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

[megatiger78]

Somedody make this a mod

[fairytalefox]

Guys, what are you talking about?

That's Sea Dragon:

The first stage was to be powered by a single enormous 80,000,000 pounds-force (360 MN) thrust engine

That's real life:

RD-171M Most powerful liquid-fuel rocket engine in the world. Vacuum thrust (N): 7,904,000

And that's the finishing shot:

Several Soviet and Russian rocket engines use the approach of clustering small combustion chambers around a single turbine and pump. During the early 1950s, many Soviet engine designers, including Valentin P. Glushko, faced problems of combustion instability, while designing bigger thrust chambers. At that time they solved the problem by using a cluster of smaller thrust chambers.

combustion instability

[Northstar1989]

Guys, what are you talking about?

That's Sea Dragon:

That's real life:

And that's the finishing shot:

combustion instability

Combustion instability is, I believe, one of the reason for the high predicted failure rates (up to 1/3rd) of the Sea Dragon or Aquarius. But as pointed out, it's still a cheaper way of getting low intrinsic-value stuff to orbit, such as fuel (for interplanetary transfers and station-keeping), spare parts, and food/consumables for manned missions; even taking the high failure rate into account (due to the low value of the target payloads, it's easy to replace them at minimal cost after a failed launch, and launch the payloads in advance of need so there's a capability to launch backup missions in case of a launch failure...)

Trying to solve problems like that also creates new room for engineers looking to advance the state of technology to do their work. Whoever said Big Dumb Boosters wouldn't leave create impetus for technological advancement couldn't have been further from the truth (in fact, with the already high base failure rate and low-cost payloads, there's a lot less penalty for throwing in unproven technologies like aerospike rocket engines, Microwave thermal rocketry, or Space-X style recovery to a Big Dumb Booster...)

Regards,

Northstar

[Red Iron Crown]

(in fact, with the already high base failure rate and low-cost payloads, there's a lot less penalty for throwing in unproven technologies like aerospike rocket engines, Microwave thermal rocketry, or Space-X style recovery to a Big Dumb Booster...)

That sort of goes against the BDB concept though. New technology prototypes are not cheap.

[Northstar1989]

That sort of goes against the BDB concept though. New technology prototypes are not cheap.

The idea would to be to use an existing Big Dumb Booster (BDB) design as a low-cost test platform for some of these experimental technologies- not to make it a primary part of the BDB design. Additionally, some technologies, once refined, would actually be both cheaper and more reliable than conventional chemical rockets- thermal rocketry for instance (which has fewer moving parts and potential points of failure than a chemical rocket engine, and is actually much cheaper to manufacture..)

Aside from that, some technologies would actually benefit from the size and low cost of a Big Dumb Booster, without adding any cost to the mission, for entirely different reasons...

For instance, ff you choose to leave the upper stage of a Sea Dragon in orbit, instead of bringing up the fuel to de-orbit it, you not only save on rocket complexity (the guidance system doesn't need to be complex enough to perform a de-orbit burn), cost, and mass- you also put a rather huge (compared to any other rocket upper stage) hunk of metal into space that you might eventually be able to tear apart for scrap metal to build things in orbit (especially feasible since the Sea Dragon would have been built out of durable, easy-to-machine steel instead of more finicky composites...)

I've discussed orbital recycling on these forums before- but the conversation eventually boils down to the fact that the majority of the mass of most modern rocket upper-stages is made out of difficult-to-recycle composites that you couldn't cheaply re-use in orbit (except as extra micrometeorite plating for a space station or something), limiting you to mostly just tearing apart spare rockets to get at spare/replacement parts from the guidance systems and turbopump and such. However the Sea Dragon is made out of steel, and steel is durable (it won't degrade nearly as much floating around in space as debris) and can much more easily be machined into whatever shape/size you need it- structural pieces for a rocket built partially in-orbit, for instance...

Regards,

Northstar

Edited July 16, 2014 by Northstar1989

[Red Iron Crown]

The idea would to be to use an existing Big Dumb Booster (BDB) design as a low-cost test platform for some of these experimental technologies- not to make it a primary part of the BDB design. Additionally, some technologies, once refined, would actually be both cheaper and more reliable than conventional chemical rockets- thermal rocketry for instance (which has fewer moving parts and potential points of failure than a chemical rocket engine, and is actually much cheaper to manufacture..)

