I read in this article that NASA is building its own rocket for the moon mission.

Why would they build their outdated and inefficient rocket, when they could instead use a SpaceX rocket and use their time to help with that production or do other stuff?

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    $\begingroup$ A cynic would say: Because it keeps thousands of people employed and help spending billions of taxpayers money. $\endgroup$ Commented Mar 15, 2020 at 21:29
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    $\begingroup$ I'm not sure how cynical that actually is, keeping people working in high-tech industries isn't necessarily a terrible thing. $\endgroup$
    – GdD
    Commented Mar 15, 2020 at 21:31
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    $\begingroup$ It would be interesting to describe the main technical milestones SpaceX should reach to be ready to fly people to Moon. I think most people would be surprised how much should be done yet. $\endgroup$
    – Heopps
    Commented Mar 16, 2020 at 13:14
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    $\begingroup$ @GdD it would be a bad thing to occupy and pay people to do something ultimately pointless, especially if these people have high-tech skills that could be more useful elsewhere. (Which is not to say SLS is pointless.) $\endgroup$ Commented Mar 16, 2020 at 16:23
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    $\begingroup$ @DavidsaysReinstateMonica: It's an expendable hydrolox sustainer using RS-25 engines salvaged from the Shuttles and Shuttle-derived SRBs lengthened by one segment. It's using repurposed and modified Shuttle components wherever possible, with the stated intention of reducing cost and development risk by doing so (the real-world results being rather different). It doesn't develop any new technologies or advance the state of the art (it is actually a regression, being fully expendable), it just lifts a lot of mass at exorbitant cost and with a very limited flight rate. $\endgroup$ Commented Mar 16, 2020 at 22:10

4 Answers 4


In the defense of NASA, SpaceX does not per se have an operational vehicle for the purposes they want to use SLS. (Yet, Starship is coming)

However, missions to the moon using Falcon Heavy vehicles have been proposed by Bob Zubrin.

Once SpaceX has an actual flying Starship/Super Heavy I think the situation will change.

Ultimately the SLS program is about keeping some of the jobs from the Shuttle program (20,000+) continuing on the SLS project. Be nice to actually launch once, but that may not be critical path to success. (This is my opinion, and cynical)

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    $\begingroup$ "All the jobs from the Shuttle program" is factually incorrect. Less than 25% of my shuttle colleagues still work on NASA programs. $\endgroup$ Commented Mar 15, 2020 at 20:23
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    $\begingroup$ I don't know if this is factually correct, but a strong motivator for maintaining the SLS program could be that the contractors involved (Thiokol, Boeing, etc.) are also doing major defense work (strategic missile systems, spy satellites, etc.) and the NASA work keeps them comfortably in business on all the shared technologies. There is also the pork barrel factor. $\endgroup$
    – Anthony X
    Commented Mar 15, 2020 at 21:39
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    $\begingroup$ +1 for a sourced answer :-) $\endgroup$
    – uhoh
    Commented Mar 16, 2020 at 0:39
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    $\begingroup$ SLS is also not yet an operational vehicle. It may not even become operational before Starship. $\endgroup$ Commented Mar 16, 2020 at 3:09
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    $\begingroup$ @mothman while I generally agree with you, Falcon 9 is theoretically going to launch humans in the next couple months, so I hope it is human certified. $\endgroup$ Commented Mar 16, 2020 at 13:06

Because there are no super heavy-lift launch vehicles flying right now. In fact, simply by existing, SLS will be the most up-to-date and the most efficient super heavy-lift launch vehicle since the Saturn V (Shuttle is debatable). Super heavy-lift launch vehicle, Proposed designs

When looking at current SpaceX rockets, the Falcon Heavy are human certified. With a commercial crew, the Atlas V will be certified to launch Starliner, and the Falcon 9 the Dragon 2 capsule. US ready for human spaceflight launch by 2018

Neither capsule can provide for a human crew for deep space travel, to the moon or to Mars. For that, they would have to use Orion, a 26.5 MT vehicle that is tested and ready to go. Neither the Falcon 9 or Falcon Heavy can put 26 MT to TLI. If they were to develop a human certified variant of the Falcon Heavy, then they may be able to do so (after years of additional qualification and testing). Elon Musk has stated he has no plans to develop the Falcon Heavy for crew. SpaceX no longer planning crewed missions on Falcon Heavy

So all current SpaceX launch vehicles are out of the running.

