Big Dumb Boosters- and why we're overthinking this whole rocketry business

[Northstar1989]

For the record, some actual Sea Dragon specs:

Gross Mass: 18,000,000 kg

Payload-capacity: 450,000 - 550,000 kg (LEO, different altitude/inclination used for final orbits for each estimate)

Mass-fraction: 2.5%

Cost-per-kg to LEO: $600

Sources:

http://www.astronautix.com/lvs/searagon.htm

https://en.wikipedia.org/wiki/Sea_Dragon_%28rocket%29

As you can see, I was being more than a little conservative in the scaled-down scenario above, just to make the point (I assumed much worse mass-fractions, and much higher cost-per-kg). Note that some of these benefits come simply from scaling- i.e. a 5% mass-fraction *might* be achievable with a rocket this large to LEO using s "smart booster", but the relative benefits vs. a comparable sized "smart booster" should be preserved even with scaling.

Regards,

Northstar

- - - Updated - - -

You can't prove anything with numbers you've just pulled out of your arse, especially for something like sea dragon; it's full of 60s-era assumptions about big hydrolox engines that we know don't true today. You might remember people actually tried making a rocket with a relatively cheap hydrolox engine and poor mass fraction; it's called Delta IV. You might also remember it's one of the most expensive rockets available, because they fudged both the infrastructure and handling costs as well as demand, exactly like you're doing.

Kryten, if you can't be respectful, I'm going to have to ask you not to post here at all. We need to keep the conversation civil, and phrases like "pulled out of your arse" are not respectful.

What's more, it is not acceptable to make personal attacks. *I* did not come up with these numbers, a set of highly-trained experts in the field did. Who know more than either of us about these things. It is not acceptable to personally attack me just because you don't like a piece of scientific or engineering data that clashes with your preconceived notions.

NASA had an independent firm, TRW separately investigate the numbers for Sea Dragon, for precisely the kind of reasons you state- they were concerned the numbers might be fudged. TRW found the statistics to be perfectly accurate.

Todd Shipyards also confirmed that the construction of the rocket to the required levels of precision was "well within their capabilities" (part of the reason the cost of the rocket was so low was because the engineering margins were wide enough that it could be built with the facilities of a shipyard rather than a highly-specialized manufacturing plant...)

Regards,

Northstar

Edited October 3, 2015 by Northstar1989

[sgt_flyer]

Still - even with BDB, if you need a reliable BDB design, you will still sink a lot of money in the engines. (That's the most expensive part on a rocket)

If you want to design a cheap, and reliable engine (not worrying on the weight), you will need to create a very simple rocket engine design, so it could be easily built in an industrial manner (manual engine assembly and checks at each step is veery costly). Your R&D team will need tremendeous time & money to design such a thing, even more than 'complex' engines. (and 'complex' engines already need a lot of R&D)

One problem for having reliable engines is combustion stability - so the combustion chamber design will need a lot of thought, to have a uniform fuel mixing across the whole chamber - which ends up requiring extremely precise arrangements of the injectors.) on top of that, you have to take into account the materials which compose your combustion chamber and exhausts, because of the thermal expansion. (Even if you go for lower ISP, to have less pressure and temps - to have any meaningful ISP you'll still face a lot of pressure + temperature)

You'll also need to face fuel flow problems - you must not have any bubbles in your circuits (ending up with cavitation in turbopumps would be disastrous - even with a very robust construction - the resulting 'water impacts' after a cavitation bubble collapse can easily damage any turbopump - even heavy industrial ones - once again, very precise design needed to minimize those problems to have big dumb boosters)

Soo - in order to create such engine (which will be a requirement for your cheap big dumb boosters) the company wanting to exploit those will need to invest an enormous amount of money in the engine R&D - and face a longer than average R&D time. (During this time you have no rocket - so can't launch anything to have more money) - you'll need to convince investors and potential customers to have confidence and wait all this time. Once you have your BDB rocket, you'll need to make up for the R&D costs with your rocket costs. (Which remains only a part of the total launch costs, including logistics, rocket assembly, etc - and you'll end up with heavier, more expensive logistics machineries (due to your heavier BDB design) for the same payloads)

In the end, if you want a reliable big dumb booster, you might face

- higher r&d costs in order to have cheaper reliable parts.

