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#1 2005-03-23 15:34:55
- Gennaro
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- From: Eta Cassiopeiae (no, Sweden re
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
This is a simple question. Speaking of ordinary chemical expendable rockets, if you wanted it big, I mean really big, how big could you do it?
Let's say either from a practical or theoretical viewpoint?
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#2 2005-03-23 16:32:53
- Palomar
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
*Gennaro, I really wish I could answer this myself. Will be looking forward to any comments.
Saturn V Forever! 
--Cindy
We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...
--John Sladek (The New Apocrypha)
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#3 2005-03-23 16:40:17
- publiusr
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Here are two of the largest seriously conceived:
http://www.astronautix.com/lvs/nexus.ht … /nexus.htm
http://www.astronautix.com/lvs/mllv.htm … s/mllv.htm
Pressure feds are cheaper, despite what many may say.
http://www.astronautix.com/lvs/bealba2. … ealba2.htm
http://www.astronautix.com/lvfam/truax. … /truax.htm
With nukes, much larger designs can be achieved:
http://www.astronautix.com/lvs/aldbaran … dbaran.htm
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#4 2005-03-31 13:19:55
- dicktice
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Stripped of everything not absolutely vital, unencumbered by any practical experience, but constrained by the laws of physics as espoused by GCNR, I've concluded the following to be the ideal unstaged rocket launcher:
An elongated thin-walled container of water-ice, however long and large in diameter, launched near the Equator from West to East, with melt-water flow at the tail end being continuous electrolyzed into hydrogen and oxygen gas, pressurized and separately fed into the combustion chamber(s) of the rocket engine(s). The container shrinks front to rear as the column of ice diminishes in length.
That's the launcher, or booster, stripped of all nonessentials. I can't fault the physics or chemistry. To me, the engineering is all that's left to do.
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#5 2005-03-31 13:33:19
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Nope, the chemistry won't allow it to be done practically.
In order to melt and split water ice into Hydrogen and Oxygen, it requires ALOT of energy. More energy infact then is yeilded by the combustion of the resultant hydrogen and oxygen. Simple thermodynamics.
Adding another energy source to do this, like a nuclear reactor, wouldn't be very efficent either. You would be better off building a huge rocket with a cluster of really big NTR engines and some massive boosters or something.
Probobly a bad idea to use any frozen molecular solid too, the vibration combined with the loading during launch would shatter whatever you make it with.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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#6 2005-03-31 13:59:58
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Lets take a minute to sit back and think about the physics of this before going on to think about what kind of rocket engine and so forth to use...
For launch off of Earth, you need a system that has a very high specific power (not to be confused with Impulse). That is, you need to release lots of propulsive energy very fast in a controlled manner for a minimum of weight.
Specific power is a big concern, much like specific impulse (weight of propellant expended per amount of energy).
Chemical rocket fuels have some okay specific power, though not that great, and lousy specific impulse. The only other rocket energy source that is to date practical is a nuclear power source, which has good-to-great specific impulse, but nuclear rockets have low-to-poor specific power because of their limited operating temperatures requires a big reactor. Nuclear "pulse" (bomb) rockets like Orion however, they release their energy REALLY fast, and hence have the best of both in theory, but the economic, engineering, and political challenges I think are insurmountable.
So, chemical rockets are probobly the best bet at the moment. Right now the limitations of size are mostly engineering and specific impulse. Using different fuels at different stages of acent makes some sense too, to use solid or kerosene down low and hydrogen up high, to maximize efficency. One trick might be to switch to aerospike or adjustable nozzle engines, complex beasts, but permit improved hydrogen performance at low altitudes (See plug-nozzle J-2 for DC-X or X-2000 linear aerospike for X-33).
