The Constellation Program [1] that preceded SLS had two vehicles - Ares I for ISS crew and supplies after Shuttle was retired, and Ares V for occupying the moon. The missions gave some justification for needing vehicles. Their design was primarily a means to preserve existing contracts and jobs. Additional wheel greasing made it happen.
That stuff about re-using parts to reduce risk is just what people say because it sounds good, but isn't inherently true. Kind of like how "drug delivery" and "machine learning application" are go-to pseudo-justifications for many research proposals.
Constellation was eventually canceled when ISS resupply went to the Commercial Crew Program [2]. Ares V was stripped down and reimagined as the mission-less SLS. SLS is not really intended to do much more than exist for the time being.
There are a lot of factors that will go into canceling SLS - infighting between NASA centers, preserving jobs and contracts with Old Space companies, even more wheel greasing. I'm interested to see how it plays out.
(Generally speaking. Maybe some of this is less of a factor or more depending on the system... point is you can’t say up front that old hardware is a good idea)
There's a lot of pressure to include hand-wavy references to "heritage hardware" in the risk assessments for various reasons, but it's not well-substantiated where it exists.
Combine this with incumbents looking to keep new entrants out of the market and heritage, and reuse become the operative words
The F1 and SSME are apples and oranges. They have separate uses and achievements for their times. I haven't heard of either being widely considered objectively superior to the other.
Shuttle size was dictated by intended cargo and maneuvers, so it's not really possible to say how changing size would affect it since you'd have completely different design constraints and objectives.
[1] https://ntrs.nasa.gov/citations/20150002964
[2] https://www.nasa.gov/pdf/293261main_62868main_1_pmchallenge_...
From another article on that website: "The RS-25 is still considered to be about the best engine ever made with a fairly high thrust to weight ratio and unmatched efficiency." [1]
Too big, too expensive, too low flight rate. These all problems contribute to each other.
Also, large solid rockets are very troublesome. They can not be fueled on the pad, so they are heavy and dangerous from casting to stacking to launch. There will never be a high launch rate reusable rocket with solids.
And a low flight rate was also a given. Delta IV Heavy only files about once every 18 months, there's insignificant demand for anything even bigger. That was why NASA decided they had to do this themselves, because it would be insane for any commercial company to build a rocket without a market.
And expensive was also part of the plan, you can't spread enough pork to make it unkillable if it isn't expensive.
Big, expensive, low flight rate. Those weren't problems, they were requirements.
Very different thing, and you actually demonstrate those points.
Everything starts with the misplaced thought that it needs to be so big. Not actually required.
Probably correct thought that it needs to be NASA-made since it wouldn't make sense commercially, but this is a consequence of misplaced thought 1.
Expensive to spend pork. Again, not needed for the mission, if something more sensible was chosen in the first place.
There could have been a capsule flying on Atlas V for many years already. The ESAS study just had all kind of really bad assumptions that made Ares happen instead.
It's an interesting alternate reality to imagine: we might have had a more interesting moon program that had the ability to naturally scale to larger and larger missions, instead of repeating basically the same thing until the public gets bored and cancels it.
We now have 54 years of repeated low earth orbit dockings so maybe the architecture designs could start taking that into account.
Even SpaceX is planning on doing orbital refueling.
Big was political. It was a requirement added because SLS could provide it, not because it was needed. It was there to stop the order-of-magnitude cheaper per pound smaller launchers from being proposed instead.
Part of all this was strong arm twisting from the politicians involved to stop all work on in-space propellant transfer and propellant depots (because with them, you might as well launch lots of smaller cheaper launchers to carry up the propellant.)
If you believe humanity has a future in space, then you must believe it's possible to do much better than SLS. So do that, not waste time on a pointless and hideously expensive diversion.
> It was also designed ultra-conservatively using mostly existing designs so there was no technical risk.
Politicians can't design a rocket and cannot get what is "ultra-conservative". Rockets are not Lego blocks that you can just mix and match. They're explicitly designed a certain way to support a certain load profile. Even if the parts of the SLS _look_ like they have low risk, they do not and that's why the vehicle has taken so long to develop.
One example, if the shuttle boosters were could actually have been used directly they wouldn't have needed to extend the number of segments from 4 to 5, redesign the liner between the segments, and completely redesign the nozzle. It's a new booster.
Second example, even though the shuttle external tank looks like it's being used, in previous iterations the shuttle external tank did not support any axial loads, it was simply held on to the bottom of the Orbiter. Now the external tank has to withstand the entire axial load of the rocket so it's basically redesigned from scratch.
