Author Topic: The Gigantism trend in rockets and other machines  (Read 27540 times)

Offline pathfinder_01

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Re: The Gigantism trend in rockets and other machines
« Reply #20 on: 07/23/2013 01:39 AM »

Those boats weren't created for the purpose of colonization but they were then mass produced and sailed for over 100 years to build those colonies.

Saturn V was used to take a couple of men for a moonwalk. It could then have been mass produced to build off world colonies.

Cost means nothing. Look at all the money in the world. A colony on Luna has been possible for 50 years.

It's hard to tell what a Lunar colony would be capable of contributing to people back on Earth.

It was simply an investment short sighted Earthlings haven't been willing to make. Strip mining and deforestation continue while off planet resources stay pristine. I know which one I'd rather conserve.

Costs mean everything in terms of human spaceflight and colonization. The colonies were expected to return something of value to the mother country. For the Americas is was crops in the form of tobacco, timber, gold from South America, Sugar from the indies, Cotton from the south among many others.  All these items need people to make. Those colonies were public private partnerships in a sense as the crown did invest some of its money plus private investments plus lotteries to raise funds. 

The boats were massed produced because transporting cargo by water is something humanity has done for thousands of years. Transporting by water is the most efficient way to move large amounts of cargo with the least amount of energy (i.e. wind, Or, even animal drawn via cannels). Going over water can sometimes be the most direct route or the only route possible hence why we still build boats. 
 
One way to control costs is to use systems that have other users.  Space X and ULA have about 2-3 thousand workers, old Saturn V required about 10,000 people to build that makes each launch of an Saturn V much more expensive to operate unless it has a very high flight rate and having just one user works against that and makes any sort of use outside of HSF hopeless and so the Government is required to fund the whole thing…not going to happen because 2 guys on the moon for three days does not yield much benefit to the mother country beside bragging rights.

The more it costs the more difficult to raise funds privately in hopes of making a profit, or to convince governments to invest in it. I think colonization will happen but the road is going to be paved with profits from the private industry and I think it won’t be done anything like Apollo.  I think what is going to happen is that costs will go down enough  and technology become capable enough(3 days on the moon is much too short for the cost) that someone could purchase enough launch capacity to get to BEO privately or mostly privately. Wither or not they make a profit might be another matter but it will be a shoot. If they make profits then other countries, companies and individuals would invest in it and drive mankind outward.

Anyway I think there has to be a commercial reason for larger rockets (and perhaps there are some) or a commercial reason for say smaller reusable vehicle that could do a prop depot run before any serious presence can happen. There is currently a big market in unmanned spacecraft that need to be launched, HSF must find a way to tap that market and use it to its advantage. 

A good example is the Falcon 9 and FH or even Atlas, they lift things other than HSF and are not directly funded by NASA(they are indirectly funded by the government for Space X and the DoD thinks having Atlas is important so it funds it).

Offline Chris Bergin

Re: The Gigantism trend in rockets and other machines
« Reply #21 on: 07/23/2013 02:33 AM »
Yeah, let's get this back on track. It's not NASABoatSailing.com ;)

Online kevin-rf

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Re: The Gigantism trend in rockets and other machines
« Reply #22 on: 07/23/2013 12:36 PM »
But for $12 a year, you could register the domain ;)

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Offline DMeader

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Re: The Gigantism trend in rockets and other machines
« Reply #23 on: 07/23/2013 05:10 PM »
It's not NASABoatSailing.com ;)

Oh I don't know...

MV Freedom Star
MV Liberty Star

maybe OT! :)
« Last Edit: 07/23/2013 05:10 PM by DMeader »

Offline R7

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Re: The Gigantism trend in rockets and other machines
« Reply #24 on: 07/23/2013 07:21 PM »
Sea Dragon was to be several times larger then the Saturn 5 but the design called for use of 8mm steel sheeting similar to ship hulls.

No, Al 2014 T6 was base line material in the study. With that first stage RP-1 tank walls would have been four inches thick, increased to eight inches at the weld joints to account for lower strength. 18% Ni maraging steel was mentioned but information about it came too late for the study so they chose to stick with Al. Steel would have reduced the wall thickness to one inch.