- potentially higher launch costs to make up for tour heavier, bigger boosters and the impact that has on the needed workforce and launch infrastructure.

At one point, once you have recouped your R&D costs, you might end up with very concurrential prices, but you'll still need a lot of launches for that. (And a sustained launch rate at that - idle workforce still costs money )

[Kryten]

Again, why are assuming a study from 1962 involving single-chamber engines that are still orders of magnitude beyond anything ever actually fired is producing credible figures?

Cost-per-kg to LEO: $600

Am I right to assume this is 1962 dollars? If it is, even the studies own result is a figure worse than the cheapest modern rockets, like Zenit.

NASA had an independent firm, TRW separately investigate the numbers for Sea Dragon, for precisely the kind of reasons you state- they were concerned the numbers might be fudged. TRW found the statistics to be perfectly accurate.

In 1962. They'd just tested the F-1, and assumed scaling it up would work out just fine. Here in 2015, we know from component tests that it would not, and F-1 remains the largest engine ever fired.

Edited October 3, 2015 by Kryten

[Northstar1989]

Still - even with BDB, if you need a reliable BDB design, you will still sink a lot of money in the engines. (That's the most expensive part on a rocket)

-SNIP-

Why exactly are you debating actual figures from an actual design with "what-if's" and a list of technical difficulties?

The fact is, these obstacles were overcome- that's how we got the Sea Dragon design in the first place. There's no point in rehashing a list of the problems with something and saying it can't be done, when proof it *can* be done is staring you right in the face...

Regards,

Northstar

[Kryten]

The fact is, these obstacles were overcome- that's how we got the Sea Dragon design in the first place. There's no point in rehashing a list of the problems with something and saying it can't be done, when proof it *can* be done is staring you right in the face...

Sorry, but Sea Dragon never even reached the component testing phase, and all the design details are notional. You can't give figures from something like that as infallible, especially when so much of it had never been done. For a start, we know from work done since then that scaling up single-chamber kerolox engines is much harder than they assumed.

[Northstar1989]

Again, why are assuming a study from 1962 involving single-chamber engines that are still orders of magnitude beyond anything ever actually fired is producing credible figures?

Stop minimizing the project just because you don't like the results. The feasibility was confirmed by TRW and NASA engineers. It's been re-visited multiple times by later engineers and still found feasible.

Am I right to assume this is 1962 dollars? If it is, even the studies own result is a figure worse than the cheapest modern rockets, like Zenit.

Yes, the cost estimates were $59-$600 /kg (1962 USD). By comparison, Saturn V was $2915 /kg in 1962 USD. Of course the costs have come down with modern manufacturing techniques and such- it's logical to assume that Sea Dragon would be even cheaper if built today.

Still, no currently operating modern rockets beat $4735 / kg, which is what the cost would be of Sea Dragon in 2015 dollars. The commonly-accepted figure for currently-operating launch systems is still $10,000 /kg according to NASA. Countries like France and Russia subsidize their commercial launch industries, so the listed costs are not economically accurate.

In 1962. They'd just tested the F-1, and assumed scaling it up would work out just fine. Here in 2015, we know from component tests that it would not, and F-1 remains the largest engine ever fired.

This is not the F-1. The F-1 was an engine with radically different design principles. It was a gas generator design, to be precise.

These were pressure-fed engines (on both the upper and lower stages), which, it turns out, are much simpler to design and scale up...

Regards,

Northstar

- - - Updated - - -

Sorry, but Sea Dragon never even reached the component testing phase, and all the design details are notional.

You could say that about ANY rocket that's never actually been built. The whole point of this discussion is ways we could go beyond the present launch-economics, and get to something more affordable. The logic "it hasn't been done yet, therefore it can't be done" is what has held humanity back for its entire history. If that logic had always been allowed to prevail, we would still all be skinning animal hides with Stone Age tools, or in the very least would never have gone to space in the first place.

