Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

Dayton3 · 2004-12-09 20:07:53

If we wanted to send five humans to Mars and back using the Mars Direct mission architecture and wanted to use a booster capable of lifting 200 metric tons into LEO (about 450,000 lbs-I don't know how that translates into payload to Martian surface) which would it be cheaper to build.

The "Comet" variant of the Saturn V-basically the Saturn V core vehicle with F-1 engined strap on boosters,

or

A "super" variant of the Ares launch vehicle. At least four extra segment SRBs around an external tank derived core with 4 to 6 RS-68s (is that the right designation?) engines.

Which would be cheaper to develop, build, mass produce and man rate?

GCNRevenger · 2004-12-09 21:05:17

Wish we knew for sure...

I think that the "Super Ares" would be the better choice overall, since the old engines for the Saturn rockets are no longer in production and because of the smaller number of engines involved.

The engines for Super Ares are already available today with some upgrades and modifications; the Boeing/Rocketdyne's RS-68 should be upgraded to a regenerative nozzle instead of an ablative one, and Thiokol's SRBs might need some minor modifications. The whole vehicle however, would only need ten or twelve engines total including upper stage, versus the 15-20 engines for Comet (depending on boosters & 3rd stage). The Comet's second stage was supposed to have SIX J-2 engines! Super Ares could probobly get away with a single RS-68R.

Since the SRBs are physically narrower then a Comet booster, its practical to think about using six of them. Even four on Comet would be packing them pretty tightly... Though its a valid question if the SRBs higher dry weight eliminates some of this bennefit.

The tanks would have to be new, but would be about the same size as the Saturn tankage (10m diameter) so no new facilities would have to be built. Such a vehicle should fit in the VAB at the Cape' snugly but well enough.

The control electronics for both types of engines are already in production too, and would have to be redone for a Saturn-derived rocket.

Finally though, with the five-segment SRBs and higher Isp upper stage, the "Super Ares" might reach beyond the 200MT figure to the 250MT range. Plus, since the SRBs are reuseable, they will probobly cost less then a pair of the massive F-1A engines needed to match their thrust.

Euler · 2004-12-09 22:05:45

Which would be cheaper to develop, build, mass produce and man rate?

I suspect that the Super Ares would be cheaper to develop, since it uses mostly modern components rather than trying to revive components that stopped being used a long time ago. The Super Ares should also be much cheaper to operate, and it would probably be safer. It is a much better option than trying to revive Comet.

A better comparison would be between Super Ares and a comet-like vehicle that switched out some 60's parts for modern ones. However, I think that Ares style vehicle would still come out on top.

Dayton3 · 2004-12-10 00:04:18

I keep bringing the Saturns because I've read in more than one place that five F-1s are still in storage in good condition and can easily be used to reverse engineer newly manufactured and upgraded F-1s.

And I read that the company that owns them (it is still Rocketdyne?) has said they could resume F-1 production in just 18 months from the "go" decision.

What is the thrust rating for the RS-68 by the way?

Isn't it the second most power liquid fuel rocket engine ever produced by the United States? Second only to the F-1

Euler · 2004-12-10 01:39:22

What is the thrust rating for the RS-68 by the way?
Isn't it the second most power liquid fuel rocket engine ever produced by the United States? Second only to the F-1

The RS-68 has a rated thrust of 337,807 kgf. That is the largest LH2/Lox engine that has ever been used on a launch vehicle. A larger Lh2/Lox engine called M-1 was developed for a possible successor to Saturn, but the program was cancelled and it never flew. The only other larger liquid engine produced by the US was the F-1, though the RD-180 used on the Atlas engines is a little bigger, and theoretically it will also eventually be manufactured in the US.

GCNRevenger · 2004-12-10 14:10:05

I keep bringing the Saturns because I've read in more than one place that five F-1s are still in storage in good condition and can easily be used to reverse engineer newly manufactured and upgraded F-1s.
And I read that the company that owns them (it is still Rocketdyne?) has said they could resume F-1 production in just 18 months from the "go" decision.
What is the thrust rating for the RS-68 by the way?
Isn't it the second most power liquid fuel rocket engine ever produced by the United States? Second only to the F-1

If you want an RS-68, you can call up Boeing and buy one today. Throw a few million their way to add the cooling loop and promise them you'll buy half a dozen a year for a decade. Or Thiokol, throw in another segment to the "Shuttle Special" at the VAB when you put them together.