Of course, another great thing to do would be to avoid a rocket engine at all, where you have to pack all your propellant, and instead use the atmosphere as "free" oxidizer and reaction mass. This way, specific impulse is much less important, and you get much more bang-for-your-buck for fuel. Such an engine, in limited development, is called a Scramjet. Since the time a regular rocket spends during acent in the atmosphere is short, and a Scramjet engine is a complex beast, it makes sense to put it on an airplane instead of a scaled ballistic missile.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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#7 2005-03-31 17:04:35
- dicktice
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Great stuff, GCNR. I knew you would rise to the bait, and add some fresh arguments as well. Leaving the launch stage for a moment, what is the second stage's LH2/LOX rocket engine exhaust comprised of, exactly?
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#8 2005-03-31 18:05:46
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
For a fuel-rich mixture like RS-68 (and I think RL-10), water vapor (steam) and a little hydrogen gas. A chemical engine isn't quite hot enough to induce signifigant hydrogen or water ionization. Oxidizer-rich engines (SSME?) would have excess oxygen instead of hydrogen.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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#9 2005-03-31 18:37:29
- dicktice
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Brilliant! I didn't mean to set you up. It's just that I couldn't decide how to frame my topic for Google. I used "H2L/LOX rocket engine exhaust composition." Here's a quote from a certain Henry Spencer, when asked this question. (I have to admit I was surprised that water (vapour) molecules remained intact at these temperatures.
... Different exhaust-gas mixes differ in how well they convert thermal energy to kinetic energy. It's not a matter of the variety of gas molecules--LOX/LH2 exhaust isn't all H2O, it has a lot of H2 in it--but of the way energy gets bled off into internal rotation and vibration in the more complex molecules. This is particularly important for engines built to run at sea level, as a lot of LOX/kerosene engines are; its importance diminishes with the very high expansion ratios found in engines built to operate only in vacuum (like a lot of LOX/LH2 engines).
So, using super-heated steam to propel inner asteroid (dead comet) ice by means of Solar heated not-combustion chambers looks feasible beyond cis-Lunar space, eh?
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#10 2005-03-31 18:46:38
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Some thermolosys does occur, but it isn't a whole lot. Many LOX/LH2 engines add extra H2 on purpose to increase Isp a little, where the combustion bascially heats the Hydrogen. As a consequence though, you lose a little thrust in return. You could also add excess LOX to boost thrust at the expense of Isp. I think that the Shuttle engines are like that, but I'm not certain. When cooled however, these more exotic molecules and molecular fragments will immediatly react with eachother to form water.
When he mentions vibrational and rotational energy, he's talking about the atoms themselves vibrating (shaking) with respect to eachother in a molecule, and being singly-bonded, the atoms can spin around their bond axies. Unfortunatly, both these cases, which occur normally at high temperatures, reduce the efficency because the energy released in reaction goes into vibrating/spinning bonds instead of linearly pushing the exhaust out the back (thrust).
Its worth noting that what the exhaust is made of doesn't determine Isp (in chemical engines, where fuel is the energy source), its the amount of energy liberated per mass of fuel.
Sure, if you have a big enough mirror, are close enough to the Sun, and have a good way to grind/melt water to put in the solar/thermal engine.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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#11 2005-04-01 19:35:22
- dicktice
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Nice to know. I'm almost finished, but still wonder if it's H2 and O2 that reach the combustion chamber (the liquid LH2 and LOX becoming vapourized before reaching there). Can't frame my topic to obtain a straight answer. I don't want to guess.
Re. the "ice ships," assuming interiors made habitable using customizing kits for retieval trips of a couple of months at most, might represent one of several means of prospecting the inner Solar System.
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#12 2005-04-21 14:29:34
- publiusr
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Speaking of ice ships
http://www.ckk.chalmers.se/people/thomm … astronaut/
Look at the Mars transfer vehicle. Not what you proposed--out of the Millenium Project--but ice is used as it is.
BTW Some at Marshall want clean sheet HLLV--and with UTC having bought Rocketdyne, Pratt went from being against to being for HLLV. So stay tuned.