Stop latching onto the status quo, and start thinking of what *might* be possible for once.

Alright, it's 6:15 AM here and I've been up all night. I'd better get some sleep.

Regards,

Northstar

Edited October 4, 2015 by Vanamonde

[Kryten]

Stop minimizing the project just because you don't like the results. The feasibility was confirmed by TRW and NASA engineers. It's been re-visited multiple times by later engineers and still found feasible.

Therefore Delta IV is the cheapest launcher on the planet, just like it was supposed to be at this stage of it's development. It uses a cheap, simple engine based on extensive hydrolox experience from shuttle, the performance figures show it can do the missions it's likely to do most (deliver GPS sats) without solid augmentation, it can corner the commercial market with augmentation to keep the flight rate up and thus the price down, it uses cheap aluminium isogrid to deliver better economics on the upper stage then centaur's balloon tanks; what could possibly go wrong?

[Nibb31]

Stop minimizing the project just because you don't like the results. The feasibility was confirmed by TRW and NASA engineers. It's been re-visited multiple times by later engineers and still found feasible.

I'd like to see some of those modern studies...

There were lots of studies that looked great on paper in the 1960's but would be considered totally dumb by today's standards. There were people at NASA that studied nuking the Moon or landing on Mars with a delta wing. Ford wanted to build a nuclear car. Concorde was going to make supersonic travel mainstream. Doctors claimed that smoking was good for you.

The Space Shuttle looked like a great idea in the 1970's, yet we all know how that turned out.

As always, the devil is in the details. There is a huge difference between something that works on paper and an operational design. Once the development work really starts, you typically hit roadblocks that were not apparent earlier and the designs get more complex, more expensive, and take much longer to complete that origically planned. This is particularly true for aerospace projects.

I'm hardly an uneducated purveyor in scientific and technical data (in fact I'm Ivy League educated and have a graduate-degree), and you're insulting my intelligence (which is also, according to IQ tests, off the charts- literally... )

I've always thought that boasting about one's IQ is more a proof of lack of intelligence.

[Northstar1989]

As for the Sea Dragon, *none* of the technology was unproven (except for the size of certain parts which were just scaled-up versions of smaller well-tested technologies). That was the beauty of it. And while it's possible scaling the technologies used up to that size might not have worked well, nothing about the Sea Dragon line of thinking required scaling up to such massive proportions.

Sea Dragon was a *type* of Big Dumb Booster. The basic idea was that you combine simple construction techniques (often used in shipbuilding), cheaper materials (corrugated steel instead of ultra-thin aluminum), and wider engineering margins- and you get a much cheaper per-kg rocket with higher reliability. Nothing about what goes into that was untested, and it was almost guaranteed to work because *nothing* was untested or unproven that went into it (including the construction techniques and materials- once again, often used by shipyards... Our existing fleet of warships is floating proof that this approach works, and generates lower costs...)

Saying that Sea Dragon was too large to work, therefore that entire class of Big Dumb Boosters wouldn't work is like saying "Clifford was an impossibly large fictional dog, therefore dogs cannot exist at all".

There is absolutely no reason you couldn't scale the Sea Dragon approach to rocket-building down to a more reasonable size. Or simply substitute more reasonable-sized engine clusters for its own monolithic engines. The thing that drove down it's cost was primarily, not its size or use of only one main engine per stage (the lower stage also had numerous radial boosters, in the style of the side-mounted engines in KSP, to aid in attitude control as well as provide extra Thrust) but its use of cheaper and heavier construction materials and techniques to get lower costs at the expense of mass-faction. There's nothing about that you can't scale down to (almost) any size you want...

Regards,

Northstar

Edited October 4, 2015 by Vanamonde

[Kryten]

But you still have the same assumptions... without an actual prototype, and without looking at the economic assumptions in the plan, there's no reason to believe Sea Dragon achieves the same results at any scale.

