Author Topic: SLS as propellant truck  (Read 38960 times)

Offline Warren Platts

SLS as propellant truck
« on: 12/21/2011 05:35 PM »
Now that there's talk about going back to the Moon, if we're going to do it, then we should do it right. That means we should go in as aggressive as our budget will allow.

If we did it right, we could be launching 5 or 6 crewed and cargo missions to the Lunar surface per year. But to do that, we're going to need like 700+ mT of propellant in LEO per year. That's a daunting amount of propellant.

This is where SLS could really shine. The big theoretical advantage of BFR's is the superior mass fraction to orbit they offer. Even so, it would take an SLS Block 2 about 6 flights per year to get it done.

Meanwhile, any crew/landers/MPCV's etc. could be launched on the existing commercial fleet.

Advantages:

1. we wouldn't have to manrate the SLS, at least at first;
2. by getting the flight rate up, the per mission SLS cost goes way down;
3. cost per kilogram for propellant to LEO could get down into the $3K/kg range.

Disadvantages: can't think of any unless it's that hauling propellant isn't as glamorous as hauling human loaded spacecraft.

By hauling propellant, it ensures that the cargo capacity of the SLS is maxed out every single time. Hauling other payloads will often not be able to take advantage of the entire payload capacity, thus resulting in unnecessary waste.

I'm afraid if we proceed down the current path, we'll be lucky to get two couple-week sorties per year, and a permanently manned research station will be beyond our grasp as a result.
« Last Edit: 10/28/2012 05:04 PM by Warren Platts »
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline 93143

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Re: SLS as propellant truck
« Reply #1 on: 12/21/2011 05:46 PM »
Manrating SLS is really not that big of a deal.

Offline Warren Platts

Re: SLS as propellant truck
« Reply #2 on: 12/21/2011 05:56 PM »
OK fine.

But that still begs the question of whether hauling humans around is the highest best use of  a 70 to 130 mT HLV.

Plus the low flight rate is going to send marginal costs through the roof!

Seems like overkill to me. We don't use semitrucks to haul humans: we use them to haul big tanks filled with gasoline. Or if we do use a big vehicle to haul humans, it's usually a bus that can carry 70 people at a time. That's not the plan with SLS....
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline A_M_Swallow

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Re: SLS as propellant truck
« Reply #3 on: 12/21/2011 06:19 PM »
LEO to EML-1 is 3.77 km/s
EML-1 to Earth surface is 0.77 plus heat shield
3.77 + 0.77 = 4.54 km/s
Maximum mass total mass 70 mT including payload, structure, propellant, RCS and boiloff.

A reusable spacecraft launches on the SLS that complies with those specification could take people directly to the EML-1 spacestation and return them to the Earth.

Offline Lobo

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Re: SLS as propellant truck
« Reply #4 on: 12/21/2011 10:14 PM »
Manrating SLS is really not that big of a deal.

Yea, the RS25's and SRB's are already man rated.  The eventual switch to the advanced booster could require a bit of tweaking, but I imagine NASA will only entertain bids on that are already fully man-rating compliant.

Offline Zed_Noir

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Re: SLS as propellant truck
« Reply #5 on: 12/22/2011 03:37 AM »
The SLS as a propellant hauler to LEO only makes sense if it's cheaper than the DIV-H, AV-H, FH or the A5 in $/kg. Which I think not.

Offline Warren Platts

Re: SLS as propellant truck
« Reply #6 on: 12/22/2011 10:16 AM »
LEO to EML-1 is 3.77 km/s
EML-1 to Earth surface is 0.77 plus heat shield
3.77 + 0.77 = 4.54 km/s
Maximum mass total mass 70 mT including payload, structure, propellant, RCS and boiloff.

A reusable spacecraft launches on the SLS that complies with those specification could take people directly to the EML-1 spacestation and return them to the Earth.

Launch the MPCV on an Atlas V instead. That's what depots are for.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline space_dreamer

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Re: SLS as propellant truck
« Reply #7 on: 12/22/2011 10:59 AM »
I like the idea, anything which can up the flight rate of the SLS has got to be a good thing.

I can't see the point of paying for all the ground infrastructure and then launch just once a year!

If NASA could achieve ten launches per year the cost per launch could be down to around $500millon which would be better per Kg than the ELVs

Offline Warren Platts

Re: SLS as propellant truck
« Reply #8 on: 12/22/2011 01:15 PM »
I like the idea, anything which can up the flight rate of the SLS has got to be a good thing.

I can't see the point of paying for all the ground infrastructure and then launch just once a year!

Exactly! That's what those Direct guys were saying trying to sell us the BFR concept. Where did that idea go?

I call Bait 'n' Switch!! 

