Is it possible to create Saturn V(esqe) rocket but with entirely modern/newer technology? What its performance will be like?

[derega16]

It is quite well known that it is impossible to relaunch the production of Saturn V due to lacks of supply chain and lost of some know-how. But what if keep just the concept but replace everythings with modern or atleast newer tech.

No big instrument ring, replaced it with much smaller modern computer, removed every components thet are no longer needed,  fuselage made with modern structure and fabrication techniqes. Both should allowed much lighter structure than in the 50's

5 F-1b mainengines for S-I, same number of J-2X for S-II (alternatively 7 to 9 BE-3U) and S-IV (alt. 2 BE-3U) as J-2, maybe 3 of RS-25,68 or AJ-22 for S-II as these are J-2 descendants (They are too powerful for S-IV, however)

streched tanks allowed because of more powerful engines.

Well, it is basically develop nearly a entirely new rocket but what its performance and launch cost (not developnent cost) will be like compared to the original Saturn V and maybe SLS which suppose it be SV's replacement in terms of usage.

Edited April 21, 2020 by derega16

[Wjolcz]

I'm guessing you've seen it already and that's where the question is coming.

Saturn V was designed to achieve a very specific goal of landing humans on the Moon relatively quickly. Right now the goal is slightly different: apart from landing a couple of crew members at once, NASA also wants to do some other lunar activities and SLS was the only option so far. And a full scale Starship is yet to fly, re-enter at orbital speeds and land in one piece. So why would you want to build an expensive and expendable rocket when there are more and better options in development right now?

Edited April 21, 2020 by Wjolcz

[derega16]

I mean just purely in term of performance and construction viability and cost compared to the original and SLS and ignoring the reason to build completely becase that have much more things to consider like "keep shuttle contractor" bulls**tsary and it is too late to consider such thing now, maybe possible to consider it in 2010 but not nowadays. As both J-2X and F-1b have been develop (well, F-1b is kinda) means 2 important components to revive SV are aviable

Edited April 21, 2020 by derega16

[Bill Phil]

We could, and the rocket would be much better. We can get larger specific impulses for both kerolox and hydrolox, so a similar vehicle would be even better today.

Not only that but the staging affects efficiency - SLS's use of hydrolox as a core stage hurts its performance. Using kerolox as a first stage would be more efficient.

It's entirely possible, and a modern day Saturn-V like vehicle would perform better than the original. More efficient rocket engines, smaller computers, and a better understanding of the dynamics of flight. 

It wouldn't really be a Saturn V, it'd be a brand new rocket.

[RCgothic]

My fantasy modern Saturn would have 50 Merlin 1Ds in the first stage. More thrust than 5 F1Bs, less weight, better ISP, and fit really well within a 10m diameter footprint. Most importantly - it would be the Saturn 50! Saturn L! And rather than increase the payload with all that extra thrust, I'd reserve enough margin for RTLS landing.

Saturn L1 would RTLS.

Saturn L2 would be agnostic to payload and get to LEO.

On top you'd either have Saturn L3 for BLEO, or just a massive payload.

Of course crew would be allowed nowhere near this beast - commercial crew has crew-rated to LEO covered.

Edited April 22, 2020 by RCgothic

[kerbiloid]

Because it's always easier to make a project from scratch than to support the legacy.

And the prices are better. Why spend you qualified staff and expensive equipment working hours on reviving the old for obviously less money.

[K^2]

12 hours ago, Bill Phil said:

We can get larger specific impulses for both kerolox and hydrolox, so a similar vehicle would be even better today.

I_SP difference isn't huge for modern LH2 rockets. There have been some improvements, but if that's all we had, it wouldn't be much. Materials that would let us squeeze all available I_SP out LH2 without melting just don't exist and probably can't exist. We can do 10-15% better, and again, that doesn't make as much difference as it does for kerlox, because the g*I_SP factor for LH2 is already a large fraction of delta-V. So you don't get these exponentially growing benefits of improving I_SP like you do with kerlox. But when you couple that with better TWR and MUCH better weight to capacity ratio of tanks we can build with modern materials, the net performance can be significantly better.

Switch to kerlox or some other hydrocarbon makes sense if you're trying to optimize for launch cost. Which, you know, is probably the sensible thing to do. But then, yeah, you really are building a very different rocket.

[Hannu2]

18 hours ago, derega16 said:

It is quite well known that it is impossible to relaunch the production of Saturn V due to lacks of supply chain and lost of some know-how. But what if keep just the concept but replace everythings with modern or atleast newer tech.