After all, Delta IV was designed to be the cheapest booster ever built, by people with a lot more experience than the ones behind Sea Dragon and working within the scales they knew: they just designed with the assumption that the boom in GTO comsat sales would allow 40 cores launched/year. Given the masses it is supposed to be built for, Sea Dragon is similarly built for a market that never happened, so we can't use those numbers without major casveats even if the engineering all somehow turns out to completely sound.

Oh, and in case you were wondering, the problem with the Delta IV wasn't just the flight rate; the main engine failed to hit their design targets, despite those being set after the kind of sub-scale component testing Sea Dragon never got. This is rocket science, as the saying goes, and in rocket science you can't assume something will just work.

[SomeGuy12]

Historically, every rocket project for decades has ended up costing much more than initial estimates. It is not very intelligent of you to trust 1962 figures for a design that was never flown. What you should know, and any real genius would immediately know, is that a review like you describe can only be done for known knowns. When you actually try to do something like a Sea Dragon...or even something vastly simpler...in the real world, you get slammed in the face with all kinds of issues and difficulties and unexpected problems no amount of paper analysis could have found. And these problems drive up the cost, a lot, to overcome them.

Finally, the Sea Dragon figures had to be marginal cost per rocket launched. That is not what modern cost numbers are about : rolled into it is money to support the company doing the launches and the R&D and customizations and new engineering work done to update the design.

Edited October 4, 2015 by Vanamonde

[SciMan]

You know what a scaled-down and clustered Sea Dragon looks like?

OTRAG

Pressure fed, ablatively cooled, no thrust vectoring (differential throttle control instead).

Standard heating-grade kero (not RP-1) fuel, Nitric acid/N204 oxidizer.

And it could do anything from sounding rockets up to 10T to orbit.

It was going to take 3 stages to get something into orbit because of the relatively low performance.

Each core (called a CRPU for Common Rocket Propulsion Unit) was so small that it took 4 to make a sounding rocket. This would ensure that a production line could stay busy even if there wasn't all that much demand for launches.

At the production rate to make even a 1-ton orbital launch, assembly-line type production could be used.

For anything that used more than 4 cores, I'd be willing to bet that at least 2 cores could fail at any time in the flight and still deliver the payload to "an" orbit, even if it's slightly lower than the desired one.

This thing would probably only have had the performance to make it to LEO, so a sat going to GEO/GSO would need a solid kick stage or two.

However, the high efficiency of electric propulsion being used by many new satellites means that this would probably be much less of a problem today than it would have been in the past.

I think it would be possible to launch a satellite that has electric propulsion up to GEO/GSO by using a single solid kick stage to raise the Ap, then use the onboard electric propulsion to circularize.

This rocket would have been extremely tolerant of slowdowns in the launch market. It would also have been very cheap.

Shame it got killed off (it was actively killed, not because of "this doesn't make economic sense").

Then again, it might not fit in this thread, as it's missing the "big" of "big dumb booster".

Edited October 4, 2015 by SciMan

[Northstar1989]

You know what a scaled-down and clustered Sea Dragon looks like?

OTRAG

-SNIP-

This rocket would have been extremely tolerant of slowdowns in the launch market. It would also have been very cheap.

Shame it got killed off (it was actively killed, not because of "this doesn't make economic sense").

Then again, it might not fit in this thread, as it's missing the "big" of "big dumb booster".

No, OTRAG perfectly fits the category of "Big Dumb Boosters". It worked too, from what I understand (although I know less about it that Sea Dragon or Aquarius). Proving, we could do better than we are doing right now. Thanks for bringing that up.

Regards,

Northstar

Edited October 4, 2015 by Northstar1989

[technicalfool]

This is your obligatory "the moderators are watching" post. Do behave. Less of the personal insults. No, I don't care who started it, but I'll end it if you like.

