SpaceX Starship vs Saturn V vs N-1

[Silencer1]

Hi!
I'm not space specialist, so my question definitely amateurish - I try to understand, what's reasons for use on proposed SpaceX Heavy launcher the a large number (~28) of engines for first stage?
In the times of "Moon Race" Saturn V has been equipped with just 5 engines and works well.
Soviet N-1 launcher has been based one quite complex arrangement of 30 NK-15 engines, controlled by KORD system.
All N-1' launch attempts have failed, due to various reasons, including KORD misfunction.
Of course, it hasn't be sole reason of N-1 fate, so the question is: what's advantages and disadvantages have Starship' first stage due to it's powerplant configuration?

Thanks in advance for your's opinions.

P.S. And it's very fun to find such "Starship User Guide"

 

[Moose]

The complexity certainly is something they have to tangle with, but SpaceX's decision-making is driven heavily by the need to do things like land and take off Starshipfrom Mars, as well as to land and re-fly the Super Heavy booster stage on Earth. The standard and vacuum Raptors are are well sized for these, but it means using a whole bunch to lift the first stage. A massive engine would be, well, challenged to throttle far enough down to land with the multi-engine redundancy SpaceX wants on manned interplanetary missions.

They could develop a separate large booster engine purely for the first stage ascent phase, but that would take substantial time and money they'd rather spend elsewhere. And they're hoping the economies of scale really pay off by building so many Raptors, even if it makes their plumbing and software challenges a bit larger than they otherwise might be.

 

[Hobbes]

Large engines are more difficult to develop because the large combustion chamber makes it easier for combustion instability to develop. It took several years to fix this in the F-1 program.

A large number of small engines has its own complications: engine interactions via vibrations, complex plumbing etc.

The N-1 suffered mostly from underfunding, which meant they didn't have a test stand for the first stage. A test stand would have allowed them to sort out the engine interactions before the first launch.
KORD was a rather primitive system (don't forget, the US basically invented the microcomputer during the space race: KORD was a very early computer).

SpaceX has gained a large amount of experience with 'many engines' setups in their Falcon 9. They also had the freedom to choose any engine size they wanted, and (after much dithering over engine sizes) they chose a smallish engine. We've even seen early renders of a Falcon 9 with a single "Merlin 2" engine.
That tells me they've done tradeoff studies and concluded the problems of a large number of small engines are easier to solve than the other way round.

 

[Dilandu]

I'm not space specialist, so my question definitely amateurish - I try to understand, what's reasons for use on proposed SpaceX Heavy launcher the a large number (~28) of engines for first stage?

Because large number of smaller engines are simpler to design & produce, than a small number of very big, high-performance engines.

Soviet N-1 launcher has been based one quite complex arrangement of 30 NK-15 engines, controlled by KORD system.
All N-1' launch attempts have failed, due to various reasons, including KORD misfunction.

Yes, but it's an example of technology marching on; in 1960s, it was impossible to even envision a number of digital sensors, processors and control systems, that now could be easily implemented to coordinate the multi-engine arrangement.

 

[mkellytx]

Large engines are more difficult to develop because the large combustion chamber makes it easier for combustion instability to develop. It took several years to fix this in the F-1 program.

A large number of small engines has its own complications: engine interactions via vibrations, complex plumbing etc.

The N-1 suffered mostly from underfunding, which meant they didn't have a test stand for the first stage. A test stand would have allowed them to sort out the engine interactions before the first launch.
KORD was a rather primitive system (don't forget, the US basically invented the microcomputer during the space race: KORD was a very early computer).

SpaceX has gained a large amount of experience with 'many engines' setups in their Falcon 9. They also had the freedom to choose any engine size they wanted, and (after much dithering over engine sizes) they chose a smallish engine. We've even seen early renders of a Falcon 9 with a single "Merlin 2" engine.
That tells me they've done tradeoff studies and concluded the problems of a large number of small engines are easier to solve than the other way round.

One of the key choices SpaceX made early on was to design for manufacture, the production system, versus absolute performance. This allows them to assure the production system rather than the product produced. That's a big saving in time and cost. Compare F9 to EELV, both for quite a while launched roughly 10 launches a year, EELV 12 cores a year, 9 singles and a heavy. An average year EELV would do 5 Delta cores and 7 Atlas cores, which comes to 5 RS-68's, 3 RL-10B's, 7 RD-180's and 7 RL-10A's, each new engine produced every 1.5-2 months. The 10 F9's require 100 Merlin's, pretty much a new engine every 3 days, 10 of those with a different nozzle and a few mods to operate in a vacuum.

Elon has often stated the hard part isn't building the rockets, it's building the production system. Do his rockets leave pounds to orbit on the table, yes. Do they leave dollars per pound to orbit on the table, no.

Another interesting aside, while I worked EELV from 2010-2012 got to hear an interesting discussion around why we didn't just restart building F-1's vs developing completely new engines to replace the RD-180's. It pretty much came down to we lost the subject matter expertise to solve the combustion instabilities on a rocket that big.

So, the answer to the original question is that Elon and company have decided solving the vibration/harmonics problem is a more cost effective route than building bigger engines.

 

[TomcatViP]

@mkellytx : Nice and informative. Thank you.

Solving the vibrational problem might have been influenced with their choice for a conventional material instead of composite: it's fairly easy nowadays to get accurate results with metallic structure in simulation while the gap with composites in their flight envelope might be too great without countless prototyping loops b/w each design iteration.

 

[TomS]

The 10 F9's require 100 Merlin's, pretty much a new engine every 3 days, 10 of those with a different nozzle and a

OTOH, 10 F9 launches do not require 100 engines anymore. They expend one vacuum Merlin per launch but get many launches out of their regular Merlins (7 is the record so far!). That eases a lot of pressure on Merlin production.

Raptor, OTOH, seems to be a performance-optimized beast of an engine. And they need a lot of them. But Merlin did give them good experience in building an engine production pipeline, even if Raptor is technically quite different.

 

[Orionblamblam]

It pretty much came down to we lost the subject matter expertise to solve the combustion instabilities on a rocket that big.

Bingo. Tribal knowledge evaporates when not used. It can be only fragmentarily recorded.

 

[mkellytx]

@mkellytx : Nice and informative. Thank you.

Solving the vibrational problem might have been influenced with their choice for a conventional material instead of composite: it's fairly easy nowadays to get accurate results with metallic structure in simulation while the gap with composites in their flight envelope might be too great without countless prototyping loops b/w each design iteration.

While the isotropic properties of stainless steel certainly do make it easier to model, the strength properties at very high and low temperatures led to the move from carbon fiber composites to the 30X series of stainless on SS/SH. FWIW SpaceX does use carbon fiber on F9.

 

[mkellytx]

The 10 F9's require 100 Merlin's, pretty much a new engine every 3 days, 10 of those with a different nozzle and a

OTOH, 10 F9 launches do not require 100 engines anymore. They expend one vacuum Merlin per launch but get many launches out of their regular Merlins (7 is the record so far!). That eases a lot of pressure on Merlin production.

Touché, back 2012 after we published the New Entrant Certification Guide that was still three years in the future and a lot of the old gray beards thought it couldn't be done. Reuse certainly does free up resources to focus on Raptor and change the economics of space launch, it wouldn't be surprising to see F9 and Merlin retired before the end of the decade when SS/SH come online.

 

[Hanse]

Another interesting aside, while I worked EELV from 2010-2012 got to hear an interesting discussion around why we didn't just restart building F-5's vs developing completely new engines to replace the RD-180's. It pretty much came down to we lost the subject matter expertise to solve the combustion instabilities on a rocket that big.

