Author Topic: Sea Dragon class LV thead  (Read 140407 times)

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3748
  • Earth
  • Liked: 148
  • Likes Given: 3114
Re: Sea Dragon class LV thead
« Reply #220 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. 
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3748
  • Earth
  • Liked: 148
  • Likes Given: 3114
Re: Sea Dragon class LV thead
« Reply #221 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? 
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline RanulfC

  • Senior Member
  • *****
  • Posts: 4445
  • Heus tu Omnis! Vigilate Hoc!
  • Liked: 805
  • Likes Given: 32
Re: Sea Dragon class LV thead
« Reply #222 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
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2438
  • Claremore, Ok.
  • Liked: 395
  • Likes Given: 11
Re: Sea Dragon class LV thead
« Reply #223 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).
My God!  It's full of universes!

Offline Vultur

  • Full Member
  • ****
  • Posts: 1086
  • Liked: 156
  • Likes Given: 11
Re: Sea Dragon class LV thead
« Reply #224 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.

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2438
  • Claremore, Ok.
  • Liked: 395
  • Likes Given: 11
Re: Sea Dragon class LV thead
« Reply #225 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!
My God!  It's full of universes!

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2438
  • Claremore, Ok.
  • Liked: 395
  • Likes Given: 11
Re: Sea Dragon class LV thead
« Reply #226 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.
My God!  It's full of universes!

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3748
  • Earth
  • Liked: 148
  • Likes Given: 3114
Re: Sea Dragon class LV thead
« Reply #227 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.
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline b0objunior

  • Member
  • Posts: 97
  • Liked: 24
  • Likes Given: 0
Re: Sea Dragon class LV thead
« Reply #228 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.

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2438
  • Claremore, Ok.
  • Liked: 395
  • Likes Given: 11
Re: Sea Dragon class LV thead
« Reply #229 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.
My God!  It's full of universes!

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3748
  • Earth
  • Liked: 148
  • Likes Given: 3114
Re: Sea Dragon class LV thead
« Reply #230 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. 
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline JasonAW3

  • Senior Member
  • *****
  • Posts: 2438
  • Claremore, Ok.
  • Liked: 395
  • Likes Given: 11
Re: Sea Dragon class LV thead
« Reply #231 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.
My God!  It's full of universes!

Offline Hanelyp

  • Full Member
  • ***
  • Posts: 369
  • Liked: 65
  • Likes Given: 252
Re: Sea Dragon class LV thead
« Reply #232 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.

Offline pacojoe

  • Member
  • Posts: 17
  • USA
  • Liked: 2
  • Likes Given: 3
Re: Sea Dragon class LV thead
« Reply #233 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.

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4400
  • Liked: 182
  • Likes Given: 359
Re: Sea Dragon class LV thead
« Reply #234 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.
« Last Edit: 04/22/2018 09:06 PM by Patchouli »

Offline pacojoe

  • Member
  • Posts: 17
  • USA
  • Liked: 2
  • Likes Given: 3
Re: Sea Dragon class LV thead
« Reply #235 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?

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3748
  • Earth
  • Liked: 148
  • Likes Given: 3114
Re: Sea Dragon class LV thead
« Reply #236 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
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline pacojoe

  • Member
  • Posts: 17
  • USA
  • Liked: 2
  • Likes Given: 3
Re: Sea Dragon class LV thead
« Reply #237 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/

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)

Tags: