and how does it compare to the alternatives? One horse is surely faster than another, but which one matters.
The third common fallacy, fortunately not on display, is the false assumption of mission risk. I will mention it for completeness — if you assume launch success is a fixed figure — say 97% success — then the more launches you have, the more the chance one of them will be a failure. This is a fallacy for two reasons — first, mission success is NOT a fixed figure, it is subject to a learning curve. Early flights are more likely to fail than are later flights, so reducing the number of flights means more of them are high risk flights and therefore the overall failure statistics are not equivalent. Secondly, the greatest leverage obtained by splitting the mission in to several pieces is to take advantage of the fact that most of the mass is not spacecraft, but propellant, and so not all launches are of equal value. Once you introduce the concept of “mission spares” for elements like propellant tanks, you can reduce the mission risk to whatever value is desired by building flight spares for hardware and not committing the mission until you have successfully launched the elements required. Indeed if you desire a still lower risk you can build spares for higher value elements — again, there is a tradeoff, in that spares for everything maximizes cost and minimizes risk, and spares for nothing maximizes risk, so a cost-benefit tradeoff is needed, rather than an immediate flight to either extreme to avoid the effort of thinking.
I agree with your formulation. I’d add this as well:
On risk:
Also, you can introduce intentional independence into the design by using independent, smaller pieces. This could be supported by a giant rocket (like Apollo) or by several launches of a smaller rocket. Having independently functioning pieces allows for some lifesaving, degraded performance — the classic example being Apollo 13.
Mitigating mission risks argues **AGAINST** one monolithic spacecraft, sent up on a giant rocket.
Your talent Jeff, is not just the voice of reason, but being able to explain it so anyone should be able to understand it. Best wishes on your new venture.
An excellent analysis, which is useful not only in interpreting Spudis’s piece, but many others on the same general topic.
Could I ask whether you have any comment on Spudis’s contention that the Augustine Committee did not adequately consider Shuttle side-mount configurations? He seems to believe that a side-mount launch-vehicle would have allowed for a significant lunar program under an FY2010-like budget.
The problem is it doesn’t matter what a bad deal the SLS is. I foolishly thought, once FH comes online they’d have to kill SLS, but that just isn’t true.
It is a jobs program. So regardless of how stupid it is technically it has legs politically. (A good reason to hate politics!)
To kill SLS would be difficult to do in one stroke. So it will be done gradually over time. Even Trump will be stuck on this knot.
Previously, the performance of the F9 was listed at 13,160 kg to LEO. The crossfed configuration of the FH was listed as 53,000 kg. So the FH could lift 4.0 times the payload.
If now the improved F9 can lift 22,800 kg to LEO then the crossfed FH version of that ought to be 4.0 times that which comes to 91,824. That’s about the performance to LEO of the 90 tonne version of the SLS at a small fraction of the cost.
If the SLS Block 2 can place 130 tonnes to LEO then it could place about 60 tonnes of cargo at an EML staging point (Isp of 453 sec & DV of 3.43 km/sec). If a crossfed FH could place 91,824 kg to LEO and then solar electric propulsion were to push it to an EML staging point then this approach should deliver about 69,004 kg (Isp of 2,500 sec & DV of 7,000). Engines and propellant tanks would have to be subtracted. So, using this approach, it seems that the FH would outperform any version of the SLS for cargo.
A non-crossfed FH will place 54,400 kg to LEO. It could then chemically place 17,590 kg to an EML staging point (Merlin 1D vac: Isp of 310s and DV of 3,430 m/sec). This is substantially more mass than the Orion capsule.
So, are we looking at a FH architecture which could replace the SLS?
So, are we looking at a FH architecture which could replace the SLS?
I’m not sure how to answer that given that nothings been designed for SLS that won’t fit on FH.
Oh, has anything been designed for SLS at all? I’m not able to think of even one payload that fits that description.
There are a couple of deep-space cubesats that will ride around the moon with it. Designed for SLS
To me the issue seems less who is supposed to do what, and more that we need a better definition of what kinds of activities are to be undertaken, from which flows the requirements for needed tech and hardware, and then who will address those requirements.
This is to some extent what I tried to point out in my Cislunar Econosphere article at The Space Review back in 2012. I will note that the ULA cislunar econosphere roadmap looks remarkably like the graphic I created for the article. As people become better aware of the kinds of activities we can do in cislunar space, they can bring products to market that will allow us to do those things. ULA is an example of this, as they begin marketing their upper stages to allow movement of cargo between points of interest in cislunar space. They foresee activities beyond LEO, they know those activities will require transport, and so they are marketing a transport solution.
Sometimes I can’t help but be convinced that space folks are their own worst enemies, constantly missing the forest for the trees.