No big instrument ring, replaced it with much smaller modern computer, removed every components thet are no longer needed,  fuselage made with modern structure and fabrication techniqes. Both should allowed much lighter structure than in the 50's

5 F-1b mainengines for S-I, same number of J-2X for S-II (alternatively 7 to 9 BE-3U) and S-IV (alt. 2 BE-3U) as J-2, maybe 3 of RS-25,68 or AJ-22 for S-II as these are J-2 descendants (They are too powerful for S-IV, however)

streched tanks allowed because of more powerful engines.

It is certainly possible, if you have couple of billions extra money for development and building and not intention to get it ever back as profit. But I would not ask funding for such project from anyone else.

I can not believe that you can compete with SpaceX's or Blue Origin's coming big rockets in any part of performance or economy. As far as I understood the most important reason to choose methane as a fuel is better reusing properties. It will be essential in economic competition of next generation rockets. It seem also that optimal engine size for effective staged combustion is smaller than F1 was. 5 huge engines is probably worse than large number of smaller ones. Etc. Saturn V was very specific solution under conditions of limited time and unlimited budget and therefore many basic design choices was not suitable for modern requirements of economy and reusability. Of course you can build modern rocket about the same size and call it Saturn VI for nostalgic reasons, but technical solutions will be very different.

 

[magnemoe]

28 minutes ago, Hannu2 said:

It is certainly possible, if you have couple of billions extra money for development and building and not intention to get it ever back as profit. But I would not ask funding for such project from anyone else.

I can not believe that you can compete with SpaceX's or Blue Origin's coming big rockets in any part of performance or economy. As far as I understood the most important reason to choose methane as a fuel is better reusing properties. It will be essential in economic competition of next generation rockets. It seem also that optimal engine size for effective staged combustion is smaller than F1 was. 5 huge engines is probably worse than large number of smaller ones. Etc. Saturn V was very specific solution under conditions of limited time and unlimited budget and therefore many basic design choices was not suitable for modern requirements of economy and reusability. Of course you can build modern rocket about the same size and call it Saturn VI for nostalgic reasons, but technical solutions will be very different.

 

Methane is kind of an compromise between hydrogen and RP1, Cryogenic but at LOX level so not much of an problem as you use LOX anyway. Lower density than RP1 but much denser than hydrogen. 
Performance is also between. Its also cheep who is an nice bonus. 
For spaceX, that you can produce it on Mars is critical but that is not an factor for Blue Origin. 
And yes starship will get Saturn 5 level performance while being reusable and refuelable in orbit. 

Most rockets today uses SRB since its an cheap way to give high trust. This don't work well with reuse and its pretty pointless to build an new rocket today and not plan for reuse 

[Bill Phil]

4 hours ago, K^2 said:

I_SP difference isn't huge for modern LH2 rockets. There have been some improvements, but if that's all we had, it wouldn't be much. Materials that would let us squeeze all available I_SP out LH2 without melting just don't exist and probably can't exist. We can do 10-15% better, and again, that doesn't make as much difference as it does for kerlox, because the g*I_SP factor for LH2 is already a large fraction of delta-V. So you don't get these exponentially growing benefits of improving I_SP like you do with kerlox. But when you couple that with better TWR and MUCH better weight to capacity ratio of tanks we can build with modern materials, the net performance can be significantly better.

Switch to kerlox or some other hydrocarbon makes sense if you're trying to optimize for launch cost. Which, you know, is probably the sensible thing to do. But then, yeah, you really are building a very different rocket.

The Isp difference isn't huge, no. But don't be so sure that it wouldn't significantly alter performance. 

Just looking at the S-IVB, an Isp increase from 421 seconds to 465.5 seconds would improve TLI payload by ten tonnes. And that's taking into account the instrument unit as part of the stage dry mass, so you could probably get another 2 tonnes of payload with a modern vehicle. Essentially, the J-2 rocket engine wasn't a good hydrolox engine by modern standards. The real question would be whether or not 465.5 is possible. Something in the 450s may be more reasonable. 

But that performance improvement would cascade down the entire rocket - doing the same to the first and second stages would likely allow us to use a larger third stage and not even need to fire it to enter low orbit like the Saturn V did. And that's before taking into account structural advances like you mention.

I wouldn't be surprised if we could get 100 tonnes to TLI with a vehicle similar in size to the Saturn V. Improved mass ratios, improved specific impulses for every stage of the vehicle, and so on. 