 

[Hobbes]

One of the key choices SpaceX made early on was to design for manufacture, the production system, versus absolute performance. This allows them to assure the production system rather than the product produced. That's a big saving in time and cost. Compare F9 to EELV, both for quite a while launched roughly 10 launches a year, EELV 12 cores a year, 9 singles and a heavy. An average year EELV would do 5 Delta cores and 7 Atlas cores, which comes to 5 RS-68's, 3 RL-10B's, 7 RD-180's and 7 RL-10A's, each new engine produced every 1.5-2 months. The 10 F9's require 100 Merlin's, pretty much a new engine every 3 days, 10 of those with a different nozzle and a few mods to operate in a vacuum.

Elon has often stated the hard part isn't building the rockets, it's building the production system. Do his rockets leave pounds to orbit on the table, yes. Do they leave dollars per pound to orbit on the table, no.

In the 1980s and 1990s ESA/Arianespace investigated reusing the first stage of the Ariane 5. They found that reuse on the scale they were looking at (12 launches/year), has one major drawback: the production system for the first stage would be idle most of the year, with only 1 or 2 new stages being built. This meant cost savings were minimal: to retain institutional knowledge, you have to retain personnel even if they're doing nothing. The SpaceX strategy of commonality between the first and second stage, and of using a large number of engines on the first stage, really pays off here.

 

[TomcatViP]

That sounds typical of some push papers mentality, engineering the middle-age of the industrial era.
Thanks God for Musk.

As a side note LM just offered to buy Rocketdyne, the last remain of the great North American legendary aerospace company. At +33% the share, it's an honest financial offer that also promises to open opportunity for that company.

Lockheed Martin inks $4.4 billion deal to acquire Aerojet Rocketdyne

Lockheed Martin Corp said on Sunday it has agreed to buy U.S. rocket engine manufacturer Aerojet Rocketdyne Holdings Inc for $4.4 billion, including debt and net cash.

in.mobile.reuters.com

 

[Hanse]

That sounds typical of some push papers mentality, engineering the middle-age of the industrial era.
Thanks God for Musk.

As a side note LM just offered to buy Rocketdyne, the last remain of the great North American legendary aerospace company. At +33% the share, it's an honest financial offer that also promises to open opportunity for that company.

Lockheed Martin inks $4.4 billion deal to acquire Aerojet Rocketdyne

Lockheed Martin Corp said on Sunday it has agreed to buy U.S. rocket engine manufacturer Aerojet Rocketdyne Holdings Inc for $4.4 billion, including debt and net cash.

in.mobile.reuters.com

If you watch the second video I posted up there it explains why we can't build an F-1 - using the techniques they used back in the day. Of course they did explain we could make a BETTER one, with a fraction of the number of parts, with modern manufacturing methods.

 

[TomcatViP]

My remark was only related to the portion of your comment on the ESA.

 

[Voidhawk9]

Keep in mind also that SpaceX has already launched a few Falcon Heavies - and they run 27 engines on the first stage (across 3 cores). So Starship isn't much more than what they are already doing in that sense.

 

[Sherman Tank]

At the moment it's far more N-1 than Saturn V in terms of successful launches.

 

[Hobbes]

well, the development method used for Starship has more in common with the N-1 than with the Saturn V.
For the N-1, the Soviets decided to do 'all-up' testing. Instead of building a test stand large enough to accommodate the first stage, they planned a bunch of launches with a functioning first stage, plus boilerplate items for the other stages. Once the first stage bugs had been worked out they'd add the second stage etc. Originally, 14 launches were planned for this test campaign, and they fully expected to have explosions on the way.

NASA spent a lot of time generating fireballs on test stands before the first Saturn V launch.

The SpaceX 'incremental development' model starts flight tests at an even earlier stage, with incomplete vehicles (hopper, then empty starship with only 3 engines).

 

[Levsha]

NASA spent a lot of time generating fireballs on test stands before the first Saturn V launch.

None of the combined 28 launches Saturn Program, including the Saturn 1, Saturn 1B and Saturn V ended in a "fireball" - almost all were completely successful launches.