[Northstar1989]

Again, nobody with even the vaguest idea of real development of any product would blithely assume that a paper study was accurate. Someone with an Ivy league degree might even have a vague idea that a paper study is just a series of rough estimates, especially in 1962. A real engine bell, just to name one of the simplest to model parts, is subject to very complex stresses that 1962 computers could not model accurately, so a paper estimate really is just a wild guess.

Edited October 4, 2015 by Vanamonde

[Vanamonde]

A fair number of personal remarks have been edited or deleted entirely from this thread. The off-topic personal remarks, from all sides, need to stop, now.

[Northstar1989]

The only place where meaningful scientific or technical obstacles are raised is in the post I quote below. However...

Still - even with BDB, if you need a reliable BDB design, you will still sink a lot of money in the engines. (That's the most expensive part on a rocket)

The design was made without sinking large amounts of money into it. Sea Dragon was designed very cheaply in fact. Whether it would work is another story, but the facts refute this assertion entirely.

If you want to design a cheap, and reliable engine (not worrying on the weight), you will need to create a very simple rocket engine design, so it could be easily built in an industrial manner (manual engine assembly and checks at each step is veery costly). Your R&D team will need tremendeous time & money to design such a thing, even more than 'complex' engines. (and 'complex' engines already need a lot of R&D)

Also wrong. The whole point was that, by simplifying, the design process became very quick and easy. Relying on pressure-fed engines instead of *anything* using a turbopump removed a *large* number of design hours, for instance.

One problem for having reliable engines is combustion stability - so the combustion chamber design will need a lot of thought, to have a uniform fuel mixing across the whole chamber - which ends up requiring extremely precise arrangements of the injectors.) on top of that, you have to take into account the materials which compose your combustion chamber and exhausts, because of the thermal expansion. (Even if you go for lower ISP, to have less pressure and temps - to have any meaningful ISP you'll still face a lot of pressure + temperature)

No. By relying on very wide engineering margins the whole point was they did *not* have to spend much thought on the materials of the combustion chamber and exhaust. Low ISP combined with use of materials much stronger than should by any means by necessary meant that they didn't have to spend large amounts of time modeling the stresses to determine *precisely* how thick the engine bell needed to be at any given point. They just designed it with tons of margin, knowing that they were well over-engineering compared to any of the possible stresses.

As for the injector placement, yes, this still takes some time- but Sea Dragon didn't need to eliminate *all* the difficult parts of the design process to work, just simplify the majority of them...

You'll also need to face fuel flow problems - you must not have any bubbles in your circuits (ending up with cavitation in turbopumps would be disastrous - even with a very robust construction - the resulting 'water impacts' after a cavitation bubble collapse can easily damage any turbopump - even heavy industrial ones - once again, very precise design needed to minimize those problems to have big dumb boosters)

The Sea Dragon team was aware of how finicky turbopumps can be- which is why they avoided using any in the first place. The design was to be entirely pressure-fed: as would any smaller versions of the basic deisgn-concept for this class of Big Dumb Booster. Thus, these issues were avoided outright.

Soo - in order to create such engine (which will be a requirement for your cheap big dumb boosters) the company wanting to exploit those will need to invest an enormous amount of money in the engine R&D - and face a longer than average R&D time. (During this time you have no rocket - so can't launch anything to have more money) - you'll need to convince investors and potential customers to have confidence and wait all this time. Once you have your BDB rocket, you'll need to make up for the R&D costs with your rocket costs. (Which remains only a part of the total launch costs, including logistics, rocket assembly, etc - and you'll end up with heavier, more expensive logistics machineries (due to your heavier BDB design) for the same payloads)

In the end, if you want a reliable big dumb booster, you might face

- higher r&d costs in order to have cheaper reliable parts.

- potentially higher launch costs to make up for tour heavier, bigger boosters and the impact that has on the needed workforce and launch infrastructure.

At one point, once you have recouped your R&D costs, you might end up with very concurrential prices, but you'll still need a lot of launches for that. (And a sustained launch rate at that - idle workforce still costs money )

All this is false. Because it relies on the grossly inaccurate assumption of a longer R&D phase, when in fact the whole point of something like Sea Dragon is that it has:

(1) A much shorter R&D phase than a "smart booster" by avoiding using any of the components (such as a turbopump) which are extremely difficult to design whenever possible, and over-engineering things with huge margins rather than laboriously calculating maximal stress-levels whenever it's not.