And 100 tonnes to TLI... man we could do some cool stuff.

[Hannu2]

26 minutes ago, magnemoe said:

Methane is kind of an compromise between hydrogen and RP1, Cryogenic but at LOX level so not much of an problem as you use LOX anyway. Lower density than RP1 but much denser than hydrogen. 
Performance is also between. Its also cheep who is an nice bonus. 

Some times ago there was discussion that important reason for methane development was lower sooting in combustion (compared to kerosine, supercold superflammable hydrogen is in any case too impractical for safe rapid reuse). Soot causes problems or at least need for extra cleaning between uses in kerosine engines, like Merlin. I did not remember was it in turbopumps, it does not sound reasonable that soot accumulates in actual chamber.

 

[RCgothic]

Hydrogen alone generally doesn't have enough thrust to get off the ground.

Yes, we absolutely could build a more capable Saturn V with modern tech.

An expendable Kerolox 1st stage with 50 Merlins and an expendable Methalox 2nd stage with 7 Raptors could comfortably put 200t in LEO with structural fractions comparable to F9 and a form factor similar an all-10m SaturnV.

The first stage would probably be about 10m shorter due to densified propellants, common bulkhead and shorter engines.

Stage 2 would similarly probably lose about 10m due to much denser propellants.

"Saturn L" would therefore be about 20m shorter than the equivalent Saturn V two stages. (45m vs 60m)

If SpaceX built it it would probably cost approx half a billion a launch. (Suck it SLS!).

But could it compete with the likes of Starship and New Glenn and reusability? No.

Edited April 22, 2020 by RCgothic

[tater]

I suppose you could use existing engines to make it using the same stack arrangement (kerolox, hydrolox, hydrolox, hypergolics). Multiple RD-180s or Merlins as S1? Else you start looking at methane as suggested (Be-4 or Raptor).

[Bill Phil]

6 minutes ago, tater said:

I suppose you could use existing engines to make it using the same stack arrangement (kerolox, hydrolox, hydrolox, hypergolics). Multiple RD-180s or Merlins as S1? Else you start looking at methane as suggested (Be-4 or Raptor).

Might want to use RD-191s since they have a smaller size than the RD-180s. And they have much higher SL ISP than the F-1s, so we can shrink the first stage a bit or we can have heavier upper stages. The limit is likely thrust, but a higher thrust is possible, 24 RD-191s could fit nicely on a 10 meter stage and we'd get more thrust than 5 F-1s. Though the TWR isn't much better so we'd have more engine mass. Still, that much thrust may be overkill, but larger upper stages would be pretty good for boosting TLI throw weight. Couple that with better hydrolox ISP and better stage mass ratios and 100 tonnes to TLI is possible for a 10 meter rocket. Heck, maybe more. Something like 130 tonnes to TLI is probably possible. Then the major issue is probably payload fairing size and structural limitations.

Though 24 engines may be a bit too much... maybe RD-171s would be better but you'd need some thrust augmentation since they're larger than RD-191s. 

Probably would have been a better bet to build a brand new 10 meter rocket than SLS... 

[wumpus]

21 hours ago, RCgothic said:

My fantasy modern Saturn would have 50 Merlin 1Ds in the first stage. More thrust than 5 F1Bs, less weight, better ISP, and fit really well within a 10m diameter footprint. Most importantly - it would be the Saturn 50! Saturn L! And rather than increase the payload with all that extra thrust, I'd reserve enough margin for RTLS landing.

Saturn L1 would RTLS.

Saturn L2 would be agnostic to payload and get to LEO.

On top you'd either have Saturn L3 for BLEO, or just a massive payload.

Of course crew would be allowed nowhere near this beast - commercial crew has crew-rated to LEO covered.

50 Merlins is not a fantasy Saturn but a fantasy N1.

11 hours ago, kerbiloid said:

Because it's always easier to make a project from scratch than to support the legacy.

And the prices are better. Why spend you qualified staff and expensive equipment working hours on reviving the old for obviously less money.

Depends what you pick and choose from "legacy".  NASA's prototype reborn F1 engine would make a lot of sense for a Super Heavy lifter, especially if you are not concerned with reuse (pretty much starts and ends with SLS).  Building the rest of the rocket?  You'll find a lot of "use asbestos here" and "perform a ton of hand welding operations that haven't been done since 1975 there" and "include lots of MIL-SPEC parts that haven't been available since 1990".  And don't forget that everything electronic assumes lead-based solder and that could be important in the temperature ranges they encounter...