It stops being a low cost booster then, though. The most expensive part by far of any rocket is the engines and associated pump/plumbing. Fuel tanks and fuel are reasonably cheap in comparison, whether exotic materials or cheap ones. So you might reduce the tank cost by 50% (generous here) but still only reduce the total launch vehicle cost by 10% or less.

The place to refine those propulsive technologies is on the test stand. Once proven there, they'll go on the high reliability "smart" boosters first. Then, once the tech is relatively commonplace, it will trickle down to the BDBs.

[TheScareCake!]

Wow, i can see how this is relative to other things. I got myself a nice casio watch, made in japan from stainless steel, waterproof and beautiful. It costs about 60-70 euros (we dont have euros in our country yet so i dont know the true cost). And it broke two days ago. I still have my old legit watch i got for few euros, it looks lame, but its still ticking after 3-4 years. Did it broke? Not even once.

[Kryten]

You simply got ripped off. That's an entirely separate issue.

[Northstar1989]

It stops being a low cost booster then, though. The most expensive part by far of any rocket is the engines and associated pump/plumbing. Fuel tanks and fuel are reasonably cheap in comparison, whether exotic materials or cheap ones. So you might reduce the tank cost by 50% (generous here) but still only reduce the total launch vehicle cost by 10% or less.

I wasn't talking about using swapping in high-cost internal plumbing- like you said that kind of defeats the point. I was suggesting testing out technologies like trying to land the thing after launch (like with Space-X, except if it somehow causes loss of rocket and payload it's a lot less of a big deal), throwing microwave thermal rockets on as strap-on boosters (the engines are a lot cheaper than chemical rockets, even in their experimental stages- all the cost is in the ground infrastructure- and if a thermal engine exploded and took out the whole rocket somehow, once again it wouldn't be as bad as with a "smart" booster), or swapping in an aerospike nozzle on the bottom (it's a *nozzle design*, not a plumbing design- so it shouldn't take all that much modification or additional cost) or using a smaller liquid rocket with an aerospike nozzle as a strap-on booster (so you don't have to alter the BDB at all).

None of these ideas add significantly to the cost of the Big Dumb Booster. The booster can be just as cheaply-made and over-engineered as ever: having a new (and equally cheaply-made) strap-on booster with a different nozzle or even cheaper propulsion system (than chemical rocketry) isn't going to change that equation at all, and *might* even add to the payload capacity a bit...

The place to refine those propulsive technologies is on the test stand. Once proven there, they'll go on the high reliability "smart" boosters first. Then, once the tech is relatively commonplace, it will trickle down to the BDBs.

Not at all. Why would you risk an expensive "smart booster" by trying out an unproven technology with it when you could just strap the same experimental technology (once again, talking about something like an aerospike engine or a thermal rocket) in parallel to the BDB's normal propulsion systems, as in with a strap-on booster, not as a replacement) to a much cheaper rocket, and not care as much if the whole thing goes up in flames (not only is the rocket cheaper to begin with, but there's a good chance it might have gone up in flames even without the experimental technology...)

What I'm working off here is that there are basically 3 main classes of failures:

(1) Failures that destroy the rocket and payload- these are much less of a big deal with a Big Dumb Booster carrying a cheap payload like fuel (the BDB is cheap, the payload is cheap, and there's a chance as high as 1 in 3 with Aquarius it would have failed/exploded WITHOUT the new technology). Of course, just because a strap-on booster with risky experimental technology explodes doesn't mean the main rocket will fail- but it's likely to as it will probably cause some serious damage in the process.

(2) Failures that simply fail inertly- they don't do ANYTHING. Such as an engine the simply fails to ignite, or cuts out in flight without causing catastrophic failure. The dead weight of a dead strap-on booster (which could then be decoupled anyways if this didn't cause loss of control) would be much less significant with a hugely powerful BDB than with a smaller and more efficient rocket- especially since BDB's don't normally operate with strap-on boosters to begin with (most BDB designs are two-stage-to-orbit), so it wasn't exactly relying heavily on strap-on boosters to begin with (it might just have to settle into a lower orbit, assuming the payload was increased due to the addition of the strap-on booster with experimental technology). And, if it causes mission failure in the end, once again that's less of a big deal than with a "smart" booster.

(3) Failures that have some other unintended, but deleterious effect, falling somewhere in-between an inert failure and total mission loss. The possibilities are many, but as always, it's less of a big deal with a Big Dumb Booster in almost all cases.