Probobly much easier then fooling around with the F-1 engines. The Russian RD-170, not the half-size 180, is the competitor to the F-1, and is used on the Zenit medium/light launcher. America would have to buy the rights for it probobly and learn how to build them...

Anyway, you would need alot of RD-170's, 11-13 or so, for the boosters and first stage instead of only five RS-68R's and recycled SRBs.

GCNRevenger · 2004-12-10 16:58:08

You know, calling it "Super Ares" is kinda silly... it needs another name. Janus has already been taken by another HLLV concept... Jupiter? Hmmm...

Austin Stanley · 2004-12-11 03:27:40

Heh, well as it seems to be your idea, you should have the honor of naming it. Jupiter is a good one though, IMO.

GCNRevenger · 2004-12-11 13:22:54

Or perhaps the Zeus rocket (*insert hubris here*)... returning to Mount Olympus (Mons)?

I suppose the next question is, how much would it cost to develop versus an Ares/Magnum/Shuttle-Z style SDV? How much would it cost per-flight versus a pair of Ares vehicles? How much money or mass would it save to skip orbital assembly? Would congress foot the bill for "the next big thing" that would be needed following the exploration phase instead of Ares now and Zeus later rather then just Zeus?

GraemeSkinner · 2004-12-11 13:26:23

Or perhaps the Zeus rocket (*insert hubris here*)... returning to Mount Olympus (Mons)?

What about Achilles, its only one weak spot

Graeme

GCNRevenger · 2005-01-10 12:28:41

On contemplating modifications to NASA's DRM arcitecture to make it partially reuseable once a base with access to water is established would call for a light-medium HLLV in the 80-100MT range, but the initial missions and heavy cargo flights may be better served by a larger superheavy 200MT class launcher. The smaller HLLV and the use of an optional upper stage would also increase the flexibility for non-Mars missions.

SO, the idea is to use the regular ~8m Shuttle tankage tooling and modify/stretch it as needed for an in-line launcher like NASA's Magnum rocket except with increased structural strength.

The core stage would use either two or three RS-68R engines, which would be surrounded by two or four Shuttle SRBs of either four or five segments each. For superheavy payloads, the core would also be flanked by a pair of "EELV+" updated Delta-IV core stages, perhaps stretched to hold more fuel. The upper stage would be either the small kick stage for orbital circulization, or a heavy-duty cryogenic upper stage with a single RS-68 tailored for vacuum performance and maximum Isp.

If you need light payloads to Earth orbit, use only the core with a pair of SRBs of either size. Medium or Earth-escape payloads would include the heavy upper stage. Heavy payloads would use all four SRBs and the heavy upper... And finally, for superheavy loads you would add the Delta-IV boosters on the sides.

Improved flexibility, smaller core stage, and increased performance with more staging events... but at the cost of reduced tankage efficency, reduced/eliminated engine-out capability on the core stage, and higher complexity.

Euler · 2005-01-11 01:04:46

The core stage would use either two or three RS-68R engines, which would be surrounded by two or four Shuttle SRBs of either four or five segments each. For superheavy payloads, the core would also be flanked by a pair of "EELV+" updated Delta-IV core stages, perhaps stretched to hold more fuel. The upper stage would be either the small kick stage for orbital circulization, or a heavy-duty cryogenic upper stage with a single RS-68 tailored for vacuum performance and maximum Isp.
If you need light payloads to Earth orbit, use only the core with a pair of SRBs of either size. Medium or Earth-escape payloads would include the heavy upper stage. Heavy payloads would use all four SRBs and the heavy upper... And finally, for superheavy loads you would add the Delta-IV boosters on the sides.

Rather than ending up with the heavier versions of this vehicle using huge numbers of multiple types of large boosters, I would start out with a much larger core. It would be similar the http://astronautix.com/lvfam/alsnls.htm]ALS/NLS family of rockets that were proposed to launch Star Wars, but using upgraded RS-68 engines in place of the "STME" engines. It would also be a bit bigger than the ALS/NLS cores, with a larger diameter than the shuttle ET.