  >:(

Quote
If NASA could achieve ten launches per year the cost per launch could be down to around $500millon which would be better per Kg than the ELVs

Gee, I was hoping it would be better than that. $5B/year doesn't leave a lot left over....

At 70 mT/launch, that's still $7000/kg. I was hoping they could keep the annual launch costs to around $3.5B/year, which would yield a $5K/kg figure.

But at the rate we're going, we're looking at $20K+/kg to LEO. That is awful and the wrong direction we need to be going IMO.

YMMV...
« Last Edit: 12/22/2011 01:56 PM by Warren Platts »
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline JohnFornaro

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Re: SLS as propellant truck
« Reply #9 on: 12/22/2011 01:32 PM »
Manrating SLS is really not that big of a deal.

They are saying that SLS-2 will be launched manned for an Apollo 8 redux, so I guess you're probably right.  But "manrating" is a showstopper with other rockets, to hear it being stated on other threads.  Like the Atlas for example. 

Anyhow, I think that SLS, in the 70 ton version would make a great wet or dry cargo rocket.  If only they would build it on time and on budget.
Sometimes I just flat out don't get it.

Offline Warren Platts

Re: SLS as propellant truck
« Reply #10 on: 12/22/2011 08:56 PM »
I think that SLS, in the 70 ton version would make a great wet or dry cargo rocket.  If only they would build it on time and on budget.

See John? We can agree on some things! :)
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline Lobo

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Re: SLS as propellant truck
« Reply #11 on: 12/22/2011 09:27 PM »
The SLS as a propellant hauler to LEO only makes sense if it's cheaper than the DIV-H, AV-H, FH or the A5 in $/kg. Which I think not.

Maybe, maybe not.  If using SLS for propellents got it's flight rate up, it could lower the per launch costs.

Also, it can get much more propellent into orbit with it's upper stage than EELV's can with theirs, even the EELV-heavies.  Every one of those will need a DCSS, Centaur, or ACES upper stage that will need to be expended.  So if you need 4-5 D4H launches to equal one SLS launch, then you need to calculate all of those 1st stage costs (which too will come down with the higher flight rate), with all the 2nd stage costs, vs. SLS 1 first stage, and 1 second stage.

I don't know know which way would be the more economical, but it might be pretty close when you factor everything in.  *shrug*

Offline gregzsidisin

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Re: SLS as propellant truck
« Reply #12 on: 12/22/2011 09:42 PM »

Exactly! That's what those Direct guys were saying trying to sell us the BFR concept. Where did that idea go?

I call Bait 'n' Switch!! 

  >:(

As a former member of the DIRECT Team, speaking strictly for myself here, SLS and its flight manifest are NASA's, not DIRECT's.  You'll recall that we advocated vehicles *directly* derived from Shuttle, including existing four-segment solids, a "non-stretch" cryo tank, and even upper stages without the J2-X.  Similarly, we advocated for a frequent flight rate that would in part loft propellant depots.

In short, we hoped to see minimized new development in favor of moving quickly ahead to flight and implementation.  All I can say is:  welcome to the real world of NASA and politics.
Greg Zsidisin

"Space pioneers have long studied the laws of the Universe. Now they must learn the ways of the World." -GZ, 1996

"In essence, rocket science is about blowing a lot of hot gas out an orifice. There are more experts in this field than you might realize." -GZ, 2011

Offline Warren Platts

Re: SLS as propellant truck
« Reply #13 on: 12/22/2011 10:19 PM »

Exactly! That's what those Direct guys were saying trying to sell us the BFR concept. Where did that idea go?

I call Bait 'n' Switch!! 

  >:(

As a former member of the DIRECT Team, speaking strictly for myself here, SLS and its flight manifest are NASA's, not DIRECT's.  You'll recall that we advocated vehicles *directly* derived from Shuttle, including existing four-segment solids, a "non-stretch" cryo tank, and even upper stages without the J2-X.  Similarly, we advocated for a frequent flight rate that would in part loft propellant depots.

In short, we hoped to see minimized new development in favor of moving quickly ahead to flight and implementation.  All I can say is:  welcome to the real world of NASA and politics.

Hey I was just kidding about that--thanks for the comment!

My feeling is that as long we're going with SLS, let's use it as much as we can.

What do you guys think is realistically possible, forgetting about budget for a minute:

I mean is 10 launches per year for SLS even physically possible with the one launch pad?

And if possible, then how much would it cost for 10 launches, not counting payloads? $2.5B? $3.5B $5.0B?

"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline gregzsidisin

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Re: SLS as propellant truck
« Reply #14 on: 12/23/2011 03:45 PM »

Exactly! That's what those Direct guys were saying trying to sell us the BFR concept. Where did that idea go?

I call Bait 'n' Switch!! 

