way behind schedule by 5 years. It will be an uncrewed test by June if things go as planned . It’s pretty similar to the Saturn V moon rocket in capacity it can handle also similar in height and width to Saturn V
I thought that they were going to be going with the Falcon line from SpaceX (in particular, the equivalent to the Saturn V would be the Big Falcon Rocket).
The Falcon Heavy only has a fraction of the advertised capability of the SLS Block 1B and Block 2 launch vehicles (based on geosynchronous transfer orbit of the former versus trans-Lunar injection of the latter, which are not exactly head to head but are close enough for a first order comparison ) and is not crew-rated, nor are their plans to do so. Of course, whether Lockheed’s Orion Crew Module and the Airbus European Service Module will successfully pass qualification is still an unknown, and the exorbitant cost of the SLS leaves the question of whether an ongoing Lunar program is viable, notwithstanding the questions about what the program will actually accomplish given that most of the technology on the critical path for the Artemis program as scheduled is years behind in even basic development, much less being qualified for human crew.
If the Artemis 1 mission actually launches any time in 2022 I’ll be shocked, and even provided that it is a complete success as an “all-up”, the planned launch cadence of one flight per year means that any reduction in budget or flight failure will probably result in multi-year delays and supply chain problems. SLS started life as the DIRECT proposal Jupiter-130 and Jupiter-246 launch vehicles, which were supposed to be maximal resuse of Shuttle-derived hardware and systems as an interim to developing the next generation launch vehicle and spacecraft, but instead has become an enormous development project onto itself with no clear end goal or development pathway to a better system. Like the Space Transportation System “Shuttle”, it grown to become an obstacle to its own viability.
Stranger
really don’t see the point in all that money spent to repeat something from 50 years ago.
Mars would be better but I know that’s much harder to get to. 9 months to get there , probably need to stay 3 months to get in position to get back and 9 months back.
Ahh yes, the Big “Falcon” Rocket. At least, that’s what we tell the children.
If one were to design a beyond-LEO system using only extant launch hardware, a combination of Falcon 9 and Falcon Heavy wouldn’t be a bad start. F9 is man rated and is among the most reliable launchers available. Crew Dragon has proven to be a safe and effective crew launch system.
A single Dragon isn’t enough for BLEO missions, but additional hardware such as service and propulsion modules could be launched on Falcon Heavy (they wouldn’t need to be crew rated). Yes, the max lift capacity is less than SLS, but the development cost of developing a modular system that can be lifted 50 tons at a time is surely vastly less than the SLS development.
That of course ignores the elephant in the room, Starship (aka BFR). It’s not actually derived from any Falcon technology; it’s an entirely new design, from the materials (stainless steel instead of aluminum-lithium), propellant (methane-oxygen instead of kerosene-oxygen), full reusability, and many other things.
Musk has made some bold claims about launch costs but SpaceX’s costs don’t have to come anywhere close to his hopes for it to be the vastly cheaper launcher. Even if their second-stage reusability fails, and Starship remains partially expendable instead of fully reusable, it will likely still only cost around $100M to launch 200+ tons into orbit. That’s 1/40 the cost of the SLS for a larger payload. Again, that’s virtually the worst-case scenario, assuming basically everything new in the design doesn’t work. If you assume it basically works but is still more expensive than Musk’s goals, it’s more like 1/200 the cost.
As it happens, NASA has fully bought into the Starship concept as it forms the centerpiece of their lunar landing system. They are still using SLS to keep the senate happy, but it is almost a complete irrelevance.
I think it’s mainly a handout to big defense contractors. Robots can do much more for less money but they probably don’t get people excited
The problem with SLS isn’t that it’s designed for human missions. Humans vs. robots is a different argument, and I don’t think you should underestimate the getting people excited aspect.
The problem isn’t even with handouts to defense contractors, exactly, though the cost-plus accounting model that they’re using with SLS certainly isn’t helping.
Fundamentally the issue is that SLS is a bad design because it was created to preserve the contractors that serviced the Space Shuttle. Solid rocket boosters do not belong near any modern launcher design, especially a man-rated one, but SLS uses them because the Shuttle’s boosters were manufactured in Utah by Thiokol (now ATK), and Orrin Hatch was an influential senator there. Basically the same things can be said for the entire SLS program.