The Al weld thickness was above current SoA back then and was considered critical design issue. Methods to reduce it was discussed, such as stacking two plates of two inches thick and four inch weld depths or replacing weld with mechanical joining a laminate of 1/4 inch sheets with inner lining.

Otherwise great example of blatant utilization of gigantism. First stage engine chamber pressure was 300 psia but LOX ullage pressure was 226 psia. The thing was tall enough to provide the pressure difference plus injector pressure drop from hydraulic head :)

(source: the study itself)

Existing REAL markets have driven the terrestrial gigantisms. There's no market for rockets this big, it remains to be seen if there's even market for 50t payloads. Delivering smaller payloads more often ought to be more economic for both ELVs and RLVs.
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Offline go4mars

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Re: The Gigantism trend in rockets and other machines
« Reply #25 on: 02/13/2014 03:52 AM »
Sea Dragon was to be several times larger then the Saturn 5 but the design called for use of 8mm steel sheeting similar to ship hulls.

No, Al 2014 T6 was base line material in the study. With that first stage RP-1 tank walls would have been four inches thick, increased to eight inches at the weld joints to account for lower strength. 18% Ni maraging steel was mentioned but information about it came too late for the study so they chose to stick with Al. Steel would have reduced the wall thickness to one inch.

The Al weld thickness was above current SoA back then and was considered critical design issue. Methods to reduce it was discussed, such as stacking two plates of two inches thick and four inch weld depths or replacing weld with mechanical joining a laminate of 1/4 inch sheets with inner lining.

Otherwise great example of blatant utilization of gigantism.
I thought the main reason to use steel was manufacturability/cost.  Shipyards all over could do steel...
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Online Robotbeat

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Re: The Gigantism trend in rockets and other machines
« Reply #26 on: 02/13/2014 05:04 PM »
Lighter-than-air craft are much smaller now than they used to be. The Hindenberg has never been exceeded, even though that was ~80 years ago. Arguably the most successful domestic airline (Southwest) uses the 737, not the 747.

Not all scale-laws point to larger-is-better. Titan IVB was smaller than Shuttle. Russia's rockets are much smaller today than their older rockets like N-1 and Buran.

There are scale laws that work both ways. What I do notice, however, is the Freudian obsession with the biggest-possible-rocket among the space enthusiast community.

There are scaling laws that limit the length of a rocket and scaling laws which make ultra-large structures become much more susceptible to bending than smaller structures (at a certain point). Another problem is that larger structures inherently take longer to move around than smaller ones, so their at-scale advantage is diminished by some of the operational advantages of smaller structures. For instance, it takes much, much longer to deplane a huge 747 than, say, a 727. So it makes no sense to use a 747 for short-hop flights on the East Coast of the US, for instance since you'll take half your time boarding or deplaning.

http://spacecraft.ssl.umd.edu/akins_laws.html
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Online Robotbeat

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Re: The Gigantism trend in rockets and other machines
« Reply #27 on: 02/13/2014 05:15 PM »
Also, a lot of the biggest launch vehicles in your list do not exist and probably will never exist.
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Offline R7

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Re: The Gigantism trend in rockets and other machines
« Reply #28 on: 02/14/2014 01:21 PM »
I thought the main reason to use steel was manufacturability/cost.  Shipyards all over could do steel...

Yes but regular grades used in ship building may not be suitable to construct hydrogen tanks because they become too brittle as 20K and there's the hydrogen embrittlement issue on top of that. Stainless works in Centaur.
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Online Robotbeat

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Re: The Gigantism trend in rockets and other machines
« Reply #29 on: 02/14/2014 02:17 PM »
Aluminum is cheap, and stainless is about the same price (okay, maybe like 50% less cost for scrap price). It's like $2/kg. Rockets generally go for about $2000/kg of dry mass, about the same as jet airliners. The cost advantage of regular steel is completely irrelevant here.
« Last Edit: 02/14/2014 02:23 PM by Robotbeat »
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Offline DarkenedOne

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Re: The Gigantism trend in rockets and other machines
« Reply #30 on: 02/14/2014 02:45 PM »
To pretty much sum up what has been said it is definitely true that for a number of reasons larger launch systems have a lower cost per kg into orbit than smaller ones when measuring the direct cost of a single launch.  However the downside is that larger launch systems have higher fixed costs such as the cost to develop, the cost to build infrastructure, and the cost to maintain.  If the flight rate is high enough than lower incremental cost will more than justify the higher fixed cost.