The base vehicle would just be the core by itself as an expendable SSTO with a payload a little larger than the payload provided by a Delta IV heavy. Since the vehicle would have engine out capability and zero staging, it should be extremely reliable. To make heavier versions, just add SRBs. Since the core is bigger, the superheavy version of this vehicle would only need as many boosters an the heavy version of your rocket. This system would get the benefits of simplicity, reliability, and tankage efficiency without losing any flexibility.

GCNRevenger · 2005-01-11 08:09:31

That would be initial preference too, a 10m core using five RS-68R's with 2-3-4-6 possible SRBs strapped to the side with a target payload of 200-250MT, more then double that of the NLS HLLV concept.

The trouble is, that building such a huge core is an excessive amount of trouble for launching intermediate sized payloads (80-120MT), where a smaller core with a pair of SRBs would be preferable. It would also be nice not to have to design new tankage. I also have doubts that the core stage alone would have a high enough thrust/weight ratio to reach orbit on its own efficently, nor is it that much bigger versus the NLS core which obviously doesn't have the require payload.

Using multiple types of boosters I don't think is a big problem because these boosters will already be available and tested in that role, albeit on smaller vehicles. The decreased tankage efficency would be partially compensated for by the extra staging event perhaps too.

Euler · 2005-01-11 12:45:19

Technological improvements and increases in size increase the competativeness of a SSTO vehicle like this with respect to all other types of expendable vehicle. If it made sense for a medium sized 80s vehicle, it should certainly make sense for a large 21st century vehicle.

If you assume that the fuel tanks of the core have the rame weight/surface area ratio as the Shuttle ET, a 1.4*10^6 kg core would have about 40 tons of tankage and 6 RS-68 would be about another 40 tons. The payload should be about 75 tons to LEO, mabey only 70 after deducting the payload fairing. That is still pretty good for a vehicle that is as simple, reliable, and relatively cheap as this. Presumably with upgraded RS-68 engines it could do even better.

Using multiple types of boosters I don't think is a big problem because these boosters will already be available and tested in that role, albeit on smaller vehicles. The decreased tankage efficency would be partially compensated for by the extra staging event perhaps too.

Using Delta IV core CBCs as boosters in the superheavy vehicle might actually decrease staging efficientcy. The CBCs would have a lower T/W ratio than the small core with 4 SRBs, meaning they would actually be dragged along by the vehicle rather than boosting it in the early stages of flight.

SpaceNut · 2005-01-11 12:45:49

Well here is a little something on the solid fuels (perchlorate)contained in the SRB's and the effects it has on humans.

Report Assesses Health Implications of Perchlorate Exposure

GCNRevenger · 2005-01-11 17:17:52

Technological improvements and increases in size increase the competativeness of a SSTO vehicle like this with respect to all other types of expendable vehicle. If it made sense for a medium sized 80s vehicle, it should certainly make sense for a large 21st century vehicle.
If you assume that the fuel tanks of the core have the rame weight/surface area ratio as the Shuttle ET, a 1.4*10^6 kg core would have about 40 tons of tankage and 6 RS-68 would be about another 40 tons. The payload should be about 75 tons to LEO, mabey only 70 after deducting the payload fairing. That is still pretty good for a vehicle that is as simple, reliable, and relatively cheap as this. Presumably with upgraded RS-68 engines it could do even better.
Using Delta IV core CBCs as boosters in the superheavy vehicle might actually decrease staging efficientcy. The CBCs would have a lower T/W ratio than the small core with 4 SRBs, meaning they would actually be dragged along by the vehicle rather than boosting it in the early stages of flight.

But it doesn't make sense then nor does it now, because you can't put heavy payloads into orbit efficently this way versus a staged/boosted vehicle. The target benchmark is to hit 100MT and 200MT with the same vehicle, and 70MT does not meet this minimum. A rocket of similar proportion to Shuttle using only a pair of RS-68s and a pair of SRBs could hit the 100MT goal that six of the big 68s' cannot is more efficent. The RS-68 is also physically pretty large, I doubt you could fit more then three of them comfortably under an ~8m tank or five under a 9-10m. It would neither be as simple (larger # of liquid engines) nor as cheap.

