WI: SLS is Sidemount?

After the election of Obama in 2008, it was apparent that the then-major program of NASA, Project Constellation, was not long for the world. Essentially the response of President Bush to the Space Shuttle Columbia disaster, it had become bogged down in ballooning cost estimates and insufficient funding, with all of the major development programs being more or less disasters, and was, of course, a Bush initiative and thus not especially popular with the incoming President. After assembling a blue ribbon commission, as is traditional, Obama went ahead and cancelled the program without really planning for a replacement program of similar scale.

Congress, however, didn't like this, mostly because with the Shuttle winding down and Constellation cancelled a lot of Shuttle-related facilities would also be closing down in the near future, reducing the flow of dollars to their districts. They therefore pushed the administration, which was not really inclined to fight them very much, to begin a new major development program "based on Shuttle" to rectify some of the issues identified with Constellation, which became SLS. Although there were some studies feinting at alternative designs for SLS, there were really only two contenders that had any chance, both of which were essentially versions of the same Shuttle-derived vehicles that had been looked at since the 1970s. One, which was the one we got, took the basic components of the Shuttle design and rearranged them to create an "inline" vehicle, more similar architecturally to other launch vehicles. The other was basically a rehash of Shuttle-C and envisioned instead largely reusing the Shuttle design except with a disposable cargo pod in place of the Orbiter, and was called sidemount.

As I said, we got the first. But from several points of view, the second offers a number of advantages over the SLS we got, mainly because of being even more shuttle-derived. In the first place, it easily covers the Congressional desire to maintain jobs given that Michoud would still be producing external tanks, ATK would still be producing solid rocket boosters, and new jobs would be needed building the cargo pods, not to mention Orion capsules, iCPS upper stages, and other payloads and equipment. Somewhat fewer new jobs would be created, perhaps, since less new infrastructure and equipment throughout the supply chain would be needed, but by the same token costs would also likely be less. The smaller number of changes would also make it more likely that sidemount could get into service in a reasonable period of time than our SLS has proved capable of doing, making it more likely to actually be able to fly missions. The main downside is that growth options were somewhat more complex, but not nonexistent; the main study on the concept proposed that increasing SSME thrust (since they would only be used once, and so could be run at levels that would be incompatible with reuse), stretching the external tank, and perhaps adding five-segment boosters would allow for considerably increased payloads to low Earth orbit, reasonably comparable to OTL's SLS.

Thus, it seems that NASA and Congress embracing (or "embracing") sidemount was reasonable and plausible. What would the consequences have been if, to wave hands a little bit, they had done so? Would SLS have flown by now, with or without Orion? What impact would a somewhat accelerated (and possibly cheaper?) SLS have had on other plans (Artemis...)?
 
SLS wasn't serious to actually do anything, beyond pork to congressional districts, no matter where the pod or capsule would mount
Senate Launch System, indeed
 
SLS wasn't serious to actually do anything, beyond pork to congressional districts, no matter where the pod or capsule would mount
Senate Launch System, indeed
This is a simplistic answer at best. Yes, the primary Congressional interest was in maintaining jobs, as I foregrounded in my post by specifically mentioning this as their primary interest and then listing the preservation of jobs as the first justification for going with sidemount (since it would require many of the same supply chains as Shuttle). But they had to at least pretend that it was going to launch (originally by 2015...), and once it did get close to launching NASA and Congress did have to figure out something to do with it, which turned out to be Artemis. Those are not completely ignorable effects, especially since even with the inevitable Congressional interference and inevitable schedule delays a sidemount SLS would be considerably more likely to have actually flown by now than our SLS.
 
I think SDHLV would be ready to go, if not by 2016, then by 2017--an unmanned test flight either in 2016 or during Trump's first year in office. This might light a fire under the Orion program office to get that spacecraft ready by 2017--since now there's actually a reason to have it ready. If Commercial Crew is as underfunded and delayed as IOTL, that could lead to the (for SpaceX, mildly embarassing) case of a crew flying on Orion before Crew Dragon is ready.
What else to do with SDHLV once it's ready? Until and unless funding for a lander materializes, something like Gateway or circumlunar flights are basically all it can handle. One can imagine a lander made from partially off-the-shelf hardware that can accelerate it--crasher stages derived from existing systems, for example. But the timing largely depends on Trump/Pence/Space Council lighting a fire under it--and since the OTL 2024 landing goal wasn't announced until 2019, I'm a bit skeptical that it was a high priority for Trump. But, who knows? If it flies in 2017 and he gives a speech taking the credit ("We've Made Space Great Again!"), he might take a shine to it.
 
