The SLS and its usage

[Kibble]

There is a benefit to having in-production hardware (especially capable launchers!) lying around even if you have no payloads for them. Otherwise to start something big like a manned lunar landing or whatever the project would include designing both mission-specific hardware, and the system to launch it. And one of the laws of space engineering is any project that includes developing a new launch system, is a launch system project! One that will doubtless get overrun with delays and take billions of dollars. The overhead on keeping System production facilities is worth it, even if it doesn't start regularly flying until decades from now.

[King Arthur]

It isn't NASA's job to lay out its own plans. NASA gets its goals from laws that emanate from the US Congress, which are either followed up or not with funding. If Congress can't get its act together (see what I did there?), it's not NASA's fault.

I debated whether I should place the onus there on NASA (the people who do), the US Congress (the people who order), or hell, the US President (the guy who says) as I was writing it, but ultimately I think we can both agree that third-parties are not to blame for the lack of missions and payload for the SLS.

[Tiberion]

It's pretty simple, there isn't any other mission to be designing or planning yet. The per-year budget is too low due to 'reasons' that it takes 8 to 10 years for something like SLS. Block2 doesn't even have a final design yet.

NASA isn't and will not have a moon landing program, so they don't need to design a lander. They don't need SLS to launch people to ISS or to launch their robotic missions to Mars or where-ever; the private heavy lift rockets will do that cheaper. There is no plans for "ISS2" and again the private rockets will do that job as well.

SLS is built to throw people around the Moon, and eventually to Mars (in some form.) They don't need anything but Orion to do the 1st part, and the 2nd part can only come after a lot of experience and science is done, we aren't ready to throw people to Mars yet. There is nothing else to build or plan, and even though they have this 'cool rocket' that could launch stuff, that doesn't mean there is money to start new projects just to utilize it.

Maybe when our government changes hands in 2016 they'll scrap everything once again and we'll start over. Hopefully not. Any potential private or foreign agencies are going to wait until its done before they commit, because they can't be responsible and still commit their money to an unfinished rocket that isn't done, especially after what happened with the Constellation project. And not every project will take 10+ years to finish, so while they may not launch 4 or 5 a year, it won't sit around 5 years between launches either.

The only thing to do is wait. They're really building the thing now, and we're too far down the road to turn around at this point (barring another ignorant President or Congress)

Edited December 8, 2014 by Tiberion

[Fuzzy Dunlop]

SLS desperately needs a payload - a launch system without one is not only economically inefficient but politically indefensible. Fortunatly one of the best ways to convince Congress to open its chequebook is to convince them that an earlier investment will be wasted if they don't (this is one of the ways military contractors get so much money - at first a project only costs $2 billion, then they come back an tell you it will cost $5 billion but if you cancel it the $2 billion has been thrown away).

[cantab]

Ah, the good old sunk cost fallacy.

[Dkmdlb]

Nothing convinces the people in charge of signing checks like fallacious logic.

[m4rt14n]

Somebody should just make a study to the Senate that says a sending people to Mars To Stay would make x million jobs in x number of states. Then, maybe we'll get somewhere

[Bill Phil]

NASA is building a skyscraper, without a foundation. You always need the foundation. Once SLS gets cancelled eventually, what will there be? Some flags and footprints on mars and that's about it.

What we need is a system using LEO as a gateway to the solar system. Much like in the 1969 Proposal for the Space Transportation System. It was an optimistic proposal ( a large space station by 1975? Yeah, that'll happen), but it was a good idea and we should have done it. I think we still can, and should try to do it.

SLS will be cancelled, probably before 2025. But who knows?

[Woopert]

Here's some more PDF files showing SLS possibilities. Regardless of whether you believe they're actually going to happen, they're still well done and nice to look over. NASA NTRS is a wondeful thing!