Even operating under the assumption that we want expensive human missions and that supporting big defense contractors is a goal, we could have had a much better system than SLS. If you’re already set on spending a few tens of billions, why not at least get the best bang for the buck? But because SLS had to support a few specific contractors, the basic design was set in stone at the start, and not driven by engineering or physics concerns.
Thankfully, NASA is at least partly onboard with a new procurement model, that does not dictate how something is achieved but just sets the high level needs (payload capacity, crew rating, etc.). SpaceX is doing well in this new role. Other providers are doing less well, but perhaps in time they can internalize how best to act like a real competitor, benefitting everyone. Boeing especially is learning some tough lessons with their Starliner program but I hope they can come out of it better than they were.
It’s on the launch pad now for the test coming up.
I forgot one thing is supposed to be different from Apollo, they are sending a woman this time
And no rope memory (I assume). 
Wow, I didn’t know this was such a boondoggle. Any chance it could get canceled soon, and NASA could just work with Musk and others toward the truly best, most cost-efficient design?
Hard to imagine it being totally cancelled at this point, but it may simply drift into oblivion. The SpaceX Starship is clearly the future, and is the core of the HLS program (Human Landing System, the landing part of the new Moon program). Once it starts flying it’ll become obvious to everyone how superior it is to SLS. A few missions will get thrown SLS’s way, but probably much less than one per year. I can only hope that, despite the exorbitant costs, it’ll just be infrequent enough that it’s not a significant chunk out of NASA’s budget.
The $4.1 billion per flight is actually a dramatic underestimate of the costs because it is just the marginal cost. I would be shocked if it flew more than 10 times, ever, which means you need to add another $5B per flight to cover the ~$50B development costs. And even that $50B probably doesn’t cover all the cancelled programs along the way, such as the Ares V (the SLS is just a slightly rejiggered Ares V). It also doesn’t cover future development such as the Block 1B, Block 2, etc. Hopefully, these at least get cancelled before too much is spent on them.
They might have over estimated the excitement that a moon landing could generate.
solid rockets are either off or on, right? One they start they cannot be stopped?
If they have a hollow core all the way through, they can be killed by blowing out the top end. Then exhaust gases go out both top and bottom and it’s no longer accelerating. The Shuttle solid rockets had such a core and I expect these do to.
The Shuttle Solid Rocket Booster (SRB) has redundant linear shaped charges for the Iflight termination system (FTS) that run down the raceway (the channel going down one side of the booster carrying flight control and instrumentation cables); I assume the SLS, using what are just slightly redesigned system actually using surplus SRB components, has a very similar FTS. If the charges are functioned, they cut through the D6AC steel case, destructing it by splitting the case open and rendering it incapable of retaining pressure. The interior pressure will blow the motor apart, literally fragmenting the propellant grain into small chunks, and will work whether it is an ‘end burner’ or a ‘thru bore’ design.
There are motors like the SR73 (LGM —30G ‘Minuteman III’ third stage) that incorporate thrust termination in the form of radially symmetric ports that are cut into the forward dome in order to provide controlled shutoff of the motor without creating fragments or endangering the upper section (payload and post-boost vehicle) but this is different than flight termination and most motors do not use this because it complicates the design and qualification of the motor.
To answer the previous question, with the exception of some experimental motors, solid propellant rocket motors cannot be shut down and restarted the way some liquid and hybrid propellant motors can. Because solid propellant motors are primarily used in weapon system applications, and occasionally in apogee ‘kick’ motors to transfer a satellite from a lower orbit into a higher one, it isn’t a necessary capability. The use of solid propellant boosters on STS (and thence on SLS) was driven in part by schedule and cost, and also because they are extremely compact for the level of thrust they provide (even though their vacuum specific impulse is poor compared to even moderately performing liquid engines) and don’t have to be offloaded and refueled in the case of a launch abort they way cryogenic oxygen and hydrogen have to.
Stranger
Pretty sure that’s a downside. SLS has to be vertically integrated and transported by that gigantic crawler at 0.5 mph because of those boosters. They weigh 1600 tons total, while the dry mass of the core stage is only 94 tons. Aside from all the other issues, it’s a huge disadvantage to not be able to transport with the propellants unloaded. Especially considering that they still have to do so with the core stage.