Ultimately building a launcher rocket it worth it if you have the demand. 



Offline floss

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Re: The Gigantism trend in rockets and other machines
« Reply #31 on: 02/21/2014 12:34 PM »
At present NASA are building two rockets with no demand  the problem is that it takes 10 years to build a new launcher and then ten years to build payloads .That is why rockets evolve so slowly.With the unreliability of rockets historically nobody will build a payload for just one launcher .


The only exception to this rule is Saturn 5 the payload derived the size of the launcher.

Offline muomega0

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Re: The Gigantism trend in rockets and other machines
« Reply #32 on: 02/21/2014 02:05 PM »

Wikipedia defines "Gigantism" as a condition characterized by excessive growth and height significantly above average.  Aircraft are seeing the same growth trend, with new versions (787 & A350) being larger than the ones they replaced (767 & A330).  Tractors and combines are also getting larger and more powerful, with the biggest combines 40 years ago (Class V) now being dwarfed by Class IX combines today.  This trend though is especially pronounced amongst cargo ships.  In the 1950s, the world's first container ship could move just 58 containers at a time.  Today the Triple E-class container ships built for Maersk will haul 18,000 containers at a time. 

While I realize some of what's driving this increase in size is demand, like demand for launching bigger payloads to space, that can't be all of it.  Then I happened across an interesting site: http://gcaptain.com/part-design-efficient-ship/.  What caught my eye was what they had to say with regards to scaling. 

Quote
A larger ship will in most cases offer greater transport efficiency  – “Efficiency of Scale” effect.  A larger ship can transport more cargo at the  same speed with less power per cargo unit.  Limitations may be met in port handling.  Regression analysis of recently built ships show that a 10% larger ship will give about 4-5% higher transport efficiency.

After thinking about it, this makes sense, as these ships can take advantage of the Square-Cube Law of physics (http://en.wikipedia.org/wiki/Square-cube_law).  This states that when increasing a shape in size, its volume increases faster than its area.  This results in less power being needed per ton of payload, which allows payloads to increase at a faster rate than the ship's jump in volume.  So it seems that part of what's driving this trend toward gigantic machines seems to be the laws of physics.  It made me wonder, just how much does this apply to rockets?  If, for instance, there was sufficient demand, would the laws of physics push rocket designers towards larger designs because they're more efficient or because of economies of scale?  Also, given trends in increasing rocket size, just how large do you predict the common launchers of the world will be in 30 years compared to today?  If you also want to talk about this Gigantism trend amongst other vehicle categories as well, feel free.

The same mistake is made over and over in the HLV trade space by narrowly focussing on the square cube law for a single LV and neglects the rest of the distribution network, the *efficiency* of only one element of the problem.

The ship has all the goods in containers that fit on trains and semis, sent directly to stores or warehouses, arriving at the destination via UPS or a car.    Hubs with smaller aircraft or other means of transport serve the larger planes.

The key figure of merit is average annual metric tonnes per year, followed by the mass of any individual segment   as shown in How to make the SLS Business Case Close.  Note that development costs should be also be included, making the business case even worse.

In the attached plot, the life cycle cost per pound of payload is plotted vs payload.  Also included is the Industry Price Trend line.   The plot clearly shows that the majority of the cases considered can carry more payload than the price line, but at a higher cost.  Further, it shows that as the payload size increases, none of the options drop below the price line.  Why is that?  Simple, too much capacity so the fixed costs dominate.

Filling any transfer stage on orbit takes advantage of Amplification Factor and thus dramatically shrinks the LV size required.

However, SLS is the most cost effective approach because Congress makes the rules

Worse, it neglects the politics of the HLV trade space over the decades, especially the ability to assemble the payloads and the HLV itself due to transportation constraints:

Quote from: Max Faget
Then John Yardley came up with the idea of using solid rockets alongside...I was working very closely with the people from Boeing, and they pointed out, well, you could do that. You could also still keep the liquid stage behind the thing and light the engines at the same time. But the NASA officials had already shown the solid rocket configuration to the President, and he said, "Go ahead," and pretty much set things in motion.

