Battle of the Heavyweight Rockets - SLS could face Exploration Class rival

[Greg Hullender]

I agree that SLS sure does seem to be a colossal mistake and a vast waste of money, but the inescapable truth is that it has flown and it has delivered a payload to the moon (or around it, to be picky). Starship is vastly cheaper, but it still hasn't gone anywhere yet. As long as there's some chance that Starship won't actually work, no one can credibly argue that SLS should be dumped.

Could Starship fail? After all, Falcon 9 worked spectacularly. But this is a whole new design with new materials, new fuels, a whole new landing system, etc. It might not work for years. If ever. Yeah, I'm hopeful that Elon will pull this off--as he so often does--but worry nags at me, and it will continue to do so until Starship actually flies and SpaceX successfully reuses both stages.

Once that happens then, yeah, I think it'll be pretty hard for anyone to justify the continued existence of SLS--politics or no politics.

[DanClemmensen]

I agree that SLS sure does seem to be a colossal mistake and a vast waste of money, but the inescapable truth is that it has flown and it has delivered a payload to the moon (or around it, to be picky). Starship is vastly cheaper, but it still hasn't gone anywhere yet. As long as there's some chance that Starship won't actually work, no one can credibly argue that SLS should be dumped.

Could Starship fail? After all, Falcon 9 worked spectacularly. But this is a whole new design with new materials, new fuels, a whole new landing system, etc. It might not work for years. If ever. Yeah, I'm hopeful that Elon will pull this off--as he so often does--but worry nags at me, and it will continue to do so until Starship actually flies and SpaceX successfully reuses both stages.

Once that happens then, yeah, I think it'll be pretty hard for anyone to justify the continued existence of SLS--politics or no politics.

SLS has flown once.  Starship has not flown. I think we need to wait until each has flown at least twice before we start making comparisons. based on actual flights.

[VSECOTSPE]

As long as there's some chance that Starship won't actually work, no one can credibly argue that SLS should be dumped.

Assuming it gets that far, NASA has reduced Orion/SLS to putting four astronauts into lunar orbit once every year or two for $4B+ to $8B+ and over 30K in careers with a probability of killing each crew that is in the same ballpark as STS.  Starship could magically disappear tomorrow, and the Artemis Program would still be better off pursuing more capable, higher cadence, lower cost, and safer lunar crew transport capabilities on different vehicles, and NASA better off deploying that huge workforce to higher priority exploration needs.  When it comes to HLVs and capsules (FH, NG, Vulcan, Dragon, Starliner, etc.) the US has an embarrassment of riches to build upon.

Starship won’t kill Orion/SLS.  Other, better alternatives have existed for nearly a decade and a half and have been equally ignored.  Only leadership waking up to the sober reality of just how much Orion/SLS limits and endangers Artemis and wastes the workforce will kill Orion/SLS.  And that may take an accident or budget meltdown, but Starship flights will have no impact.

[laszlo]

[T]he Artemis Program would still be better off ... deploying that huge workforce to higher priority exploration needs...

Except what other program needs workers trained in manufacturing huge segmented SRBs, large high-performance hydrolox engines, etc. ? The workforce is not interchangeable. While many could be retrained, it would require a major effort, and many would also have to be replaced.

This also begs the question of what  higher priority exploration needs have been identified for Artemis, especially ones that don't depend on SLS and are likely to be funded.

[VSECOTSPE]

Except what other program needs workers trained in manufacturing huge segmented SRBs, large high-performance hydrolox engines, etc. ? The workforce is not interchangeable. While many could be retrained, it would require a major effort, and many would also have to be replaced.

It won’t be one for one, but many of these knowledge and skill sets are not specific to SLS, STS-derived vehicles, or even launch vehicles.  Almost everything in aerospace involves building big steel or aluminum structures.  We need high-Isp hydrolox engines for in-space transit, not ETO launch.  We need EDL techniques for big landers at Mars, not Apollo capsule reruns.  Etc.

The govt should not be (very poorly) competing with industry in ETO launchers and capsules when industry is delivering those in spades.  The govt should be leveraging those capabilities, pocketing the savings, and applying it to more advanced and missing capabilities.  NASA should be the tip of the spear, not the haft.

This also begs the question of what  higher priority exploration needs have been identified for Artemis, especially ones that don't depend on SLS and are likely to be funded.

As constrained by Orion/SLS, Artemis is admittedly an anemic, sub-Apollo, Potemkin human lunar program.  It’s not going after ISRU, nuclear, etc. in any significant way partly because the bulk of its resources are going to the nation’s fifth HLV and third or fourth capsule.  Replacing the crew transport function allows Artemis to be redefined and fundamentally upgraded.

[deltaV]

As long as there's some chance that Starship won't actually work, no one can credibly argue that SLS should be dumped.

Starship and SLS aren't the only possible launchers. There are also Falcon Heavy, New Glenn, or possible three-core upgrades of Vulcan or Terran R. These launchers aren't quite as big as Starship and SLS but they all get a respectable 45+ tonnes to LEO (I'm guessing for the three-core upgrades). It's highly likely that if NASA invests a little money in two of these rockets at least one of them will work (even if you exclude Falcon Heavy because it has the same manufacturer as Starship). The Augustine report (https://www.nasa.gov/pdf/617036main_396093main_HSF_Cmte_FinalReport.pdf) estimated minimum mass to LEO per launch of 25 to 40 tonnes on page 65 and 40 to 60 tonnes on page 93 so these launchers are in the right ball park. I'd guess that a well designed human space flight program based on these smaller launchers would produce more and better exploration than the program of record for the same cost given the much lower cost of the launchers.

When NASA procures the second lunar lander we'll probably learn some examples of designs using these smaller launchers. Those designs won't include launching people from Earth of course but launching people using smaller launchers is well established e.g. with the commercial crew program.

Except what other program needs workers trained in manufacturing huge segmented SRBs, large high-performance hydrolox engines, etc. ? The workforce is not interchangeable. While many could be retrained, it would require a major effort, and many would also have to be replaced.

If huge segmented SRBs and large high-performance hydrolox engines were almost as good as the alternatives then retraining costs might be a legitimate reason to keep them around but experience with rockets such as shuttle, SLS, Delta IV, and Falcon suggest that SRBs and hydrolox are no where near competitive with reusable liquid rockets with easier to handle propellants.

Innovation usually requires retraining workers so you're basically arguing we shouldn't innovate. If humanity had followed that logic in the past we'd still be using horse-drawn wagons and elevators would have a human operator. Our society would be frozen in time and consequently much poorer than it is today. Retraining is annoying for the workers involved but is much better for society long term.

[Robotbeat]

I feel like SLS workers should feel insulted by people claiming they cannot be retrained or do anything else. Contributing to SLS looks good on the résumé even if many of us have reservations about the overall program’s wisdom. Working on any kind of Moon rocket, especially one that has launched stuff around the moon, is impressive. No rocket gets to orbit by accident or pure luck. They shouldn’t have difficulty going elsewhere. But more generally:

A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
—Robert A. Heinlein