Once you complete redesigning your rocket, you also have to redesign launch procedures as they really weren't documented well enough to replace the *entire* army of technicians needed to launch the rocket.  You are essentially going to design an entirely new rocket.

But don't ever assume you can ignore legacy altogether.  Building any kind of Saturn-sized rocket almost certainly wants to use Cape Kennedy's Vertical Assembly Building, although I'm not sure of the status of the crawlers (which you want if available).  You want any available launchpad, and should try to integrate your rocket with an available pad (replumbing for methalox will be expensive).  Any available testing facilities will also dictate limits on just what you need to do (you don't want to build your own from scratch).  And of course there are all the regulations that have been written in blood over the last 70-odd years (plenty of which were written *after* Apollo, especially the updates after Apollo 1).

[K^2]

8 hours ago, Bill Phil said:

Just looking at the S-IVB, an Isp increase from 421 seconds to 465.5 seconds would improve TLI payload by ten tonnes. And that's taking into account the instrument unit as part of the stage dry mass, so you could probably get another 2 tonnes of payload with a modern vehicle. Essentially, the J-2 rocket engine wasn't a good hydrolox engine by modern standards. The real question would be whether or not 465.5 is possible. Something in the 450s may be more reasonable.

Which isn't bad, but not groundbreaking. It lets you bring more equipment on a similar type of mission, giving you either more mobility on the Moon or allowing for longer stay. If we were building a permanent outpost on the surface, that kind of boost could even be critical. But this doesn't instantly open up doors for completely new missions. Lighter engines and tanks on top of the I_SP boost does. A similar sized rocket could be used for a direct Mars fly-by mission with room to spare. And we are talking about getting a sufficiently large hab unit to get the crew there with their mental faculties intact. With two launches, we might seriously discuss a landing mission. That's not something you could have done with original Saturn-V without multiple launches to assemble an interplanetary rocket in orbit. I know there were proposals for something simpler and more direct with Saturn-V, but they weren't really taking into account things we learned about extended stay in microgravity since then.

[Bill Phil]

2 minutes ago, K^2 said:

Which isn't bad, but not groundbreaking. It lets you bring more equipment on a similar type of mission, giving you either more mobility on the Moon or allowing for longer stay. If we were building a permanent outpost on the surface, that kind of boost could even be critical. But this doesn't instantly open up doors for completely new missions. Lighter engines and tanks on top of the I_SP boost does. A similar sized rocket could be used for a direct Mars fly-by mission with room to spare. And we are talking about getting a sufficiently large hab unit to get the crew there with their mental faculties intact. With two launches, we might seriously discuss a landing mission. That's not something you could have done with original Saturn-V without multiple launches to assemble an interplanetary rocket in orbit. I know there were proposals for something simpler and more direct with Saturn-V, but they weren't really taking into account things we learned about extended stay in microgravity since then.

I was only considering the S-IVB in that situation - a ten tonne improvement for it translates to a 20% improvement in payload with only a 10% improvement in specific impulse. But the same could be done for the S-II. It's throw weight could be improved 20%, allowing for a larger upper stage. This would make the third stage and its payload 220 tonnes. That 20% improvement stacks, and becomes a 44% improvement in payload - 72 tonnes to TLI. The same case is true for the S-IC, though the ratio is different. The increase would be around 37% - TLI increases to 98.6 tonnes. But wait - I've been assuming the 2 tonne instrument unit is still on the S-IVB, so really that's an underestimate by at least 2 tonnes, more in reality. So a "modern" Saturn V with no improvements in tank ratios and taking advantage of scaling the upper stages to account for better lower stage performance gives the vehicle 100 tonnes to TLI. And that's just a few hundred m/s short of TMI. Manned missions to orbit Mars would be possible. Better tank ratios is only icing on the cake at this point. 

[sevenperforce]

This topic got me thinking more about how different kinds of propellants are more or less efficient and effective for different applications. What IS the most efficient way to get a bunch of mass to the moon, assuming an expendable vehicle? How do you measure efficiency? How many staging events are too many?

If we were to build a better Saturn V today, we would once again try to spread the costs across as many contractors as possible. So it would not be surprising to have two or even three different propellant choices. Plumbing the pad for even more multiple prop feeds is expensive but is something they'd absolutely do.

