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SLS / Orion / Beyond-LEO HSF - Constellation => Missions To Mars (HSF) => Topic started by: tnphysics on 09/07/2007 04:31 am

Title: Sea Dragon class LV thead
Post by: tnphysics on 09/07/2007 04:31 am
What are your suggestions on 440+ tons to LEO LVs?

My favorite would be Sea Dragon built out of aluminum. What would its payload be?

And why does Sea Dragon-2 have only 320 Isp? That sounds too low for even a pressure-fed oxyhydrogen engine.

The application would be manned Mars missions (about 1200 tons IMLEO, 500 tons of which is radiation shielding against cosmic rays, using NTP for TMI).
Title: Re: Sea Dragon class LV thead
Post by: Kaputnik on 09/07/2007 08:15 am
There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.
Title: Re: Sea Dragon class LV thead
Post by: halkey on 09/07/2007 09:11 am
Quote
Kaputnik - 7/9/2007  3:15 AM

There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.

I disagree about a smaller booster being better for lunar missions.  If the USA plans to install a permanent outpost on the moon that's more than just a tent with some guys camping in it, a large booster like the Sea Dragon could prove immensely valuable.   And it'd prove valuable also if you plan to send multiple missions to Mars.  People seem to believe that it's better to have a lot of little launches than one big launch, but I doubt if that's always a good strategy.  Just launch a big booster from the ocean and be done with it!
Title: Re: Sea Dragon class LV thead
Post by: rumble on 09/07/2007 12:56 pm
My question is from a slightly different angle.

It seems we have a history of building "right-sized" rockets, that then suffer weight increases and/or performance shortfalls, then we have to optimize the crap out of them to get the job done.

Is a really big, dumb booster more expensive than all the effort expended on optimization & advanced materials?

Is there harm in overkill?  Granted, if we tried to build something with 30 F-1 engines, now we're hit with high engine expense, and duplicated complexity.  But, for example, a sea dragon is a single enormous 1st stage engine.  Nobody would win awards for efficient design, but it would give us tremendous capacity to put virtually anything into space.

Maybe something the size of a sea dragon is out of the question, since launch rates would be so low (the rarity of having a payload in this mass range).  But for that matter, we don't have payloads that large because we can't.  If an oversized launcher was available, how much cheaper could spacecraft be built?  If weight weren't much of an issue, how much would that change design considerations?  Redundancy?  Safety?

How fast could one fill a massive propellant depot if a sea dragon were available?

At one point in time, I thought we didn't make massive rockets because we couldn't.  Now I realize it's just because we never think ahead like that.  I know it's not easy to make things scale like that (whole new worlds of combustion instability, etc), but it would be an effort worth while, IMHO.

Matt
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 09/07/2007 04:10 pm
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Kaputnik - 7/9/2007  7:15 PM

There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.

Ask Richard P. Speck of Micro-Space. He thinks he can put 1 man (or 2 petite women) on Mars using one Falcon 9. Not a heavy either, just a regular.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 09/07/2007 08:53 pm
How?
Title: Re: Sea Dragon class LV thead
Post by: rumble on 09/07/2007 11:06 pm
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kkattula - 7/9/2007  11:10 AM

Quote
Kaputnik - 7/9/2007  7:15 PM

There's no need for 400mt+ boosters. It would be much better to develop a smaller booster suitable for lunar missions which can then fly three to five times to build up a Mars mission.
Your IMLEO estimates are far too high, IMHO. A Mars mission can be done for under 500t total.

Ask Richard P. Speck of Micro-Space. He thinks he can put 1 man (or 2 petite women) on Mars using one Falcon 9. Not a heavy either, just a regular.
Does the passenger survive in this plan?
Title: Re: Sea Dragon class LV thead
Post by: meiza on 09/07/2007 11:08 pm
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How?
Use the search function, have some effort yourself.
Title: Re: Sea Dragon class LV thead
Post by: MKremer on 09/07/2007 11:35 pm
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tnphysics - 7/9/2007  3:53 PM

How?

Click the Search button on the top menu. Type in Speck. Click the Search All Posts button. Start browsing.

Just how long do you expect folks here to do all the research work for you just so you can easily click on a single link or two? Quit asking obvious questions that you can easily search for the answers yourself.
 :angry:
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 09/08/2007 02:34 pm

Sorry.

   You must surround the entire living quarters with shielding that has the same effectiveness as five feet of water in a tank. This requirement should be used for all mass calculations for extremely long duration missions. Lighter elements are more effective per unit mass, so using liquid hydrogen gives the lightest shield. A thin layer of boron-10 would be needed as a neutron absorber.
 
    It is not possible to get away with less shielding, owing to the fact that the incoming cosmic rays have enough energy to create electron-positron pairs. These pairs are called secondary radiation, and they, too, must be stopped. However, these, in turn, create more electron-positron pairs until their energy drops below 1.1 MeV (the minimum energy needed to create an electron-positron pair) (At some point, each positron will annihilate an electron, producing two gamma rays). Because, for a given total energy of ionizing radiation, alpha radiation is more damaging than beta radiation which is more damaging than gamma rays, and lower frequency (longer wavelength) gammas are more damaging than shorter wavelength gammas, a thinner shield would actually be counterproductive, so far as cosmic rays are concerned.

 

Title: Re: Sea Dragon class LV thead
Post by: Kaputnik on 09/08/2007 04:23 pm
I'm not an expert on this, but what's the difference in radiation exposure between LEO and the Earth-Mars interplanetary space? I like to believe that Zubrin got it right when he calculated that radiation wouldn't be a show-stopper for a Mars mission.
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 09/08/2007 05:27 pm
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.
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 09/08/2007 05:45 pm
Quote
tnphysics - 9/9/2007  1:34 AM

Sorry.

   You must surround the entire living quarters with shielding that has the same effectiveness as five feet of water in a tank. This requirement should be used for all mass calculations for extremely long duration missions. Lighter elements are more effective per unit mass, so using liquid hydrogen gives the lightest shield. A thin layer of boron-10 would be needed as a neutron absorber.
 
    It is not possible to get away with less shielding, owing to the fact that the incoming cosmic rays have enough energy to create electron-positron pairs. These pairs are called secondary radiation, and they, too, must be stopped. However, these, in turn, create more electron-positron pairs until their energy drops below 1.1 MeV (the minimum energy needed to create an electron-positron pair) (At some point, each positron will annihilate an electron, producing two gamma rays). Because, for a given total energy of ionizing radiation, alpha radiation is more damaging than beta radiation which is more damaging than gamma rays, and lower frequency (longer wavelength) gammas are more damaging than shorter wavelength gammas, a thinner shield would actually be counterproductive, so far as cosmic rays are concerned.

 


I think you've got a lot of this wrong. 5 feet of water is only needed in an emergency shelter for solar flares.  Alpha radiation can be stopped by tissue paper, and is next to harmless, unless an emitter is ingested or inhaled. Higher frequency gammas are much more damaging than lower.

Cosmic ray exposure over a 3 year mission with minimal shielding would only approach the carreer safe limit.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 09/08/2007 10:48 pm
Cosmic rays may be more damaging.
Title: Re: Sea Dragon class LV thead
Post by: Christine on 09/10/2007 06:50 am
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Kaputnik - 8/9/2007  11:23 AM
I'm not an expert on this, but what's the difference in radiation exposure between LEO and the Earth-Mars interplanetary space?

The flux of solar protons drops off at the inverse square of distance from the sun. At mars, you'd be looking at ~40% of the exposure at earth outside the Van Allen belt. In LEO the belt shields those on ISS from almost all solar protons.  Galactic cosmic rays are much more energetic and pretty much the only thing that will shield from them is a 30km stratosphere or 10m+ of lead. Fortunately the flux is pretty low. Considering what else could go wrong on a mars trip, risking a 10% increase in your lifetime incidence of cancer would be the least of your worries.

The best way to shield from solar protons during a flare in my mind would be to put a giant water filled polyethylene tank on the sun-facing side of your habitat.
Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 09/10/2007 02:46 pm
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Christine - 10/9/2007  7:50 AM
The best way to shield from solar protons during a flare in my mind would be to put a giant water filled polyethylene tank on the sun-facing side of your habitat.

That sounds like a description of a fuel tank.   :cool:
Title: Re: Sea Dragon class LV thead
Post by: khallow on 09/11/2007 01:50 am
I think it's a terrible idea to ignore the economies of scale from using small LVs launched more frequently. I don't know what the future launch market will look like, but I think it possible for a market of competitive 25t LVs (with heavy commercial activity on the side) to be cheaper and more reliable than a 400+t LV. Perhaps, a mix of launch vehicles with most of the payload covered by the cheapest commercial vehicles (in $ per kg) and the rest by a specialized HLV with a decent launch rate. But I don't see a place for a 400t LV unless it is used a lot (more than a few times a year).
Title: Re: Sea Dragon class LV thead
Post by: Kaputnik on 09/11/2007 12:37 pm
Payload volume and fairing diameter are one aspect in which multiple small LVs cannot compete with HLLVs. With current technology, fairing diameter represents a major bottleneck in capabilities for a manned Mars mission, because it restricts the size and mass of individual entry vehicles to  the point where manned vehicles become very hard to design.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 09/11/2007 08:58 pm
In principle, why couldn't you make the spacecraft able to withstand launch loads without a fairing?
Title: Re: Sea Dragon class LV thead
Post by: Kaputnik on 09/11/2007 10:06 pm
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tnphysics - 11/9/2007  9:58 PM

In principle, why couldn't you make the spacecraft able to withstand launch loads without a fairing?

No reason other than that it is usually more mass-efficient to have a disposable fairing than a toughened spacecraft. For an entry vehicle it makes less difference because it needs to be quite sturdy anyway, hence the Shuttle has no fairing.
However doing away with the fairing wouldn't remove the constraint on payload diameter. Increased payload size will adversley affect the centre of pressure, potentially causing guidance problems duirng ascent; it will also increase the aerodynamic drag on the vehicle, reducing performance.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics 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?
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 09/13/2007 03:45 pm
Just a WAG but probably over 1000 mt.
Title: Re: Sea Dragon class LV thead
Post by: bad_astra 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.
Title: Re: Sea Dragon class LV thead
Post by: Tergenev 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:  

Title: Re: Sea Dragon class LV thead
Post by: renclod 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 ?
Title: Re: Sea Dragon class LV thead
Post by: J05H on 09/18/2007 07:54 pm
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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.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 09/18/2007 11:34 pm
LNG/LOX stage 1 and LH2/LOX stage 2 is my preference.
Title: Re: Sea Dragon class LV thead
Post by: khallow 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.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics 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.
Title: Re: Sea Dragon class LV thead
Post by: MKremer on 09/20/2007 05:20 am
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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.)

Title: Re: Sea Dragon class LV thead
Post by: Vladislaw 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.
Title: Re: Sea Dragon class LV thead
Post by: William Barton 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.
Title: Re: Sea Dragon class LV thead
Post by: J05H 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
Title: Re: Sea Dragon class LV thead
Post by: publiusr 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.
Title: Re: Sea Dragon class LV thead
Post by: meiza 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.
Title: Re: Sea Dragon class LV thead
Post by: publiusr on 10/26/2007 07:07 pm
He never got the chance to do so.
Title: Re: Sea Dragon class LV thead
Post by: meiza 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
Title: Re: Sea Dragon class LV thead
Post by: publiusr 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.
Title: Re: Sea Dragon class LV thead
Post by: meiza 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.
Title: Re: Sea Dragon class LV thead
Post by: Michael Bloxham on 11/14/2007 12:07 am
Quote
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
Title: Re: Sea Dragon class LV thead
Post by: Jim on 11/14/2007 05:12 am
Quote
Michael Bloxham - 13/11/2007  8:07 PM


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
b

because it is inefficient and there are most disadvantages than advantages.  The 7 core D-IV was a quick and dirty study and not a really viable vehicle
Title: Re: Sea Dragon class LV thead
Post by: publiusr on 11/16/2007 04:17 pm
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meiza - 2/11/2007  1:38 PM

Just mentioning that bigger is not always the most cost effective approach. It depends on a lot of details.

And smaller is certainly not always the most cost effective approach--otherwise we'd ship oil on thousands of bass boats than in supertankers--that may very well be a harder build than Sea dragon--a simple tube. We just have to get rid of this bias that LVs cannot grow in size--while airplanes and ships continue to grow. They're not cheap either. It took Brunel, the Mike Griffin of another age, to show the virtue of not being limited to clipper ships.
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 11/17/2007 04:13 am
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Michael Bloxham - 14/11/2007  11:07 AM

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).

Did you see the launch transient fireball of the recnt D-IVH?
Imagine one from 7 CBC's!
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 12/14/2007 02:43 am
Sea Dragon with a third stage is 970mt to LEO.

That is more than double the payload without the third stage.
Title: Re: Sea Dragon class LV thead
Post by: gospacex on 12/14/2007 06:01 am
Quote
publiusr - 16/11/2007  11:17 AM
Quote
meiza - 2/11/2007  1:38 PM
Just mentioning that bigger is not always the most cost effective approach. It depends on a lot of details.
And smaller is certainly not always the most cost effective approach--otherwise we'd ship oil on thousands of bass boats than in supertankers--that may very well be a harder build than Sea dragon--a simple tube. We just have to get rid of this bias that LVs cannot grow in size--while airplanes and ships continue to grow.

They grow - and viability of this is tested by the market. "Big" LVs were also used. Let's look at the results?

Saturn V (~100 mt class) is abandoned
Shuttle (120 mt gross) is going to be abandoned
Altas and Delta (10 - 20 mt) are flying
Pegasus (less than 1 mt) - flying
Energiya (~100 mt) - abandoned
Soyuz (~10 mt class) - flying
Zenit, Proton (10-20mt class) - flying

See the trend? Market does not (yet?) require 100 mt vehicles. What's the point in trying to build 100 mt LV again? We need smaller steps. Build 40-80 mt (DIRECT) ans see how well that will work, economically.
Title: Re: Sea Dragon class LV thead
Post by: grakenverb on 12/15/2007 12:38 pm
[
Quote
tnphysics - 9/9/2007  1:34 AM



 Higher frequency gammas are much more damaging than lower.


Just look at what happened to Dr. Bruce Banner.  I'd hate to have the astronauts travel all the way to Mars, only to have them turn green and smash everything.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 12/19/2007 03:11 am
Has anyone thought of the problems involved in designing an LAS for a spacecraft to go on top of Sea Dragon?

I don't think that you can pull someone from on top of a medium-sized nuclear weapon to safety in about two seconds.
Title: Re: Sea Dragon class LV thead
Post by: ChrisInAStrangeLand on 12/19/2007 04:30 am
Someone who's name is 'tnphysics' ought to know the difference between detonation and combustion.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 12/19/2007 04:41 am
I was referring to a worst-case LV detonation. If events that would cause this were detected it would then be necessary to get the crew to a safe distance from a detonation that has the energy of a nuclear weapon with only two seconds warning time. This may not be practical.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 01/28/2008 01:42 am
Similar to last year's Sea Launch failure.
Title: Re: Sea Dragon class LV thead
Post by: MKremer on 01/28/2008 02:28 pm
If the Sea Launch failure would have been a true detonation/explosive event, it would have taken out (ie- destroyed/shattered/mangled) most of the *entire* rear section of the launch platform vessel.
Obviously that didn't happen.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 01/28/2008 09:30 pm
Or like one of the N1 falures.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 02/04/2008 11:50 pm
Or a thrust chamber disintigration.
Title: Re: Sea Dragon class LV thead
Post by: guru on 07/10/2008 08:35 pm
It will be cool if someone would build something like the Sea Dragon.  I don't think it's fair to say that it is too big just because the Saturn V and Space Shuttle have no market.  Obviously, those are both really complex and thus expensive launch vehicles which are made even more so because they are intended to carry human cargo.

I would suggest, though, that those two vehicles didn't last because they are in the wrong payload lift range.  They are too big for all current applications, yes, but they are too small and too expensive to make a first generation space based industry feasible.  If you could put 2 million pounds into LEO with one of these things at a cost of 200 million dollars, and launch twelve of them per year, then space based solar power would suddenly be a lot more reasonable.   This is an option that is every bit as cheap as using propellant depots if your goal is eventually to mine gold and vanadium out of asteroids.

On another note, for as many formal analyses as were done on this, and for as much enthusiasm as some people have for this rocket, I can find precious little documentation regarding it.  I have seen the Wikipedia entry, the Encyclopedia Astronautica entry, the Truax website, and some page that says "Lots of pictures.  Loads slowly, but worth it."  But none of these sites seem to include any information on the method of guidance and control, for example.  Was this vehicle supposed to use liquid injection for thrust vectoring?  I doubt an engine that big was supposed to gimbal.

How were the engines to be cooled, if at all?

What type of propellant injector was assumed?

I've known about this concept for over a decade, but these are things (mostly about the engines) I have just never been able to find with a casual internet search.
Title: Re: Sea Dragon class LV thead
Post by: guru on 07/10/2008 08:42 pm
Has anyone thought of the problems involved in designing an LAS for a spacecraft to go on top of Sea Dragon?

I don't think that you can pull someone from on top of a medium-sized nuclear weapon to safety in about two seconds.

Most people don't drive their oil tanker to work for the same reason.  They drive smaller, safer cars, or atleast ride safer buses.  Likewise, one would fly human cargo on a smaller rocket.
Title: Re: Sea Dragon class LV thead
Post by: tnphysics on 07/10/2008 11:30 pm
It will be cool if someone would build something like the Sea Dragon.  I don't think it's fair to say that it is too big just because the Saturn V and Space Shuttle have no market.  Obviously, those are both really complex and thus expensive launch vehicles which are made even more so because they are intended to carry human cargo.

I would suggest, though, that those two vehicles didn't last because they are in the wrong payload lift range.  They are too big for all current applications, yes, but they are too small and too expensive to make a first generation space based industry feasible.  If you could put 2 million pounds into LEO with one of these things at a cost of 200 million dollars, and launch twelve of them per year, then space based solar power would suddenly be a lot more reasonable.   This is an option that is every bit as cheap as using propellant depots if your goal is eventually to mine gold and vanadium out of asteroids.

On another note, for as many formal analyses as were done on this, and for as much enthusiasm as some people have for this rocket, I can find precious little documentation regarding it.  I have seen the Wikipedia entry, the Encyclopedia Astronautica entry, the Truax website, and some page that says "Lots of pictures.  Loads slowly, but worth it."  But none of these sites seem to include any information on the method of guidance and control, for example.  Was this vehicle supposed to use liquid injection for thrust vectoring?  I doubt an engine that big was supposed to gimbal.

How were the engines to be cooled, if at all?

What type of propellant injector was assumed?

I've known about this concept for over a decade, but these are things (mostly about the engines) I have just never been able to find with a casual internet search.
I believe that a pintle injector was to be used, but that's just based on similar (but much, much smaller) rocket designs such as the Apollo LM DPS.
Title: Re: Sea Dragon class LV thead
Post by: Ronsmytheiii on 08/18/2008 07:24 pm
This concept was tested on a smaller scale on the sea bee program which used an aerobee rocket fired from underwater.  It was shown that reusing the rocket cost 7% that of building a new one. My source is astronautix, however I could not find more information.

http://www.astronautix.com/lvs/seabee.htm
Title: Re: Sea Dragon class LV thead
Post by: randomly on 08/30/2008 06:37 pm
SeaDragon Documents
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880069339_1988069339.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880069340_1988069340.pdf
Title: Re: Sea Dragon class LV thead
Post by: guru on 09/04/2008 02:55 pm
SeaDragon Documents
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880069339_1988069339.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880069340_1988069340.pdf

That is some good documentation.  Thank you, randomly.
Title: Re: Sea Dragon class LV thead
Post by: publiusr on 10/03/2008 08:09 pm
What I find interesting is that simple, ship-building technology would allow large rugged, but simple designs. There were folks in NASA at the time that claimed the concept was "technically uninteresting."