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140010999.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140010196.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140010120.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140010098.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140008583.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140012914.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140012590.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011078.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140010993.pdf

http://www.nasa.gov/pdf/630147main_4-Olson_Planning%20Partnerships%20Priorities%20030612_508.pdf

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090012109.pdf

Enjoy

Edited December 8, 2014 by Woopert

[Fuzzy Dunlop]

NASA is building a skyscraper, without a foundation. You always need the foundation. Once SLS gets cancelled eventually, what will there be? Some flags and footprints on mars and that's about it.

What we need is a system using LEO as a gateway to the solar system. Much like in the 1969 Proposal for the Space Transportation System. It was an optimistic proposal ( a large space station by 1975? Yeah, that'll happen), but it was a good idea and we should have done it. I think we still can, and should try to do it.

SLS will be cancelled, probably before 2025. But who knows?

Yeah this! (though I acctually have a gut feeling SLS will be a survivor). Seriously the shuttle programme failed to meet it's objectives, that doesn't mean that we should abandon those objectives. Throughout its history America's most effective moto has been "If you at first you fail, try again!"

[kzauner]

Yeah this! (though I acctually have a gut feeling SLS will be a survivor). Seriously the shuttle programme failed to meet it's objectives, that doesn't mean that we should abandon those objectives. Throughout its history America's most effective moto has been "If you at first you fail, try again!"

Well there is a similar quote, a little bit less friendly 'You can always count on Americans to do the right thing - after they've tried everything else.' (W. Churchill). And I hope hope for the world, that they finished trying everything else, and build that damn thing. Especially as there are some missions which will for sure be co-funded by other agencies (especially the Telescopes).

Thanks to budget-constraints there seems also to be an opening concerning cooperation for the whole system (like: SM coming from ESA, somewhat unthinkable years ago). International cooperation will for sure lead to further delays, but makes canceling a little bit harder as you won't go through the hassle if you as politician are just 'ignorant', it will require some deep rejection of the whole idea.

[78stonewobble]

That's the problem. It will take 10-20 years to build a payload, and in the meantime the SLS and all related things are just sitting there, eating money while doing nothing.

To make a successful heavy lift vehicle you have to guarantee that it won't be cancelled and that deadlines will be met. That way people will be confident enough to develop payloads. NASA and its related contractors have a very poor track record when it comes to continuing with programs...

The reverse could be true... Having a payload waiting around, while waiting for the launch capability, if there isn't money for doing both.

In any case, big space ambitions are one thing, they come and go along with politicians and public support. One thing I think that should be done, is having policies in place, that even if "we" don't need the SLS right now, that production, launching, managing, servicing abilities and what not... be saved in someway... So if we ever "need it" (asteroid deflection) or "want it" (definately have will and money for big space ambitions), don't have to reinvent a heavy lift capability for a 3rd time (4-5th time if we count russian attempts).

PS and more back on the topic:

What I'm also hoping is that the SLS will allow for... Is a new range of large space born observatories, that can be placed and serviced and thus have even longer lifetimes, even further from the earth.

PPS: As a european I don't expect the US to undertake mega projects by themselves, but I do hope for increased cooperation in the future (going both ways offcourse). I know alot of americans, sometimes, have quite a bit of the "buy american" thing going... but even with some presumably very good deals... I don't think I can count how much ie. weapons technology european countries have bought over the years.

Edited December 8, 2014 by 78stonewobble

[jfull]

The SLS could be useful for constructing ISS2, allowing fewer launches and larger interior spaces. I can see a combination of SLS and Falcon Heavy launches working very well for that. Then again, the pessimistic side of me sees there being no ISS2.

I don't see much of a use for another International Space Station.

China will have its own space station comparable to Mir in the next decade, and we will hopefully have the the first commercial space station in that timeframe as well.

Those stations will meet the demand for LEO-based facilities.

Unless, of course, the ISS2 you're referring to would be built somewhere other than LEO.

[Tommygun]

I would think the same motivation that caused congress to create the SLS will also keep it from canceling it.