Better than the launch success rate in the 1950s - just highlights how much rocket technology had progressed in the space of 10 years.

 

[TomS]

NASA spent a lot of time generating fireballs on test stands before the first Saturn V launch.

None of the combined 28 launches Saturn Program, including the Saturn 1, Saturn 1B and Saturn V ended in a "fireball" - almost all were completely successful launches.

"Fireballs on test stands" refers to the many F-1 engines they blew up before getting to the point of actual launches.

 

[Michel Van]

The N1 suffer too much problems
It's Designer Korolev died in 1967 and his successor Mishin had very serious issue with Alcohol.
The Launcher was revised over and over again, do changes in Mission architecture and increase in Payload mass.
Mishin put 6 additional Engines in center and Super chilled the Propellants
He also consider 12 test launches until N1 was ready to send Humans to moon.
The engine manufacturer Kuznetsov not tested every of there NK-15 just sample one out production and some of NK-15 failed.
I'm thing not that 30 engines were main problem of the N1, since World record is Falcon Heavy with 27 engines !
but allot POGO and rupture of LOX feed-lines, were main cause of failure of N1 !
Also was problem that N1 program run on Shoestring budget with lackluster by Politburo...

The Saturn V was more lucky
It's Designer Team under Von Braun had learned with Saturn I & IB how to build Saturn V
next truckloads of Money by Capitol Hill what let Program to run fast.
But there were problems like F-1 engine combustions problems they way to deal with it: Testing, testing, testing.
After 2471 Test runs, the F-1 was ready for first test Launch of Saturn V
in mean time the manufacturers had problems building the Stages and integration into one system.
Von Braun wanted 12 test launches but higher up in NASA say NO WAY, Two to Three test launches !
So flawless was the Saturn V not, Apollo 4 & 13 suffer of J-2 engine failure, other had POGO issues

Starship/Superheavy
SpaceX want to go radical new way, next total reusability, Low operation cost and low manufacturing cost.
Therefore they goes for low cost Steel (Like Atlas ICBM) and also Testing, testing, testing (Like Atlas ICBM)
With a breath-taking speed if you see the progress SpaceX made in last year!
Goal is to build a fleet of Starship/Superheavy of hundreds even thousand launch rocket
biggest problem is not to build&launch the prototypes, but get the mass production up and running !
if SpaceX manage those problems, Starship/Superheavy will become the DC-3 of Spaceflight.

 

[Josh_TN]

As noted, SpaceX went about setting up the simplest production process for rockets. This includes using almost identical engines in the 1st and 2nd stages, and perhaps more importantly the same propellants - you'll notice other rocket designs often have different fuels/engines (my understanding is that this is in order to get more specific impulse on the 2nd stage). F9 doesn't taper the way some other boosters do for the same reason - they wanted the tank diameters to be identical so that the lower and upper stages shared as much production commonality as possible. The choice to use RP1 and LOX also represents the easiest fuel to produce and store. All in all, F9 is a rather inefficient beast and SpaceX compensates with sheer number of engines and volume of fuel to get the performance they wanted. As someone noted above quite succinctly, it is fuel inefficient but extremely dollar efficient, even before taking into account reusability.

Starship/Superheavy seems to go the same route, but with a change of fuel. There are a lot of reasons for fuel choice but I think in this case the single biggest driver was to build something that could be refueled with local resources in the solar system (specifically Mars), which limited the options to H2 or methane. Of those two, one is a lot easier to store and cool. But other than that the same design philosophy of simplicity and commonality of parts stream seems to have driven SS/SH development.

 

[mkellytx]

As noted, SpaceX went about setting up the simplest production process for rockets. This includes using almost identical engines in the 1st and 2nd stages, and perhaps more importantly the same propellants - you'll notice other rocket designs often have different fuels/engines (my understanding is that this is in order to get more specific impulse on the 2nd stage). F9 doesn't taper the way some other boosters do for the same reason - they wanted the tank diameters to be identical so that the lower and upper stages shared as much production commonality as possible. The choice to use RP1 and LOX also represents the easiest fuel to produce and store. All in all, F9 is a rather inefficient beast and SpaceX compensates with sheer number of engines and volume of fuel to get the performance they wanted. As someone noted above quite succinctly, it is fuel inefficient but extremely dollar efficient, even before taking into account reusability.

