Author Topic: Sea Dragon class LV thead  (Read 141086 times)

Offline tnphysics

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Re: Sea Dragon class LV thead
« Reply #20 on: 09/12/2007 07:48 PM »
What would be the payload of Sea Dragon be if 3 first stages where clustered together with one upper stage on top in a manner simaler to Atlas V Heavy?

Offline kkattula

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Re: Sea Dragon class LV thead
« Reply #21 on: 09/13/2007 03:45 PM »
Just a WAG but probably over 1000 mt.

Offline bad_astra

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Re: Sea Dragon class LV thead
« Reply #22 on: 09/13/2007 04:10 PM »
Unless you're building an Oneal colony from Earth Materials (exactly the opposite of how it should be built, anyway), there is no reason, ever, for a Sea Dragon.

How many launches of this kind of vehicle could be needed by one country in one year? One? Maybe one every 2? You still need standing army to maintain it, it's prep facilities, etc during the off time so you really get no savings from having such a monster. And if you LOSE a Sea Dragon, how many years are you unable to go to space at all because you bet the farm on one LV and killed off the rest of the competition?

What is far more reasonable and robust is a diverse lv's with high flight rates.
"Contact Light" -Buzz Aldrin

Offline Tergenev

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Re: Sea Dragon class LV thead
« Reply #23 on: 09/13/2007 04:43 PM »

kkattula wrote: "Basically, if you take a bunch of smokers, send them to Mars and back over 3 years, (without cigarettes), their life expectancy on return would be higher than if they'd stayed on Earth and continued smoking."

If you take a bunch of smokers and put them into a small aluminum can together on a trip to Mars,  without cigarettes . . .and I guarantee their life expectancy will be no more than 2 weeks. They'll all kill each other!  :laugh:  


Offline renclod

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Re: Sea Dragon class LV thead
« Reply #24 on: 09/14/2007 09:19 AM »
They could grow some stuff in zeegee and delay the fight.  :cool:
Tobacco seeds and seedlings on STS-95 ?

Offline J05H

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Re: Sea Dragon class LV thead
« Reply #25 on: 09/18/2007 07:54 PM »
Quote
Kaputnik - 11/9/2007  6:06 PM
No reason other than that it is usually more mass-efficient to have a disposable fairing than a toughened spacecraft. ... it will also increase the aerodynamic drag on the vehicle, reducing performance.

A possible solution is to split an updated Ultra-heavy Lift Vehicle (ULV) into 2 stages that function together or separate. The bottom stage can be used for harbor-to-harbor ballistic launches. Combined with a standard-sized/interfaced upper stage, it can deliver 250-500t cargo and the upper stage to LEO. The craft can be a LEO-only cargo booster or using the same mold-lines be an interplanetary transport, with additional propellant.

Fuel is your choice, but one possibility is propane or LNG and LOX. Both are available in quantity and Propane/LNG is available on refrigerated ships, which serves the SeaDragon-type operations well.

Offline tnphysics

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Re: Sea Dragon class LV thead
« Reply #26 on: 09/18/2007 11:34 PM »
LNG/LOX stage 1 and LH2/LOX stage 2 is my preference.

Offline khallow

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Re: Sea Dragon class LV thead
« Reply #27 on: 09/19/2007 06:31 PM »
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bad_astra - 13/9/2007  9:10 AM

Unless you're building an Oneal colony from Earth Materials (exactly the opposite of how it should be built, anyway), there is no reason, ever, for a Sea Dragon.

How many launches of this kind of vehicle could be needed by one country in one year? One? Maybe one every 2? You still need standing army to maintain it, it's prep facilities, etc during the off time so you really get no savings from having such a monster. And if you LOSE a Sea Dragon, how many years are you unable to go to space at all because you bet the farm on one LV and killed off the rest of the competition?

What is far more reasonable and robust is a diverse lv's with high flight rates.