[Bill Phil]

I would think the same motivation that caused congress to create the SLS will also keep it from canceling it.

More likely that same reason would cause another rocket just as capable to be built.

[cantab]

I don't see much of a use for another International Space Station.

China will have its own space station comparable to Mir in the next decade, and we will hopefully have the the first commercial space station in that timeframe as well.

Those stations will meet the demand for LEO-based facilities.

The main use of the ISS is as a lab in zero-g. I'm not sure commercial stations will be looking to fill that role. The Chinese stations probably will, but will the US and Europe really like China being the only country with that capability?

[King Arthur]

Russia's planning on making OPSEK, initially using the Russian Orbital Segment from the ISS when it's decomissioned. Russia has always held the lead with space stations and long-term habitation of LEO, the ISS would literally not be able to operate without the Russian Orbital Segment, so I suspect this will actually become a reality presuming funding doesn't become too precarious an issue.

I personally don't expect anything of the Chinese space program though, including their stations. If there's a space program that's an even bigger political farce than the SLS right now, it's the Chinese.

[Bill Phil]

They at least actually HAVE rockets........ and spacecraft to go with them.

[Northstar1989]

Here's the thing about SLS- once it's designed, and the facilities have been upgraded, it's not actually that expensive for its payload capacity.

The vast, vast majority of costs related to SLS are development and facilities-upgrade costs. Once that money has already been spent, those become sunk costs

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

Pleas, please take the time to read a little bit of that Wikipedia article on sunk costs. So many people (*especially* politicians) fail to understand this simple concept, and so make completely irrational decisions as a result.

What is rational to consider is only the prospective costs of SLS once it has been fully-developed. That is, the cost of building and launching an SLS, completely independent from any earlier development costs, once the SLS is in active production and fully-developed.

When you look at it from that perspective, SLS isn't actually all that expensive. In fact, it becomes quite competitive with any other launch vehicle on the market.

Ignoring the fat/waste from overpaying government contractors to build SLS (that money technically recycles into the economy and creates high-paying jobs), it's technically a more efficient rocket than many existing launch vehicles thanks to its large size...Why are larger rockets more efficient?

(1) Larger rockets can have proportionally less massive flight and guidance systems (a flight computer that can guide a Falcon 9 or Arianne 5 should work equally well for something the size of SLS). Alternatively, they can have the same mass-fraction of flight computers and greater redundancy of critical flight systems- which lowers insurance costs (and the likelihood of failure) for the rocket.

(2) Larger rockets have better ballistic coefficients due to the Square-Cube Law. This means they experience proportionally less atmospheric drag in relation to their size/payload, and it takes them slightly less Delta-V to reach orbit. And we all know what that means.

(3) Larger rockets require proportionally less payload fairing, assuming the payload is correctly-shaped. This is because you can enclose a larger space with proportionally less surface area, per the Square-Cube Law. The Square-Cube Law also applies to interstage fairings (equating to mass-savings if the engine nozzles aren't any taller, or the fuel tanks are designed to fit around the nozzles to minimize fairing mass...)

(4) Larger rockets experience proportionally less boil-off of cryogenic fuels (such as Liquid Hydrogen). This is as fuel-tanks are pressure-vessels influenced by the Square-Cube Law. The fact that they are pressure vessels means that tank mass scales linearly with volume- for instance a tank with four times the volume requires four times the tank mass. However the Square-Cube Law dictates that larger tanks have less surface area- so larger fuel tanks end up with thicker walls instead (so that tank mass still scales linearly).

This means that a tank with 4x the volume might only have 2x the surface area, but twice as thick walls. However Thermal Leakage (what drives boil-off of any cryogenic fuel) is proportional to tank surface area, and inversely related to tank wall thickness and number of layers of insulation. For instance, the 4x sized fuel tank would have LESS than 2x the boil-off of a 1x sized tank as its surface area is only doubled, and its walls are thicker. If, say, the tank had 4 layers of insulation, this would weigh the same as 2 layers of insulation on a 1x sized tank- but reduce boil-off a lot more. If there were 2 layers of insulation coated onto the tank, you still get greater insulation of the fuel (the tank walls are thicker, and thus better insulators, to start with) for proportionally less mass.