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#13 2005-04-21 19:32:30
- SpaceNut
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
well after reading about the ice ship I have realized that you could be talking about a comet.
on the note of aerospike engines solid fuels have also been used but I am not sure if there is enough of a merit to do so
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#14 2005-07-22 02:41:27
- srmeaney
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Single stage cylinder five hundred meters in diameter and five hundred meters in height encasing ten shuttle fuel tanks and ten shuttle motor packages to burn the liquid fuel (six to launch from earth and three to make a Mars landing, A tenth fuel tank and motor to make the trip from earth orbit to Mars orbit plus just enough space for twenty colonists and all the food they need for two years). Surrounded by a hundred solid fuel boosters.
Once L5, transfer over a colonist crew of twenty from a passenger shuttle, Send them to Mars.
Cost Estimate $250 billion all up?
It is going to be big.
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#15 2005-07-22 12:41:23
- publiusr
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
That's a bit big even for my standards. If you are going to do that--why not build the 400 meter diameter Super Orion and put 8,000,000 tons to the moon.
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#16 2005-07-22 14:49:13
- srmeaney
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
They want big... No one asks funny questions when you give them a rocket that is 80% fuel tank, 10% Motors, 6% life support, and 4% crew.
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#17 2005-07-23 07:53:43
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Um... a half-kilometer wide rocket could fit ~2,000 Shuttle tanks... just around the circumferance. If each of these have three or four SSME engines, the chance of one of them failing catastrophically every time they are fired is probobly waaay to high. If something that size blew up on the pad, the firestorm would take out all of southeastern Florida.
Oh, and most of your landing fuel would boil off enroute, so you won't have anything left on Mars.
How about a twenty-seat colony ship for, say, four or five 100MT HLLV launches? You make a GIANT version of the TransHAB module, with a telescoping internal structure, which ought to be a little cozy but liveable for a 20-person crew. The next piece would be the logistics section, with the life support/docking ports/airlock/storage and so on. The next launch would carry half of the fuel tanks, rated for in-space Hydrogen storage, and the nuclear power plant for the ship. Oh and a cryogenic condenser too. The last and most important piece would be the other half of the fuel tankage, and the gasseous-core nuclear thermal rocket engine, the GCNR.
You then send up the crew in one launch of Shuttle-II, an unmanned flight with supplimentary supplies and luggage in #2, and the rest of the fuel in a number of unmanned flights after that. The ship uses its very high Isp/thrust engine to get to Mars in a relativly shorter time frame with an all-propulsive trajectory, offloads the outbound crew on a reuseable Mars-based lander, and spends the next year or two in orbit a little at a time from said lander. Then pick up any inbound crew, and back to Earth the same way.
A simpler version of the vehicle could be used for cargo (particularly time-sensitive stuff) by omitting the logistics/docking section and perhaps the powerplant section too, instead just bringing up a GCNR engine and tankage and mate it to a deployable "bus" with traditional solar power with a cryogenic condenser and the rest of the fuel tanks.
Another option, build a GCNR-powerd cycler that delivers an expendable aerobrake-equipped bus to Mars and just does a gravitational swingby and returns to Earth via a free-return trajectory... perhaps kicked up a little with a main engine burn.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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#18 2005-07-23 10:12:54
- srmeaney
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
What fun is that? Single Stage Vehicles are necessary to keep the orbital waste volume from turning into a nightmare.
You are right, We need a single stage vehicle with fission motors, thats five hundred metres diameter and a kilometre in length. Florida is an ideal launch site, And Texas is where we test fire the engine...
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#19 2005-08-12 15:57:23
- publiusr
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
Here are some nice links to HLLVs
http://www.space.com/businesstechnology … d_cev.html
http://images.spaceref.com/news/2005/il … go.med.jpg
http://images.spaceref.com/news/2005/ilc.chart.med.jpg
http://images.spaceref.com/news/2005/esmd.study.lrg.jpg
http://images.spaceref.com/news/2005/es … on.lrg.jpg
http://www.spaceref.com/news/viewnews.html?id=1057
http://www.nsschapters.org/ny/nyc/Comme … r_25,_2003
http://www.spacedaily.com/news/oped-03zzs.html
http://www.starbooster.com/TALAYPanel3FINAL.pdf
http://www.starbooster.com/aquila.htm
http://www.starbooster.com/032504SlidesAldrin.pdf (AQUILA DROP TANK!)