These are no doubt the same folks who think that RS-68 shouldn't have been built--and who cry over the costs of Ares V, while wanting more expensive SSTO designs--just because they look cool and have wings, scramjets, lifting-body construction, etc.

But building a simple tube that just happens to be large--no--THAT is 'too hard'...'too expensive'... 

One of the big charges lobbed at me is that I am more in love with the rocket than with the payload.

This charge is actually a better critique of the enemies of big dumb boosters who want LVs to be overly complex for their own sakes.

 THEY are the ones who care more for the platform than the payload.

Same with Ares V. Ares allows large simple payloads, and anti-HLLV forces tell lies about Ares V craft being more complex--when complexity is all but forced upon smaller vehicles due to smaller shrouds and lower lift capability. More complex engines and more launches are what drive costs up.

Six engines cost less than 21.

Sea Dragon is the ultimate Big Dumb Booster, allowing massive amounts of raw materials/propellant loads to be orbited via large (but simple) payloads.

LVs could become even larger with MLLV or Nexus, but Sea Dragon is simple compared to them--and should be the next step after Ares V. With any luck, some Asia Pacific power will give Truax's vision new life.
Title: Re: Sea Dragon class LV thead
Post by: Jim on 10/04/2008 01:27 pm

1.  One of the big charges lobbed at me is that I am more in love with the rocket than with the payload.

2.  This charge is actually a better critique of the enemies of big dumb boosters who want LVs to be overly complex for their own sakes.

3.  Same with Ares V. Ares allows large simple payloads, and anti-HLLV forces tell lies about Ares V craft being more complex--when complexity is all but forced upon smaller vehicles due to smaller shrouds and lower lift capability.

4. More complex engines and more launches are what drive costs up.


1.  The charge is correct

2. and it is not applicable to enemies of BDB. 

3.  Wrong, you have showing any proof of your statements

4.  Unsubstantiated statement again.

publiusr, before you post another one of your unsubstantiated rants on this forum or others, why don't you provide some numbers to back up your claims.  Real hard numbers and not your biased opinions.  Show us a study that supports your claims (all of them, not just one) that fits within current funding realities.  Until then don't bother posting the same garbage.
 
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 10/05/2008 12:39 pm
SeaDragon Documents
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880069339_1988069339.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880069340_1988069340.pdf

The links seem to be to Volume 1 and Volume 3, anyone have volume 2?
Title: Re: Sea Dragon class LV thead
Post by: randomly on 10/05/2008 05:48 pm
I believe NASA has volume 2 but it's not available online yet.
Title: Re: Sea Dragon class LV thead
Post by: publiusr on 03/20/2009 08:00 pm

http://adsabs.harvard.edu/abs/2002iaf..confE.282T
That is all I have for now. I think one of the reports may still be classified.

Try scott's unwanted blog over at www.up-ship.com

He will be revisiting the Sea Dragon concept--and I am still looking for Quest to do a story on Truax.
Title: Re: Sea Dragon class LV thead
Post by: malenfant on 10/07/2009 01:14 pm
First off I should say that I don't believe that there is any probablility that a government or commercial entity will fund a sea dragon sized vehicle in the next 50-100 years.  However I don't think we could have a viable off-world colonization effort without a chemical rocket in that class so in the long term my opinion is that building one is essential for the species.  I don't feel the need to be any more realistic than that about the politics or economics of the thing.

It's the sea launch component of Sea dragon that has always bugged me.  Have any serious investigations been done into land launched options?  I'm not convinced enough study has been done of land based systems to commit to a sea based launch and the attendent transportation problems being the best of all available options for a booster of that class.  I'm also not convinced that there is as much advantage as people might imagine in using an existing ship yard to do build the item.

What I have wondered about before was whether you could actually fabricate a BDB of sea dragon size on the pad.  Does anybody know of any studies into that?

When I say on the pad I am actually envisaging more of a silo structure.  A vast cylindrical shaft set into the ground that could act as the basis for both assembly jig and launch gantry.

I freely admit that the concept is born out of a science fiction flight of fancy rather than solid engineering knowledge.  However, realism is a relative concept when discussing boosters of this class and based on an almost complete lack of data I prefer this to rental of a nimitz class support vehicle and semi submerging your booster in the ocean for launch.

Apart from solving transport issues the concept still suffers from all the other problems of any BDB.  A high flight rate is needed with several of these assembly/integration/launch facilities working in paralelel to keep all the different teams in near continuous employment.  Nothing except colonization could justify it.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/07/2009 02:50 pm
What would be the dimensions of a "Sea Dragon" class launch vehicle to deliver 50 or 100 tons to orbit?  If it would fit existing launch facilities like the VAB.  Would a clean sheet rocket like a "Sea Dragon" pressure fed vehicle be much less expensive to operate and orbit?
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/07/2009 06:19 pm
I think I answered my own question.  This rocket could launch 55 tons, and is about the size of a Saturn V.  Cheap.  So why couldn't this be used cheaply to build moon and Mars craft and still use VAB for assembly?

http://www.astronautix.com/lvs/exclibur.htm
Title: Re: Sea Dragon class LV thead
Post by: kraisee on 10/07/2009 06:25 pm
SeaDragon was supposed to be able to launch about 550mT in each flight.   It was simply gargantuan at 75ft in diameter (23m).

It was designed along robust large-scale "ship building" / "submarine building" manufacturing lines, not the typical expensive aerospace manufacturing techniques.   This "big metal" approach was also planned to make it 100% reusable too, with the Upper Stage being able to re-enter 'hot' and then be recovered from a splashdown in the Ocean.

The whole vehicle was to be Ocean Surface launched.   There was going to be no "Pad" under it, it was quite literally going to be floating in the ocean, pointing upwards when the engines were lit and the bottom half of the vehicle would rise up out of the water.

Truax had already pioneered and proven this launching method at much smaller scales with the Sea Bee and Sea Horse rockets, so the principle is sound although the scale of Sea Dragon was certainly something else...

The most complex part of Sea Dragon, IMHO, is the two *VAST* engines it uses, one on each stage and each with nozzles over 20 meters in diameter!   While enormous and very powerful, neither engine is actually all that highly "stressed", with both operating at lower internal pressures well below that used by most currently operational engines in the world today -- so other than their formidable size, they are both based on relatively 'simple' and readily available technology.

Aerojet designed Sea Dragon in 1962 and NASA then got TRW to assess their costings independently for them.   NASA was very surprised when TRW confirmed all of Aerojet's claims of achieving a cost of less than $60 per lb to LEO (in FY1962 dollars = $429 today)!

I personally think Sea Dragon is the smartest "low tech" approach I have ever seen for Super Heavy Lift missions.

Ross.
Title: Re: Sea Dragon class LV thead
Post by: Lars_J on 10/07/2009 07:19 pm
It's the sea launch component of Sea dragon that has always bugged me.  Have any serious investigations been done into land launched options?  I'm not convinced enough study has been done of land based systems to commit to a sea based launch and the attendent transportation problems being the best of all available options for a booster of that class.  I'm also not convinced that there is as much advantage as people might imagine in using an existing ship yard to do build the item.

But why would you? It is the sea launch that allows you to have so little launch infrastructure. That would be major part in its low cost. Shipyards already exist capable of building structures on that scale. Large seagoing support vessels are easily available. (no need for a carrier) And launching from the seas is great... Ballast the thing to vertical, and go...

Or you can imagine a land-based launch facility. KSC scaled up 5-10x?
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/07/2009 07:29 pm
The Excalibur that I linked above is a reduced scale Sea Dragon about the size of a Saturn V that could fit the VAB building and not have to be sea launched, but it only lifts 55 tons.  It is reusable though.  If a 3rd stage could be added it could probably lift more. 
Title: Re: Sea Dragon class LV thead
Post by: Robotbeat on 10/07/2009 07:39 pm
The Excalibur that I linked above is a reduced scale Sea Dragon about the size of a Saturn V that could fit the VAB building and not have to be sea launched, but it only lifts 55 tons.  It is reusable though.  If a 3rd stage could be added it could probably lift more. 

Don't bother! Just launch it twice. It's supposed to be reusable, and it's optimized that way, so you'd better use it like a reusable rocket if you're expecting it to be worth developing and using.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/07/2009 08:15 pm
I can't understand why the leaders at NASA will not use a "Sea Dragon" type vehicle.  If it is a low pressure engine, and pressure fed, no turbopumps etc.  It can't be that expensive to build out of sheet steel at a navy shipyard.  We could then concentrate on a reusable flyback lifting body craft that is smaller than shuttle with a flyback booster.  Then we could build large spacecrafts to fly between Earth and Moon, Mars etc.  Just use the smaller craft to ferry people between Earth and the spacecraft.
Title: Re: Sea Dragon class LV thead
Post by: Robotbeat on 10/07/2009 08:19 pm
I can't understand why the leaders at NASA will not use a "Sea Dragon" type vehicle.  If it is a low pressure engine, and pressure fed, no turbopumps etc.  It can't be that expensive to build out of sheet steel at a navy shipyard.  We could then concentrate on a reusable flyback lifting body craft that is smaller than shuttle with a flyback booster.  Then we could build large spacecrafts to fly between Earth and Moon, Mars etc.  Just use the smaller craft to ferry people between Earth and the spacecraft.

No flybacks for the Sea Dragon launch vehicle. It would be designed to be dunked in the ocean. Launched from the ocean, landed in the ocean. Cheaper infrastructure that way.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/07/2009 08:33 pm
I was saying develop a small flyback booster to launch a small lifting body craft for human ferry.  Use the Sea Dragon concept to launch large components to build large spacecraft to travel in space only.  Just send up the small lifting body craft to ferry the human cargo.  Use the Sea Dragon for non human cargo, supplies and building materials for the large spacecraft, spacestations, Moon and Mars bases.  500 tons on the Sea Dragon could launch a Mars craft in one launch, or the Excaliber type Sea Dragon and launch 55 ton components to assemble Moon and Mars crafts. 
Title: Re: Sea Dragon class LV thead
Post by: meiza on 10/07/2009 09:35 pm
So, this 550 ton launching reusable rocket would launch how many times per month?

Would it perhaps bring some economy to instead start smaller and launch more often?
Title: Re: Sea Dragon class LV thead
Post by: 93143 on 10/07/2009 10:35 pm
So, this 550 ton launching reusable rocket would launch how many times per month?

Depends what you're trying to do.

If you want to get a serious sci-fi-style space program going without having to worry about the mass of radiation shielding, nuclear reactors, huge pressurised spin-gravity systems, massive space drydocks and such, you've probably got a job for Sea Dragon.  Assuming an Orion isn't available.  If you want to piddle around with complicated, infrequent tinkertoy missions and SEP and hypergolic depots and ingeniously-folded heat shields and trying to minimize astronauts' time in space because you can't afford the mass budget to protect them from cosmic rays, don't bother.

There's a reason no one's built this thing yet.
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/08/2009 12:54 am
This is interesting. I agree that for the moment at least a full scale Sea Dragon probably would not have a market. So what if it were made to launch 80mT to LEO and was a completely reusable launcher? The AeroJet study cited above showed that if it were reusable, it could be launched again for 7% of the cost of building another copy and launching it, in expendable mode. Ideally, there would be a small fleet of these maintained for use, perhaps six or seven launchers; similar to the way Shuttle was originally envisioned. Flown at a nominal Shuttle launch rate, using these reusable launchers, the cost per kilo would be lower than anything else I can imagine, at any sustainable launch rate, perhaps as low as $500 per kilo. The AeroJet study showed that when pressurized properly, at ~300 psi (a fraction of flight pressure), that the vehicle could impact the ocean, in an axial orientation at 600 fps and be basically unfazed by that, ready to be cleaned up and flown again. It would deploy a large conical drag balute to slow it's initial re-entry velocity, keeping the plasma down to around 1,000 degrees F, and then just go straight in. A robustly built, thick-skinned rocket would easily withstand that temperature and then hit the water with a terminal velocity of 600 fps.

I wonder how many times it could fly before you would need to recycle the steel and bring a new one online to replace it? Comparatively speaking, the replacement would be dirt cheap. Some shipyard could be contracted to provide 1 new one per year for some number of years. It wouldn't even need to be it's only product. If we actually get on with exploration, being able to fly at $500 per kilo would go a LONG way to making the entire VSE affordable.

Interesting.
Title: Re: Sea Dragon class LV thead
Post by: malenfant on 10/08/2009 02:48 pm
But why would you? It is the sea launch that allows you to have so little launch infrastructure. That would be major part in its low cost. Shipyards already exist capable of building structures on that scale. Large seagoing support vessels are easily available. (no need for a carrier) And launching from the seas is great... Ballast the thing to vertical, and go...

I thought the reason for suggesting a carrier was that they would use electricity from it's nuclear reactor to electrolize seawater for the LOX (astronautix).  Without the nuclear reactor I suspect you're left looking for a towing vessel that can carry all that LOX.  I don't have figures for the total launch mass of LOX.  Also I don't know how long it takes to tow it to site and prepare for launch.  Boil off is going to be  fairly significant isn't it?

Or you can imagine a land-based launch facility. KSC scaled up 5-10x?

I think it's pretty clear you can't scale up what they have at KSC with the seperate VAB, the Crawler, and bringing in entire dry stages by barge.  That isn't anything like what I was suggesting.  The fact that the infrastructure at Kenedy can't be scaled up doesn't mean there aren't alternative ways to organise fabrication/integration/launch of a super booster on land without adopting this extra design constriant of emersing your vehicle and all the support equipment in brine.

If you start from the pressumption that the thing is immovable until launch and must be built already raised in it's launch orientation then a big hole in the ground seems to me the simplest of all solutions.  Maybe concrete lined shafts of this diameter have already been dug for mining?  I suspect the technology and experience is available.

I really started thinking about this when I saw how N1 was welded up inside the MIK and thought about how Orion would have to have been built at launch site (can't exactly move one around!).

I just have this suspicion that the cart has been placed before the horse on this one and that a sea launch only make sense if you are the US navy.  Otherwise it might make more sense to start your own "shipyard" in a desert somewhere rather than to acquire and opperate an expensive and highly specialised support vessel and to design your booster so it has to be a boat as well as a rocket.
Title: Re: Sea Dragon class LV thead
Post by: Robotbeat on 10/08/2009 03:31 pm
But why would you? It is the sea launch that allows you to have so little launch infrastructure. That would be major part in its low cost. Shipyards already exist capable of building structures on that scale. Large seagoing support vessels are easily available. (no need for a carrier) And launching from the seas is great... Ballast the thing to vertical, and go...

I thought the reason for suggesting a carrier was that they would use electricity from it's nuclear reactor to electrolize seawater for the LOX (astronautix).  Without the nuclear reactor I suspect you're left looking for a towing vessel that can carry all that LOX.  I don't have figures for the total launch mass of LOX.  Also I don't know how long it takes to tow it to site and prepare for launch.  Boil off is going to be  fairly significant isn't it?

Or you can imagine a land-based launch facility. KSC scaled up 5-10x?

I think it's pretty clear you can't scale up what they have at KSC with the seperate VAB, the Crawler, and bringing in entire dry stages by barge.  That isn't anything like what I was suggesting.  The fact that the infrastructure at Kenedy can't be scaled up doesn't mean there aren't alternative ways to organise fabrication/integration/launch of a super booster on land without adopting this extra design constriant of emersing your vehicle and all the support equipment in brine.

If you start from the pressumption that the thing is immovable until launch and must be built already raised in it's launch orientation then a big hole in the ground seems to me the simplest of all solutions.  Maybe concrete lined shafts of this diameter have already been dug for mining?  I suspect the technology and experience is available.

I really started thinking about this when I saw how N1 was welded up inside the MIK and thought about how Orion would have to have been built at launch site (can't exactly move one around!).

I just have this suspicion that the cart has been placed before the horse on this one and that a sea launch only make sense if you are the US navy.  Otherwise it might make more sense to start your own "shipyard" in a desert somewhere rather than to acquire and opperate an expensive and highly specialised support vessel and to design your booster so it has to be a boat as well as a rocket.

I am really convinced that a sea-landing is far easier accomplished than a land-landing. As the vehicle becomes larger, it seems that this becomes more and more the case, since you only need to protect the outer layer of material from seawater (i.e. If you need to protect a brick from seawater, you need a certain thickness of material around the brick. That thickness stays the same as the brick becomes larger, but the volume of the brick grows faster than the surface area of the brick.)

Honestly, what's the big deal with being in seawater? I think a little care for ensuring seawater compatibility--making your rocket "also a boat"--is far easier than making your rocket "also an airplane" and landing it horizontally on a landing strip!
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/08/2009 03:34 pm
I am really convinced that a sea-landing is far easier accomplished than a land-landing. As the vehicle becomes larger, it seems that this becomes more and more the case, since you only need to protect the outer layer of material from seawater (i.e. If you need to protect a brick from seawater, you need a certain thickness of material around the brick. That thickness stays the same as the brick becomes larger, but the volume of the brick grows faster than the surface area of the brick.)

Honestly, what's the big deal with being in seawater?

Nothing, as long as you design for it from the beginning; which this would be.
Title: Re: Sea Dragon class LV thead
Post by: 93143 on 10/08/2009 03:43 pm
and to design your booster so it has to be a boat as well as a rocket.

You've got to do that anyway.  Ocean splashdown and recovery of the stages is an important part of the cost structure of this scheme.  So all you really need is a nuclear reactor...

...or a Polywell, but if you've got a Polywell there may be better ways to build cheap reusable Nova-class space launchers...

I suppose Greenpeace wouldn't be all right with the acoustic effects of a Sea Dragon launch?  How far away would a whale have to be to survive one?
Title: Re: Sea Dragon class LV thead
Post by: Robotbeat on 10/08/2009 03:57 pm
and to design your booster so it has to be a boat as well as a rocket.

You've got to do that anyway.  Ocean splashdown and recovery of the stages is an important part of the cost structure of this scheme.  So all you really need is a nuclear reactor...

...or a Polywell, but if you've got a Polywell there may be better ways to build cheap reusable Nova-class space launchers...

I suppose Greenpeace wouldn't be all right with the acoustic effects of a Sea Dragon launch?  How far away would a whale have to be to survive one?

You don't need a nuclear reactor. You could use any electrical source, as long as you could connect to the grid.
Title: Re: Sea Dragon class LV thead
Post by: 93143 on 10/08/2009 04:10 pm
You don't need a nuclear reactor. You could use any electrical source, as long as you could connect to the grid.

I was talking about the requirements for a standard ocean launch of a Sea Dragon.  If you can connect to the grid, you're far too close to a lot of expensive shoreline properties to launch something with an 80 Mlb kerolox engine.
Title: Re: Sea Dragon class LV thead
Post by: malenfant on 10/08/2009 04:30 pm
I was never envisaging that the thing would be reusable.  I thought the baseline version of Sea Dragon was supposed to be expendable.  Never figured for landing the vehicle.  It just seems like more complexity.  It's better to keep the production line busy by commiting to being expendable than to try to recover the dead stage a few times and insert lengthy stand-downs into your production?