Starship/Superheavy seems to go the same route, but with a change of fuel. There are a lot of reasons for fuel choice but I think in this case the single biggest driver was to build something that could be refueled with local resources in the solar system (specifically Mars), which limited the options to H2 or methane. Of those two, one is a lot easier to store and cool. But other than that the same design philosophy of simplicity and commonality of parts stream seems to have driven SS/SH development.

Design for manufacture, automation, reuse of tooling, iterative design/build/test/fly. The F9 of 2012 is not the F9 of today but it is good enough to get to LEO and GTO far cheaper than Atlas, which out performs F9 the further away you get from LEO. Insourcing the production helps a lot also, SpaceX build's 90% of the rocket themselves, EELV seemed to spread the supplier base all over the US to get congressional support...

The choice of methane for SS/SH is three fold, first it's pretty hard to produce RP1 on Mars, H2 is a very difficult molecule to store long term and methane burns really clean so won't coke the engines like RP1. The last piece was a big consideration for engines targeting up to 100 reuses.

 

[Hanse]

but it is good enough to get to LEO and GTO far cheaper than Atlas, which out performs F9 the further away you get from LEO.

Due to the Centaur upper stage, not anything special about the booster.

 

[mkellytx]

but it is good enough to get to LEO and GTO far cheaper than Atlas, which out performs F9 the further away you get from LEO.

Due to the Centaur upper stage, not anything special about the booster.

Yes, the beer can upper stage, specifically the RL-10A, it's one of the highest ISP engines ever manufactured, but my reply was already getting wordy, didn't want bog down in the Atlas/Delta comparison and how the higher ISP RS-68/RL-10B was more "efficient" than the RD-180/RL-10A but cost more and lifted less...

 

[ADVANCEDBOY]

This is only one of hundreds of mathematical calculations and research done on F-1`s actual thrust and its real capabilities. Some of this research comes from Bauman Moscow State Technical University ` employees` and some from actual rocket engineers. No matter how they yanked the available data they could get F1 work only if it had a weight reduction by 1200 tons and thrust reduction by 40%.

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13-3

Soot calculation on F-1 ( over specified limits.)

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13-2

​

 

[jstar]

Conclusion of «ПЕПЕЛАЦЫ» ЛЕТЯТ НА ЛУНУ №13-3:

"Instead of 690 tons, the F-1's thrust at launch was 40% less!

This conclusion is the key to the discussion about the reality of manned missions to the Moon with rockets " Saturn 5 " , equipped with five engines F-1 .
With such a starting thrust, the mass of a rocket with a thrust-to-weight ratio n = 1.19 could not exceed m o = 5 · 405 / 1.19 ≤ 1700 tons.

The launch weight of the Saturn-5 rocket was 1200 tons less than the official one!​

Lightened by more than 40%, the Saturn-5 rocket could in no way send a real manned spacecraft to the Moon.
The sole purpose of this rocket is to launch primitive unmanned dummies into space for the amusement of the public to simulate space flights.

In the next chapter, No. 14, we will dwell in detail on the fundamental problems of the F-1 , because of which it turned out to be a hopeless and meaningless curiosity in the history of astronautics."

 

[Sherman Tank]

Oh goody, the moon landing deniers are here.

 

[Levsha]

This is only one of hundreds of mathematical calculations and research done on F-1`s actual thrust and its real capabilities. Some of this research comes from Bauman Moscow State Technical University ` employees` and some from actual rocket engineers. No matter how they yanked the available data they could get F1 work only if it had a weight reduction by 1200 tons and thrust reduction by 40%.

