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The Saturn V rockets were the "tallest, heaviest, and most powerful rocket ever brought to operational status and still holds the record for heaviest payload launched and heaviest payload capacity to Low Earth orbit (LEO)"[1]

In A Short History of Nearly Everything, the author states the following:

We no longer possess a rocket powerful enough to send humans even as far as the Moon. The last rocket that could, Saturn 5, was retired years ago and has never been replaced.

In recent years, there has been on and off discussion about manned flights to go back to the Moon. Does NASA have plans for a rocket that will replace the deprecated Saturn V? Do modern (post-1972) advancements drastically change the design of the rocket NASA would use to get back to the Moon, or would it closely resemble the Saturn V design?

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The largest US rockets currently in practical development are the Falcon Heavy (aka Falcon 9 Heavy) and the NASA SLS Block 1.

NASA is likely to use the Falcon Heavy should SLS funding be cut; the SLS is subject to Congressional appropriations and executive budget decisions, neither of which could kill the Falcon project.

According to the Wikipedia entry, the SLS Block I is slated to have a 70,000kg lift to LEO, and an estimated in-service date of 2017. The Block II is supposed to life 129,000kg - higher than the Saturn V's 118,000kg.

The Falcon Heavy has a current design lift capacity of 53,000kg. and an estimated in service date of late 2014.

Discussion and Extrapolation

Elon Musk has noted that his goal is to get a colony off-Earth; he's also said the Falcon Heavy is not the endgame for SpaceX. It is likely that, in the event of a budget crisis canceling the SLS, SpaceX will upscale to a larger engine than the Merlin, but use the same basic pattern of design as the Falcon Heavy.

It's already noted by SpaceX sources that the goal is reusable stages; the Falcon Heavy is slated to use reusable 1st stage cores once the vertical landing system is perfected.

Given the rapid development pace of SpaceX, and the slower pace of SLS development, it's entirely possible that SpaceX will have a comparable lift option before the 2017 first service launch date slated for the SLS.

In the interim, NASA may need to make use of the Falcon Heavy; 3 Falcon Heavy launches should cost less than 1 SLS launch, and have another 20,000kg total capacity, some of which will be lost to interconnection equipment, for deep space capability.

Bottom Line

NASA Plans to use the SLS; Political & Budget considerations may require them to use the Falcon Heavy.


References

http://en.wikipedia.org/wiki/Comparison_of_orbital_launchers_families

SpaceX Falcon Heavy

http://www.buildtheenterprise.org/spacex-breaking-the-1000-per-pound-launch-cost-barrier
http://www.spacex.com/missions
http://www.spacex.com/falcon-heavy
http://en.wikipedia.org/wiki/Falcon_Heavy

SLS

http://en.wikipedia.org/wiki/Space_Launch_System
http://www.nasa.gov/audience/foreducators/rocketry/home/what-is-heavy-lift-launch-vehicle-k4.html
http://www.nasa.gov/exploration/systems/index.html#.Ufn5vWTwKzo
http://www.nasa.gov/exploration/systems/sls/index.html

Elon Musk's Mars plans

http://www.forbes.com/sites/alexknapp/2012/11/27/spacex-billionaire-elon-musk-wants-a-martian-colony-of-80000-people/
http://www.space.com/18596-mars-colony-spacex-elon-musk.html

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  • $\begingroup$ I would be interested in where you get a cost of 375 million for an SLS launch? Falcon Heavy has been quoted at 375 million for an SLS launch? Falcon Heavy has been quoted at 125 million, and of course that will likely grow as it actually gets to launching. But SLS is going to be very expensive, because of the standing army it requires, which must be paid, even if it does not launch. So current manifest has it launching close to once every 4 years. Which is of course ridiculous. But even so, no way is it going to be just 375M nor will the marginal cost be that low. Shuttles BEST case esti $\endgroup$ – geoffc Aug 1 '13 at 12:53
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    $\begingroup$ It's pulled from a source listed in the references. I find it incredulously low, as well, except that SLS is using entirely pre-extant lines. As for Falcon Heavy - SpaceX expects the price to DROP due to being so highly overlapping with the Falcon 9 and Falcon 9 VLS; further, the FH stage 1 components are expected to be reusable, as well, further dropping the Falcon costs. I did, however, just use the figures I found online for both. $\endgroup$ – aramis Aug 2 '13 at 8:58
  • $\begingroup$ Nice answer. You missed NASA's Commercial Crew Development program. I'll add that as an answer. $\endgroup$ – David Hammen Mar 8 '14 at 11:57
  • $\begingroup$ CCDev is unlikely to survive, and really, CCDev isn't developing a separate launcher; CCDev is JUST the capsules, with the various capsule programs selecting their own testbed launchers. Boeing is using the Atlas V, SpaceX the Falcon 9, etc. Eventual compatibility with the SLS Block II launcher is a goal. $\endgroup$ – aramis Mar 9 '14 at 7:57
  • $\begingroup$ "Falcon Heavy... estimated in-service date of late 2014" Ah, nostalgia. $\endgroup$ – smci Feb 13 '18 at 23:31
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NASA believes you need a large 70mT or 110mT rocket (SLS v1 and v2) to do that.