You don't need a nuclear reactor. You could use any electrical source, as long as you could connect to the grid.

I was talking about the requirements for a standard ocean launch of a Sea Dragon.  If you can connect to the grid, you're far too close to a lot of expensive shoreline properties to launch something with an 80 Mlb kerolox engine.

Exactly.  Seems like the Nuke reactor is prretty essential to the sea launch scheme.

I start to think I should have started a new thread or just not mentioned sea dragon at all.  I'm inspired by the conventional, heavy (and therefore hopefully cheap) construction and by the simple but massive engine tech.  The prospect of needing a seagoing nuclear reactor and a large towing vessel doesn't thrill me.  Nor am I particularly convinced that because a yard builds ships using similar construction methods that turning them over to building a rocket will be particularly cheaper than just starting a whole new facility somewhere else.

My gut feeling is that building and launching something like this on land has simply never been properly studied and that that's at least partly why people are in love with the sea launch concept.  (because it got so far and is known to be vaguely plausible from an engineering standpoint)
Title: Re: Sea Dragon class LV thead
Post by: 93143 on 10/08/2009 04:58 pm
I was never envisaging that the thing would be reusable.  I thought the baseline version of Sea Dragon was supposed to be expendable.  Never figured for landing the vehicle.  It just seems like more complexity.  It's better to keep the production line busy by commiting to being expendable than to try to recover the dead stage a few times and insert lengthy stand-downs into your production?

Tests with Sea Bee indicated that relaunch of a used rocket was about 7% as expensive as launching a brand new one.  Landing isn't all that complex; you just need an inflatable air brake.  The stages themselves are really quite tough, and the engines are dead-simple pressure-fed designs.

Since you'd be using a shipyard to build this thing, they'd have other things to do when they weren't building Sea Dragons.  You'd probably save a fair bit of money by not building a whole new dedicated facility, especially with production rates being as low as you'd hope for a reusable vehicle.

With reusability, if you launch from land, you have to get the rocket out of the water and haul it overland back to the launch site.  For something as big as Sea Dragon, that might be a showstopper.

A Nimitz-class supercarrier costs about $4.5B according to Wikipedia.  It might be substantially cheaper to build a dedicated nuclear-powered support ship or two, and considering what you'd probably have to spend on payloads to make Sea Dragon worthwhile, a couple billion on a one-off isn't all that much money...
Title: Re: Sea Dragon class LV thead
Post by: mlorrey on 10/09/2009 05:40 am
The Excalibur that I linked above is a reduced scale Sea Dragon about the size of a Saturn V that could fit the VAB building and not have to be sea launched, but it only lifts 55 tons.  It is reusable though.  If a 3rd stage could be added it could probably lift more. 

OK, you need to cut with the idea that a launch system is about the hardware. The major malfunction of NASA is its big standing army, all the launch infrastructure, VAB, tower, etc etc etc to ensure safety so rocket parts dont come raining down on tax payers. Then they go build the most expensive tightly toleranced high performance rocket they can that operates at the highest possible risk of failure.

And THEN they wonder why its so expensive, as if everything they've done to that point was not purposely done to spend as many tax dollars as possible for as many different congressional districts.

A launch system is about the operational perspective and methodology. NASAs design imperative historically has been to push the technological edge while doing so in as many congressional districts as possible, NOT to achieve a cost effective responsive launch fleet.

Sea launch enables a LOT of what we think we know about space launch from dry earth to be thrown out the window, because theres nobody around at sea to worry about.

When you design a rocket launcher you have to ask, what is your mission? Is it to put 1000 kg in orbit? to put 3 men on the moon? Or to put 550mT of cargo in LEO? With each mission there are different directions to take to reach an optimum design for minimum cost. It is counterproductive to apply rules for one mission to another mission without strenuously testing the assumptions about why you would need those rules.

For instance, 1 space shuttle orbiter costs about twice as much to build as one, much larger and heavier, Ohio class nuclear ballistic submarine, a vessel whose hull is comparable to what would be needed for Sea Dragon. Assuming that the low pressure rocket engines for the Sea Dragon are less complex and difficult to build than multiple submarine nuclear power plants (a fair bet), it stands to reason that for the cost of one space shuttle orbiter (which can put 7 astronauts and 65,000 lb of cargo in LEO) you could have two sea dragon launch vehicles which can put 1100mT of cargo in LEO.

The entire STS fleet has not delivered even a tiny fraction of 1100 mT of cargo to LEO over the entire life of the fleet.

I would argue that you need to come up with reasons why a miniseadragon SHOULD be operated on land when it hasnt been designed for it and doing so abandons the biggest cost saving advantages of the whole concept.
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 10/09/2009 03:40 pm
I can't understand why the leaders at NASA will not use a "Sea Dragon" type vehicle.  If it is a low pressure engine, and pressure fed, no turbopumps etc.  It can't be that expensive to build out of sheet steel at a navy shipyard.  We could then concentrate on a reusable flyback lifting body craft that is smaller than shuttle with a flyback booster.  Then we could build large spacecrafts to fly between Earth and Moon, Mars etc.  Just use the smaller craft to ferry people between Earth and the spacecraft.

How would they show what great rocket scientists they are if they went with a low-tech, 'Big Dumb Booster'?
Title: Re: Sea Dragon class LV thead
Post by: Gregori on 10/09/2009 04:05 pm
If there was a serious drive towards Space colonization, a Sea Dragon style rocket would make a good propellant tanker to a HUGE depot!!!

A surplus of propellant and water in orbit would make colonization much easier.
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/09/2009 04:44 pm

A Nimitz-class supercarrier costs about $4.5B according to Wikipedia.  It might be substantially cheaper to build a dedicated nuclear-powered support ship or two, and considering what you'd probably have to spend on payloads to make Sea Dragon worthwhile, a couple billion on a one-off isn't all that much money...

The nuclear powered USS Enterprise (CVN-65) is about to be retired (per wikipedia):

Quote
The USS Enterprise, the oldest active combat vessel in the Navy as of 2009, had been scheduled to be decommissioned as late as 2014. On April 6, 2009 Admiral Gary Roughead, Chief of Naval Operations, stated that he would be seeking a congressional dispensation to speed up the process. Under this new timetable, the ship would complete one final deployment before being decommissioned in late 2012 or early 2013.

There is our Sea Dragon support vessel, right there.
Title: Re: Sea Dragon class LV thead
Post by: Patchouli on 10/09/2009 07:03 pm
It would be nice if someone would try the Seadragon concept it just seem so logical once you really give it some thought.

Though I agree it probably would be best to start with a smaller vehicle such as the Excalibur first.
A 55T vehicle probably will find a market very quickly while the 550T vehicle would pretty much be a pad queen even though it has no pad for several years before applications can take advantage of it.
The small half ton payload Excalibur S would be perfect for proving the concept and probably would be in the reach of many alt space companies.

Though an early application for Seadragon could an Ares V replacement.
Ares V already is a monster at 188tons so 550T doesn't sound too insane when viewed in that context.

As for a support ship for a Seadragon class LV why not modify a LNG tanker?
http://en.wikipedia.org/wiki/LNG_carrier
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/11/2009 03:27 pm

As for a support ship for a Seadragon class LV why not modify a LNG tanker?
http://en.wikipedia.org/wiki/LNG_carrier

If the nuclear reactor was going to be used for "house power" such as LOX refrigeration (or extraction) rather than propulsion then adding one or more US Navy nuclear reactors to an existing LNG carrier could be a good solution.

Load up on RP-1 kerosene (and LOX?) at the dock and transport those fuels out to the launch site while towing the Sea Dragon. RP-1 and LOX together with a LEO depot facility to distribute same would be a good payload for a Sea Dragon.   

An LNG carrier could also carry the payload and pump it into the Sea Dragon just prior to launch. A Sea Dragon with empty propellant tanks and empty payload tanks should float rather nicely.

That said, an LNG carrier could probably transport LOX without nuclear power for refrigeration and RP-1 of course needs no refrigeration and therefore maybe we don't even need a nuclear reactor.

= = =

A Sea Dragon could also launch a truly ginormous inflatable LEO sports stadium and space hotel. 

I mean truly ginormous! 8)
Title: Re: Sea Dragon class LV thead
Post by: 93143 on 10/11/2009 08:25 pm
Just a note:  Sea Dragon's upper stage runs LOX/LH2.  The reactor is needed for electrolysis, not just refrigeration.
Title: Re: Sea Dragon class LV thead
Post by: Lars_J on 10/12/2009 04:15 am
But if simplicity is your goal, why not run the 2nd stage on KeroLox as well? Sure you lose payload, but with a SeaDragon type launcher, efficiency is not your ultimate goal anyway.

And if that makes the nuclear reactor unnecessary, even better.
Title: Re: Sea Dragon class LV thead
Post by: Patchouli on 10/12/2009 05:36 am
Just a note:  Sea Dragon's upper stage runs LOX/LH2.  The reactor is needed for electrolysis, not just refrigeration.

It should be possible to convert one of the tanks to lH2 storage even though lH2 is about 90C cooler then the methane they originally carried
Worst case you have the ship fitted with a new tank very similar to what NASA uses for storage.

Use the boil off from the lH2 to help refrigerate the LOX and then burn it as supplementary fuel for the diesel engines.

Since it is a methane carrier it also may be possible to make the whole rocket simply burn methane which has a slightly higher ISP then Kerosene it should compensate somewhat for not having an lH2 upper stage.

All methane lox might be the simplest route of them all esp considering LOX and liquid Methane have similar temps.
Tanks will be larger by 38% over Kerosene but you might make it back on savings on the common bulkhead's insulation.
Though methane will want to still be a little warmer unless you're planning to burn methane slush which might make the tanks more compact.
Though I think that might be be too exotic for what is supposed to be a simple LV.

I know it's not as cool as converting an aircraft carrier but converting and operating a natural gas tanker probably would be a lot cheaper.
Being realistic they probably won't let a Spacex or OSC operate an old nuclear carrier heck even NASA might have difficulty getting permission.
It likely would have to remain owned and operated by the US navy.
Besides I believe a naval museum already has dibs on the big E after the reactors are removed.
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/12/2009 03:37 pm
Enterprise was the CV depicted in that Sea Launch painting from the early 1960s meaning that would have been an appropriate choice. 

http://www.astronautix.com/graphics/s/seadrag1.jpg

That said, I stand persuaded on using a converted LNG carrier as the support ship with no nuclear reactors needed.

= = =

Interesting thing about Sea Dragon is that it is 1960s technology and any nation capable of building submarines can build one.

Carry liquid hydrogen as payload and you got a super-cheap fuel depot transport launcher.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/12/2009 03:59 pm
A sea dragon could be launched right off Cape Kennedy and fuel from the cape.  I don't think it would have to be in deep water to launch.  Barges already bring the shuttle tank from LA.  It could be towed from whereever it was built to the cape for fueling, loaded, towed a short distance and launched. 
Title: Re: Sea Dragon class LV thead
Post by: JayP on 10/12/2009 10:28 pm
Enterprise was the CV depicted in that Sea Launch painting from the early 1960s meaning that would have been an appropriate choice. 


Uhh. Enterprise was the ONLY CVN back in the 60s. The USS Nimitz wasn't launched until 1972, so it's not like they really had a choice.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/15/2009 01:08 pm
I still say the Excaliber type Sea Dragon launch 55 tons each and the size of the Saturn V can use the same barge size as the Shuttle tank, fueled at the Cape, towed out and launch these 50 ton cargo sizes.  A lot can be done with a cheap reusable, simple to build and operate, sea launched vehicle at 50 tons each.   
Title: Re: Sea Dragon class LV thead
Post by: MichaelF on 10/16/2009 05:27 am
But what, specifically, are you launching?

If it's a NASA (or RSA/ESA/JAXA, etc) operation, $$ ROI is not really an issue (.gov agencies aren't mandated to generate earnings)...but budget (the amount of money sliced to the agency, per given period) is.

What payload is NASA going to put on top of Sea Dragon?  What mandate does it help address?  NASA isn't funded (those payloads are often much more expensive than the actual launch operation) to build* a Lunar Base (any bigger than the Constellation program envisioned, at any rate) or colonize* Mars.

You'd need to build up a mandate ("Colonize Mars", "Mine the Moon and Asteroids", etc) that required frequent launches of that scale.
As it is, NASA isn't funded to do anything beyond LEO, and, even if it was, no realistic level of funding will ever allow operations on the scale that will require multi-hundred ton capacity LVs.  NASA gets 1/35th the funding, annually, that the DoD gets.  We are not serious about expanding into Space.  Not even close.


# and size (mass & volume) of payloads, not capacity, is the driving force.  If you build it, they will not come.  If they come, you can build it.

Bottom Line: You need to have a well-funded program that is aquiring payloads that need that scale of launch capacity.

*-Nor is it the appropriate organization to do either (if it did, it would have to drop everything else).  A Congressionally-chartered federally owned corporation, like the Tennessee Valley Authority (or the British East India Company), is a much better candidate, as it could focus on that one task.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/16/2009 01:48 pm
The EELV crowd says anything can be done using 25-50 ton increments, moon, Mars, fuel depots at L1 or L2.  What I am saying is the Sea Launch concept will get all your parts, supplies, fuel, etc in orbit for assembly or transfer.  This will not be used for human cargo, just a cheap way to dump 50 ton cargo supplies and equipment to orbit.  If it works, then build the Sea Dragon to launch 500 tons to orbit at a future later date.  The smaller concept will prove the cost, efficiency, and safety aspects before going to the larger vehicle. 
Title: Re: Sea Dragon class LV thead
Post by: MichaelF on 10/16/2009 02:05 pm
I'm not part of the EELV crowd.  However, neither do I see the utility of moving toward an architecture that is so far in excess of current and future needs that it borders on a vanity project.

There are no payloads for such a LV.  Nor will there be (NASA not having anywhere close to the funding required to pay for such payloads).  Not in such a span of time that actually developing the LV will be the speedbump.
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/16/2009 04:49 pm
What the Sea Dragon concept does (IMHO) is invalidate claims that LEO fuel depots will facilitate crewed RLV development - if those crewed RLVs are intended to act as fuel tankers filling such depots.

I've never bought into the idea that fuel depots are an enabling step for crewed RLV development and deployment as I believe a Sea Dragon class vehicle would be able to deliver fuel to LEO for a fraction of the cost of a crew capable RLV.

Of course, a Sea Dragon first stage is an RLV if recovered and refurbished and re-launched, even if it lands by smacking the ocean and survives because of its thick metal construction.

= = =

For those who desire crewed RLVs, I suggest an application that requires significant rotation of people to and from LEO -- such as hotels and zero gravity sports facilities.
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/16/2009 05:14 pm
I've never bought into the idea that fuel depots are an enabling step for crewed RLV development and deployment as I believe a Sea Dragon class vehicle would be able to deliver fuel to LEO for a fraction of the cost of a crew capable RLV.

Hmmm. Perhaps the SSTO Sea Dragon could "be" the depot, and instead of filling it on orbit, it arrives full, and when emptied, deorbits itself for refilling and reuse to be replaced by another "reusable" depot. Just thinking.
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/16/2009 07:21 pm
I've never bought into the idea that fuel depots are an enabling step for crewed RLV development and deployment as I believe a Sea Dragon class vehicle would be able to deliver fuel to LEO for a fraction of the cost of a crew capable RLV.

Hmmm. Perhaps the SSTO Sea Dragon could "be" the depot, and instead of filling it on orbit, it arrives full, and when emptied, deorbits itself for refilling and reuse to be replaced by another "reusable" depot. Just thinking.

What would be the residual value of the pieces that come back? How much thermal protection do you need for a big fluffy tank?

Do you believe that would trade well?

Seems to me that a TSTO Sea Dragon would allow repeated use of the giant pressure fed 1st stage and after the 2nd stage reached the depot you could extract the expensive bits - avionics & engines & maneuvering thrusters & so forth - and return them separately but once the giant tank was empty, just dump it in the Pacific.

Recycle the small but expensive stuff and dispose of the cheap bulky stuff.

The 2nd stage engines & avionics would give you the last mile guidance and propulsion to the depot but could be removed from the giant tank before disposing of the tank itself.

What would the duty cycle of a liquid hydrogen tank be, anyway? How often could you fill it and empty it before you couldn't trust it any more?

= = =

One major advantage of ocean launch supported by a converted CNG carrier would be the ability to launch from international waters anywhere on the planet, solving issues related to reaching various orbital inclinations.

 
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/16/2009 07:58 pm
Sea Dragon, regardless of payload, was originally conceived as a RLV. Couple that with the biggest objection that has been offered against orbital depots (lots of little tankers filling one big depot), then this model becomes more like what we see in the automotive industry today; one huge tank truck providing fuel for hundreds of smaller automobiles. The SSTO wouldn't be a light fluffy stage, but something really robust, able to withstand the thermal re-entry and drop into the ocean at 600fps without sustaining any damage to either the vehicle itself or the one huge single pressure-fed engine. Remember that the tank wall would not be measured in mm's of aluminum, but in fractional inches of steel.

A vehicle this large and robust may seem gargantuan to those of us used to the current state of affairs of launch vehicles - light as possible, making up for robustness with very, very complicated subsystems (translated: expensive), but by the standards of shipyards that would roll the steel and make these things this is a really small vehicle. They regularly build ships 5 times the size of this thing. Sea Dragon was designed around KISS; overly large, overly heavy, overly tough, all to put massive payload into orbit in the simplest way possible. The Aerojet studies showed not only could this SSTO be reusable, but could be refurbished and re-flown for only 7% of the cost of expending the vehicle and flying a new one. They showed unequivocally that after a certain point the economy of scale beat the economy of launch rate hands down. So build it HUGE and make it SIMPLE. Make it really, really tough and fly it a dozen times before you send the big tank to the smelter.

They conceived of huge payloads; spacecraft and the like. But what if it was just a huge gas tank in the sky? What if in a single shot you put 500mT of propellant into LEO for outbound spacecraft to sip from? And as for cost, 500mT of propellant is still a lot cheaper than any 25mT payload put up by the EELV's today. If you loose one, the cost of the propellant lost is an insignificant loss and because the RLV is really simple and relatively speaking really cheap to build, who cares? The insurance industry would write its relatively small check to the launch provider without batting an eye and looking back. It's just a big heavy tank with a really, really simple pressure-fed engine on it full of dirt cheap propellant.

Just musing here. Humor me.
Title: Re: Sea Dragon class LV thead
Post by: William Barton on 10/16/2009 08:07 pm
Whatever happened to the radially segmented launch vehicle? Stainless steel milk-tank rocket parts. I see an earmark request for it from only last year, but nothing really new.

http://www.legistorm.com/earmarks/details/member/316/Rep_Ron_Kind/page/1/sort/amount/type/desc.html
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/16/2009 08:13 pm
I agree, Chuck.

We can quibble the details but I agree entirely with the main point.

A 1960s tech rocket (built with 21st century submarine yard skills) could loft enough fuel - in a single throw - to supply a great many Earth departure stage missions.

You could also loft a great many Bigelow habitats, all connected to a central hub, in a single throw creating a large capacity station or a ginormous Earth departure vessel.


Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 10/17/2009 02:55 am
What the Sea Dragon concept does (IMHO) is invalidate claims that LEO fuel depots will facilitate crewed RLV development - if those crewed RLVs are intended to act as fuel tankers filling such depots.