What would have been a more conservative design? Reusing the Apollo design was considered and discarded because so much knowledge and tooling had been lost that it was considered to be less conservative than the SLS design.
The SSME was selected for the SLS (and Ares V before it) because it had twice the burn hours of the F-1 and the SRBs existed and were a known quantity. The SLS (and Ares V) can reuse more of the Shuttle's infrastructure than an F-1 based design. The SRBs allow for use of smaller first stage tankage and the less powerful SSMEs which allow for reusing Shuttle launchpads which replaced the Saturn launchpads at LC-39.
While the SLS is moving into boondoggle territory the Ares V and SLS designs made economic sense to reuse Shuttle designs and infrastructure. It didn't have anything to do with the myth of lost engineering knowledge.
> Ares V and SLS designs made economic sense to reuse Shuttle designs and infrastructure
Theoretically made economic sense.
* An unbelievable amount of scientific data about biology and microgravity comes from the ISS. To say this is “aimless” only is true if you believe humans will always live on Earth and only Earth.
* A wealth of fundamental knowledge about the universe comes from spaced based telescopes. These are helping us understand the laws of nature, some of the most raw R&D.
* There are significant military applications to our space program. These range from GPS, surveillance, communications, and potentially weapons. There are some government space launches that we know very little about their mission because it is highly classified. The Space Shuttle had a use case for rapid troop deployment. There is significant military applications to the engineering knowledge of rockets. The difference between a rocket and a missile is mostly the application.
* Our exploration of our solar system provides possible future avenue for economic development. There is more fresh water, raw minerals, and energy inside our solar system but outside of Earth than there is water, mineral wealth, and energy on Earth. Certain things we consume are non-renewable, and we will need to find sources for them outside of Earth.
* It gives hope, inspires young people to become engineers and scientists, and gives us a feeling of awe as we go through the process of understanding our existence in the context of the cosmos.
EDIT: This isn’t to say there is major bloat inside the space program, and that NASA is not in need of a significant culture change.
The space shuttle could also only land at a handful of runways on the planet.
The shuttle did have a military requirement: the air force wanted to be able to launch into an orbit over the south pole, then up across Russia from the south, to return and land after that single orbit. That pretty much forced the use of wings that could glide, vs capsule style re-entry, and opened the path to most of the shuttle's design flaws.
As for why the air force wanted this, the presumption is surveillance, but I don't think they've ever officially answered, other than denying that they ever considered a bomber mission for the shuttle.
On the other hand Soviets were reportedly scared to death of shuttle starting on a "normal" mission only to use it's wings and heat shield to dip into the atmosphere and change it's inclination, so that the new orbit passes directly over Moscow, from an unexpected angle. Then it would drop a 20 ton worth of RVs with nukes in a decapitation strike without any warning.
It is estimated that this is one of the reasons why the Energie & Buran program were started - they also wanted part of the "fun".
I think the actual shuttle had a life support capability for like 7 people. Not sure of the actual flight crew requirement, there's probably room for like 3-4 other guys. It can land on a runway, but it's gotta be really long, and there's only one shot, and it'll be really obvious and has no ability to evade defenses. No chance of it landing in Moscow unless the Russians let it. And then you'd be in the middle of a huge military base or something, and what are 4 guys going to do except be killed or captured immediately.
Maybe they could get there in an hour. From a specific launch pad in Florida, and if the shuttle is all set up to launch, which takes months. And it'll be blindingly obvious to everyone in the world that something just launched heading straight at Moscow.
It's interesting looking at the military and space, since the military seems to be more objective focused than NASA. Early on (1960's), the military was planning on a manned station (MOL), but ended up going with automated satellites in the end because they made more sense. Likewise the Space Force believes it might eventually send up astronauts, but doesn't think that will happen for decades. They're interested in sending people up when it's useful to do so, not just sending them up for the sake of sending them up.
"Microgravity research" is entirely pointless. A total waste of time. It's an excuse to stay on the ISS, that is all. There would have to be a thousand problems solved with fundamental human biology for us to live in microgravity, some of which are at the genetic level. Alternatively, and much more simply, we could use rotating space stations to simulate gravity. That requires just a few dozen engineering problems to be solved, none of which are fundamental. Admitting that the problem was "solved" in the 1960s would remove the excuse to keep sending people to the ISS, cut NASA's budget, and retrench a bunch of bureaucrats. So of course, NASA management is carefully ignoring the simple solution so that they can keep receiving funding for solving the difficult problems.