My gut says that for sending a 100-150 tonne payload to the moon (or the equivalent for a Mars/Venus direct flyby), the beefiest, most powerful approach would be to do 3.5 stages: kerolox with strap-on SRBs, a methalox second stage, and a hydrolox third stage. Probably RD-180s or Merlin 1Ds on the first stage, probably a couple of vacuum Raptors on the second stage, and probably BE-3Us for the third stage.

But is the thrust advantage of a kerolox first stage obviated by using SRBs in parallel? Is the ideal expendable moon rocket really just a bigger Vulcan?

One advantage to going kerolox-methalox-hydrolox is you can use a common tank diameter all the way up.

[tater]

25 minutes ago, sevenperforce said:

One advantage to going kerolox-methalox-hydrolox is you can use a common tank diameter all the way up.

Very interesting and true.

[sevenperforce]

13 minutes ago, tater said:

Very interesting and true.

You can also use fewer kerolox engines on the first stage if you have the SRBs to help you off the pad. I dislike SRBs but they're useful for that.

Some useful reference values for anyone looking at what performance you need to get to the moon...

• The Saturn V S-IC first stage accelerated the vehicle to 2.06 km/s and lost 1.85 km/s to gravity drag, aerodynamic drag, and thrust drag
• The Saturn V S-II second stage accelerated the vehicle to an additional 3.55 km/s and lost  1.24 km/s to gravity drag
• The Saturn V S-IVB third stage added 2.18 km/s to reach an earth parking orbit of 191.2 km
• The Saturn V S-IVB third stage restarted to provide 2.17 km/s for the trans-lunar injection.

So you can start there.

[RCgothic]

Thrust drag?

[sevenperforce]

17 hours ago, RCgothic said:

Thrust drag?

Loss of thrust due to atmospheric pressure. 

Saves you the trouble of switching between SL specific impulse and vacuum specific impulse: just use the vacuum specific impulse and chalk losses up to thrust drag. The maths work.

Also, here are some reference values for current or near-current engines that may be useful...some estimates in here but they are good ones.

Engines
Engine	Thrust (kN)	Weight (kg)	isp_v (s)	prop mass, kg (srb only)
Merlin 1D	941.8	470	311	-
RD-180	4152	519	338	-
RL-10C-1	101.9	301	449.7	-
RL-10C-1-1	105.9	301	453.8	-
RL-10C-2	111.2	301	465.5	-
RL-10C-3	108.5	301	460.1	-
Raptor Vac	2150	1826	380	-
Raptor SL	1960	1500	350	-
BE-4 SL	2400	5246	340	-
BE-3U	710	1477	452	-
Merlin 1D Vac	934	480	380	-
RS-25 (SSME)	2279	3526	452.3	-
RS-68A	3556	6686	411	-
SLS SRB	20000	113750	268	625000
GEM-63XL	2026	5400	284	48000

Edited April 25, 2020 by sevenperforce

[RCgothic]

I guess that makes sense! I'd just never heard it described that way before!

I think your Merlin 1D figures are wrong though. 854kN thrust according to Wikipedia.

Edited April 24, 2020 by RCgothic

[magnemoe]

On 4/22/2020 at 7:36 PM, tater said:

I suppose you could use existing engines to make it using the same stack arrangement (kerolox, hydrolox, hydrolox, hypergolics). Multiple RD-180s or Merlins as S1? Else you start looking at methane as suggested (Be-4 or Raptor).

Yes, however most modern rockets uses SRB for bonus trust, yes its exceptions but they tend to be legacy, small or the new thing who is reusable. 
Hint, plan for the new thing. Now treating second stage as part of the satellite like Rocketlab working toward makes sense for them, second stage itself is very primitive and can only do one deorbit burn. Satellite buss does all the other stuff. 
Because you also has to reuse second stage unless its very cheap. 

[Reactordrone]

26 minutes ago, magnemoe said:

Yes, however most modern rockets uses SRB for bonus trust, yes its exceptions but they tend to be legacy, small or the new thing who is reusable. 
Hint, plan for the new thing. Now treating second stage as part of the satellite like Rocketlab working toward makes sense for them, second stage itself is very primitive and can only do one deorbit burn. Satellite buss does all the other stuff. 
Because you also has to reuse second stage unless its very cheap. 

RD-170s have similar thrust to an F-1 so you could do a first stage without external boosters and carry 100 tonnes less propellant for the same delta-v. That would also reduce gravity drag since your TWR would be higher (and the Saturn V had terrible TWR on the pad).