Yes I know that the CBCs would not be adding much if anything to the liftoff thrust, but that isn't what they would be there for, they would be there for an extra push following SRB burnout where they would do the most good with their hydrogen fuel. The point being that we want to use a smaller Shuttle-ET sized core and still have superheavy lift capacity without having to build a new rocket.

Originally, I cooked up the 6 SRB + 5 RS-68 on 10m core as somthing a little more then double what Shuttle-C or Energia could do, so I basically doubled all the engines. Using Delta-IV CCBs, either stretch or cut length, is simply an easy way to have it both ways with the same rocket.

Euler · 2005-01-11 22:21:26

A rocket of similar proportion to Shuttle using only a pair of RS-68s and a pair of SRBs could hit the 100MT goal that six of the big 68s' cannot is more efficent.

A shuttle with only 2 RS-68 and 2 SRBs should not be able be able to get 100MT into orbit on it's own; Shuttle C could only get 77MT into orbit and it was powered by 3 SSME. You also have to factor in that four RS-68 are probably cheaper than 2 SRBs, so it might still be a better deal to use the big cryogenic core. In addition, the SSTO gets bonuses for reliability, and it will get bigger performance bonuses when you start adding boosters than the vehicle that already has boosters. The version with 1 big core + 4 SRB would definitely have more capacity than the version with 1 medium core + 4 SRB + 2 delta IV CBCs.

Or compare it to Delta IV. 2 Delta IV heavies can deliver 50MT of cargo using 6 RS-68, 6 CBC, and 2 upper stages. If you can deliver 70 MT to orbit with 6 RS-68 and only 1 big tank, that will be a much better deal.

GCNRevenger · 2005-01-12 06:25:15

Oh but it can, Shuttle-C ought to be able to manage about 90-100MT to orbit with improved heavy SRBs, which aproximatly meets the benchmark payload for a Mars ship or its TMI stage. But that is beside the point, that if whatever rocket is put together cannot reach the payload threshold, then it isn't going to fly.

In order for a huge SSTO rocket powerd by RS-68's to do this, it would start getting truely monsterous. You would need about eight engines to do this versus Shuttle-C's four, and the Hydrogen tank could not be built on exsisting Shuttle ET lines. With so many engines, that would be too many for a Superheavy lifter with SRBs assisting launch.

One of the problems with all-cryogenic arrangements is that they have poor thrust/weight ratios that forces them to burn inefficent amounts of fuel to get off the ground and up to an altitude where their superior Isp really kicks in unless you use a huge number of engines (which will weigh you down too late in acent). The Delta-IV HLV you list takes a full fifteen seconds to clear the launch pad. Boeing's own growth-path shows that payload could be increased ~25% simply by adding a quartet of tiny SRM motors to the stack. The low specific impulse at sea level for Hydrogen engines doesn't help either.

The combination of heavy SRMs or RP1 boosters and a cryogenic core is the superior arrangement, where you get high thrust when you need it but not the extra engine/tankage weight when you don't. For a superheavy launcher, there really isn't any practical way to make it all-cryogenic and small enough to build or move, and a 100MT launcher it would be too powerful for a superheavy. I also believe that the superior reliability of a pair of SRBs versus a quartet of RS-68s is no worse then the extra staging event.

Yes, a medium core + Delta-IV CCB will not be quite as efficent as a larger core stage alone, but I do not think that it will be greatly inferior either, and it will be well worth the improved flexibility and use of only exsisting tooling.

SpaceNut · 2005-01-12 06:52:13

By RP1 boosters, you mean kerosene, alcohol and other hydrocarbon based fuels...
So I guess the question then, is how much of each fuel type per stage is then required to get the payload size we want to orbit.

GCNRevenger · 2005-01-12 09:28:21

RP1 is short for Rocket Propellant One, which is the designation for the high-grade kerosene that is used in rocket engines, particularly the RD-170/180 in Zenit and Atlas-V and Soyuz R-7/Onega first stage.

Euler · 2005-01-12 13:41:48

But that is beside the point, that if whatever rocket is put together cannot reach the payload threshold, then it isn't going to fly.