I agree. Keep in mind in every mode of transportation, we've seen progressions to larger and larger vehicles just as is occuring in launch vehicles now. Sometimes as in the case of ships, this process has repeated itself many times as new technologies are developed. But there's always a point past which growing larger becomes uneconomical. For example, rather than build larger train engines, multiple smaller engines are used to pull the larger loads. Planes and ships could technically get a lot bigger, but the infrastructure isn't able to handle them.

As I see it, the Sea Dragon is too big for us now. There's no mission that requires it nor can we guarantee a high enough flight rate (a high flight rate being the most important way to lower launch costs) to justify its existence. And as bad astra notes, there are other disadvantages from the lack of diversity.

An area of squandered opportunity is devising techniques that exploit the relatively cheap launch vehicles with smaller payloads but high launch rates and good cost per kilogram. That means orbital assembly and construction techniques, refueling, perhaps even finer grained manufacture techniques. It may be impractical or too unreliable to launch everything via the restricted spaces of these small rockets and later assemble them into larger structures.

But I dislike the impulse to assume that one can make a heavy launch vehicle and then design the mission around that. There are many examples of specialized transportation systems (for example, city subways; airport walkways, shuttles, and light rail; ore conveyance systems in mines, military transportation), but these invaribly are intended to have a lot of traffic. In current heavy LV plans, there's no high volume need.
Karl Hallowell

Offline tnphysics

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Re: Sea Dragon class LV thead
« Reply #28 on: 09/19/2007 11:14 PM »
Sea Dragon was intended to use a "brute force" approach to acheving large payloads.

What about a more clever approach?

Pump-fed reusable LRBs. Pump fed (but no more expensive) reusable core stage. Nuclear upper stage.

Online MKremer

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Re: Sea Dragon class LV thead
« Reply #29 on: 09/20/2007 05:20 AM »
Quote
tnphysics - 19/9/2007  6:14 PM

Sea Dragon was intended to use a "brute force" approach to acheving large payloads.

What about a more clever approach?

Pump-fed reusable LRBs. Pump fed (but no more expensive) reusable core stage. Nuclear upper stage.

Anyone can speculate about different pie-in-the-sky options till the cows come home. However, real life demands things concerning realistic engineering based on budget constraints, development time limits, testing time limits, and overall construction time limits. (Oh, and not to mention budgets, budgets, budgets, etc.)


Offline Vladislaw

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Re: Sea Dragon class LV thead
« Reply #30 on: 09/27/2007 05:32 PM »
the sea dragon had a core diameter of 75 feet, if you built a can with a 75 dia and put a tub in it like the tub inside your close dryer and gave it a spin of 4-10 revolutions per minute you would have all the centrifical force created artifical gravity you would need for sleep chambers on a trip to mars. it would not be 1g but it would be more than enough to offset zero g effects enough on a 5-7 month voyage.

Offline William Barton

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Re: Sea Dragon class LV thead
« Reply #31 on: 09/27/2007 06:13 PM »
The notion of gaining from economies of scale by using more frequent flights of smaller LVs sort of points back in the direction of the original notions of the 1940s and '50s. Lester del Rey's 1956 novel "Step to the Stars" depicts a space station constructed from bits and pieces shipped up in Von Braun's 3-stage RLVs, using what amount to brigde-building techniques. In it, we see space suited astronauts stringing together I-beams and sheet metal with rivet guns and welding torches. The novel actually aged well, and there's even a chapter where the station crew (lacking an assured crew return vehicle!) come close to running out of air due to a series of mishaps, including a typhoon at the launch site. They're saved at the last minute when a bold pilot launches through the storm's eye (plot element recycled less than a decade later in "Marooned").

It seems as though, if you're building a permanent (and to be maintained for decades) orbital facility, you would gain by that kind of flight-rate economy (Von Braun was talking hundreds of flights per year back then). But hereabouts, there have also been discussions about such orbital facilities not being much use. Is there actually a real point to flight-rate economy for sporadic expeditions to other planets? It seems like you'd only benefit if the flight rate already existed for some other reason, and that otherwise you might be better off with big rockets that sent off whole crewed ships to the destinations.