(2) A much cheaper manufacturing cost, because it is designed with very wide engineering margins, and greater manufacturer error become acceptable- allowing less precise facilities such as shipyards to build the rocket, with less laborious (and expensive) testing along the way.

The Sea Dragon doesn't eliminate *all* the difficult or expensive parts of rocket design, but it does avoid a large number of these obstacles altogether. And, aside from scaling up to large sizes in the case of Sea Dragon itself (which, once again, is just a prototype for the class- you could easily build much smaller designs along the same concept lines), Sea Dragon does not introduce any *new* obstacles- which means there is absolutely no logical reason whatsoever to expect anything *other* than a much shortened R&D phase and a much cheaper manufacturing cost- which all adds up to a cheaper rocket on the launchpad in the end.

Regards,

Northstar

[Red Iron Crown]

This all sort of begs the question: If Sea Dragon was such a good concept, why didn't it go anywhere? Why has literally no one gone with Big Dumb Boosters for their space programs, even those of countries which cannot afford more expensive concepts?

The concept has been around for over 50 years now, if it offered so many advantages over more conventional designs I have to wonder why not one program has gone with such a design (and in fact move to "smarter" designs as quickly as they can manage).

[Northstar1989]

This all sort of begs the question: If Sea Dragon was such a good concept, why didn't it go anywhere? Why has literally no one gone with Big Dumb Boosters for their space programs, even those of countries which cannot afford more expensive concepts?

The concept has been around for over 50 years now, if it offered so many advantages over more conventional designs I have to wonder why not one program has gone with such a design (and in fact move to "smarter" designs as quickly as they can manage).

I wonder too, actually. That is why I started this discussion in the first place- to try and answer that question.

Although, to be fair, OTRAG was classic "Big Dumb Booster" approach- and *that* was attempted, and only called off because they choose to attempt it in a horribly politically unstable country, not because of any issues with the engineering approach itself.

Thank you for bringing the discussion back on track, Red Iron Crown.

Regards,

Northstar

[Kryten]

This all sort of begs the question: If Sea Dragon was such a good concept, why didn't it go anywhere? Why has literally no one gone with Big Dumb Boosters for their space programs, even those of countries which cannot afford more expensive concepts?

Because real space programs have had need of rockets capably of putting payloads reliably into orbit at relatively low frequency, they tend to use designs that focus on lowering infrastructure costs at the expense of per-unit costs; for example, a higher-impulse first stage engine may be more expensive, but results in a smaller first stage that is easier to test and ship. BDB designs go the other way, optimising per-unit costs at the expense of either needing infrastructure that can handle very large rockets or very high flight rates; the result looks good on paper, but depends on higher demand than we have now. Sea Dragon was designed for the 60s-70s manufacturing in space boom that never happened, Delta IV in it's original form and Aqarius were for a 90s GTO comsat boom that never happened, et.c. et.c.

Edited October 4, 2015 by Kryten

[PB666]

Because real space programs have had need of rockets capably of putting payloads reliably into orbit at relatively low frequency, they tend to use designs with relatively that focus on lowering infrastructure costs at the expense of per-unit costs; for example, a higher-impulse first stage engine may be more expensive, but results in a smaller first stage that is easier to test and ship. BDB designs go the other way, optimising per-unit costs at the expense of either needing infrastructure that can handle very large rockets or very high flight rates; the result looks good on paper, but depends on higher demand than we have now. Sea Dragon was designed for the 60s-70s manufacturing in space boom that never happened, Delta IV in it's original form and Aqarius were for a 90s GTO comsat boom that never happened, et.c. et.c.