Now, we can talk about Starship. Starship has no launch abort system. Without one, I can very confidently say it will never launch NASA crew. It has no flight hardware, and with two consecutive explosive tank failures, is not as far along as people imagine in their heads. Compared to Artemis 1 hardware, it is incredibly unwise to believe that Starship will launch crew before SLS. Hardware for the first three Artemis missions

Then we can imagine fairy tales where the lovely Starship massively outperforms SLS because of NASA/Boeing's gross incompetence (of which there is a lot). Why not New Glenn? Long March? Etc. Why does SpaceX have to be the contractor, Starship the vehicle, or the US the country?

This question could be edited to produce non-biased answers more openly and start better conversations. The top level question "why is NASA using its own rocket ... Could use SpaceX?" is fine. The detailed one with "outdated" and "use their time to help production" is problematic.

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    $\begingroup$ Can you define "Most efficient" please? By what metric? The current cost/lb is entirely unsustainable. Even if you throw away all the decades of development costs (And we already threw away Shuttle derived technologies development costs) and just go with suggested manufacturing costs, it would be next to impossible to sustain an actual program with the SLS booster at its current costs. $\endgroup$
    – geoffc
    Commented Mar 16, 2020 at 12:23
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    $\begingroup$ The first part of this answer is good. The second part is an unnecessary rant, sadly. You do have good points but there's no need for the bashing, IMHO, especially not the OP/question. People ask questions here to get educated, insulting them for asking is helping nobody. $\endgroup$
    – DarkDust
    Commented Mar 16, 2020 at 12:43
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    $\begingroup$ “Starship has no launch abort system. Without one, I can very confidently say it will never launch NASA crew.” — Is that supposed to be evident because NASA never launched astronauts on a vehicle without abort system? $\endgroup$ Commented Mar 16, 2020 at 13:46
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    $\begingroup$ Among the many errors in this answer: Falcon 9 is crew-certified. Orion is not "tested and ready to go": the first test flight of the complete Orion is currently scheduled for mid to late 2021. Crew Dragon has already done its test flight to the ISS and will fly crew there in a few months. Crew Dragon would be fully capable of lunar missions if paired with a service module to provide extended life support...Orion is not needed for the moon (and not sufficient for Mars). However, if you did use Orion, Earth orbit rendezvous with a departure stage could be used to put it into TLI. $\endgroup$ Commented Mar 16, 2020 at 14:14
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    $\begingroup$ SpaceX has scheduled the first astronaut mission for May. As far as I know, Falcon 9 Block 5 has already been human-rated, and has flown the requisite number of flights to get NASA's sign-off. What was missing was human rating the Dragon 2, which was finally done with the last launch abort test. NASA has signed off on the full stack now, and the first human flight has been scheduled. So I'm not sure where your info comes from. Perhaps an outdated web page? $\endgroup$
    – Dan Hanson
    Commented Mar 16, 2020 at 19:12

SLS has been in development for a long time, although it suffers from political winds quite a bit. It started in its current form in 2011, when there was no other system in existence that even was close. Falcon Heavy was a concept then, but it would have only been slightly better than Delta IV Heavy, still nothing compared to SLS. They considered other alternatives, but determined that the best thing was to just create their own heavy launch vehicle, and not do a heavy piecemealed approach that was proposed by some.

It's easy to say with at least 3 heavy-lift, and one super-heavy lift, vehicle in development or recently launched that it seems silly to consider any other idea. The fact remains, only Starship is as capable as SLS is theoretically, and only then if you can get it to refill on orbit, otherwise you are better off using SLS. Starship will probably surpass SLS eventually, but it is still a concept. Remember that in 2011, Falcon Heavy was supposed to launch in 2013, and didn't launch until 2018.