I suspect the tankers were meant to be unmanned.  It is the spacecraft that buy the propellant that contain people.
Title: Re: Sea Dragon class LV thead
Post by: cosmicpax on 10/17/2009 05:15 pm
It could

You could also loft a great many Bigelow habitats, all connected to a central hub, in a single throw creating a large capacity station or a ginormous Earth departure vessel.


Why should they be connected to a single hub? It's much more useful if they are connected in a torus, so it can rotate and maintain artificial gravity for long trips. Also, they could be shielded with a lot of water, since lifting mass is not a problem with a Sea Dragon.
Title: Re: Sea Dragon class LV thead
Post by: Nascent Ascent on 10/17/2009 06:36 pm
Could one Sea Dragon launch an entire mission to the Moon consisting of...

Orion and Service Module

Altair Lander for crew

Big Habitat Lander(s) with supplies, rover(s), in-situ equipment, spares - autonomously landed
Title: Re: Sea Dragon class LV thead
Post by: kraisee on 10/17/2009 07:29 pm
Yes, quite easily.

The problem isn't that it could do that, the question is how do you pay for all that hardware to go fly on a single rocket -- that laundry list you suggest is worth billions and billions!   More importantly:   Do you really want to risk putting all those eggs in a single basket?

If anything happened to that launch, you would lose everything in your entire *program* not just a single element.

A Sea Dragon could just-about launch the equivalent mass of two International Space Station's in a single shot.

While we would have loved to have had that capability ten years ago when we started lifting all those modules, there isn't much in the way of payloads around today -- or even planned in the next 20 years -- which would fill a single Sea Dragon each year -- and Sea Dragon's cost benefits required it to have a decent flight rate around 12 flights per year (just like every other launcher).

If you didn't have that many launches, then the same old rules come into effect and the infrastructure costs start dominating the cost of each flight -- making the system non-viable again.

The entire world's launch requirements -- government, military and civilian combined -- amounts to just a very small fraction of the 6,600mT of LEO lift capability which this system needed to make it worthwhile.


And it's one hell of a gamble to go pay all the money needed to develop this in the hope that "if you build it they will come".   That approach failed to work out very well for either EELV, did it?

This needs a totally different business model to have any chance at all -- and I personally don't think NASA would ever choose to fly anything on it.

Ross.
Title: Re: Sea Dragon class LV thead
Post by: MichaelF on 10/17/2009 07:57 pm
Sea Dragon presupposes a massive (multi-hundred $Billion, annually) project that would require that sort of lift capacity.  Unless Space Colonization becomes a Tier One operation as a national objective (alongside DoD, SS, Medicare, etc), you won't see it.

If Congress ever went bananas and mandated an American colony on the Moon or Mars...maybe.

For the sort of limited-scale operations envisioned in the VSE/ESAS documents? No.
Title: Re: Sea Dragon class LV thead
Post by: cosmicpax on 10/17/2009 08:07 pm
Are there industrial processes that can only work in microgravity? In that case, inflatable robotic factories could be assembled and supplied using Sea Dragons. For delivery of the products, inflatable heat shields warped in basic capsules splashing on the ocean should work.
Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 10/17/2009 09:14 pm
For a Sea Dragon class LV to be economically viable the cost of the propellant will have to be cheaper than launching the propellant on its own LV.

A Falcon 9 cost $44 million to launch 10,450 kg * 80% = 8360 kg
$44,000,000 / 8360 kg = 5263 $/kg
The tanker, propellant, depot management, loan interest and profit are extra.
http://www.spacex.com/falcon9.php (http://www.spacex.com/falcon9.php)

The Falcon 9 supplied propellant will retail at something like $10,000/kg.
To be viable the Sea Dragon supplied fuel will have to cost and retail for less.
Title: Re: Sea Dragon class LV thead
Post by: Robotbeat on 10/17/2009 09:20 pm
The thing about Sea Dragon is that it is so cheap that you could beat today's launch costs even if you only used 10% of its launch capacity every launch. You aren't required to use the whole launch capacity. Its infrastructure costs are supposed to be less than Saturn V, since it is based on ship building technology and is launched in the ocean.

That said, the Sea Dragon concept nowadays seems more useful in pointing out that there must be a better, cheaper way of doing launch services than we do today.

500 tons to LEO doesn't seem to be needed today, but some of the same ideas could be used to lower our launch prices, hopefully into the realm where entirely new markets are opened up.
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 10/17/2009 09:26 pm
500 metric tons = 500,000 kilograms

500,000 kilograms @$10,000 per kilogram = $50 billion dollars.  $5 billion dollars. I did slip a decimal places. ;-(

An entire Ohio class ballistic missile submarine costs approximately $2 billion dollars (per wikipedia) and surely a Sea Dragon could be built for less than an Ohio class submarine - especially if the hull were welded in say India and the thing towed over here for outfitting.

At Falcon 9 price levels, a fully disposable Sea Dragon would seem far less expensive and if the Sea Dragon were reusable -- even less expensive than that.

= = =

500,000 kg to LEO? Heck, just keep that 2nd stage engine lit and deliver a turn key fuel depot to EML-1 or EML-2.

Because of low reliability, don't send your lunar lander via Sea Dragon, just the fuel needed for that lunar lander.
Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 10/17/2009 11:04 pm
At $10,000/kg it will take a while for NASA to be able to afford to use all 500 tonne of fuel.  Depending upon who is put in charge $50 billion may be sufficient to cover the cost of developing both the Sea Dragon and the Propellant Depot.

At $2 billion a launch the Sea Dragon will not have many launches but I suspect that it can be manufactured for a lot less.  Until more orders come in it would be prudent to only plan on a launch every couple of years.

p.s. The payment for the propellant is actually $5 billion which may not cover the development cost of LV and depot in a single trip, although it may over a flight every year for a decade.
Title: Re: Sea Dragon class LV thead
Post by: 93143 on 10/17/2009 11:49 pm
500,000 kilograms @$10,000 per kilogram = $50 billion dollars. Unless I slipped some decimal places. ;-)

You did.  That should be $5 billion.

Still not an issue, as long as the TRW review of Aerojet's plan had something to do with reality.  Sea Dragon is very cheap.

Quote
Because of low reliability, don't send your lunar lander via Sea Dragon, just the fuel needed for that lunar lander.

Why would Sea Dragon have low reliability?  Once the bugs are worked out, that is...  Isn't it basically a simpler and tougher version of the Falcon 1, only bigger?
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/18/2009 12:00 am
   
At Falcon 9 price levels, a fully disposable Sea Dragon would seem far less expensive and if the Sea Dragon were reusable -- even less expensive than that.

 Sea Dragon was designed to be reusable 20-30 times. Even if the original article cost 2 times the Falcon, the AeroJet study said that it could be refurbished and re-launched for 7% of the replacement cost.
 
 Just for comparison, Falcon 9 is priced at $44 million a copy. So if the Dragon cost twice that, or $88 million each, and can be re-launched for 7% of that, then each subsequent launch would cost $6.16 million. So 20 Falcon 9 launches would cost $880 million, but flying the one Dragon 20 times would cost $205 million, a savings of $675 million, or $10.25 million per flight, $33.75 million less than the $44 million Falcon. Impressive.

Like Robotbeat said, this thing would be so cheap that it wouldn't matter if you didn't use the full capacity of the launcher or not. Launch it for $10.25 million per launch and put whatever you wanted into orbit, without regard to the mass.
 
This is a perfect example of how economies of scale, using a RLV, beat launchrate economies hands down. Can't touch this.

The RLV people have been shoveling against the tide by keeping their designs too small. Make it huge (and extraordinarily simple) and suddenly everything drops into place.
Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 10/18/2009 02:25 am
   
At Falcon 9 price levels, a fully disposable Sea Dragon would seem far less expensive and if the Sea Dragon were reusable -- even less expensive than that.

 Sea Dragon was designed to be reusable 20-30 times. Even if the original article cost 2 times the Falcon, the AeroJet study said that it could be refurbished and re-launched for 7% of the replacement cost.
 
 Just for comparison, Falcon 9 is priced at $44 million a copy. So if the Dragon cost twice that, or $88 million each, and can be re-launched for 7% of that, then each subsequent launch would cost $6.16 million. So 20 Falcon 9 launches would cost $880 million, but flying the one Dragon 20 times would cost $205 million, a savings of $675 million, or $10.25 million per flight, $33.75 million less than the $44 million Falcon. Impressive.

Like Robotbeat said, this thing would be so cheap that it wouldn't matter if you didn't use the full capacity of the launcher or not. Launch it for $10.25 million per launch and put whatever you wanted into orbit, without regard to the mass.

These prices are less than those of the EELV for a much bigger payload.
That is going to result in a significant change in the market.

In shipping there are a lot more small cargoes than big cargoes so it could take a while for sales to build up.  A skimming form of pricing may be appropriate.
Initially assume that the LV is not reusable (R=1) and one launch last year (N=1).

Assuming development costs and capital items are to be paid off over 5 years.
Where N = number of launches last year
R = number of reuses

launch price = $manufacturing/R + $propellant + (annual launch fees + wages + $overheads + $capital_items/5 + $development/5 + $current_R&D + $interest)/N + 20%profit + $sales_tax

This formula will automatically reduce the price as sales and reuse increase.  Recalculate once a year.
Quote
This is a perfect example of how economies of scale, using a RLV, beat launchrate economies hands down. Can't touch this.

The RLV people have been shoveling against the tide by keeping their designs too small. Make it huge (and extraordinarily simple) and suddenly everything drops into place.

Only the experimental RLV need to be small.  You want parts that can be made using ordinary workshop tools.  A very expensive made-to-measure tool makes implementing design changes difficult.
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/18/2009 01:00 pm

Only the experimental RLV need to be small.  You want parts that can be made using ordinary workshop tools.  A very expensive made-to-measure tool makes implementing design changes difficult.

That was the beauty of the Sea Dragon design. It was designed to be produced in a shipyard using standard tools and basic skills. There is nothing inherently difficult or specialized about it. Other than it's size, this is actually the kind of thing where the basic structure itself could be built by almost any ordinary steel shop in the country, although a shipyard is a better choice because of proximity to the sea. It's size belies its simplicity and extremely low-cost manufacture.
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/18/2009 01:23 pm
I guess what I was advocating about the Sea Dragon concept is to build a smaller one to launch 50-100 tons to orbit.  Not the big 500 ton one.  It would be able to launch less expensive than a Jupiter, Ares V or sidemount, and be reusable.  Sure it would be big, but not as big as the 500 ton.

I think for human filght a flyback booster would cut the costs and build a robust flyback for the 25 tons or so capacity for the human cargo. 
Title: Re: Sea Dragon class LV thead
Post by: clongton on 10/18/2009 02:01 pm
I guess what I was advocating about the Sea Dragon concept is to build a smaller one to launch 50-100 tons to orbit.  Not the big 500 ton one.  It would be able to launch less expensive than a Jupiter, Ares V or sidemount, and be reusable.  Sure it would be big, but not as big as the 500 ton.

I think for human filght a flyback booster would cut the costs and build a robust flyback for the 25 tons or so capacity for the human cargo.

I would not advocate the Sea Dragon, or any variation of it, being a manned launcher at this time.
Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 10/18/2009 02:09 pm
Fortunetly we do not need a man rated Sea Dragon in the near future.  We can get people to LEO using the STS.  After that the Falcon 9 and possibly the Taurus II will lift people.

In a decade or so an opportunity may arise to fly a space coach.
Title: Re: Sea Dragon class LV thead
Post by: MP99 on 10/18/2009 10:33 pm
I guess what I was advocating about the Sea Dragon concept is to build a smaller one to launch 50-100 tons to orbit.  Not the big 500 ton one.  It would be able to launch less expensive than a Jupiter, Ares V or sidemount, and be reusable.  Sure it would be big, but not as big as the 500 ton.

I think for human filght a flyback booster would cut the costs and build a robust flyback for the 25 tons or so capacity for the human cargo.

I would not advocate the Sea Dragon, or any variation of it, being a manned launcher at this time.

Use Sea Dragon as the EDS launch for DIRECT phase 2 (no depot).

Re-size J-241 JUS for ascent only (say ~100mT payload after margin), and use the EDS (also resized, maybe with multiple J-2X) for TLI, LOI & 75% of Lunar descent (507.5 m/s remaining delta-V, per CARD). Requires ~385mT launch for EDS + fuel.

Delivers 97mT to separation and, with a hypergolic lander, 81mT landed mass (I'd guess maybe 70mT of payload). Of course, the same could be achieved with J-241 CaLV + depot + 16x EELV/ACES-41 launches, although that'd be a coupla billion dollars worth of fuel, I think (4x J-241 tanker/EDS launches would be wa-a-ay cheaper).

cheers, Martin

PS I also think more fuel (still well within that 550mT limit) could brake the lander to a hover at any arbitrary altitude. I suspect that could convert a larger proportion of that initial 97mT into payload.

PPS 550mT of EDS+fuel could push 110mT through TMI and then perform a major pre-EDL braking burn so that a reasonably-sized  heatshield can, maybe, finish the job.

PPPS we now return you to your normal programming.


Edit:
"86mT landed mass" -> "81mT landed mass";
"well over 75mT of payload" -> "maybe 70mT of payload".
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 10/19/2009 07:53 pm

I suppose Greenpeace wouldn't be all right with the acoustic effects of a Sea Dragon launch?  How far away would a whale have to be to survive one?

Does anyone know if any of the studies for any kind of sea-launched vehicle have examined the noise issue?
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/20/2009 12:12 am
I was advocating a smaller 50-100 ton sea launch for cargo, and a separate manned launcher with a flyback booster. 
Title: Re: Sea Dragon class LV thead
Post by: Patchouli on 10/20/2009 12:30 am

I suppose Greenpeace wouldn't be all right with the acoustic effects of a Sea Dragon launch?  How far away would a whale have to be to survive one?

Does anyone know if any of the studies for any kind of sea-launched vehicle have examined the noise issue?

Maybe just avoid the whale migration routes in the first place since they are documented plus employ a means to repel them.
Staying away from the plankton blooms also should help keep you away from any sea mammals.

Title: Re: Sea Dragon class LV thead
Post by: spacenut on 10/23/2009 01:56 pm
I still say a Saturn V size Sea Dragon wouldn't have to be towed very far to launch off shore.  Fill at the cape, tow out a few hundred yards, lift and launch.  The Kennedy space center has a location for barges bringing in the shuttle tanks (and in the past Saturn V stages).  Barges exist and could be used to tow and launch them.  Use Kerolox first and second stages for cost effectiveness.  Either load the lox at the center or use a natural gas ship to load the lox.  Since it would be less expensive per lb or Kg to orbit.  It could launch fuel or building supplies and materials to orbit.  If it proves to be reliable, then launch a lunar lander, large telescope, or parts for a fuel depot. 
Title: Re: Sea Dragon class LV thead
Post by: William Barton on 10/23/2009 02:11 pm
I've always had this fantasy of using something like Sea Dragon (or bigger) to lift a Project Orion "battlestar" above the atmosphere before lighting off the H-bomb Drive. I guess the EMP effects might still be annoying...
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 10/23/2009 02:54 pm
Sea Dragon and Excalibur both use a single large engine per stage.

What would br the economics of large pressure fed boosters with multiple engies?

I'm thinking something along the lines of TRW's Low Cost Shuttle Surrogate Booster.

The LCSSB configuration was very similar to the original baseline vehicle in the 1969 NASA study. The booster had three pressure-fed stages, with a first-stage thrust of 30.25 million Newtons (6.8 million pounds). The first stage used four engines, each with a thrust of 7.56 million Newtons (1.7 million pounds). These four engines were identical to the second-stage engine, except that the first-stage engines had a higher chamber pressure and an expansion ratio of 6:l (for sea-level/low-altitude operations), compared with the second-stage engine expansion ratio of 31:l (for high-altitude/vacuum operations). Keeping the designs of the first- and second-stage engines essentially the same would have kept development costs down. The booster had a payload capacity to low earth orbit of 29,756 kilograms (65,600 pounds) when launching due east from Cape Canaveral. When launching into a 90-degree polar orbit, the LCSSB had a lift capacity of 23,178 kilograms (51,100 pounds). The system had a launch cost for production vehicles of $59.2 million per launch (including all launch processing and support costs). This equated to a cost of $1,989 per kilogram ($901 per pound) to LEO, assuming an easterly launch.
Title: Re: Sea Dragon class LV thead
Post by: steve kelsey on 10/26/2009 02:56 pm
Good afternoon all, this is a first time post,  but I am a long time lurker on this excellent site.
I am not sure if this is the right place to ask the following question so Chris please bin this if it's in the wrong place.
I have always liked the simplicity of the Sea Dragon approach and I understand that part of the original Truax approach was to pressure feed the propellant and oxidiser using compressed gas to pressurise the propellant and oxidiser tanks headspace. In theory this avoids the complexity of pumps and therefore potentially increases reliability and reduces cost, the downside being a performance penalty.
My question is would it be possible to generate the tank pressure by bleeding oxidiser into the propellant tank and propellant into the oxidiser tank so that they 'combust' and provide the headspace pressure? If so could this be a way to reduce the complexity even further and generate relatively high pressures? The volume of propellant and oxidiser could be metered to deliver a constant pressure.
No doubt there are big issues with the introduction of combustion into a tank but as the pressure fed system is already designed to handle high pressure it is only the source of the pressure that is changing. Does this make any sense as a proposal?
Title: Re: Sea Dragon class LV thead
Post by: Jim on 10/26/2009 03:03 pm
Russians did that in some of their missiles.
Title: Re: Sea Dragon class LV thead
Post by: steve kelsey on 10/26/2009 03:06 pm
Thanks Jim. Only good for one shot then?
Title: Re: Sea Dragon class LV thead
Post by: Arb on 11/21/2009 09:40 pm
As this thread is somewhat hypothetical, let's suppose for the sake of discussion that a major space colonisation effort is under-way and that Sea Dragon could be man-rated. Given its 550MT capacity, approximately how many people could it lift to LEO in a single launch?

-Arb.
Title: Re: Sea Dragon class LV thead
Post by: MKremer on 11/22/2009 06:25 am
As this thread is somewhat hypothetical, let's suppose for the sake of discussion that a major space colonisation effort is under-way and that Sea Dragon could be man-rated. Given its 550MT capacity, approximately how many people could it lift to LEO in a single launch?

-Arb.

May be a bit too hypothetical. Your question might also need to include a time frame - within the next year or two, or further out, in which time SpaceX might have been able to fine-tune or even slightly upgrade their booster and stage 2 engines, and possibly further reduce mass in the first or second stages to allow greater mass to LEO. Dragon itself might also be able to lose some mass once several successful flights have taken place and the final data examined (or not, maybe gets heavier).

And there's also the fact that nobody, not even Elon, knows for sure what final mass any cargo or crewed Dragon would have - because none have been flown yet, neither boilerplate or preliminary orbital test final production modules. The final mission launch mass might decrease slightly, or be required to increase drastically to ensure launch and reentry safety.

Title: Re: Sea Dragon class LV thead
Post by: A_M_Swallow on 11/22/2009 07:09 am
As this thread is somewhat hypothetical, let's suppose for the sake of discussion that a major space colonisation effort is under-way and that Sea Dragon could be man-rated. Given its 550MT capacity, approximately how many people could it lift to LEO in a single launch?

-Arb.