I think SDHLV would be ready to go, if not by 2016, then by 2017--an unmanned test flight either in 2016 or during Trump's first year in office. This might light a fire under the Orion program office to get that spacecraft ready by 2017--since now there's actually a reason to have it ready. If Commercial Crew is as underfunded and delayed as IOTL, that could lead to the (for SpaceX, mildly embarassing) case of a crew flying on Orion before Crew Dragon is ready.
I had thought that it might fly in 2018 or 2019, but probably in an uncrewed mode similar to EFT-1, with a crewed flight following in 2020 or 2021. Actually, it may end up replacing EFT-1, since if the SLS program is going relatively well it may seem less useful or necessary to test Orion in a one-off flight instead of waiting and achieving the same goals while also testing SLS itself.

I do agree that it's unlikely any lunar flights will occur, but I do expect that plans for landers will be sped up somewhat, if only so that Congress can continue the gravy train by actually having some mission for SLS and Orion to carry out. More in the vein of issuing study contracts a year or two earlier than in improvising something with crasher stages, though.
 
Does the sidemount SLS have to worry about the external tank/main stage shedding foam and such? I'm sure the Orion's heat shield would not be exposed but there might be other important bits exposed.
 
Does the sidemount SLS have to worry about the external tank/main stage shedding foam and such? I'm sure the Orion's heat shield would not be exposed but there might be other important bits exposed.
Sort of, but not really. None of the bits that would be exposed would be intended to come back, so the effect of foam shedding would be far less serious than with the Shuttle. The sidemount was intended to provide an aeroshell around the payload that would protect sensitive bits from falling foam (especially since given the time period they would be aware of the threat and take steps to mitigate it).
 
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I had the thought that maybe the asteroid-redirect or visit mission might be closer to fruition when it's inevitably canceled.
 
Thus, it seems that NASA and Congress embracing (or "embracing") sidemount was reasonable and plausible. What would the consequences have been if, to wave hands a little bit, they had done so? Would SLS have flown by now, with or without Orion? What impact would a somewhat accelerated (and possibly cheaper?) SLS have had on other plans (Artemis...)?

I have to wonder what they'd be launching on such a vehicle. The sidemount option the Augustine Commission examined could put 71 tonnes into LEO in its most basic configuration. 83 tonnes with an appropriate upper stage. More than an Orion needs. Is the US going back to the moon or adding a major addition to the ISS? Launching a large space telescope?

fasquardon
 
I have to wonder what they'd be launching on such a vehicle. The sidemount option the Augustine Commission examined could put 71 tonnes into LEO in its most basic configuration. 83 tonnes with an appropriate upper stage. More than an Orion needs. Is the US going back to the moon or adding a major addition to the ISS? Launching a large space telescope?

fasquardon
It was the SLS, so it would be doing SLS missions. In this case, they would probably be launching Orion around the Moon, in circumlunar missions like Artemis 1 and 2 are planned to be. Even under Obama NASA was planning on going into lunar orbit, it just wasn't planning on landing on the Moon, and it's unlikely that even sidemount would be ready on the original schedule.

Theoretically you could launch it to ISS as a crew rotation and logistics vehicle (stuff a Cygnus under it or something...), which was sort of proposed as an option for our SLS as well, but was more or less dropped because it was too expensive. Probably the same would be true ITTL as well, with the option quietly dropped as commercial crew proceeds and it becomes apparent that SLS will be too expensive to use routinely.
 
I was a big fan of DIRECT back in the day, so let's see what I can remember. Though there are clearly people on here a lot more knowledgeable about this than me.

IIRC, sidemount only really makes sense when you're flying the shuttle at the same time; on its own all the compromises (payload diameter is a big one) don't really make sense. As for being any cheaper, I'm not sure. By the time Obama is inaugurated the Ares I and V have been in development for about five years; stuff is far along enough that cancelling it won't save you much time or money. The five-segment booster is going to have its first static fire in September 2009; so the sidemount launcher will end up having to use it. At which point you might as well stretch the tank to take advantage of it, etc. None of the political forces have changed. You just end up with the same SLS, only different.

I think the only way a post-shuttle launcher would be developed in any reasonable amount of time is to have it far enough in development by the time Obama takes power that switching to something else won't make sense. If they picked the Jupiter 130/246 right out of the gate in 2004 that might do it; although there's probably less than a 50/50 chance the Jupiter Upper Stage (Ganymede?) ever gets developed.
 
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