http://www.projectconstellation.us/news … ion_system
http://www.lunadude.com/images-pfolio/l_ashuttle-02.jpg
http://www.lunadude.com/images-pfolio/l … huttle.jpg
Misc
http://www.moonbase-usa.org/
http://www.geocities.com/uncle_rocket/img001.html
http://space.designerz.com/space-launch-vehicles.php
More buran photos
http://pg.photos.yahoo.com/ph/dtomko1962/my_photos
Subject: [Inside KSC] Re: In-Line Payload Cradle idea for lifting 6 Shuttle payloads at once
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#20 2005-08-12 16:58:37
- John Creighton
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
If your going to build a giant rocket why go chemical the economics and engineering challenges will be too immense. I normally wouldn't think orion is feasible but if build a rocket of 1000MT or much larger I really think the situation starts to change. I started this thread:
Project Noah (Big cousin of Project Orion)
while perhaps not realistic, if enough people believed in it perhaps it could be done. The rocket could be built by private groups without access to the bombs and if it ever needed to fly then some deal could probably be struck with the government.
Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]
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#21 2005-08-12 17:01:35
- John Creighton
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
What fun is that? Single Stage Vehicles are necessary to keep the orbital waste volume from turning into a nightmare.
You are right, We need a single stage vehicle with fission motors, thats five hundred metres diameter and a kilometre in length. Florida is an ideal launch site, And Texas is where we test fire the engine...
I say if you are launching a truly massive vehicle launch it off an island where the fallout of toxic fumes in the case of chemical or radiation in the case of nuclear won't effect the neighbouring places too much.
Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]
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#22 2005-08-12 17:14:54
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
If your exhaust is that toxic, then that is usually a sign your rocket shouldn't be using it to get off the ground.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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#23 2005-08-13 18:13:40
- PurduesUSAFguy
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
The largest chemical launcher I think would have been viable was the Sea Dragon.
http://astronautix.com/lvs/searagon.htm
Alot of work was actually done on production viability and it was found that it would be realativley easy to produce in an existing ship yard at a individual unit cost much lower then the Saturn V due to cheaper componets and simpler construction more then off setting it's larger size. It was capable of launching 550 tonnes to LEO. [/url]
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#24 2005-08-15 03:12:45
- idiom
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
That thing is Massive. And made out of steel? Saves a pretty penny on launch pad costs. Imagine launching the ISS twice over in one shot, and for less than the cost of a shuttle.
23 Metre fairing ain't to shoddy either.
Not like the Nexus though, the Nexus was meant to be recoverable!
By the way the reason nuclear stuff has a really bad name in the pacific is because all the great powers tested their great sodding weapons on us. It pretty freaky having an island disappear (with a crater left in the ocean floor bigger than the original island). If you're going to spray toxic fumes everywhere launch out of Fresno or some place.
Come on to the Future
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#25 2005-08-15 10:46:40
- GCNRevenger
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Re: What's the Biggest Rocket Concievable? - How big can you really build it?
The Dragon was just insane... magnificent if it would work, but insane just the same.
The biggest problem with it is that it was TOO big, that whatever payload you would put on the thing would be so incredibly valuble, that you would be taking an awful risk that the whole thing would be gone. And what would you put in it? I mean, even the older "big" NASA DRM-I Mars ships would only take about a third of its payload capacity.
It also has an inherint lack of "granularity," that if you only want to launch a smaller payload, you would have to wait a very, very long time so you could pool smaller payloads or piggyback on a larger one. Not a very good situaiton, and would add complexity to the mission.
I don't think it would be that easy to build or fly either, that something of its size would be more expensive then they think it would have been. In any event, if all you wanted to do was haul "dumb" payloads like fuel, a true "no kidding" RLV would still be cheaper per-pound.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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