Direct 3.0 believes you can build such a rocket cheaper than SLS.

Pretty much anyone NOT involved in building shuttle components (and thus future SLS components) seems to think that fuel depots are the way to go.

You launch your translunar vehicle in orbit out of pieces. You build a fuel depot (It better be reusable more than one mission or you are wasting your time) and then you let any commercial launch vendor compete (and generate a market) for lots of flights as cheap as possible. And if any of the fuel/oxidizer launches fail, oh well. Launch again.

The days of the super large, single launch is probably long past.

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    $\begingroup$ It might be helpful to point to the economic benefits of smaller launches (production volume, faster progress up learning curves [for manufacturing cost, reliability, etc.], lower risk per launch), though that might be better for a separate question which could be linked here for further reading. Also I think fuel depot depends on relatively high traffic, so bigger/fewer could be faster (more politically attractive) but more expensive (less sustainable). $\endgroup$ – Paul A. Clayton Jul 16 '13 at 22:41
  • $\begingroup$ 130 tons rather than 110 tons for SLS Block II, isn't it? And there are benefits with being able to launch a couple of astronauts directly to the Moon together with their return vehicle. It's maybe old fashioned, but super heavy launch is the only way HSF beyond LEO has been done. And SpaceX is developing their "BFR" super heavy launcher too, aren't they? The Chinese seem to at least be talking about it. $\endgroup$ – LocalFluff Aug 9 '15 at 18:10
  • $\begingroup$ To build a fuel depot in orbit requires a storable fuel. LOX and LH2 could not be used, the boil off loses would be too high $\endgroup$ – Uwe Sep 19 '16 at 9:58
  • $\begingroup$ @Uwe Perhaps raises the question of whether it could be feasible/economical to build a solar or nuclear powered orbiting refrigeration plant. $\endgroup$ – Anthony X Feb 13 '18 at 19:22
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It is actually true that NASA, at the moment, does not have any way of transporting people into space. And lately, they are finding servicing their spacecrafts so expensive that they are involving private contractors to ferry goods from Earth to the ISS. I believe it is a possibility that NASA will hire private contractors for any manned missions, at least in the near future.

NASA has been exploiting SpaceX's services for a while now. SpaceX probably has the largest operational spaceship fleet in the US as of now. They recently used their Dragon for an official NASA resupply mission to the ISS.

A to some sources, SpaceX should be capable of manned missions by early 2015. Therefore, it could be a possibility that NASA uses SpaceX for their manned missions as well.

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In addition to NASA's in-house SLS (see aramis's answer), NASA is sinking a good deal of cash into its Commercial Crew Development (CCDev) program, \$1.5 billion between 2010 and 2014.

What is CCDev?

CCDev is essentially "son of COTS" (Commercial Orbital Transportation Services). COTS was a remarkably successful program. For a mere \$800 million, NASA has two new vehicles at its disposal for delivering cargo to the International Space Station. The goal of CCDev is to continue the spirit of the COTS program, but this time with a goal of putting humans into space.

The first phase of the project, CCDev1, involved \$49.8 million spread amongst five companies: Blue Origin, Boeing, Paragon, Sierra Nevada, and ULA. The second phase, CCDev2, involved \$315.5 million spread amongst four companies, three of which were in CCDev1. Those three were Blue Origin, Boeing, Paragon, and Sierra Nevada. SpaceX was also selected for CCDev2. The third phase, Commercial Crew integrated Capability (CCiCap) involved \$1167.5 million spread amongst only three companies: Boeing, Sierra Nevada, and SpaceX.

What's next?

The final part, Commercial Crew Transportation Capability (CCtCap) is expected to be even bigger. The FY14 budget for this final part is \$696 million (cut from a request of \$821 million). The first phase of this final part, CPC1, involved \$29.6 million, spread amongst the CCiCap contractors. How many of those three finalists will receive CCtCap is undetermined. (Note: Any company could submit a CCtCap proposal. However, the three companies that had collectively received over a billion have a huge leg up on any newcomers.) Rumor has it that CCtCap will involve two companies to foster competition, but budget concerns might make it one.

Who's building what?

Boeing is working with Bigelow Aerospace on a new capsule, the CST-100. The Boeing capsule is designed to be compatible with the Atlas V, Delta IV, and Falcon 9 launch vehicles. The initial work is targeting launch with the Atlas V.

Sierra Nevada is working on the Dream Chaser that Sierra Nevada acquired with it's purchase of SpaceDev. The Dream Chaser is the only lifting body left in the CCDev competition. Plans are to have it be launched on an Atlas V.

SpaceX has been working on outfitting its Dragon capsule with life support and making its Falcon 9 launch vehicle human rated.