Another thing of some consideration is that Orion can't actually launch on a Falcon Heavy directly to the Moon. It's easy to say that you could do two launches, and with some work, it probably could be done to get the payload to the Moon, but in the current form, it just isn't quite workable.

NASA needs to push something forward, and the political winds have dictated using SLS as the rocket of choice. It does make sense for now, but will make much less sense once Starship is launching regularly.

Bottom line: In theory Falcon Heavy, or New Glenn could be used to fulfill SLS's mission, but they are still not quite as capable as SLS, so a complete redesign of the architecture would be required to use one of these rockets. And unless both of them was available, then NASA needs to have their own system to have some means of redundancy.

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    $\begingroup$ The conclusion that "otherwise you are better off using SLS" assumes that large payloads are the only way to solve the problem. The Shuttle could only lift 16 t payloads no more than 4.6 m in diameter, and that was enough to build the ISS. The most recent module attached to the ISS is 4 m long and 3.2 m in diameter, and was launched in a Cargo Dragon's trunk. Yes, distributed launch will increase the cost of building and assembling the components, but for the price of one SLS Block 1 launch putting 95 t into LEO, you could instead launch 21 Falcon Heavies for a total of 1200 t. $\endgroup$ Commented Mar 17, 2020 at 16:01
  • $\begingroup$ @ChristopherJamesHuff Sure, but the architecture that NASA has been using does not allow for distributed launch. Falcon Heavy can't even get Orion to the Moon in its full configuration theoretically, unless some of the fuel from Orion is used. Also, the cost for a single SLS launch is varied, but may be as low as \$1 billion. An expendable Falcon Heavy launch for NASA would probably cost \$200 million. 21 Falcon Heavy launches for a single SLS is absolutely not realistic. $\endgroup$
    – PearsonArtPhoto
    Commented Mar 17, 2020 at 16:48
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    $\begingroup$ Your \$1 billion per launch for SLS is far too low. The OMB estimates over \$2 billion per launch (page 7: whitehouse.gov/wp-content/uploads/2019/10/…). SpaceX offered a Falcon Heavy launch with partial reuse and 90% of the maximum payload for \$95M in 2018. In reality, the \$2 billion estimate is likely low (other estimates go a lot higher), and if you're committing to a large number of launches from SpaceX, you'll likely get better prices, so you'd probably do better than 21 Falcon Heavy launches. $\endgroup$ Commented Mar 17, 2020 at 17:12
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    $\begingroup$ The "overall architecture" at present consists of the Orion and SLS, neither of which will be fully operational for another 4 years at least (Artemis 3 would actually be the first Orion to fly with a final propulsion and docking system). All other components exist only as rough outlines specifying the general capabilities to companies making proposals. There is no compelling technical reason to complete Orion and build an architecture around it if it requires a launch system that is so much more expensive than the alternatives. $\endgroup$ Commented Mar 17, 2020 at 19:04
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    $\begingroup$ Falcon 9 and Heavy have been launching for years, and will launch crew on a Dragon within a few months. The Crew Dragon is actually ready now, only some parachute tests with new-manufacture parachutes remain (tests have already been done with reused parachutes). Developing a service module to make Dragon capable of cislunar missions based on LEO assembly is no major task in comparison to developing all the other elements involved in actually landing people on the moon, and those elements could be made safer and more capable with the extra lift capacity this would allow. $\endgroup$ Commented Mar 18, 2020 at 3:35

Possible answer:

Another answer not yet explicitly listed could be: to limit the loss of-/build/maintain/expand their independence on other parties when it comes to launch technology (usage). For example, an agency might account for uncertainties in the availability of the technology provided by other parties, or contracts might be such that it becomes difficult/inefficient to continue development on the dependent technologies after use.


This is not saying nor suggesting that this is the case, merely stating that it might be a reason why an agency, such as for example NASA, could opt to develop their own rocket/launcher technology rather than use another, available one. A rationale, tending towards opposite, might be equally/more/less valid, where for long term availability of technology, an agency might want to stimulate other parties in their launcher technology development.


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