Why didn’t Nasa cluster four solid fuel shuttle boosters around an Atlas V booster. The thrust would be substantially more than that of the SLS, with no fueling problem on the launch pad. It would be much less expensive and if using old technology anyway, why not develop new technology while building a base on the Moon which should have been done decades ago?
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1$\begingroup$ Part of the answer will be about human rating, see e.g. this question and its answers and this other answer. I also doubt your design would meet the mission requirements for SLS, even if you did figure out a way to mount Shuttle SRBs to an Atlas core. Nonetheless, welcome to the site $\endgroup$– Erin AnneCommented Nov 19, 2022 at 21:00
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2$\begingroup$ oh also the title should align with the body of the question. Sorry for missing that; it's what I get for coming in from the review queue instead of the front page $\endgroup$– Erin AnneCommented Nov 19, 2022 at 23:00
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$\begingroup$ So if human rating is a problem with Atlas V, why not change the question to 4 solid fuel boosters around the existing SLS core that already uses new tchnology ? The fueling problems seem now solved. $\endgroup$– CornelisCommented Nov 20, 2022 at 11:53
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$\begingroup$ According to this article, fool.com/investing/2021/12/20/… new SLS boosters will cost more than $290 million. $\endgroup$– CornelisCommented Nov 20, 2022 at 15:04
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2 Answers
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The difficulty is that rockets are not made of Lego, you can't just bolt on an extra couple of rocket motors and expect nothing to change. It would be a bit like trying to bolt on an extra set of wheels to a car.
SpaceX found it far more difficult than they had at first thought to create the Falcon Heavy from three Falcon 9's. The inner core section had to be considerably modified to allow for the greatly increased thrust and the same would be true for SLS. It would effectively be a different rocket although it might look similar.
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$\begingroup$ Although starship development feels like Lego sometimes. $\endgroup$ Commented Nov 22, 2022 at 13:30
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1$\begingroup$ Yes! Ha - development the SpaceX way is move quickly and break things, find out what's broken, fix it then rinse and repeat quickly. Spectacular development with plenty of explosions thrown in. $\endgroup$– SlartyCommented Nov 22, 2022 at 17:17
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Yet another “why don’t we just graft X to Y?” notion.
You don’t work in systems engineering… or validation/compliance, flight-like testing, safety/quality, project management (scheduling/budgeting), etc.
https://www.incose.org/systems-engineering
Changing one part of a complex, slim-margin, high-consequence AND high-dollar system results in: a new system, with new risks, failure modes, effects chains, and thus verification schedule… and thus verification cost.
“ It would be much less expensive ”
No, it wouldn’t.
“ why not develop new technology “
??? Why develop new technology??? Do you think the question is its own answer- circular logic?
“ while building a base on the moon which should have been done decades ago?”
For what- is this another ill-posed question, let alone a circular question? Are you not aware of chondrites versus differentiation?
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$\begingroup$ According to this article, fool.com/investing/2021/12/20/… Falcon Heavy rockets could make it much less expensive. $\endgroup$– CornelisCommented Nov 20, 2022 at 15:24
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1$\begingroup$ @Cornelis Except that FH doesn't have the payload capacity required for Artemis, especially the fairing diameter is too small. You'd also need several max load (so no booster reuse) launches of FH to achieve the equivalent in mass in orbit to a single SLS launch, negating any cost benefit with way higher complexity for the operation (and thus risk). $\endgroup$– jwentingCommented Nov 21, 2022 at 13:25
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2$\begingroup$ @Cornelis reading the linked article it is clear that they are no rocket engineers "on paper NASA could build a 40% more powerful SLS -- and spend half as much on its boosters -- by discarding Northrop Grumman's contribution and strapping a pair of SpaceX Falcon Heavies to the SLS core stage instead" is laughable. The key things to remember about SLS are that it is a political beast and at 1-4 billion a shot (depending on how you calculate it) has nothing to do with making anything less expensive and everything to do with maintaining jobs to the aerospace industry. $\endgroup$– SlartyCommented Nov 22, 2022 at 12:46
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1$\begingroup$ @Cornelis Falcon Heavy has a nominal payload capacity of 70 tons vs. SLS 95 tons. And the fairing can be enlarged pretty cheaply. If FH can only fit 50 tons in a large fairing thats still only two FH launches at \$300M total to replace a single \$3B SLS launch (not including Orion). And FH is likely lower risk than SLS, given SpaceX has 150+ launch streak, can likely launch FHs every week (2 planned for January). SLS can only launch once per year and hydrolox booster launches have lots of problems and delays. In orbit assembly is easily doable, but was rejected for Artemis to justify the SLS. $\endgroup$ Commented Nov 24, 2022 at 1:21