A 550MT payload is sufficient to lift two Boeing 787-9 Dreamliners, each containing 290 passengers.  Since the aircraft lift-off mass includes fuel you can carry a lot more people than that.
http://www.boeing.com/commercial/787family/787-9prod.html (http://www.boeing.com/commercial/787family/787-9prod.html)
Title: Re: Sea Dragon class LV thead
Post by: Downix on 11/22/2009 10:36 am
As this thread is somewhat hypothetical, let's suppose for the sake of discussion that a major space colonisation effort is under-way and that Sea Dragon could be man-rated. Given its 550MT capacity, approximately how many people could it lift to LEO in a single launch?

-Arb.

May be a bit too hypothetical. Your question might also need to include a time frame - within the next year or two, or further out, in which time SpaceX might have been able to fine-tune or even slightly upgrade their booster and stage 2 engines, and possibly further reduce mass in the first or second stages to allow greater mass to LEO. Dragon itself might also be able to lose some mass once several successful flights have taken place and the final data examined (or not, maybe gets heavier).

And there's also the fact that nobody, not even Elon, knows for sure what final mass any cargo or crewed Dragon would have - because none have been flown yet, neither boilerplate or preliminary orbital test final production modules. The final mission launch mass might decrease slightly, or be required to increase drastically to ensure launch and reentry safety.


What does Elon have to do with the price of tea in China?

Sea Dragon has nothing to do with the SpaceX Dragon capsule.  The Sea Dragon was a proposed ocean-launched superrocket developed by the NASA Future Projects branch before it was shutdown in the mid 60's.  It was designed to be built using many of the same shipyard tricks used to build submarines.  Its fuel would be seawater cracked into its components hydrogen/oxygen by the tender craft.  It could lift 550mT into orbit.  The second stage of the Saturn V could fit inside of its massive rocket nozzle.
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 11/23/2009 01:58 am
As this thread is somewhat hypothetical, let's suppose for the sake of discussion that a major space colonisation effort is under-way and that Sea Dragon could be man-rated. Given its 550MT capacity, approximately how many people could it lift to LEO in a single launch?

-Arb.

About 7,000 average people or maybe 5,000 Americans.

A lot less if you want them alive when they get there. ;)

Seriously, I'd roughly estimate 1,000 kg per person in seat, cabin, life support & personal effects mass.

If you really need to move tens of thousands of people, you should probably just spend the money to build a space elevator.
Title: Re: Sea Dragon class LV thead
Post by: Bill White on 11/23/2009 02:00 am
As this thread is somewhat hypothetical, let's suppose for the sake of discussion that a major space colonisation effort is under-way and that Sea Dragon could be man-rated. Given its 550MT capacity, approximately how many people could it lift to LEO in a single launch?

-Arb.

About 7,000 average people or maybe 5,000 Americans.

Cold! Too cold!

 ;D
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 11/23/2009 02:01 am
...
Sea Dragon has nothing to do with the SpaceX Dragon capsule.  The Sea Dragon was a proposed ocean-launched superrocket developed by the NASA Future Projects branch before it was shutdown in the mid 60's.  It was designed to be built using many of the same shipyard tricks used to build submarines.  Its fuel would be seawater cracked into its components hydrogen/oxygen by the tender craft.  It could lift 550mT into orbit.  The second stage of the Saturn V could fit inside of its massive rocket nozzle.

Nitpick: Sea Dragon first stage was LOX / RP-1
Title: Re: Sea Dragon class LV thead
Post by: Downix on 11/23/2009 02:53 am
...
Sea Dragon has nothing to do with the SpaceX Dragon capsule.  The Sea Dragon was a proposed ocean-launched superrocket developed by the NASA Future Projects branch before it was shutdown in the mid 60's.  It was designed to be built using many of the same shipyard tricks used to build submarines.  Its fuel would be seawater cracked into its components hydrogen/oxygen by the tender craft.  It could lift 550mT into orbit.  The second stage of the Saturn V could fit inside of its massive rocket nozzle.

Nitpick: Sea Dragon first stage was LOX / RP-1
Yes, which helps enable the Sea Dragon to float as RP-1 is lighter than water.  I was thinking of the second stage when talking of the LH2
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 11/23/2009 03:12 am
Liquid Hydrogen is a LOT lighter than water. There's no way Sea Dragon wouldn't float, even if the first stage fuel was denser than water. In fact, with the RP-1 it needed ballast tanks to sink the base and bring it vertical. They were to be discarded at launch.

I'm a little uncomforatable with using N2 to pressurize the tanks:

1)  It's a lot heavier than Helium. I suppose that much He might be too expensive, although it could be recovered from the spent first stage and re-used.

2)  Nitrogen tends to disolve in LOX causing combustion instabilities.

If I was designing a Sea Dragon today, I might consider using He or N2 to drive a pistonless pump. (See Flowmetrics). The driving gas could even be produced by a gas generator.

This would have the advantage of reducing the weight of the main tanks, while increasing the combustion chamber pressures, without requiring expensive, complicated turbo-pumps.
Title: Re: Sea Dragon class LV thead
Post by: Robotbeat on 11/23/2009 03:58 am
Liquid Hydrogen is a LOT lighter than water. There's no way Sea Dragon wouldn't float, even if the first stage fuel was denser than water. In fact, with the RP-1 it needed ballast tanks to sink the base and bring it vertical. They were to be discarded at launch.

I'm a little uncomforatable with using N2 to pressurize the tanks:

1)  It's a lot heavier than Helium. I suppose that much He might be too expensive, although it could be recovered from the spent first stage and re-used.

2)  Nitrogen tends to disolve in LOX causing combustion instabilities.

If I was designing a Sea Dragon today, I might consider using He or N2 to drive a pistonless pump. (See Flowmetrics). The driving gas could even be produced by a gas generator.

This would have the advantage of reducing the weight of the main tanks, while increasing the combustion chamber pressures, without requiring expensive, complicated turbo-pumps.

Having lighter tanks (and not being as highly pressurized) means the rocket would be more difficult to survive impact and reuse, right? That's my feeling, but I've never done an in-depth analysis.

Also, the smaller surface-area-to-volume ratio of a larger fuel tank (like the Sea Dragon is) would seem to me to mean that proportionally less N2 would be dissolved in the LOX than for a smaller rocket, correct?
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 11/23/2009 10:16 am
Even 30 to 50 psi would give the tanks an awful lot of strength.

For a cylinder that ratio will mostly be equal to the depth of propellant in the tank. Sea Dragon's tanks are fairly squat, and at the end of the burn, won't have much depth. OTOH, I'm not an expert on exactly how N2 disolves in LOX. Could be some weird chemistry.  I've heard anecdotal evidence of problems with N2 pressure fed rockets. Pump fed ones don't seem to have as many problems with N2 pressurization, because the pressure is about 1/10th as much. YMMV.

Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 12/15/2009 11:17 am
km
Even 30 to 50 psi would give the tanks an awful lot of strength.

For a cylinder that ratio will mostly be equal to the depth of propellant in the tank. Sea Dragon's tanks are fairly squat, and at the end of the burn, won't have much depth. OTOH, I'm not an expert on exactly how N2 disolves in LOX. Could be some weird chemistry.  I've heard anecdotal evidence of problems with N2 pressure fed rockets. Pump fed ones don't seem to have as many problems with N2 pressurization, because the pressure is about 1/10th as much. YMMV.



To bad we can't develope some form of gas impermiable material that would remain flexibile ane elastic at cryogenic temperatures.
     Then one could make both the LH2/LOX and the LH2 / LN  bulkheads out of said material and be able to pressurize the LH2 and LOX tanks without mixing, gasses.

Jason
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 12/15/2009 11:39 am
I have a basic question;

     Development costs and construction of four Sea Dragons, (including smaller sub scale versiona used for testing) were estimated to be 16 billion dollars back in 1961.

     As much of the testing can now be done in computers, alot of practical testing was done with the Sea-Bee and Sea-Horse programs, and the construction techniques have chenged a great deal since 1961, How much would it cost to build test and impliment a group of 4 of these, including a semi-dediacted shiyard  facility.

Jason
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 12/15/2009 11:48 am
If you want to get really creative,

     Install some ISS style hatchways between bulkheads on the upper stage, a docking adaptor to the topof the upper tank, use a 4 petal payload shroud, 2 being solar power panels and 2 being heat sinks, go dry for wet, bring a good chunk of the payload into the inside of the beast, and you now have a Skylab style space station with many times the internal volume of bothe Skylab and the ISS COMBINED.

Jason
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 02/01/2010 10:15 am
What was the planned payload fairing size for Sea Dragon and the smaller Excaliber?
Title: Re: Sea Dragon class LV thead
Post by: JasonW3 on 02/01/2010 02:45 pm
Yes, quite easily.

The problem isn't that it could do that, the question is how do you pay for all that hardware to go fly on a single rocket -- that laundry list you suggest is worth billions and billions!   More importantly:   Do you really want to risk putting all those eggs in a single basket?

If anything happened to that launch, you would lose everything in your entire *program* not just a single element.

A Sea Dragon could just-about launch the equivalent mass of two International Space Station's in a single shot.

While we would have loved to have had that capability ten years ago when we started lifting all those modules, there isn't much in the way of payloads around today -- or even planned in the next 20 years -- which would fill a single Sea Dragon each year -- and Sea Dragon's cost benefits required it to have a decent flight rate around 12 flights per year (just like every other launcher).

If you didn't have that many launches, then the same old rules come into effect and the infrastructure costs start dominating the cost of each flight -- making the system non-viable again.

The entire world's launch requirements -- government, military and civilian combined -- amounts to just a very small fraction of the 6,600mT of LEO lift capability which this system needed to make it worthwhile.


And it's one hell of a gamble to go pay all the money needed to develop this in the hope that "if you build it they will come".   That approach failed to work out very well for either EELV, did it?

This needs a totally different business model to have any chance at all -- and I personally don't think NASA would ever choose to fly anything on it.

Ross.

Ross,

      Here's another point that I'm not sure has been addressed;
     With this much liftingv capacity, you can "Dumb Down" the equipment launched to oldere VASTLY more reliable equipment that could last decades on the moon or Mars instead of only a few months.
      As muich as I hate to say it, maybe we should have the Russians design things like the Rovers and habitat modules.  They have far more experience when designing equipment cheaply that will work in almost any terrestial environment, thus adding a couple of factors such as vaccum and corrosive dust shouldn't be too much of a stretch for them.  Yes, Mir could be brought up as an example of bad engineering with the fire that they had, but still, keeping that thing aloft for over twenty YEARS on almost no budget, when it wasn't designed for half as long?  Pretty awsome if you ask me.

     Sometimes it's better to use a low tech, heavier, highly reliable solution to a high tech, questionable reliability, lightweight component.  If my life were to depend upon it, by god, I'd rather have a system with plenty of spares that I had to swap out the filter once a week than a system that if it failed, I'd have to jury-rig a solution that might not work.  Apollo 13 shows BOTH sides of this coin when the life support of the capsule was failing but they used the square air treatment cannisters from the LEM using duct tape, hoses, a plastic bag, parts of a notebook and a sock, (yes a freaking SOCK, good thing they weren't using one of mine, the smell would have killed them instantly) to rig a system where they could use square cannisters in a round fixture.  Again, low tech, cheap solution, but with life or death consequences.  If, as had at one time had been designed into the Shuttle, the crew cabin had been built to be able to detatch, re-enter, and splashdown, we MIGHT (VERY, VERY slim chances in both Challenger's and Columbia's cases) have been able to save the crews.  But instead of upping the mass to orbit ability, we choose to eliminate that ability.  (Admittedly, it was early on inb the design phase that this was eliminated, but it WAS considered at one time, much like the ejectible crew capsule of the FB-111)  It was eliminated due to low probability of that sort of catastrophic failure and the limited mass requirements that they had.

     But the point here is;  If you use it STRICTLY as a cargo lofter, and use low cost, reliable equipment that could bee easily replaced, (with plenty of spares) the loss of a single booster would not be a show stopper.

     In fact,  If I had the money, I'd be willing to bet, with the combination of a relaible man rated lofter of some sort, (and I prefer a lifting body design of some sort, either as the whole craft or the manned section) and the Sea Dragon, within a VERY few years, 10 to 20 at the most, the payloads would grow in to the max capacity of 650 tons in a very short order.

     And my final point is; I'd rather have too much payload capacity to orbit than just enough.  Too many comprimises have been taken in the past to right mass a payload to the available capacity, rather than have enough excess available to avoid those kind of life threatening issues.

     So screw it, let's design and build a series of two stage reusable non-cryogenic, ocean launched, steel hulled, cargo launch vehicles in the 200, 300 400 and 500 plus tons to orbit ranges, and start going to the other planets!  If we build the 200 and 300 ton to orbit beasts NOW and start using them, by the time we NEED the 400 to 500 ton plus monsters,the tech will have matured enough that they wilol bed MUCH more affordable.

     The Excalibur would be a good start at 200 tons lofted, but we need to be ready to go up qui8ckly in mass from there.

Jason
Title: Re: Sea Dragon class LV thead
Post by: JasonW3 on 02/01/2010 02:54 pm
Ok,

     I'm probably whipping a dead horse with this one, but;

     Assuming one were to build the Sea Dragon today with today's tech, costs etc, assuming one went for hydrogen peroxide / kerosene for both stages,  (Yes, I know that there would be a drop in mass to orbit, but how much would it be?) and assuming that you were to make two versions, both cargo rated, for now, one that would boostp to 500 tones to orbit and one that boosted 200 tons to orbit, (the upper stage using a plug nozzle and ballute for re-entry and splash down, the lower stage using simply the ballute system) how long would it take to test, using bthe testing that has gone before as a starting point, (and the smaller, 200 ton bird as a proof of principle craft) and how much would such a program cost to set up and operate today?

     I put forth that construction costs, (at least labor) should be lower due to advances in technologies, the avionics should cost a fraction of what they would have in the 1960's and due to the fact that that your using non-cryogenic fuels fueling costs should also be lower.
     However, I realize that hydrogen peroxide is both somewhat corrosive and volitile in high concentrations, but the savings in cryogenics costs should offset this cost greatly.

     Again, I need to know how much mass is sacrificed by going all hydrogenperoxide on both stages, instead of the Kerosene / LOX mix for the first stage and the LH2 / LOX mix for the upperstage.
     Then I need real world costs for construction, testing, towing out to sea, launching, recovering the ballist tankage, and both the first and second stages.  Could this be a cost effective alternative, due to economies of scale, to what we now have?  (Which is nothing).

     From what I have gathered so far, the current administration doesn't want NASA piloting ANY craft, but simply a conmmercial company boosting scientists into space, flying them to the Moon and Mars, and acting as the maintenance people for the craft involved, while the scientistsare chauffered there.  (Maybe even to the point of both b ase constrruction and ground vehicle driving?  Great.  First dune buggy driver/mechanic on Mars.   Hmmm... Still...  That WOULD be one hell of a title, now wouldn't it?)

Jason
Title: Re: Sea Dragon class LV thead
Post by: Patchouli on 02/03/2010 02:09 am
I'd still go with lox methane or lox kerosene for the LV vs messing with any odd propellant combinations such as high concentration hydrogen peroxide.

Turning a natural gas tanker into a lox carrier shouldn't be too hard.
It almost would be within the reach of a well funded altspace company.

Heck if you go smaller a 100 to 200T LV you probably could get by with a used container ship and several off the shelf industrial lox storage tanks.

Handling liquid oxygen is a lot more common then you think and it's considered safe enough to have large lox tanks near hospitals and welding supply shops in town.

Just about any industrial town with a population larger then 10K has a few large lox tanks.
I see them all the time in any town that has any oil industry or manufacturing.
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 02/03/2010 11:21 am
Japanese study for LH ships.

http://www.enaa.or.jp/WE-NET/ronbun/1996/e1/ishikawa1996.html

http://www.enaa.or.jp/WE-NET/ronbun/1996/e1/ishikawa1996fig.html#z2
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 07/15/2010 05:02 am
     The idea of using one upper stage of a Sea Dragon as a dry-for-wet space station is not too bad.  So long as you don't intend on rotating it along the long axis to produce a quarter Gee of gravity.
     You'd be using a radius of 37.5 feet and the rotation would be a bit too fast for normal dockingprocedures, and the torque that the rotation would put on an off center docked craft's docking mechanism would be excessive and, if using it for a nine month trip to Mars, might not be able to detach or, might give way during the flight.
     There is also the issue of corealis effects with such a small radia for the rotation.  The difference in Gee load between a persons head and lower extremities would be enough for a serious amount of disorientation, and possibly health issues.

     I think the use of three to five of these upper stages, using one as a center module and the others docked to it at 90 degree angles to the center module, and in opposition to each other, and tied together with girdework.
     With each of these upper stages being 200 feet long and 75 feet wide, not only would it require a slower rotation for 1/4  Gee at a radius of 237.5 feet, but docking or docked space craft would have much less stress put on docking mechanism, and docking with the rotating structure becomes that much easier.  Physiological and psychological issues are likewise reduced.

     As the upper stage would be 200 feet tall, one should be able to set up at least 14 decks, allowing for the curvature of both the LOX and LH2 tanks. Which would give a ,uch more gradual drop off of centripedial force and largely eliminate Corealis effect disorientation.

The central hull would be configured with three concentric decks, with a meter of water, (some recombined from risidual fuel stores in the tanks of the upper stages, some possibly from the Moon, and some shipped up from Earth) surrounding all three of these decks.
     Assuming that each deck is normally 10 feet in height, the innermost 'deck', or 'core' would have a width of 24 feet, allowing it to both act as a storage area for much of the consumables, as well as a central "storm cellar" and. in the LOX tank, a central control and communications center for the entire structure.

     A three tank configuration, using a set of four to six VASMIR style engines, and at least one to six nuclear power plants, would not only allow for enhanced redundancy, but would allow for a much larger crew than either the NASA baseline mission concept, but also allows for isolation of potentile contamination from Mars bourne contaminantes.  The infected crew would be isolated in the hydrogen tank section of one of the 'Spoke ' habitats, with sufficent supplies to survive a return trip to Earth and a central core 'storm cellar' to protect against radiation.
     Once the contaminated personnel and equipment are isolated in the Hydrogen tank section of the craft, and all vacume sensitive equipment and materials ar removed from the oxygen ection of that spoke, the hydrogen tank would be set to local enviromental recycling with a dedicated power supply, (multiply redundant, nuclear, solar and fuel cell, as well as batteries) the oxygen tank between the lower section of the spoke and the core  would be emptied of air, further isolating the contaminated from the rest of the ship.  While this may seem harsh, the health and safely of the rest of the crew should be paramount to the mission.
     a craft using five of the Sea Dragon upper stages would have the central core with four spokes, which would make it large enough to to act as an aldrin style cycler.  (Although, personaly I'd prefer having six spokes to maximize the potentile  volume of living space.

Jason
Title: Re: Sea Dragon class LV thead
Post by: go2mars on 07/22/2010 04:32 pm
I never thought of stringing a few of them together like that for the rotational gravity at greater radius.  An elegant solution! 

Another way to slow down the middle one further for docking/unloading would be have 7 of them, the central one, and attach 2 more end-to end so they go in 400 foot long spokes from the central point.  With fairly short rotation.  Gravity could almost feel natural at the bottom of those. 

Here's an interesting document I found...

http://neverworld.net/truax/Truax_Engineering.pdf

Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 07/22/2010 05:50 pm
I never thought of stringing a few of them together like that for the rotational gravity at greater radius.  An elegant solution! 

Another way to slow down the middle one further for docking/unloading would be have 7 of them, the central one, and attach 2 more end-to end so they go in 400 foot long spokes from the central point.  With fairly short rotation.  Gravity could almost feel natural at the bottom of those. 