There is a technical aspect that was an important cosideration. They were relying on the electric output from an ACC on board nuclear reactor to provude liquid oxygen and hydrogen, both stages required Liguid O2. The storage capacity of the gases woukd require a third vessel, and the production time would have benn horrific at 1960s electrlyisis capability. To make this rocket feasable they would need vessel much larger than a carrier with several nucear facilities and a large storage capacity, in addition placing these liquid fuels under water would generate a large icing problem that also would have to be dealt with. if the USN needs nuc powered vessels to improve performance they are going to get the best, but the per watt cost of power on land are not as good as other fuels, and when we deduct the sheer size of the rocket and the inefficiency of electrolysis at sea, its a genuinly bad idea. On land, there is always excess capacity at night and so the capital costs of power don't need to be considered, and hydrogen can be made from methane. Oxygen can be made from sulftate but can also be generated by photrophs really easily.

The design solves one problem, gravity of massive objects versus boyancy, but creates several other problems that need to be dealt with.

These could be solved by builting a storage barge made of steel

Drafting the use of several carriers for a few days/weeks- risk issue for other intended uses.

Specifically designed heaters over pipe insulation to prevent icing.

In addition they claim to make the rocket out of steel but steel stages have a higher density in air and make recovery mor difficult. I think the concept tries to solve too many problems at once.

[Guest]

One of the big things is safety. They would likely be defunded if they just threw something together.

[Northstar1989]

Just to be clear, Big Dumb Boosters a la Sea Dragon didNOT have safety issues.

Let me put this in KSP terms for you.  A Big Dumb Booster in the style of Sea Dragon would be like if there were a line of parts you could buy in KSP that were quite a bit heavier and had inferior performance, but cost a third as much.  You'd end up needing a bigger rocket in the end, but you'd still save money.

A rocket like Aquarius, I won't even refer to as a Big Dumb Booster anymore to avoid the potential for confusion.  Instead I'll call it a Discount-Cost Low-Reliability (DCLR) Rocket.

A DCLR rocket like Aquarius is an entirely different concept.  It would be like if you could buy a line of parts in KSP that were slightly lighter and a third the cost, but had a random chance of failing in a mission-breaking way during launch.  It would save you money, but only on low-cost payloads like fuel...

 

Regards,

Northstar

Edited September 18, 2016 by Northstar1989

[Nibb31]

5 hours ago, Northstar1989 said:

Just to be clear, Big Dumb Boosters a la Sea Dragon didNOT have safety issues.

That's a pretty bold claim for something that was barely even a paper proposal.

5 hours ago, Northstar1989 said:

Let me put this in KSP terms for you.  A Big Dumb Booster in the style of Sea Dragon would be like if there were a line of parts you could buy in KSP that were quite a bit heavier and had inferior performance, but cost a third as much.  You'd end up needing a bigger rocket in the end, but you'd still save money.

The idea was that you would build a rocket using shipbuilding techniques instead of aircraft techniques.

The problem with that reasoning is that ships aren't exactly cheap or quick to build. There is no way building a rocket the size of a supertanker in a shipyard, and blow it up in the process (Sea Dragon was not reusable) would be anywhere near economical. It might have seemed that way in the 1950's with the wartime experience of the old Liberty Ships, but with modern shipyards and the cost of a qualified workforce and materials, no way.

 

[Bill Phil]

2 minutes ago, Nibb31 said:

The idea was that you would build a rocket using shipbuilding techniques instead of aircraft techniques.

The problem with that reasoning is that ships aren't exactly cheap or quick to build. There is no way building a rocket the size of a supertanker in a shipyard, and blow it up in the process (Sea Dragon was not reusable) would be anywhere near economical. It might have seemed that way in the 1950's with the wartime experience of the old Liberty Ships, but with modern shipyards and the cost of a qualified workforce and materials, no way.

 

If I recall, the idea was to use the already existing ship construction infrastructure for rocket construction, not actually using the techniques associated with it... Although, I do seem to remember that the construction firm they worked with said that it wasn't unlike submarine construction. Then you'd get the added bonus of not having to build a launch pad. Not to say it's practical, though.

http://www.astronautix.com/s/seadragon.html