Liquid boosters with the capability to replace the Shuttle SRBs would require almost twice the volume even if they were RP-1 and LOX, and more than four times if LH2 and LOX. Having to unload those and refill them in the case of a launch slip—which were so common in Shuttle flights that they occurred more frequently than not—would have been an enormous logistical effort and would put tighter limits on launch availability, whereas the SRBs could be left in place with lightning protection indefinitely, only requiring loading and unloading of the External Tank, which was substantial in and of itself.
This isn’t to say that solid propellant boosters are ideal for large launch systems—they’re generally used to increase payload capability to orbit without having to completely redesign the vehicle—but there are positive tradeoffs to the downsides of having to handle such heavy items, and negative trades to trying to replace them. The ideal for STS, of course, were the RP-1 based liquid flyback boosters and keeping the downrange zone completely clear of commercial and recreational traffic for the entire launch window, but the costs of both of those ended up being far too prohibitive to ever be seriously considered.
Stranger
If they switched the whole thing to RP1 or methane, they could still have a reasonable cross-section. Super Heavy has a 9 m diameter and more thrust than SLS; the SLS core stage is 8.4 m.
A pure hydrolox design would of course require a giant diameter, like the Chrysler SERV you’ve mentioned before.
Well, for a system that was ostensibly like snapping together Shuttle parts like Lego bricks (or rather, it was sold that way), the $50B+ they spent on SLS and prior “Shuttle-derived launch systems” sure ended up being a lot of money anyway. A whole lot of that was sheer waste, but I think a non-negligible portion was dedicated to reengineering systems that were never meant to be in that configuration. It’s not always the case that developing something from scratch is more expensive than reusing proven components, and that gets worse the more distant the new design is from the old.
A clean-sheet design, something more like a next-gen Saturn V (in the sense of being a large, single-stack, 3-stage vehicle, but using modern engines and materials) would probably have been cheaper and undoubtedly better.
The Shuttle SRBs are 146 inches (3.7 meters) in diameter. Because of the Shuttle “one-and-a-half stage” configuration it would not have made sense to have a single larger core as the large thrust was only need during the first couple of minutes before the Orbiter/External Tank was above the bulk of the atmosphere. Using solid rocket boosters minimized development effort (as the US Air Force and its contractors Thiokol and Aerojet had already done extensive research on large diameter solid boosters) and simplified the launch site logistics even with the complexity of transporting, handling, and integrating large diameter segmented solid rocket motors.
The Chrysler SERV wasn’t large diameter because of the propellant system; the diameter was driven by architecture of a capsule-style base re-entry mode and (to an extent) a modular base plug aerospike ascent system. Most people think that this would be prohibitive because of the (form) drag of the large frontal aspect but in fact it is a pretty minor loss while the gains in volumetric efficiency are significant (and this despite the need for jet engines and fuel carried to orbit and back just to get sufficient crossrange and soft-landing).
Nobody involved in the DIRECT 2.0 proposal that ultimately lead to the SLS ever claimed that the system would be “snapping together Shuttle parts like Lego bricks”, nor was it ever sold in that way; this is a characterization made by people unfamiliar with any aspect of vehicle integration and largely promulgated by critics of the system. The original proposal was simply for maximal reuse of Shuttle-derived systems and ground support equipment with the bare minimum of modification and requalification to maintain US spaceflight continuity while a next generation system was developed. It was not designed to be lowest operating cost, or highest throughput, or even particularly competitive, but just to get a fastest return-to-space for NASA operations in the interim. Instead, SLS has become an effort onto itself without any clear objectives or real need in the context of an overall program and no plan for a subsequent generation. I can’t really say anything in defense of what it has become other than this is problem that actually dates back to the Nixon Administration and the initiation of STS/Shuttle.
A “clean-sheet design” should not be a “next-gen Saturn V”; it is pretty clear that with modern mechanical design and structural materials a two stage to orbit vehicle an optimum balance of performance versus complexity, and frankly NASA should have been working on both a heavy lift and personnel space launch systems. But, of course, NASA doesn’t actually get to make those kinds of high level decisions; Congress defines the overall budget and designates the major programs (although the NASA Administrator has plenary authority to define specific funding line items) and Congress decreed that Constellation and then SLS would be the way forward after the failure of the X-33 program.
Stranger
Good, because there’s nothing else we should be spending money on, right?