Here's an interesting document I found...

http://neverworld.net/truax/Truax_Engineering.pdf


Interesting document.
     The plan, as given, allows for an incremental evelopment and deployment of technologies for the Sea Dragon, through the design, testing and use of the smaller craft.

     Thank you for the complement, however, I am uncertain as to the capibility of the upper stage with another stage attached, of withstanding the stresses that would be applied.  At the mid point between the two stages in the spoke, there would be just over 1/2 Gee of loading on any connectors, (actually more like 1 Gee, due to the mass and the 1 Gee of gravity at the last deck of the spoke, plus the tortional stresses that the Corialis effects would have on any connections between the two stages as well as the hulls of the upper and lower segments of the spokes.
     Overall, bad juju.  Plus one would have to rig outrider cabling and towers to stablize the longer spoke length against these stresses and help to avoid a catastrophic failure of the whole structure.
     From an engineering standpoint, simpler is always better.  There would still have to be cabling to hold the whole thing together, but not only as much, but it would be less vurnrable to damage ore overstressing.

Jason
Title: Re: Sea Dragon class LV thead
Post by: go2mars on 07/23/2010 06:23 pm
I wonder how rigid Bigelow's inflatables will be...  Perhaps a long inflatable habitat tube could touch the tips of all these tanks and keep them in proper alignment.  Air pressure can provide a lot of rigidity.  It would look like a bike tire with really really fat spokes and a big fat hub. 

This would enable useful volume at higher G's and connect access to the tips.  You could go jogging along the entire outside wall of the inflatable tube.  Mission duration is less relevant if you have lots of volume for astronaughts to roam at higher g-force. 

If they were attached stage to stage for the extra length, perhaps you could weld or bolt the nozzles together.  That would provide even more space.  Agreed that some well placed cables would be highly desirable. 

Central hub tank would have docking ports, nuclear reactor, and engines (perhaps vasimr).  Or polywell drive...


Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 07/23/2010 06:54 pm
I wonder how rigid Bigelow's inflatables will be...  Perhaps a long inflatable habitat tube could touch the tips of all these tanks and keep them in proper alignment.  Air pressure can provide a lot of rigidity.  It would look like a bike tire with really really fat spokes and a big fat hub. 

This would enable useful volume at higher G's and connect access to the tips.  You could go jogging along the entire outside wall of the inflatable tube.  Mission duration is less relevant if you have lots of volume for astronaughts to roam at higher g-force. 

If they were attached stage to stage for the extra length, perhaps you could weld or bolt the nozzles together.  That would provide even more space.  Agreed that some well placed cables would be highly desirable. 

Central hub tank would have docking ports, nuclear reactor, and engines (perhaps vasimr).  Or polywell drive...


     I actually consideredt that possibility at one time.  An inflatable torus, continious, with docking hubs at each spoke point, a curved rigid structure would be rigged to the outside of the torus, with cable rigging back to the central hub supporting them, much like on a suspension bridge.
     One issue that had occured to me; A rotating torus would tend to wobble as mass is moved from one side of the torus to another.  I had considered the use of water tanks under the walking surface using computer controlled pumps to transfer water between tanks on the opposite side of the torus from the offcenter mass, to compensate for and counteract the wobble.

Jason
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 07/23/2010 07:24 pm
Good idea.  Water also is a good insulator for radiation.  It can be cracked for fuel with solar power attached. 
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 07/23/2010 11:40 pm
Good idea.  Water also is a good insulator for radiation.  It can be cracked for fuel with solar power attached. 

Not so much fuel as rad shielding, balance and drinking water.

     I considered the possibility of putting a layer of water around the whole structure, but that would mass hundreds of tons, and, unless one would be lifting the water from the moon or grabbing it from comets or wet asteroids, it would be WAY too expensive to boost from Earth.

Jason
Title: Re: Sea Dragon class LV thead
Post by: go2mars on 07/26/2010 03:24 pm
A few hundred tons of water isn't a problem.  Just use one of those Sea Dragon Launches with water as a primary payload.  Perhaps with something high volume and low weight on the same up-ment.  Like hydrogen?
Title: Re: Sea Dragon class LV thead
Post by: mrbliss on 07/26/2010 03:45 pm
One question - if the Sea Dragon model reduces cost by an order of magnitude, and it seems to scale down well, then why isn't it being seriously pursued by *somebody*?

I can see an issue with going after the full-scale Sea Dragon - no one needs that much launch capacity, or even 10% of it.  But why not a smaller scale Sea Snake or Sea Crocodile or Sea <insert your creature here>?

Seriously, what's the fly in the ointment?  The showstopping problem?  Is it technological, political, or something else?
Title: Re: Sea Dragon class LV thead
Post by: spacenut on 07/26/2010 04:33 pm
It has been considered.  This vehicle is Saturn V in size but delivers 55 tons to LEO.  So, is is less expensive than existing EELV?  EELV heavies can approach 50 tons now with modifications.  Or is the very large version less expensive due to scale.  Infrastructure would basically be support ships.     

http://www.astronautix.com/lvs/exclibur.htm
Title: Re: Sea Dragon class LV thead
Post by: go2mars on 07/26/2010 07:14 pm
I think there may be 2 main reasons.  1st is political/paradigm. Partly hasn't been done before (submerged sea launch)/partly "technically uninteresting"/partly if we do it, some rogue nation might become space superpowers on the cheap by following the example and open a can of worms that we don't yet want geopolitcally (least likely).

Second reason might be somewhat technical.  The ratio of mass at lift-off vs mass in orbit is really large for Sea Dragon.  If you shrink the volume of the tanks, then your surface area to volume ratio changes negatively.  It becomes more metal to fuel ratio the smaller you get...  Eventually you reach the endpoint where all you can get to orbit is your upper stage with no payload as the rocket shrinks.  Is that point at the excaliber size?  I suspect it's a lot smaller than excaliber, but I don't know.  The effect on your margins would become apparent at some point.  Who can say where...  If you get much smaller than excaliber, you have to start optimizing your structural margins a lot more closely, through high tech materials and extra careful design/manufacture margins and you get back to the expense range of conventional rockets again.  It's a game of diminishing returns as you get smaller.  The opposite is true as you get bigger.


The game becomes 'Go big or go home'.  Excaliber would mainly be to test the idea of a Sea Dragon sized follow-on rocket which would have better performance just by being bigger. 

This is all imho.
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 07/26/2010 08:41 pm

 I actually consideredt that possibility at one time.  An inflatable torus, continious, with docking hubs at each spoke point, a curved rigid structure would be rigged to the outside of the torus, with cable rigging back to the central hub supporting them, much like on a suspension bridge.
     One issue that had occured to me; A rotating torus would tend to wobble as mass is moved from one side of the torus to another.  I had considered the use of water tanks under the walking surface using computer controlled pumps to transfer water between tanks on the opposite side of the torus from the offcenter mass, to compensate for and counteract the wobble.

Jason

Bit like this you mean?

There was a paper in the December 1991 issue of the Journal of the British Interplanetary Society by Michael A Minovitch of Phaser Telepropulsion Inc proposing the building of rotating 2001 type stations 100 metres diameter for at least 150 crew by using automatic wrapping machines rotating round inflated Kevlar torus’ to wind thin layers of aluminium until the required thickness had been made.

The rotating toroidal living section would have a major and minor radii of 100m and 2m while the two central column cylinders with labs etc and constructed in the same way would each be 100m long x 10m diameter. The two column cylinders would connect into a pre-fabricated central hub into which three spokes 100m long x 4m diameter also constructed in the same way would be fitted to join the hub to the toroidal living section.

The station also served as the basis for a 'cycling' ship and would take about 10 HLLV (assuming 100 tons/launch) or 14 Shuttle-C launches and 1 STS flight with minimal EVA.

Costs were about $400 billion for an Earth orbit station, a Mars orbit station and a cycling ship
Title: Re: Sea Dragon class LV thead
Post by: neilh on 07/26/2010 09:16 pm
One question - if the Sea Dragon model reduces cost by an order of magnitude, and it seems to scale down well, then why isn't it being seriously pursued by *somebody*?

I can see an issue with going after the full-scale Sea Dragon - no one needs that much launch capacity, or even 10% of it.  But why not a smaller scale Sea Snake or Sea Crocodile or Sea <insert your creature here>?

Seriously, what's the fly in the ointment?  The showstopping problem?  Is it technological, political, or something else?

I've sometimes wondered if this is a route that SpaceX could optionally pursue in the future. Their engines are already apparently designed to survive seawater immersion, although launching underwater is of course presumably a different issue. Also, they seem to have put a lot of effort into minimizing the launch infrastructure needed.
Title: Re: Sea Dragon class LV thead
Post by: go2mars on 07/30/2010 02:58 pm
I don't think spacex will go sea launch.  At the Boulder CO. Mars Society convention, someone in the crowd asked Elon if he would ever consider a Sea Dragon type of approach.  His response was something to the effect of "I prefer solid ground launches". 

Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 08/10/2010 05:52 am

 I actually consideredt that possibility at one time.  An inflatable torus, continious, with docking hubs at each spoke point, a curved rigid structure would be rigged to the outside of the torus, with cable rigging back to the central hub supporting them, much like on a suspension bridge.
     One issue that had occured to me; A rotating torus would tend to wobble as mass is moved from one side of the torus to another.  I had considered the use of water tanks under the walking surface using computer controlled pumps to transfer water between tanks on the opposite side of the torus from the offcenter mass, to compensate for and counteract the wobble.

Jason

Bit like this you mean?

There was a paper in the December 1991 issue of the Journal of the British Interplanetary Society by Michael A Minovitch of Phaser Telepropulsion Inc proposing the building of rotating 2001 type stations 100 metres diameter for at least 150 crew by using automatic wrapping machines rotating round inflated Kevlar torus’ to wind thin layers of aluminium until the required thickness had been made.

The rotating toroidal living section would have a major and minor radii of 100m and 2m while the two central column cylinders with labs etc and constructed in the same way would each be 100m long x 10m diameter. The two column cylinders would connect into a pre-fabricated central hub into which three spokes 100m long x 4m diameter also constructed in the same way would be fitted to join the hub to the toroidal living section.

The station also served as the basis for a 'cycling' ship and would take about 10 HLLV (assuming 100 tons/launch) or 14 Shuttle-C launches and 1 STS flight with minimal EVA.

Costs were about $400 billion for an Earth orbit station, a Mars orbit station and a cycling ship


     
     Could you get me a link to this?  I am kind of curious about this.

     It occurs to me that constructing a dual wheel station, ala 2001, could be done for much less than $400 billion, via the use of the upperstages of the Sea Dragon, being used dry for wet, as hub and spokes, and boosting up the materials with those stages, to actually build the wheels.
     By including the upperstages as part of the payload, you reduce the overall cost of the station signifigantly.  The large spokes themselves would have different levels of gravity, as you go up, closer to the Hub.  This could prove useful for both scientific and medical purposes.
     I'm in the camp of having too much available usaeble volume is far better than not having enough usable volume, as this space, on a station, could be rented out, while on a manned Mars mission, one could store redundant supplies and raw materials for Cad/CAM and 3d printing systems, to manufacture parts as needed during the mission.  (Obviously
  some mission critical parts should be kept for safety's sake, but creating new toold or parts to augment the mission, would be of great value on such a flight.

Jason
Title: Re: Sea Dragon class LV thead
Post by: PMN1 on 08/10/2010 06:42 pm

     Could you get me a link to this?  I am kind of curious about this.

   

Unfortunately not, the only place it seems to exist in the the paper JBIS article.

I've had a look for the author on google but nothing much turned up.

The system was also proposed in the same article for building bases on Mars.
Title: Re: Sea Dragon class LV thead
Post by: ciscosdad on 11/11/2010 10:12 pm
This whole concept reminds me a lot of the old studies that came out of Orion (nuclear pulse propulsion). It seems to me that this idea has the same advantages (as mentioned by various posters here). The construction methods there were a lot more akin to shipbuilding than "rocket science". For that reason I would avoid any use of Liq H2 or anything else exotic. There should be enough margin to make both stages Lox/RP1 and still get 100's of tons to orbit.
I haven't done the maths though
Has anyone seen any studeies that focus more on the payloads, especially taking advantage of the huge weights available and the possibility of "low tech" equipment on the payloads?
500 tons in orbit in one go allows for an awful lot of leeway in almost everything.

You could build something right out of Buck Rogers!
Title: Re: Sea Dragon class LV thead
Post by: Obsidian on 11/14/2010 08:59 pm
I am new to this forum, and I am a bit out of my element here.  I am a student of public policy, not an engineer, though I have a reasonable literacy when it comes to science and technology.  I have been interested in the Sea Dragon concept for the last two years, ever since I stumbled upon the Truax Engineering Multimedia Archive while researching a report on the economic feasibility of solar power satellites. 

My question is as follows.  According to the Truax site (http://neverworld.net/truax/), the numbers are quite different than what everyone has been citing.  The estimated payload to LEO is 1,000 tons (~900 metric tons) instead of the 550 metric tons that has been cited.  The estimated cost in 1983 dollars was $20 per pound which, in 2010 dollars, translates to roughly $440 per kilogram (assuming a 400% inflation between 1983 and 2010) instead of the $1000 per kilogram that had been cited.  Could someone please explain these discrepancies? 
Title: Re: Sea Dragon class LV thead
Post by: Jorge on 11/14/2010 09:20 pm
The estimated cost in 1983 dollars was $20 per pound which, in 2010 dollars, translates to roughly $440 per kilogram (assuming a 400% inflation between 1983 and 2010)

Think you might want to rerun those numbers. 400% inflation would turn $20 into $100, not $440.
Title: Re: Sea Dragon class LV thead
Post by: kch on 11/14/2010 10:07 pm
The estimated cost in 1983 dollars was $20 per pound which, in 2010 dollars, translates to roughly $440 per kilogram (assuming a 400% inflation between 1983 and 2010)

Think you might want to rerun those numbers. 400% inflation would turn $20 into $100, not $440.

And converting from pounds to kilograms would take it up to $220 (not $440).
Title: Re: Sea Dragon class LV thead
Post by: Obsidian on 11/15/2010 12:58 am
Yes, I looked at my number and I transferred them incorrectly, thank you for the correction.  With the correction, that would be $220/kilogram.  Still, that is even a larger difference from the numbers that were given earlier in the forum.
Title: Re: Sea Dragon class LV thead
Post by: Max_Peck on 11/15/2010 01:38 am
SD was proposed before the F-1 got on the test stand and revealed the problems with large engines and combustion instability. The guarantee of combustion instability on a single-bell 80 million pound thrust first stage engine, or a 7 million pound thrust upper stage engine is simply ridiculous.

The cost is also prohibitive. How expensive was the 1 million pound thrust RS-84 was going to be? How expensive is the quarter-million pound thrust J-2X? Warp drives would be cheaper to develop than an 80 million pound single-bell engine.

That amount of power in the ocean will kill everything within miles. Environment groups will make it illegal long before the first test flight ever came close.

Nice idea. Totally impractical.

-MP.
Title: Re: Sea Dragon class LV thead
Post by: kkattula on 11/15/2010 02:03 am
So you put 30 F-1 class engines on it and launch from the Dead Sea.

Problem solved.  ;)
Title: Re: Sea Dragon class LV thead
Post by: Sparky on 11/15/2010 04:17 am
So you put 30 F-1 class engines on it and launch from the Dead Sea.

Problem solved.  ;)

Putting what is probably the world's largest man made vessel of combustible material afloat in a lake in one of the most fought-over regions on Earth. What could go wrong? :P
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 11/16/2010 03:59 pm
http://www.astronautix.com/lvs/ur700m.htm

Zhang Guitian (Apparently a Chinese "acamedician") was talking at a conference in 2006 referring to Chinese plans to build something on the scale the UR-700M.  That's more payload mass than my beloved Sea Dragon!

Does anyone know more about this/able to verify/dispel it?  Or know where it was discussed on another thread?

Thanks in advance. 
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 07/20/2011 07:57 pm
Will SpaceX borrow half of the Sea Dragon idea?

SpaceX has talked about making their rocket sea-water resistant.  When I was picturing the fully-reusable future SpaceX launcher, I was picturing a first stage which after separation, turns around, re-ignites some or all of its engines with residual fuel, and boosts back to the launch pad for a propulsive landing.  Might SpaceX instead just propulsively slow it down above the ocean enough to slip in without sustaining damage, to be pulled up, perhaps by an amphibious erector tower or tow-cable to be taken back to the pad? 

Is one of the reasons for building a new Texas pad a range rule against boosting your stages back in the direction of a Florida pad?   
Title: Re: Sea Dragon class LV thead
Post by: Jim on 07/20/2011 08:02 pm

Is one of the reasons for building a new Texas pad a range rule against boosting your stages back in the direction of a Florida pad?   

Same rule would apply to Texas.  Also, TX pad is a rumor
Title: Re: Sea Dragon class LV thead
Post by: Jim on 07/20/2011 08:04 pm
Will SpaceX borrow half of the Sea Dragon idea?

SpaceX has talked about making their rocket sea-water resistant.  When I was picturing the fully-reusable future SpaceX launcher, I was picturing a first stage which after separation, turns around, re-ignites some or all of its engines with residual fuel, and boosts back to the launch pad for a propulsive landing.  Might SpaceX instead just propulsively slow it down above the ocean enough to slip in without sustaining damage, to be pulled up, perhaps by an amphibious erector tower or tow-cable to be taken back to the pad? 

Is one of the reasons for building a new Texas pad a range rule against boosting your stages back in the direction of a Florida pad?   

See Kistler.   Also, why do you keep reading things into spacex that aren't there?
Title: Re: Sea Dragon class LV thead
Post by: DLR on 07/31/2011 12:37 pm
Sea Dragon is not needed.

It's $300 per kg to orbit in 1963 is $2160 per kg in 2011 dollars, which means it would be competing with Russian rockets (Zenit) and Falcon Heavy on a cost per kg basis.
Title: Re: Sea Dragon class LV thead
Post by: Downix on 07/31/2011 04:46 pm
Sea Dragon is not needed.

It's $300 per kg to orbit in 1963 is $2160 per kg in 2011 dollars, which means it would be competing with Russian rockets (Zenit) and Falcon Heavy on a cost per kg basis.
You only measure to LEO.  To BEO, it crushes everything else.
Title: Re: Sea Dragon class LV thead
Post by: Jason1701 on 07/31/2011 08:45 pm
Why was Sea Dragon so much more efficient at BEO?
Title: Re: Sea Dragon class LV thead
Post by: Downix on 07/31/2011 09:08 pm
Why was Sea Dragon so much more efficient at BEO?

High energy upper stage.  While not as good as the RL-10, it still was over 400.  Using the same launch costs as above, of ~$1 billion per launch in todays dollars with the projected GTO payload of 294 metric tons would give $3593 per kg, which is over $1000 less per kg than the Falcon for the same.
Title: Re: Sea Dragon class LV thead
Post by: Prober on 07/31/2011 10:05 pm
Aerojet did some fantastic engine work and doesn't get the credit like the bigger boys LM, Boeing etc.

Title: Re: Sea Dragon class LV thead
Post by: clongton on 07/31/2011 10:10 pm
Aerojet did some fantastic engine work and doesn't get the credit like the bigger boys LM, Boeing etc.



Wait till you see the finished performance of the AJ-500.
Title: Re: Sea Dragon class LV thead
Post by: robertross on 08/01/2011 01:24 am
Is someone going to correct the thread title? ;)
Title: Re: Sea Dragon class LV thread
Post by: kraisee on 08/02/2011 02:25 am
I don't know where DLR's $300 figure originates, but it is not a figure from any of the original AeroJet reports into Sea Dragon, nor the TRW (nee STL) independent assessment reports that von Braun ordered.