Addendum (to address comments)

The end goal of CCDev has always been an end-to-end Crew Transportation System. The initial work focused on various parts of that ultimate goal, with most of the funding going toward the vehicles that will dock with the ISS and return to Earth. However, a small portion of the very first chunk CCDev money did go to United Launch Alliance to work toward making their launch vehicles human rated.

The RFP for the final phase of the CCDev program, CCtCap, was released in its final form in November 2013 with a submission deadline of January 22, 2014. All proposals had to be for an end-to-end Crew Transportation System with a manned demo mission in late 2017 (budget pending). The capsule or lifting body is but a part of that end-to-end system. The launch vehicle is another rather important part.

The goals of CCDev and SLS are largely orthogonal to one another. The primary goal of CCDev is to restore the ability of the US to send humans to the International Space Station (ISS) "and other low Earth orbit destinations". The primary goal of the SLS is to restore the ability of the US to send humans beyond low Earth orbit and eventually, outside of Earth orbit. CCDev is not intended to send humans beyond LEO; SLS is not intended to go to the ISS.

The launch vehicle proposed by a CCtCap bidder will not be the Space Launch System (SLS) vehicle. There is a backup plan to use SLS for human flights to the ISS, but only if CCDev fails.



General discussion on CCDev:
http://en.wikipedia.org/wiki/Commercial_Crew_Development
http://www.thespacereview.com/article/2370/1
http://www.thespacereview.com/article/2406/1
http://www.thespacereview.com/article/2443/1

Vehicles:

Boeing's CST-100: http://en.wikipedia.org/wiki/CST-100
Sierra Nevada's Dream Chaser: http://en.wikipedia.org/wiki/Dream_Chaser_(spacecraft)
Human-rated Atlas V: http://en.wikipedia.org/wiki/Atlas_V#Future_developments
SpaceX's Dragon and Falcon 9: http://en.wikipedia.org/wiki/Dragon_(spacecraft) and http://en.wikipedia.org/wiki/Falcon_9

CCtCap:

GSA solicitation page: https://www.fbo.gov/?s=opportunity&mode=form&id=e016cb01d032ec7468ca85035072a43c&tab=core&_cview=0 NAIS solicitation page: https://prod.nais.nasa.gov/cgibin/eps/sol.cgi?acqid=158768

SLS/MPCV:

SLS/MPCV as a backup to CCDev: http://www.nasa.gov/sites/default/files/files/Dumbacher_MPCVSLS_508.pdf, slide #10.
SLS as a backup to CCDev: http://www.nasa.gov/pdf/510449main_SLS_MPCV_90-day_Report.pdf

From page 7 of the latter,

The vehicle must be capable of serving as a backup system for supplying and supporting cargo and crew delivery requirements for the International Space Station (ISS) in the event such requirements are not met by available commercial or partner-supplied vehicles.

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  • $\begingroup$ CCDev is all about the capsules - the various capsule developers are required to select an already space rated launcher. Boeing is using the Atlas V, SpaceX the Falcon 9. Only SpaceX is actually codeveloping launcher and capsule, and that's under a separate block of funding. CCDev provides the successor to the Apollo Capsule, not the Saturn V launcher. $\endgroup$ – aramis Mar 9 '14 at 8:04
  • $\begingroup$ If they use a launch vehicle that can't be man-rated, game over. If they use a process that can't be man-rated, game over. The final phase, CCtCap, is about the whole system, end-to-end, not just the capsule. The goal of CCtCap is to send people into space. Sending people to the ISS is the key and final milestone of CCtCap. The contractors can't achieve that goal with only a human-rated capsule. The launch vehicle, the capsule, the entire process, all need to be human-rated. $\endgroup$ – David Hammen Mar 9 '14 at 9:01
  • $\begingroup$ None of the CCDev projects include nor allow man-rating a launcher. SpaceX is manrating the dragon as a separate project that just happens to also be a NASA project. ALL the CCDev projects are slated to (eventually) use the SLS launchers. $\endgroup$ – aramis Mar 10 '14 at 6:02
  • $\begingroup$ @aramis - What you wrote, and why you apparently downvoted me are wrong in many regards. That's wrong in many regards, aramis. The very first phase of CCDev included a \$6.7 million contract with ULA toward human-rating ULA's launch vehicles. In the interim between that initial CCDev work and the final CCtCap RFP, NASA chose those proposals that focused primarily on the capsule (or lifting body in the case of Sierra Nevada). The end goal has always been an end-to-end Crew Transportation System. (continued) $\endgroup$ – David Hammen Mar 10 '14 at 12:42
  • $\begingroup$ @aramis - (continuation) That end goal is the sole goal of CCtCap. It's in the RFP. The contractor must propose an end-to-end Crew Transportation System. It's not just a capsule. It's the whole enchilada, and the entire system must be human-rated. If all goes according to plan, the first launch will be late 2017. The launch vehicle is an integral part of the system and an integral part of any CCtCap proposal. That CCtCap launch vehicle will not be the Senate Launch System vehicle. The SLS won't be ready for human spaceflight in 2017. (continued) $\endgroup$ – David Hammen Mar 10 '14 at 12:56

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