  >:(

As a former member of the DIRECT Team, speaking strictly for myself here, SLS and its flight manifest are NASA's, not DIRECT's.  You'll recall that we advocated vehicles *directly* derived from Shuttle, including existing four-segment solids, a "non-stretch" cryo tank, and even upper stages without the J2-X.  Similarly, we advocated for a frequent flight rate that would in part loft propellant depots.

In short, we hoped to see minimized new development in favor of moving quickly ahead to flight and implementation.  All I can say is:  welcome to the real world of NASA and politics.

Hey I was just kidding about that--thanks for the comment!

My feeling is that as long we're going with SLS, let's use it as much as we can.

What do you guys think is realistically possible, forgetting about budget for a minute:

I mean is 10 launches per year for SLS even physically possible with the one launch pad?

And if possible, then how much would it cost for 10 launches, not counting payloads? $2.5B? $3.5B $5.0B?



Sorry I didn't catch the humor. :)  I can speak only for myself, based on personal speculation since the team is now disbanded. 

A launch rate matching that of the Shuttle (6 times a year or more) should have been possible, the long pole becoming SSME production.  Costs should in turn drop with flight rate due to volume production.  What those costs could really be I personally don't know, but again I think we could have at least matched STS program annual costs.  Arguably, we were substituting Orbiter maintenance with expendable SSME production.  (We abandoned the RS-68 engine in DIRECT Version 3 for technical and performance reasons.) 

Not to turn this into a DIRECT discussion, but the advantage of swapping Shuttle for a large launcher like Jupiter was to fly a lot more payload for the program costs.  Personally, I'm disappointed that SLS isn't being used more creatively for things like propellant depots.  But we'll see what develops.
Greg Zsidisin

"Space pioneers have long studied the laws of the Universe. Now they must learn the ways of the World." -GZ, 1996

"In essence, rocket science is about blowing a lot of hot gas out an orifice. There are more experts in this field than you might realize." -GZ, 2011

Offline Warren Platts

Re: SLS as propellant truck
« Reply #15 on: 12/30/2011 08:51 AM »
This came up on the linked thread, but is more appropriately treated here:

using SLS for just a LEO tanker seems like a really poor use of resources.

1. It's a job that's ideally suited to commercial providers (who can optimize cost...

2. it's ideal for reusable launch vehicles if the annual propellant needs are high enough),

3. and it doesn't fit with what SLS is supposed to be used for.

4. Now, if that means SLS doesn't have a job, that's fine with me, but that's not the topic of this thread.

1. (a) as OV-106 constantly points out, the commercial/governmental distinction is largely a false dichotomy: SLS will be built and largely operated by commercial contractors (and meanwhile ULA's and SpaceX's pretty much sole customer is the US government), and (b) there's nothing preventing NASA from optimizing cost; (c) according to the rocket equation, SLS, in theory, should be the more optimal solution because as you increase the absolute payload, the payload mass fraction improves; (d) increasing SLS flight rates lowers SLS incremental costs.

2. (a) using SLS to launch Apollo-on-junk-food, fart-burning Lunar missions will guarantee that the demand for propellant to LEO will be minimized because the number of missions will be limited to 1 or 2 per year at best--and 0.5 missions per year is not outside the realm of possibility; (b) by having SLS haul propellant, there will be enough propellant for like 5 missions per year, thus providing more business for the likes of SpaceX and ULA to launch high value payloads (the reusable space capsules, landers, depots, space tugs, tankers).

3. Huh? Just what is SLS "supposed" to be used for? I thought it was to best further the ends of the US space program....

4. I, for one, would like to see the US space program succeed, and therefore, since we are going with SLS anyway, then let's focus on what the highest and best use of SLS is going to be. I am not convinced that Apollo-on-junk-food is the highest and best use of SLS.
« Last Edit: 12/30/2011 11:34 AM by Warren Platts »
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline Warren Platts

Re: SLS as propellant truck
« Reply #16 on: 12/31/2011 06:34 AM »
As a former member of the DIRECT Team, speaking strictly for myself here, SLS and its flight manifest are NASA's, not DIRECT's.  You'll recall that we advocated vehicles *directly* derived from Shuttle, including existing four-segment solids, a "non-stretch" cryo tank, and even upper stages without the J2-X.  Similarly, we advocated for a frequent flight rate that would in part loft propellant depots.

A launch rate matching that of the Shuttle (6 times a year or more) should have been possible, the long pole becoming SSME production.  Costs should in turn drop with flight rate due to volume production.

What those costs could really be I personally don't know, but again I think we could have at least matched STS program annual costs. Arguably, we were substituting Orbiter maintenance with expendable SSME production.  (We abandoned the RS-68 engine in DIRECT Version 3 for technical and performance reasons.) 