Offline J05H

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Re: Sea Dragon class LV thead
« Reply #32 on: 10/01/2007 01:27 AM »
Bob Truax primary innovation was this: the capabilities of a rocket do not greatly affect design costs. A 500mT booster can be designed for not much more than a 40mT booster.

If SeaDragon-class rockets existed, what we consider an acceptable payload would be much different than current practices.

I'm not sure about Humans-to-Mars on regular Falcon 9, but we've been discussing "Mars 9 tons at a Time" on uplink:

http://uplink.space.com/showflat.php?Cat=&Board=businesstech&Number=743430&page=0&view=collapsed&sb=5&o=0&fpart=12&vc=1

Offline publiusr

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Re: Sea Dragon class LV thead
« Reply #33 on: 10/26/2007 06:40 PM »
9 tons at a time? Ugh. That is really grasping at straws.

On the other hand (provided Sea Dragon is do-able) you could get away with a Sea Dragon insertion stage living hab with a simple Soyuz parked on its nose and you have at least a 1.5 flyby mission right there.

By-the-by, QUEST is going to have a future issue on Truax/ Sea-Dragon IIRC.

Offline meiza

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Re: Sea Dragon class LV thead
« Reply #34 on: 10/26/2007 07:03 PM »
Bob Truax never proved that it costs as much to develop or build or launch a sea dragon as a smaller vehicle. I could invent plenty of reasons why bigger vehicles would actually be much more expensive.

Offline publiusr

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Re: Sea Dragon class LV thead
« Reply #35 on: 10/26/2007 07:07 PM »
He never got the chance to do so.

Offline meiza

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Re: Sea Dragon class LV thead
« Reply #36 on: 10/27/2007 12:10 AM »
Yes, but anyway the point stands, BDB advantage is NOT proven.

Just look at Antonio Elias' talk about building the Cygnus / Taurus II launcher. They wanted to avoid solids since they are heavy and require expensive ground infrastructure to handle.

A dumber booster would be bigger and thus would require more ground infrastructure. Or dock, port and sea infrastructure from the Sea Dragon point of view. A bigger booster requires potentially bigger infrastructure than a smaller rocket that launches more often, even if both are as dumb/smart...

It's not easy to say "just make it bigger, you don't need more people taking care of it".

What if it's so huge that floating it out to the sea is a huge operation needing lots of tugs etc... that ain't gonna be cheap. There are tradeoffs. Sometimes bigger is better:
http://techepics.com/files/largest_digger_1.jpg
, sometimes it is not:
http://content.answers.com/main/content/wp/en/6/65/Oil_sands_open_pit_mining.jpg

Offline publiusr

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Re: Sea Dragon class LV thead
« Reply #37 on: 11/02/2007 03:58 PM »
How'd we get to oil sands?  Sea Dragon would be simpler than a nuclear submarine which has a lot going on inside it. It took Hyman Rickover a lot of pushing to prove that concept. And a lot of money that Truax could have used for his concepts.

Offline meiza

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Re: Sea Dragon class LV thead
« Reply #38 on: 11/02/2007 05:38 PM »
Just mentioning that bigger is not always the most cost effective approach. It depends on a lot of details.

Offline Michael Bloxham

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Re: Sea Dragon class LV thead
« Reply #39 on: 11/14/2007 12:07 AM »
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khallow - 11/9/2007  3:50 PM

I think it's a terrible idea to ignore the economies of scale from using small LVs launched more frequently.

What about clustering smaller rockets in parallel to allow for the occasional oversized payload?

Boeing envisions this for the Delta IV: A first stage consisting of 7 CBC's clustered together is their ultimate configuration. A configuration like this might be capable of lifting more than 7-times as much as a Delta IV Medium with just one CBC ("more than" due to the advantages of parallel staging).

I used this as inspiration for my PARIS VII rocket, which envisions a cluster of 7 Ares V-derived tanks to allow for payloads of over 500 tonnes:

http://cleanslate.editboard.com/free-chat-f1/paris-launch-system-t11.htm

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