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13-3

Soot calculation on F-1 ( over specified limits.)

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13-2

​

And I know for a fact that that bees are totally aerodynamically unsuited for flight and cannot do so.

Although sadly I'm not a graduate of Bauman University I was still able to check this fact using the calculator that comes with the Windows operating system and an Excel spreadsheet.

 

[Moose]

That sounds typical of some push papers mentality, engineering the middle-age of the industrial era.
Thanks God for Musk.

As a side note LM just offered to buy Rocketdyne, the last remain of the great North American legendary aerospace company. At +33% the share, it's an honest financial offer that also promises to open opportunity for that company.

Lockheed Martin inks $4.4 billion deal to acquire Aerojet Rocketdyne

Lockheed Martin Corp said on Sunday it has agreed to buy U.S. rocket engine manufacturer Aerojet Rocketdyne Holdings Inc for $4.4 billion, including debt and net cash.

in.mobile.reuters.com

If you watch the second video I posted up there it explains why we can't build an F-1 - using the techniques they used back in the day. Of course they did explain we could make a BETTER one, with a fraction of the number of parts, with modern manufacturing methods.

Indeed, in the early 2010s Dynetics was charged by NASA with studying an RP-1 booster upgrade for future SLS blocks, hoping to find performance and cost advantages over the huge solid boosters. Their design used a modern F-1 variant emphasizing lower cost.

 

[Hobbes]

This is only one of hundreds of mathematical calculations and research done on F-1`s actual thrust and its real capabilities. Some of this research comes from Bauman Moscow State Technical University ` employees` and some from actual rocket engineers. No matter how they yanked the available data they could get F1 work only if it had a weight reduction by 1200 tons and thrust reduction by 40%.

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13-3

Soot calculation on F-1 ( over specified limits.)

«ÏÅÏÅËÀÖÛ» ËÅÒßÒ ÍÀ ËÓÍÓ ¹13-2

​

typically, this is what happens:
Someone with insufficient understanding of the physics involved does some calculations which contain an error. Rather than identifying the error, they go down a rabbit hole of ever-more convoluted calculations, none of which have anything to do with the truth.
A calculation of Saturn V payload from first principles fits on one or two pages.

 

[Silencer1]

I wonder how WW2-era Allied' scientist should think about mysterious German invention, whiсh later became well known as V-2/A-4?
Are their knowledge, experience and calculations allows them to quickly believe in the existence of wingless vehicle pwered with unvonventional engine, that could rise at 80 km height?
It was easy to believe in V-1, because it's similar to conventional airplane, at least by overall shape.
But gian flying cigar? What a strange idea or worst - Axis' desinformation!

 

[mkellytx]

Indeed, in the early 2010s Dynetics was charged by NASA with studying an RP-1 booster upgrade for future SLS blocks, hoping to find performance and cost advantages over the huge solid boosters. Their design used a modern F-1 variant emphasizing lower cost.

Why on Earth would NASA ever want to move away from proven Space Shuttle technology to use something with more performance and lower cost , they might actually have to adjust the size of their workforce and congress would be terribly upset.

 

[Hobbes]

I wonder how WW2-era Allied' scientist should think about mysterious German invention, whiсh later became well known as V-2/A-4?
Are their knowledge, experience and calculations allows them to quickly believe in the existence of wingless vehicle pwered with unvonventional engine, that could rise at 80 km height?
It was easy to believe in V-1, because it's similar to conventional airplane, at least by overall shape.
But gian flying cigar? What a strange idea or worst - Axis' desinformation!

By 1940, the concept of a rocket was already known, and a sound theoretical basis laid by Tsiolkovsky, Goddard, etc. All that remained was a practical implementation. The Allies received enough information from spies to be able to conclude the value of Peenemunde and started bombing the site in 1943, long before the V-2 became operational.

 

[bobbymike]

SpaceX moves Starship to launch site, and liftoff could be just days away

No fooling—Starship rolled back to the launch pad on April 1.

arstechnica.com