Not to turn this into a DIRECT discussion, but the advantage of swapping Shuttle for a large launcher like Jupiter was to fly a lot more payload for the program costs. Personally, I'm disappointed that SLS isn't being used more creatively for things like propellant depots.  But we'll see what develops.

Hi Greg: I've been thinking about this: the way you put it offers a possible means to get a ballpark figure for SLS flight costs as a function of flight rate:

In 2009, $3B was budgeted for 5 flights. In other years, flights of up to 8 or 9 flights were accomplished. So 6 flights per year seems reasonable. If the operational cost is $3B/year for 6 flights, that's $500M/flight. If there's only 2 flights, then the cost is $1.5B per flight.

Under the idea that it would be best to streamline operations and maximize flight rate, then @ 6 propellant flights per year:

70 mT version ==> 6 * 70 = 420 mT to LEO ==> ~$7.1K/kg

This is less than the amount that Zegler recommended be lofted to LEO to support his "aggressive" Lunar program, which would consist of 5 Lunar surface missions to a permanently manned base per year. Moreover, the cost per kilogram isn't the best.

130 mT version ==> 6 * 130 = 780 mT to LEO ==>  $3.8K/kg

Now, 780 mT/year to LEO is just about what Zegler recommends; and the cost per kilogram pretty much beats any commercial launch provider that's out there at this   time. (Meanwhile, if there are only 2 launches per year, the cost per kg is over $10K). For the 70 mT version to loft 780 mT per year, 11 flights would be required, so we can see the power of big payload capacity combined with a higher flight rate.

Since 130 mT is going to be the upper limit of SLS, and since it's perhaps unrealistic to plan on having more than 6 flights per year on average (about the best that could be done with Shuttle when they were firing on all cylinders), the only further savings that could be had would be through lowering the operating costs.

Which brings me to another reason we should be using SLS mainly to haul propellant: it stands to reason that if the payloads are simple, low-value, and the exactly the same every single launch, it ought to be possible to streamline the launch and payload assembly process somewhat (although that's just my intuition speaking): thus, if they could get the operating cost down to $2.5B annually, then the cost/kg to LEO would only be: $3.2K/kg.

Since the cost of propellant is virtually zero on Earth's surface, if the latter streamlining could be achieved, that would leave 4.5 to 6.5 $B/year for high-value, low-mass payloads that would be launched by ULA and SpaceX.

Bottom Line: if we are going to get the cost per kg to LEO down where it needs to be with SLS, we must get the flight rate up much higher than is currently being contemplated; half a dozen propellant flights with the 130 mT version (or 11 flights with the 70 mT version) would get us there.
« Last Edit: 12/31/2011 08:34 AM by Warren Platts »
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Offline MikeAtkinson

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Re: SLS as propellant truck
« Reply #17 on: 12/31/2011 12:02 PM »
It looks like the 70 tonne SLS will only launch twice, so will not be used to launch propellant. The 105 tonne version will be available from about 2022 and the 130 (138?) tonne version from about 2027, the first few flights of each are unlikely to be propellant launches.

It seems far too early to be saying what will be cheapest for launching propellant from 2025 onwards.

If SpaceX succeed with the FH, its price for launching propellant will be about $3,500/kg, this is likely to be cheaper than can be achieved by SLS.

I consider it likely that at least one of SpaceX, Orbital, LM, Boeing, Blue Origin, etc. have achieved 1st stage reusability and perhaps 2nd stage reusability as well. If SpaceX achieve their stated gaols they will likely be on their second iteration of reusable systems by then.

If 1st stage reusability is achieved then propellant prices of below $3,000/kg should be possible from any of the launch providers. 2nd stage reusability would lower prices to under $2,000/kg. Some tanker designs use a stretched 2nd stage for the tanker, if these were reusable then I consider for prices below $1,000/kg to be reasonable.

If reusability is not achieved then a small launcher would have to have lots of flights getting into the "A rocket a day keeps the high costs away" territory where costs can be reduced by streamlining the production and launch procedures.

What I am getting at is that easily conceivable improvements to current and near future launchers will allow them to undercut the SLS in propellant launch.

Offline mmeijeri

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Re: SLS as propellant truck
« Reply #18 on: 12/31/2011 12:18 PM »
Disadvantages: can't think of any unless it's that hauling propellant isn't as glamorous as hauling human loaded spacecraft.

This would be disastrous for prospects of cheap lift. SLS will not reach price levels that would allow meaningful commercial manned spaceflight, nor would it even be available for such use.

If there is to be an SLS, it should be used to launch crew to L1/L2, as proposed in the recent Boeing plan.
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Offline JohnFornaro

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Re: SLS as propellant truck
« Reply #19 on: 12/31/2011 02:03 PM »
Two points for Mike Atkinson:

"A rocket a day keeps the high costs away."
Sometimes I just flat out don't get it.

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