Why must it meet this arbitrary threshold of 100MT or not fly at all? 70MT is still a lot bigger than an EELV, and there shoud be plenty of missions that the vehicle can perform in this configuration.

In order for a huge SSTO rocket powerd by RS-68's to do this, it would start getting truely monsterous. You would need about eight engines to do this versus Shuttle-C's four, and the Hydrogen tank could not be built on exsisting Shuttle ET lines.

Even an 8 RS-68 SSTO would still be smaller than a shuttle ET sized core with 2 big SRBs. However, it would not need 8 engines. If you are putting upgraded SRBs on your rocket, it is only fair that the SSTO should be able to use upgraded RS-68. With some relatively small improvements in thrust and Isp, the SSTO can get into the same payload range as the vehicle with SRBs.

One of the problems with all-cryogenic arrangements is that they have poor thrust/weight ratios that forces them to burn inefficient amounts of fuel to get off the ground and up to an altitude where their superior Isp really kicks in unless you use a huge number of engines (which will weigh you down too late in acent). The Delta-IV HLV you list takes a full fifteen seconds to clear the launch pad. Boeing's own growth-path shows that payload could be increased ~25% simply by adding a quartet of tiny SRM motors to the stack. The low specific impulse at sea level for Hydrogen engines doesn't help either.

Cryogenic rockets can get better T/W ratios than other liquid rockets because their fuels are much lighter. However, I was still worried about gravitational losses, which is why I gave my model vehicle a T/W ratio greater than a Delta IV rather than making the fuel tank as large as possible.

The combination of heavy SRMs or RP1 boosters and a cryogenic core is the superior arrangement, where you get high thrust when you need it but not the extra engine/tankage weight when you don't.

Using SRMs in combination with a cryogenic core does have some advantages. However, when your base vehicle is already more solid than cryogenic then the efficiency of the arrangement starts decreasing as you try to add more SRBs.

For a superheavy launcher, there really isn't any practical way to make it all-cryogenic and small enough to build or move, and a 100MT launcher it would be too powerful for a superheavy. I also believe that the superior reliability of a pair of SRBs versus a quartet of RS-68s is no worse then the extra staging event.

If Saturn 5 was small enough to build and move, then the SSTO will also be small enough to build and move. It's dimensions will be similar to the Saturn V, and it will be lighter. Also, it does not have to be moved a long way since the launch pad will be close to the factory.

100 MT too powerful for a superheavy? I though you were considering rockets in the 200MT range to be superheavies.

When you add the SRBs, you add 2 new dangers: there is the chance of something going wrong in the staging event, and the chance of an SRB failing(like Challenger). The SRBs also can't be turned off, which takes away most of your abort options. However, when you the extra RS-68 engines you add engine out capability, so that the 6 engine vehicle would likely be even more reliable than a single engine vehicle.

Yes, a medium core + Delta-IV CCB will not be quite as efficent as a larger core stage alone, but I do not think that it will be greatly inferior either, and it will be well worth the improved flexibility and use of only exsisting tooling.

Using only existing tooling is an advantage for the small core, but it is the larger core that has better flexibility. By making the core capable of launching itself, you add a new ability and increase the number of possible launch vehicle configurations.

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#1 2004-12-09 20:07:53

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#2 2004-12-09 21:05:17

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#3 2004-12-09 22:05:45

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#4 2004-12-10 00:04:18

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#5 2004-12-10 01:39:22

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#6 2004-12-10 14:10:05

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#7 2004-12-10 16:58:08

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#8 2004-12-11 03:27:40

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#9 2004-12-11 13:22:54

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#10 2004-12-11 13:26:23

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#11 2005-01-10 12:28:41

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#12 2005-01-11 01:04:46

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#13 2005-01-11 08:09:31

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#14 2005-01-11 12:45:19

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#15 2005-01-11 12:45:49

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#16 2005-01-11 17:17:52

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#17 2005-01-11 22:21:26

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#18 2005-01-12 06:25:15

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#19 2005-01-12 06:52:13

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#20 2005-01-12 09:28:21

Re: Which Would Be Cheaper To Build? - "Comet" Saturn V variant or Super Ares?

#21 2005-01-12 13:41:48

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