The AeroJet worst-case estimate was Case #7, which stated $32.80 per pound ($72.31 per kilogram) to LEO.   In today's money that worst-case would be $533.40 per kilogram to LEO.

The best case was Case #5, which stated $8.90 per pound ($19.62 per kilogram) to LEO.   In today's money that best-case would be $144.73 per kilogram to LEO.


TRW's report was able to validate all of AeroJet's claims and even went so far as to say the figures were highly conservative in all cases.


DLR - Perhaps you're thinking of Truax's "Excalibur", which was essentially a 1/10th scale (55mT to LEO!) version (Truax's 'Falcon-1' development system for his operational 'Falcon-9' heh!) ?  That was estimated around $150 per lb to LEO, which would have been much closer to $300/kg to LEO.

Ross.
Title: Re: Sea Dragon class LV thead
Post by: strangequark on 08/02/2011 06:16 am
Wait till you see the finished performance of the AJ-500.

;D

Such a pretty engine. God bless you Monica Jacinto.


Also, hopefully I'm not necro-posting too badly, but wanted to address these:
SD was proposed before the F-1 got on the test stand and revealed the problems with large engines and combustion instability. The guarantee of combustion instability on a single-bell 80 million pound thrust first stage engine, or a 7 million pound thrust upper stage engine is simply ridiculous.

The diameter on the Sea Dragon was huge. Use an aerospike with modular combustion chambers. Would be good for production as well, because you could mass produce the damn things.

The cost is also prohibitive. How expensive was the 1 million pound thrust RS-84 was going to be? How expensive is the quarter-million pound thrust J-2X? Warp drives would be cheaper to develop than an 80 million pound single-bell engine.

Pressure-fed, with modular combustion chamber design. The worst thing to design is the spike at that point. Not saying it would be cheap, but well below Dr. Cochrane's designs.


That amount of power in the ocean will kill everything within miles. Environment groups will make it illegal long before the first test flight ever came close.

-MP.

Now, this admittedly is delving outside my expertise (not a Marine Biologist). However, there are large swaths of ocean with very little life in them. Cetaceans would be the big concern, and I would suspect there are ways of annoying them away with warning sounds.
Title: Re: Sea Dragon class LV thead
Post by: Jason1701 on 08/02/2011 02:03 pm
If you change Sea Dragon to use an aerospike, it's almost Direct P2.
Title: Re: Sea Dragon class LV thead
Post by: strangequark on 08/02/2011 02:56 pm
If you change Sea Dragon to use an aerospike, it's almost Direct P2.
s

Haha, it looks like I needed to pay more attention to what Ross, Chuck, et al are up to these days. So is this what C-Star is doing?
Title: Re: Sea Dragon class LV thead
Post by: Downix on 08/02/2011 04:27 pm
If you change Sea Dragon to use an aerospike, it's almost Direct P2.
s

Haha, it looks like I needed to pay more attention to what Ross, Chuck, et al are up to these days. So is this what C-Star is doing?
From my understanding, Ross left cstar earlier this year, and this is a different venture.

And there is at least one version of the Sea Dragon researched which was to use an aerospike.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 06/21/2012 07:27 pm
How likely are reusable cores/stages from SpaceX's BFR (the colonization rocket) to launch and land from the ocean?  0% likelyhood?  5%?  more? 

Will the BFR (whether land launched or water launched) be more potent in terms of kg to trans-mars injection, or less potent, compared to sea dragon?  Guesses please. 

At this point, I would guess 20% and more potent.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 10/22/2012 08:47 pm
Several people have mentioned their concern over developing a large rocket engine due to combustion instabilities.  With modern software/analytical tools, is combustion instability still considered a practically insurmountable challenge for developing really big engines?
Title: Re: Sea Dragon class LV thead
Post by: strangequark on 10/23/2012 04:51 pm
Several people have mentioned their concern over developing a large rocket engine due to combustion instabilities.  With modern software/analytical tools, is combustion instability still considered a practically insurmountable challenge for developing really big engines?

It's not insurmountable, it's just extremely expensive. We know more than we knew during the days of the F1, but you're still looking at a very test-intensive program to get it right. Models of combustion stability have to take into account the coupled interactions of combustion kinetics, acoustics, and multi-phase fluid mechanics. Models of any one of these are happy to get within 10-20% of the real world values. Computational acoustics in particular is in its infancy.
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 12/19/2012 09:28 pm
SD was proposed before the F-1 got on the test stand and revealed the problems with large engines and combustion instability. The guarantee of combustion instability on a single-bell 80 million pound thrust first stage engine, or a 7 million pound thrust upper stage engine is simply ridiculous.

The cost is also prohibitive. How expensive was the 1 million pound thrust RS-84 was going to be? How expensive is the quarter-million pound thrust J-2X? Warp drives would be cheaper to develop than an 80 million pound single-bell engine.

That amount of power in the ocean will kill everything within miles. Environment groups will make it illegal long before the first test flight ever came close.

Nice idea. Totally impractical.

-MP.

Ok,

     Quick fix.

     Plug Nozzel for the first stage and about 10 to 15 F-1 engines on the second stage.   Problem solved.

Jason
Title: Re: Sea Dragon class LV thead
Post by: RanulfC on 12/19/2012 09:40 pm
SD was proposed before the F-1 got on the test stand and revealed the problems with large engines and combustion instability. The guarantee of combustion instability on a single-bell 80 million pound thrust first stage engine, or a 7 million pound thrust upper stage engine is simply ridiculous.
I should probably point out that as knowledge was gained in the F1 program the design was changed to several combustion chambers feeding a single nozzle so it wasn't "actually" a single engine design :)

Quote
The cost is also prohibitive. How expensive was the 1 million pound thrust RS-84 was going to be? How expensive is the quarter-million pound thrust J-2X? Warp drives would be cheaper to develop than an 80 million pound single-bell engine.
The last design upgrade I recall had the engines being developed from the F1 it self so the design costs were a lot less than expected overall.
Quote
That amount of power in the ocean will kill everything within miles. Environment groups will make it illegal long before the first test flight ever came close.
Engine "burp" or simply fireing up the turbopumps will clear the area in a hurry. A couple of "sounding-charges" (big band, little actual blast) would effectivly clear out all the life within a couple of square miles within seconds. IIRC there is actually a Navy procedure number for such an operation :)
Quote
Nice idea. Totally impractical.

Ok,

     Quick fix.

     Plug Nozzel for the first stage and about 10 to 15 F-1 engines on the second stage.   Problem solved.
Note exactly :) See the "problem" is the amount of payload one of these things could lift. Short of a sudden "emergency" colonization program, need for a super asteroid/comet defense system or solar power satillite program the SD is simply too BIG to be viable. It has such a huge payload capabilty that you can't really justify a "viable" use for a single flight, let alone the multiples that the "program" would have required.

It's an "issue" I wish we didn't have, but it is still the main issue with a SDLV type vehicle :)

Randy
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 12/20/2012 03:35 pm

Note exactly :) See the "problem" is the amount of payload one of these things could lift. Short of a sudden "emergency" colonization program, need for a super asteroid/comet defense system or solar power satillite program the SD is simply too BIG to be viable. It has such a huge payload capabilty that you can't really justify a "viable" use for a single flight, let alone the multiples that the "program" would have required.

It's an "issue" I wish we didn't have, but it is still the main issue with a SDLV type vehicle :)

Randy
[/quote]

Not exactly sure I agree with you on this.

      Yes, the payload, currently, is excessive.  However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.

     If fact, such a launcher, pound for pound (or kilogram for kilogram, if you will) would be a couple of orders of magnitude cheaper than any current launcher, including the Falcon 9.

     Mind you, justifying a 500 to 600 ton payload in a single launch could be tough, but say someone like Bigalow Aerospace wanted to put up his Space Hotel all at once, this would be the beast to do it.

     Heck, with a scond launch of a fully fueled Orbital Transfer vehicle, you could send 500 to 600 tons of Mars Base to Mars in two launches.  (Talk about establishing a foothold on Mars).

Jason
Title: Re: Sea Dragon class LV thead
Post by: Jim on 12/20/2012 06:00 pm

     If fact, such a launcher, pound for pound (or kilogram for kilogram, if you will) would be a couple of orders of magnitude cheaper than any current launcher, including the Falcon 9.

Wrong, because the development costs of the vehicle need to be included.  Also, it ignores the cost of the payload and the infrastructure need to develop, build, test, transport and prepare such a payload.
Title: Re: Sea Dragon class LV thead
Post by: Jim on 12/20/2012 06:04 pm
However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.


No, it wouldn't.  Reuseability negates the whole idea of Sea dragon.  It is designed to be built cheap and robust, not for reuse.  Also, return of huge stages is unthinkable
Title: Re: Sea Dragon class LV thead
Post by: RanulfC on 12/20/2012 07:34 pm
However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.


No, it wouldn't.  Reuseability negates the whole idea of Sea dragon.  It is designed to be built cheap and robust, not for reuse.  Also, return of huge stages is unthinkable
Actually they DID "think" about it, I recall a section of the original report on that subject :) The first stage seemed "doable" but the economics weren't really clear. As I recall, reuse only made "sense" if you had a pretty hefty flight rate which no "normal" case would justify. The conclusin that I recall was that "reuse" was pretty much a non-starter but "salvage" was a very possible set up.

Randy
Title: Re: Sea Dragon class LV thead
Post by: RanulfC on 12/20/2012 07:51 pm
Quote
Note exactly :) See the "problem" is the amount of payload one of these things could lift. Short of a sudden "emergency" colonization program, need for a super asteroid/comet defense system or solar power satillite program the SD is simply too BIG to be viable. It has such a huge payload capabilty that you can't really justify a "viable" use for a single flight, let alone the multiples that the "program" would have required.

It's an "issue" I wish we didn't have, but it is still the main issue with a SDLV type vehicle :)

Not exactly sure I agree with you on this.
You don't have to actually "agree" with me, however both NASA and others pointed out this issue in the discusions and reports on the SeaDragon. Truax never "bought" the arguments but neither as far as I can tell could he actually manage to refute them either. :)

Quote
Yes, the payload, currently, is excessive.  However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.
The payload was ALWAYS "excessive" and while it is possible ot "justify" the cost its a limited launcher without a massive and intensive NEED for materials on-orbit. And even then the projected flight rate was low enough that the costs began to dominate again just as in most "normal" launcher options

Given the right "program" to support the SeaDragon could be made to make "sense" but it utterly depended on HAVING that program to support to even be considered. And that first step simply never came to pass.

I won't say that an SD-class LV won't "ever" happen but the whole case for justifying them hinges on there already being a VERY large market for materials on-orbit to have any chance of competing with current LVs. As is any LD-class vehicle CAN simply fly off the entire worlds "payload" schedule in one flight, yet at the same time it can't actually put each and every one of those payloads where it needs to be. And one-off construction and low flight rates negates the majority of "savings" you're supposed to get from a SeaDragon.

Randy
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 12/21/2012 01:59 am
Dang it Randy, unfortunately I find myself mostly in agreement with you.

     With a launcher like the Sea Dragon, unless you WERE to use the upper stage as part of your payload, it would tend to be an expensive throw away that I think would be unjustifiable.
     As either a fuel tank or some sort of habit module, this would work quite well, but something that large, reentering uncontrolled, would prove to be a hazard vastly larger than the Skylab was, and likely larger than the Mir station could have been.  Therefore, setting up at least some sort of lightweight TPS system (cork maybe) with a ballute system to slow it down before impact, (water landing preferred) for salvage and refurbishment, possibly even to the point of melting it down and reforging them from scratch, would be a MUCH better idea tan dropping a 25 story all metal building o someone's head from orbit.

Jason
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 10/08/2013 02:23 am
Several people have mentioned their concern over developing a large rocket engine due to combustion instabilities.  With modern software/analytical tools, is combustion instability still considered a practically insurmountable challenge for developing really big engines?

It's not insurmountable, it's just extremely expensive. We know more than we knew during the days of the F1, but you're still looking at a very test-intensive program to get it right. Models of combustion stability have to take into account the coupled interactions of combustion kinetics, acoustics, and multi-phase fluid mechanics. Models of any one of these are happy to get within 10-20% of the real world values. Computational acoustics in particular is in its infancy.
Is this issue less problematic for very large pintle-injection engines?  How might the challenges be minimized?
Title: Re: Sea Dragon class LV thead
Post by: QuantumG on 10/08/2013 02:29 am
I vaguely remember some arguments that combustion instability becomes easier to solve at Sea Dragon engine sizes.

Would love some references to back up that claim :P
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 10/08/2013 02:34 pm
Geez,

     I just had a sick thought.  What if you sacrificed about 30% of your total throw mass for both stages and added landing gear to the stages like on the Reusable Falcon 9?  It COULD be recoverable then, still have a HUGE throw mass, and be reusable.

     But where the heck would you land such a monster?  It'd be like trying to land a 25 story building for each stage!

YEIKES!

     Of course landing one on MARS could prove... Interesting.  A ready, semi insulated structure that could be used dry for wet as a Mars COLONY, not just a Base.  Save any reisidual O2 from the oxidizer tanks, scrub or otherwise neturalize the kerosene from the fule tanks, having already designed in hatchways into the tanks, go inset up gridwork floors and inflate habitat segments per floor, (For further insulation amd privacy) and you have a pretty good Mars colony to start.

Jason
Title: Re: Sea Dragon class LV thead
Post by: gbaikie on 10/09/2013 01:40 am
Geez,

     I just had a sick thought.  What if you sacrificed about 30% of your total throw mass for both stages and added landing gear to the stages like on the Reusable Falcon 9?  It COULD be recoverable then, still have a HUGE throw mass, and be reusable.

     But where the heck would you land such a monster?  It'd be like trying to land a 25 story building for each stage!

YEIKES!
It takes off from the ocean, it would have to land in the ocean.

Quote
     Of course landing one on MARS could prove... Interesting.  A ready, semi insulated structure that could be used dry for wet as a Mars COLONY, not just a Base.  Save any reisidual O2 from the oxidizer tanks, scrub or otherwise neturalize the kerosene from the fule tanks, having already designed in hatchways into the tanks, go inset up gridwork floors and inflate habitat segments per floor, (For further insulation amd privacy) and you have a pretty good Mars colony to start.

Jason
If we get to point of settling Mars, it would seem a Sea Dragon could become viable.
But we should explore Mars, first.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 10/09/2013 04:07 am
What if you sacrificed about 30% of your total throw mass for both stages and added landing gear to the stages like on the Reusable Falcon 9?  It COULD be recoverable then, still have a HUGE throw mass, and be reusable.

     But where the heck would you land such a monster? 
Texas near the Mexican border I assume. 
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 10/09/2013 04:11 am
I vaguely remember some arguments that combustion instability becomes easier to solve at Sea Dragon engine sizes.

Would love some references to back up that claim :P
I would too, but I'm not sure your references exist.  I should just make an 80 million pound of thrust engine in my garage.  Figure out if combustion stability is easier.  Too many naysayers.  ;D
Title: Re: Sea Dragon class LV thead
Post by: QuantumG on 10/09/2013 04:38 am
Haha.. only cost a few million in fuel for each attempted full duration burn :)
Title: Re: Sea Dragon class LV thead
Post by: RanulfC on 10/09/2013 02:20 pm
Geez,

     I just had a sick thought.  What if you sacrificed about 30% of your total throw mass for both stages and added landing gear to the stages like on the Reusable Falcon 9?  It COULD be recoverable then, still have a HUGE throw mass, and be reusable.

     But where the heck would you land such a monster?  It'd be like trying to land a 25 story building for each stage!

YEIKES!

About the only place possible is the same as where you launched it from: The Ocean. No "landing-gear" needed or wanted :) "Technically" the SD 1st stage was considered "reusable" in some types, not sure how "reasonable" that would be though considering the system as a whole. The upper stage (which was LH2/LOX btw) you'd want to keep in orbit for the metal at the very least. Lots of work to be done on-orbit but lots of "pressuriz-able" space to be had at the same time.

Quote
     Of course landing one on MARS could prove... Interesting.  A ready, semi insulated structure that could be used dry for wet as a Mars COLONY, not just a Base.  Save any reisidual O2 from the oxidizer tanks, scrub or otherwise neturalize the kerosene from the fule tanks, having already designed in hatchways into the tanks, go inset up gridwork floors and inflate habitat segments per floor, (For further insulation amd privacy) and you have a pretty good Mars colony to start.

Jason

Upper stage was planned IIRC as a LH2/LOX stage which would make more sense. Landing it as a horizontal "structure" might be better than doing it vertically as you'd be relativly closer to the ground to work with.

As for testing the engine, fall back and punt, since we're re-building the F1 might as well go with the plug-cluster engine idea :)

Randy
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 11/20/2013 09:26 pm
All good points.  But I just noticed a rather odd fact.

     Remember the old , I think it was called the Pioneer Space Station model?  Launched all in one with 3 spoke arms rotating around a common center of gravity?  Would have used old Apollo capsules a tender craft.

     If memory serves, that whole rig was supposidly under 300 tons mass, including a nuclear reactor.  Slap that puppy on top of a Sea Dragon with an additional 150 Tons of fuel (10 ton tankage) a 40 Ton Mars lander, sent up a crew on 2 Dragon Riders and with a Nuclear motor, Mars in 55 days easy.  (Of course you'd sent about 400 tons of habitat, supplies and ERV ahead with 100 tons of fuel to get there, slow boating it).

4 main launches and you have a reusable infrastructure and a Mars colony in one main shot.
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 11/22/2013 05:44 pm
ARGH!

          Sorry about that! the model I was thinking of was Pilgrim One.  The thought was to launch it on a Saturn V as the third stage with a stretched second stage to bump it into orbit.

My bad!

Jason
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 11/22/2013 05:52 pm
<p>Sorry.</p><p>    You must surround the entire living quarters with shielding that has the same effectiveness as five feet of water in a tank. This requirement should be used for all mass calculations for extremely long duration missions. Lighter elements are more effective per unit mass, so using liquid hydrogen gives the lightest shield. A thin layer of boron-10 would be needed as a neutron absorber.
 
    It is not possible to get away with less shielding, owing to the fact that the incoming cosmic rays have enough energy to create electron-positron pairs. These pairs are called secondary radiation, and they, too, must be stopped. However, these, in turn, create more electron-positron pairs until their energy drops below 1.1 MeV (the minimum energy needed to create an electron-positron pair) (At some point, each positron will annihilate an electron, producing two gamma rays). Because, for a given total energy of ionizing radiation, alpha radiation is more damaging than beta radiation which is more damaging than gamma rays, and lower frequency (longer wavelength) gammas are more damaging than shorter wavelength gammas, a thinner shield would actually be counterproductive, so far as cosmic rays are concerned. </p><p> </p>

          What about the use of mutiple layers of sheilding, using, as an example Polyethel chloride, Boron-10 and water? seperating PEC/Boron-10 sandwich layer with a foot of water to create a large storm shelter of 5 foot thickness of water, 12 layers of PEC and 6 layers of Boron-10?

          Obviously you couldn't provide enough water to completely encapsulate the living quartersb but it could be used as both a storm shelter and possible sleeping area, to reduce overall radiation exposure.

Jason
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 11/22/2013 06:15 pm
My question is from a slightly different angle.