"Space telescopes" are fantastic! We need more of them! But NASA keeps blowing their budget on the aforementioned waste of time microgravity research they're doing on the ISS instead of the much more scientifically useful telescopes. Many have been cancelled or delayed. Remind me, where's the James Webb space telescope again? Oh yeah... on the ground, that's where.
"Military applications" are not a good thing. "Every gun that is made, every warship launched, every rocket fired signifies, in the final sense, a theft from those who hunger and are not fed, those who are cold and are not clothed."
"Resources in space" is commonly trotted out, but first consider that your argument for the militarisation of space is directly contrary to an argument that space has resources. Military spending, as the quote above by Eisenhower points out, is wasting resources that could have gone towards productive uses. But even ignoring that, the problem with resources in space is the ludicrous cost of moving them to where we want to use them, which is here. Even if, say, we get costs down to $50 per pound of returned raw material, there's only a handful of metals that would make that worth the bother, none of which are abundant (or concentrated!) in sources outside the Earth.
My point is that all of these apologetics for space, or more accurately, for NASA's current approach are false.
We can spin space stations, there's no need for microgravity research.
There's no territory in space worth fighting over. No oil wells in the desert we need to bomb. Space doesn't need to be militarised.
There are no places outside the Earth where liquid water had concentrated minerals into worthwhile deposits. A trillion tons of gold is worthless if it's evenly spread out in a billion-trillion tons of rocky asteroids.
Nobody really wants to live in space. If you think that you do, I challenge you to move to a place much nicer than any place in the solar system for a year, like Bouvet Island. It's a barren island just off the coast of Antarctica. Live there for a year, come back and tell me you like it, or shut up about how it's the inevitable future the human race is yearning for.
PS: Meanwhile, SpaceX is doing all of the truly useful things that we need in space. We need a global satellite-based Internet service that isn't slow and expensive. That's astonishingly useful, right now, and isn't something NASA could ever deliver despite a much higher budget than SpaceX.
My understanding is that the problem with 'spin gravity' is that unless you are talking about enormous truly enormous space stations, then the human vestibular system becomes a major issue.
Plus, then there's the issue with ensuring that the station remains balanced, and the additional material strength requirements.
I don't think "spinning space stations" is quite as simple a solution.
While traversing between the two parts might be tricky, the craft could be divided into manned and unmanned part connected by cables, to reduce "traffic" between the two to a minimum.
I'm no space engineer, but even I can spot a huge number of problems with going with a cable-counterweight system.
https://www.nasa.gov/image-feature/sept-14-1966-gemini-xi-ar...
"On Sept. 14, 1966, the Gemini XI spacecraft is tethered to an Agena target vehicle. Gemini XI command pilot Charles "Pete" Conrad and pilot Dick Gordon are maneuvering their craft to keep the tether taut between the two. By firing their side thrusters to slowly rotate the combined spacecraft, they were able to use centrifugal force to generate about 0.00015 g of artificial gravity."
Why this is not being used now ? I guess because it was not seen as a priority for Apollo and followup (US) missions as they usually took just two weeks at a maximum. Health effects of microgravity have been also understood in more details & how they can be overcome for the short flight durations.
With the ISS & missions lasting half a year (and longer for some crews) artificial gravity would indeed be more useful, but hard to pull off for a big permanent installation like the ISS, that needs to maneuver to accept spacecraft while also providing reasonable microgravity environment for experiments.
No it didn't. The DoD didn't even want it before it even flew.
Very little of the things you talk about has much to do with the NASA Human Directorate and that is the many part of NASA that people dislike, and this is not just from the outside, even inside NASA this is well known.
Watch the talks by Dan Rasky.
Keeping much of it secret distorts the public impression of it, when we don't know of a substantial portion of the accomplishments.
If only that was so. Using a bunch of old tech in a new way does not actually lead to great success. The re-qualification of the RS-25 alone took years and cost 100s of millions. And that is without producing new ones.
So NASA & Congress designed a program that was unkillable. It greased too many wheels and lined too many pockets to make it easy to kill. It was also designed ultra-conservatively using mostly existing designs so there was no technical risk.
So now when we complain that it's a pork-filled boondoggle that's impossible to kill, that was the plan, and there was a certain logic behind it. It makes no sense in a world with Falcon Heavy, Starship & New Glenn, but who would have predicted that with confidence in 2010?