Thus, with larger rockets you have a choice between reducing boil-off (directly reducing the mass of fuel you need, as you don't have to replace as much that boils off), or reducing tank mass proportional to volume (improving the fuel-fraction of the rocket and thus indirectly reducing the mass of fuel you need). With either option, you get a better payload-fraction.

There are other benefits as well- for instance you can trade off some of the improved ballistic-coefficient of a larger rocket for side-mounted boosters (like the SLS uses) or drop-tanks, or you can take advantage of the higher terminal-velocity which an improved ballistic-coefficient confers and launch with a higher TWR (thus reducing time-to-orbit and the Delta-V expended fighting gravity) thus trading off some of the savings in atmospheric-drag for even greater savings in gravity-drag...

Basically, larger rockets are more cost-effective (assuming you can't launch enough small rockets instead to reach the point of reaping benefits from mass-production), if you have a way to make use of their entire payload-capacity...

Although it may seem like a waste to design an entire heavy-lifter just to resupply the ISS, the SLS can even do that job more efficiently than existing rocket designs. Yes, that's not worth the development/facilities costs on its own- but if we go ahead and design SLS and then don't come up with any other uses for it, those are still sunk costs that cannot be recovered.

Per-ton of payload, heavier rockets have the capability to be more cost-effective. Of course, all this hinges on the engineering margins being equally tight. If you design the larger rocker to looser engineering standards (so, for instance, you don't need to know the mass or size of an individual part to within .001% accuracy- but instead only to w/in 0.1% accuracy), your payload capacity decreases, but the per-ton cost of getting the payload to orbit decreases as well- due to the exponential relationship between engineering standards and cost.

What worries me most is the concern that NASA/Lockheed Martin might be designing SLS to super-high engineering margins, and contracting out construction tasks in a very non-competitive manner: thus throwing away all the cost benefits of using a larger rocket, and actually leading to a MORE expensive rocket per-ton (even before you include development/facilities costs...)

Regards,

Northstar

P.S. If you take the pattern of building larger rockets with looser engineering margins to save costs to an extreme, what you end up with is a Big Dumb Booster similar to the Sea Dragon. Note that BDB's in the style of a Sea Dragon are actually MORE reliable than those built to tighter engineering margins (as a small mistake in construction is less likely to lead to mission failure), *unlike* those designed Aquarius-style (Aquarius is a BDB that is actually very small, and loosens engineering standards without increasing margins- thus trading off reliability for cost-savings and mass-production...)

Edited December 9, 2014 by Northstar1989

[jfull]

Its going to be interesting if, potentially, there will be 3 or more manned stations being operated simultaneously within the next 20 years.

It may not seem like a lot of progress has been made in space exploration, but we are on our way to having more humans working in space at one time than we've ever had before.

[King Arthur]

Its going to be interesting if, potentially, there will be 3 or more manned stations being operated simultaneously within the next 20 years.

We once twice actually had 2 manned space stations flying together, the first time being the Mir and the Salyut 7, with one of the highlights being a station-to-station flight:

On 6 May 1986, Soyuz T-15 carrying Leonid Kizim and Vladimir Solovyov docked with the space station [salyut 7] and undocked, after a 50 day stay, on 25 June 1986. The Soyuz had come from the Mir space station and returned to Mir on 26 June 1986 in a flight lasting 29 hours.

https://en.wikipedia.org/wiki/Mir

https://en.wikipedia.org/wiki/Salyut_7

And the second time being the ISS in its very early days and Mir, though by this time Mir was mostly a ghost of its former glory due to its age.

Edited December 9, 2014 by King Arthur
Completely derped out on when Mir was deorbited.