It seems we have a history of building "right-sized" rockets, that then suffer weight increases and/or performance shortfalls, then we have to optimize the crap out of them to get the job done.

Is a really big, dumb booster more expensive than all the effort expended on optimization & advanced materials?

Is there harm in overkill?  Granted, if we tried to build something with 30 F-1 engines, now we're hit with high engine expense, and duplicated complexity.

Matt, with 30 engines you run into SIGNIFICANT timing and fuel routing issues.  (An example of this is teh Soviet N-1 moon rocket).

           There are also a couple of significant issues with the Sea Dragon design. (While I am infavor of this design, I am having to play Devil's advocate here for a minute).

          First, it is designed to be launched from the ocean with all shipping and air traffic to be cleared out for at least a five mile radius.  (Not impossible, but difficult)  Should the craft suffer a catostrophic failure during any part of the ascent, it would detonate with the force of a small nuclear weapon and scatter debris over a VERY large area. (The higher it got the larger the area)

          Also, due to the Sea launch set up, it would rove a significant danger to sea life in the immediate vicinity.  (Boiled shark soup with a side of broiled whale anyone?)

          Fueling the first stage with Kerosene would be possible at shore, but should leaks develope, signifcant envionmental damage could occure.

          The noise of such a launch would FAR exceed any OSHA standards and the shockwave over water is likely going to be able to travel a significant distance with little diminimishment.

          Fueling the hydrogen for the second stage and the LOX for both First and Second stage would be very tricky using specialized cryogenics ships, similar to the current LNG tankers.  Even with a dedicated Nuclear Reactor for fuel seperation from sea water and cryogenic cooling of both LOX and Hydrogen, we are talking a significant time to fully fuel such a craft, during which storms could develope endangering both the craft and the ocean vessels.

          Assuming development of large plug nozzle systems for such craft, it MAY be possible to stretch the first stage and eliminate the second stage as plug nozzles tend to reconfigure their exhaust according to atmospheric pressure and do not require a specialized exhaust bell for low or zero pressure environments.  This would also facilitate the recovery of such a craft for reuse, but it would again, endanger sea life where it landed.

          However, even with these issues, I think that this is still a very viable launch system.

Jason
Title: Re: Sea Dragon class LV thead
Post by: RanulfC on 11/26/2013 02:37 pm
My question is from a slightly different angle.

It seems we have a history of building "right-sized" rockets, that then suffer weight increases and/or performance shortfalls, then we have to optimize the crap out of them to get the job done.

Is a really big, dumb booster more expensive than all the effort expended on optimization & advanced materials?

It would "seem" that going for "over-kill" and accepting less would be cheaper but the numbers always end up being dependent on a lot of guess-work and utilization assumptions. Operational assumptions end up driving a lot of the "baseline" assumptions around an LV in the first place. Seadragon is a classic example because while cost per unit but the "minimum" size to get those assumed prices is quite large.

Quote
Is there harm in overkill?  Granted, if we tried to build something with 30 F-1 engines, now we're hit with high engine expense, and duplicated complexity.

Yes there is actually :) If you fly a Seadragon without a full payload you're wasting a lot of money and throwing all the "assumed" operating and such costs out the window. It's very much part of why no one has build a "minimum-cost" design because just like an RLV it needs a certain amount of dedicated launches to actually BE economical :)

Matt, with 30 engines you run into SIGNIFICANT timing and fuel routing issues.  (An example of this is the Soviet N-1 moon rocket).
(Technically somewhere between 45 and 53 engines if using F1B or F1-upgraded motors respecivily for a "full-up" Seadragon, fewer for the Excalibur and "Sub-Caliber" models that NASA thought were STILL to big :))

Quote
           There are also a couple of significant issues with the Sea Dragon design. (While I am infavor of this design, I am having to play Devil's advocate here for a minute).

          First, it is designed to be launched from the ocean with all shipping and air traffic to be cleared out for at least a five mile radius.  (Not impossible, but difficult)  Should the craft suffer a catostrophic failure during any part of the ascent, it would detonate with the force of a small nuclear weapon and scatter debris over a VERY large area. (The higher it got the larger the area)

Part and parcel of the launch plans was that the launch area would be far outside the shipping lanes and pretty damn far from any possible damage should a launch accident occur. Pretty implicit in the studies was that they would be build near the equator and then towed far out to sea for launch.

Quote
          Also, due to the Sea launch set up, it would rove a significant danger to sea life in the immediate vicinity.  (Boiled shark soup with a side of broiled whale anyone?)

Not quite that bad really :) A couple of hand grenades or C4 blocks would scare everything out of the area for the launch though the "area" needed would be quite large still. Active sonar (or playing Justin Bieber through underwater speakers) should help keep the area clear through launch.

Quote
          Fueling the first stage with Kerosene would be possible at shore, but should leaks develope, signifcant envionmental damage could occure.

All propellant loading would take place on-site to avoid off-setting loads while towing the LV, though this does bring up the possibility of "building" an ocean surface launch facility using current deep-ocean platforms to house storage and processing facilities instead of running a fleet of ships for each launch.

Quote
          The noise of such a launch would FAR exceed any OSHA standards and the shockwave over water is likely going to be able to travel a significant distance with little diminimishment.

Actually after the rocket lifts from the water it tends to take a parabolic shape which directs the noise upwards instead of out. Once it gets a couple of hundered feet up though the sound is going to be rather awsome in every meaning of the word :)

Quote
          Fueling the hydrogen for the second stage and the LOX for both First and Second stage would be very tricky using specialized cryogenics ships, similar to the current LNG tankers.  Even with a dedicated Nuclear Reactor for fuel seperation from sea water and cryogenic cooling of both LOX and Hydrogen, we are talking a significant time to fully fuel such a craft, during which storms could develope endangering both the craft and the ocean vessels.

You would tend to launch from the least weather active areas you can find for that very reason. :)

Quote
          Assuming development of large plug nozzle systems for such craft, it MAY be possible to stretch the first stage and eliminate the second stage as plug nozzles tend to reconfigure their exhaust according to atmospheric pressure and do not require a specialized exhaust bell for low or zero pressure environments.  This would also facilitate the recovery of such a craft for reuse, but it would again, endanger sea life where it landed.

The disturbance of the water and noise as the vehicle descends is going to do a great deal to scare off any wildlife in the area with a powered landing. Non-powered you'd want to "land" front-end first and have blown off the forward dome to use the main tank as a water-cushion shock absorber. Given how much more robust the Seadragon class LVs were to be built you probaby wouldn't even bother with parachutes to slow the terminal velocity.

Quote
          However, even with these issues, I think that this is still a very viable launch system.

It really depends on how you use the term "viable" since it still has the major drawback of inability to be used for "incrimental" payloads. I know Truax disparraged the "Sub-Caliber" as not meeting any of the economic goals of the concept while still retaining all the technical challenges and costs of a more "normal" NASA booster but it at least would have been able to meet the more realistic "needs" of the time. I wonder if a "cluster" of Sub/Excaliber vehicles could be used to give a good variable range of payload?

Randy
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 12/17/2013 04:23 am
The nozzle extension: has anything like that been done?

Sea Dragon T-Shirt for alternate reality:

Bringing pusher plates and springs to orbit since 1972.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 02/07/2014 09:05 pm
http://www.youtube.com/watch?v=F9kaA1jNbBc

This guy briefly outlines some features of Sea Dragon (high level). 
Title: Re: Sea Dragon class LV thead
Post by: R7 on 02/08/2014 01:03 pm
This guy briefly outlines some features of Sea Dragon (high level).

Nice chap but minor nitpick: he repeats the error in Wikipedia; SeaDragon first stage planned to use methane to pressurize the RP-1 and LOX pressurized itself using heat exchanger. Only TVC engines attached to the second stage would have used nitrogen pressurization for LOX.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 02/19/2014 04:16 am
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.
Ah, so you're suggesting that just a part of the interior would spin.  Maybe just a ring in the middle somewhere.  Interesting thought.  I had assumed the whole business could rotate (or maybe a tether to some mass) but this "seems" simpler.
  I suppose if an inflatable module, like Bigelow stuff, was part of the payload, the 75 foot diameter could allow your "spinning tub" diameter to go up to 150 feet or something. 
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 01/10/2015 06:48 am
Actually after the rocket lifts from the water it tends to take a parabolic shape which directs the noise upwards instead of out. Once it gets a couple of hundered feet up though the sound is going to be rather awsome in every meaning of the word :)

          Wouldn't the water absorb (not reflect) a lot of the acoustic energy?  Also, if the focal point of your parabola is behind a supersonic rocket plume (or large grouping of convergent rocket plumes), seems like it would be hard for the rocket to acoustically destroy itself from the ground reflection.  What am I missing? 
Title: Re: Sea Dragon class LV thead
Post by: RanulfC on 01/12/2015 08:50 pm
Actually after the rocket lifts from the water it tends to take a parabolic shape which directs the noise upwards instead of out. Once it gets a couple of hundered feet up though the sound is going to be rather awsome in every meaning of the word :)

          Wouldn't the water absorb (not reflect) a lot of the acoustic energy?  Also, if the focal point of your parabola is behind a supersonic rocket plume (or large grouping of convergent rocket plumes), seems like it would be hard for the rocket to acoustically destroy itself from the ground reflection.  What am I missing? 

IIRC experiments showed that a water surface, (unlike sprayed) acts more like a solid object to heavy sound waves and you get very little absorbtion. I doubt you'd have to worry about acoustic's damaging the rocket given the way the exhaust plume is supposed to shape the water's surface the "focus" would be behind the rocket once the surface calmed from the rather awsome "bubble-burst" of the rocket breaking free in the first place.

The only time the "parabolic" effect was mentioned that I recall was in dealing with the ROMBUS lift off which was done over an artifical lagoon for specifically acoustical reasons. The SeaDragon is going to create a huge gas bubble beneath it that will cause so much surface distortion thre a parabolic surface would never happen in the first place. I was talking more of the ROMBUS case than the SeaDragon case. Sorry if that wasn't clear.

Randy
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 01/15/2015 04:43 pm
However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.


No, it wouldn't.  Reuseability negates the whole idea of Sea dragon.  It is designed to be built cheap and robust, not for reuse.  Also, return of huge stages is unthinkable

Actually, the first stage would use a ballute for return and the drag to mass ratio was sufficent to allow a safe splashdown and return.  Second stage was a bit more iffy, but was also thought to be possible.

Personally, I'm of the opinion that using 3 upper stages, one as a central hub and two as spokes, could be used as a 1 Gee orbital facility/Mars Cycler craft.

Crazy as it sounds, a rocket with a 500 ton payload to orbit capibility and having a 75 foot diameter, would give a heck of lot of room and capibilities for space exploration.  (I also considered using Bigelow style inflatible modules (supersized, of course) to line the interior tanks of the habitat spokes and the front tank of the hub (The aft tank, after being flushed of Kerosene, could be used for Hydrogen containment, (Bigelow style liner to insulate it and aconstructed inner tank to hold the hydrogen) for either a Vasmir or Fusion powered drive system).
Title: Re: Sea Dragon class LV thead
Post by: Vultur on 01/16/2015 03:49 am
However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.


No, it wouldn't.  Reuseability negates the whole idea of Sea dragon.  It is designed to be built cheap and robust, not for reuse.  Also, return of huge stages is unthinkable

Doesn't robust make it easier to survive reentry and thus reuse?

And why does size matter here? OK the terminal velocity will be higher due to square-cube law, but not so high that propulsive landing is unworkable.
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 01/16/2015 06:46 am
However; If this could be made as a reliable TSTO craft that either could have both stages reusable, OR the first stage reusable and use the upper stage as a .5 stage, (Doing Dry-for-wet) as part of either a space station or as a part of a Mars Exploration Vessel, then I think that it would more than justify the cost.


No, it wouldn't.  Reuseability negates the whole idea of Sea dragon.  It is designed to be built cheap and robust, not for reuse.  Also, return of huge stages is unthinkable

You forget a couple of important points.  The sheer volume of this thing gives the stage a significant amount of drag as it falls back down.  This would actually ted to reduce it's terminal velocity.  Second, 1/8 the of an inch managing STEEL.  Not alumininium, lithium or some other low mass metal.  Third, the stage would be using a ram air ballute for f rather lowering the velocity of the returning stage.  This was in the actual reports on the design, which TRW signed off on saying that the plan was feasible.

Unless you have access to more info than is currently available, I'd have to stand behind the current two reports available online.

I would appitciate it if you do have more info if you could send me some links to it.  The info currently available is kind of scant and anything that you could add to the discussion would be appreciated!
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 01/16/2015 07:05 am
Actually after the rocket lifts from the water it tends to take a parabolic shape which directs the noise upwards instead of out. Once it gets a couple of hundered feet up though the sound is going to be rather awsome in every meaning of the word :)

          Wouldn't the water absorb (not reflect) a lot of the acoustic energy?  Also, if the focal point of your parabola is behind a supersonic rocket plume (or large grouping of convergent rocket plumes), seems like it would be hard for the rocket to acoustically destroy itself from the ground reflection.  What am I missing? 

IIRC experiments showed that a water surface, (unlike sprayed) acts more like a solid object to heavy sound waves and you get very little absorbtion. I doubt you'd have to worry about acoustic's damaging the rocket given the way the exhaust plume is supposed to shape the water's surface the "focus" would be behind the rocket once the surface calmed from the rather awsome "bubble-burst" of the rocket breaking free in the first place.

The only time the "parabolic" effect was mentioned that I recall was in dealing with the ROMBUS lift off which was done over an artifical lagoon for specifically acoustical reasons. The SeaDragon is going to create a huge gas bubble beneath it that will cause so much surface distortion thre a parabolic surface would never happen in the first place. I was talking more of the ROMBUS case than the SeaDragon case. Sorry if that wasn't clear.

Randy

Randy,  from the experimental data that was gathered, using subscale rockets, the exact opposite is true of partially submerged rockets.  From the reports it was stated, and I am paraphrasing, that significant acoustical dampining occureddue to the subsurface launch.  This apparently be as due to the disturbed water, being mixed with the exhaust gasses as the rocket lifted off, allowed for a higher compressability than would normally be the case.  In other words, due to the fact that the water was 'foamed up' the normal incompressibility and acoustical reflectivity no longer applied.  This is similar in principle to how a ship can be sunk by a methane blow undeneith it.  When the water is foamed up, it's density is reduced, effectivly reducing the water's ability to buy up said vessel.
     The acoustical attenuation of the foamed water would act very much like the acoiustical attenuation of foamed acoustical tiling on the walls of sound booths.  If you have any questions, there are a number of books I can recommend on acoustics and acoustical properties of various materials.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 03/27/2015 04:37 am
If you have any questions, there are a number of books I can recommend on acoustics and acoustical properties of various materials.
Yes please!

Also, in your reply #223 on this thread, ...Bigelow modules within the tanks?  I'm not following the rationale.
Title: Re: Sea Dragon class LV thead
Post by: b0objunior on 09/24/2015 10:51 pm
Hi,
I just did comparaison photos of Sea Dragon to Saturn V and the F-1 engine, quite impressive. When you look at it and think of what you could do, it's awesome.
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 09/24/2015 11:08 pm
If you have any questions, there are a number of books I can recommend on acoustics and acoustical properties of various materials.
Yes please!

Also, in your reply #223 on this thread, ...Bigelow modules within the tanks?  I'm not following the rationale.

Fundamentals of Acoustics,  Master Handbook of Acoustics, An Introduction To Acoustics, to name 3.
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 10/10/2016 02:49 am
Hi,
I just did comparaison photos of Sea Dragon to Saturn V and the F-1 engine, quite impressive. When you look at it and think of what you could do, it's awesome.
Raptor makes me wonder if we'll ever see a giant engine - many smallish good ones has advantages. 
Title: Re: Sea Dragon class LV thead
Post by: JasonAW3 on 10/10/2016 02:56 am
Hi,
I just did comparaison photos of Sea Dragon to Saturn V and the F-1 engine, quite impressive. When you look at it and think of what you could do, it's awesome.
Raptor makes me wonder if we'll ever see a giant engine - many smallish good ones has advantages.

Although many smaller engines seems a good idea on the surface, having too many not only risks a higher potential for failure, (the plumbing get pretty complicated.  Ask the Russians about the N-1) they also wind up massing more than a fewer number of larger more powerful engines.

     That said, the design shown for the ITS seems to be a fair compromise between larger engines, and complicated systems.
Title: Re: Sea Dragon class LV thead
Post by: Hanelyp on 10/11/2016 04:17 am
Many small engines means a higher risk of one or more failing.  But with a good control system a few percent of engines out need not result in loss of mission.
Title: Re: Sea Dragon class LV thead
Post by: pacojoe on 02/28/2018 03:15 am
Is combustion stability the biggest technological uncertainty of the Sea Dragon concept? I've probably seen that critique more than any other. I've read that it can be a problem for bigger engines, and this would obviously be WAY bigger than anything else we've built.
Title: Re: Sea Dragon class LV thead
Post by: Patchouli on 02/28/2018 04:05 am
Good question though the combustion instability issues can be reduced by using several combustors as on the Convair Nexus. and Rombus which also were Sea Dragon class LVs.
There there each combustor is an engine in it's own right though collectively they form a plug nozzle aerospike.

Another solution build an engine with four F1 sized nozzles which should give an engine with 7.2 million pounds of thrust which would get the number of engines needed to a manageable 11.
If you can make 1 to 3 of them able to air start the throttle  you might even be able land it F9 style.

Once you're dealing with a vehicle this large you'll want to use a short wide shape like Rombus or a really squat one like Nexus since aerodynamics on the way up isn't that important but you want a high drag coefficient on the way down.
Title: Re: Sea Dragon class LV thead
Post by: pacojoe on 03/03/2018 02:29 am
You can use multiple engines, but it seems like that would add cost and complexity. It's unfortunate if that's what's necessary. Is it possible to mitigate combustion instability without overhauling the design of Sea Dragon? Is it possible to know how big of a problem it will be without building a prototype engine and testing it?
Title: Re: Sea Dragon class LV thead
Post by: go4mars on 04/20/2018 05:41 am
Now that pad landing seems straightforward, will we see reusable rockets like sea-dragon that get really into the ocean in the next 2 or 3 decades?
Is it an idea that is done? Or is it perhaps yet to come with really really big rockets?

Here's a link to more discussion by a guy named Peter Brandt with a cool rendering of Sea Dragon next to Saturn V.  Lower down the page BFR shows up.

https://peterbrandt.space/blog/2017-05-12-Big-Dumb-Booster
Title: Re: Sea Dragon class LV thead
Post by: pacojoe on 05/03/2018 05:59 am
Is it an idea that is done?

My guess is that sea-based launches are still worth exploring for a variety of reasons, but it only makes sense if the rocket is designed to be seaworthy. For example, there's a startup in Norway called Ripple Aerospace that aims to launch rockets that can be fabricated in Norwegian shipyards.
https://rippleaerospace.com/ (https://rippleaerospace.com/)

That said, I hadn't realized how insanely cheap it could be to fly a fully-reusable BFR. According to the Wikipedia page, the cost per launch is projected to be $7 million, and the rocket is designed to lift 330,000 pounds to LEO and Mars. That's $21.21 per pound. I'm sure that ignores the cost of building the rocket in the first place, but that might be even better than the Sea Dragon was hoped to achieve. That would be a real game-changer. Imagine what we could do if access to space becomes that cheap.
https://en.wikipedia.org/wiki/BFR_(rocket) (https://en.wikipedia.org/wiki/BFR_(rocket))