The mistake we made on the solid rockets, it was a major mistake. I know it was a mistake, was that we decided that we'd build the solid rockets in Utah, and that limited the size of the solid rockets. It also meant that they had to be segmented. But the size limitation was probably more serious than the segmenting. The
diameter of the solid rockets had to be less than twelve and a half feet in order for the existing rail transportation, which had to go through a number of tunnels and so forth and so on. We just simply couldn't make it any bigger around than that. What was also a factor in the design of solid rockets was that you can't make them but so long. The length-to-diameter ratio is a limiting design factor, and consequently we limited the total amount of impulse, thrust times time. The total amount of propellant in the solid rockets was limited by that, which meant that the solid rockets would only be able to help during the first couple of minutes of flight, as opposed to being attached longer. We staged those solid rockets at only a little over 4,000 feet a second, which really meant that the Shuttle and its tank had a big job to do, and it really limited the performance and inhibited any growth in the payload capability, which the program has had to suffer with all this time. When {the solid rockets} stage at 4,000 feet a second, {the orbiter} had to have an awful lot of propellant left for the insertion, which meant that you had to have enough thrust to carry the weight of that propellant, and that increased the size of the engines in the orbiter, which moved the center of mass of the orbiter farther back than we would have liked in order to make it tail-heavy. As a consequence of that, the center of mass of the orbiter was well behind the center of volume of the payload bay.  Being as we didn't have a tail on the damned thing, we had very little capability to move the center of mass and maintain stable, manageable flight. A consequence to that means that a good part of the front end of the payload bay is virtually useless, has been useless all the time

Online Robotbeat

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Re: The Gigantism trend in rockets and other machines
« Reply #33 on: 02/21/2014 02:28 PM »
The square-cube law works against LVs at times...

You also have Euler buckling that gets worse as you scale up.

You also have fundamental frequencies that get lower the bigger you are, meaning it takes longer to safely move larger structures. Related to that is thrust oscillation problems (and pogoing, related to Euler buckling and stiffness) which are more severe the larger you are.
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Offline muomega0

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Re: The Gigantism trend in rockets and other machines
« Reply #34 on: 02/21/2014 02:46 PM »
The square-cube law works against LVs at times...

You also have Euler buckling that gets worse as you scale up.

You also have fundamental frequencies that get lower the bigger you are, meaning it takes longer to safely move larger structures. Related to that is thrust oscillation problems (and pogoing, related to Euler buckling and stiffness) which are more severe the larger you are.

Great point.  The plot has a limited set of vehicle options and the price line is not extended beyond 70k lbs otherwise this priceline uptail would start to occur.  If you take "10" as the realistic number of launches possible in a year, then it should be obvious why these cases were not added.

Indirectly, one can see why it such a HUGE advantage to not fill the HLV *upper stage* on the ground, perhaps just enough to circularize the orbit, so the tanks can be sized for on-orbit rather than launch loads, increasing the transfer stage payload mass fraction and to design a separate tanker that can take more risk than a crew or hardware carrier.   Wait a minute....what would a resusable Falcon or name your favorite SSTO advanced propulsion scheme be good for on its initial flights.......?  propellant delivery provides missions and ends up being a great application for advance propulsion R&D:  launching very cheap payload that is really required!
« Last Edit: 02/21/2014 02:51 PM by muomega0 »

Online Robotbeat

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Re: The Gigantism trend in rockets and other machines
« Reply #35 on: 02/21/2014 08:00 PM »
Food for thought:
http://www.kelthaven.org/papers/rlvheuristics.pdf
"conflicting heuristics for low-cost launch vehicle architectures"
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Offline mfck

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Re: The Gigantism trend in rockets and other machines
« Reply #36 on: 03/09/2014 12:08 AM »
Food for thought:
http://www.kelthaven.org/papers/rlvheuristics.pdf
"conflicting heuristics for low-cost launch vehicle architectures"

A very nice read, thank you.

13 years after the time of writing things are surely looking more bright. While at it, I couldn't help imagining Elon murmuring "Challenge Accepted" to the paper in early 2000s. Now here we are...

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