With (1) and (2), which seem to be the most common in rocketry, it's going to be much less of a big deal with a Big Dumb Booster. It's like choosing to transport nitroglycerin on a cart drawn by a cheap workhorse vs an expensive racehorse (which you probably wouldn't use to draw a cart anyways) back in the 1800's- the big dumb animal is a much better choice when risk of total annihilation is involved.

The experimental tech may be expensive (because it represents investment in new prototypes), but it's also typically dangerous. This usually leads to a LONG approval process before an experimental new space technology can be launched atop or alongside a typical modern "smart" booster- driving up costs and stifling innovation. Imagine how much the process could be streamlined and shortened with a Big Dumb Booster...

Regards,

Northstar

Edited July 18, 2014 by Northstar1989

[Red Iron Crown]

I find it hard to imagine that the new technologies will be as cheap or cheaper than established technologies during development, especially if you factor R&D costs in. I mean, in theory the microwave powered rocket will be cheaper, eventually, once it's a mature technology, once the cost of the microwave emitter has been amortized a bit, etc, etc.

Much cheaper and less risky to fully test the engine on the test stand where it doesn't put payloads (cheap or expensive) at risk. Then use it on the higher cost rockets that can afford to pay the R&D costs for increased efficiency.

It's like new technological features in cars, they start being offered in high end models at relatively large cost, then as the tech matures and the R&D is paid down it moves downmarket until it reaches the cheapest economy cars. (Lots of examples, ABS, stability control, navigation, etc)

Basically, you can have a cheap BDB, or a new tech BDB, but not both.

[Northstar1989]

Wow, i can see how this is relative to other things. I got myself a nice casio watch, made in japan from stainless steel, waterproof and beautiful. It costs about 60-70 euros (we dont have euros in our country yet so i dont know the true cost). And it broke two days ago. I still have my old legit watch i got for few euros, it looks lame, but its still ticking after 3-4 years. Did it broke? Not even once.

Let's get one thing straight- Big Bumb Boosters are NOT more reliable than "smart" boosters. Just the opposite- they're designed and manufactured to less exacting engineering standards (still engineered and tested- but more similar in quality to what you might see used in an automobile industry, rather than a modern space program), which saves ENORMOUSLY on cost. But as a result, they're more failure prone.

The principle behind a Big Dumb Booster is that, when transporting cheap payloads (like fuel and consumables), the advantage in per-launch cost greatly outweighs the increased failure rate. They aren't cheap or sloppily-made exactly- only much LESS expensive and carefully-manufactured than a typical rocket in a modern space program.

Missions don't fail if they fail, either. Because they are meant to be used to launch IN ADVANCE OF NEED to much more expensive orbital depots (which need to be launched atop better rockets, due to the inherent cost of the payload- Big Dumb Boosters are not meant to replace smart boosters, only take them out of the market for the cheaper portion of payloads), the cheap component of the payload is already there, waiting in orbit before it's needed.

A typical mission might look like this, using the Aquarius design:

Interplanetary Probe X needs 14 tons of fuel to reach its destination. The dry mass of the probe is 1 ton.

Instead of launching the probe on a typical 15-ton "smart booster", you launch the probe completely dry as a 1-ton payload on a much smaller, cheaper smart booster.

The 14 tons of fuel, meanwhile, you launch on 21 separate Aquarius launches (1 ton payload per launch, up to 1/3rd of launches fail) in the months PRECEDING the launch of the probe, to an orbital fuel depot. The cost of these 21 launches is only a fraction of the cost of 14 launches of 1-ton smart boosters, or of a single 14 or 15-ton smart booster.

After launching dry atop the smart booster, the probe acts as the "passive partner" for a rendezvous/docking with a reusable orbital tug (part of the Big Dumb Booster system- for instance; a tug, depot, AND the rocket itself were all part of the $700 million plan for Aquarius), which then transports it to the fuel depot (the tug would have to return to the depot anyways- it might as well bring the 1 ton of probe to the 14 tons of fuel rather than the 14 tons of fuel to the 1 ton probe), where the probe is fueled up and can then proceed with its nominal mission.

Thing you DON'T have to maintain, when using an Aquarius-style Big Dumb Booster:

(1) A launchpad- most BDB's are designed for aquatic launch

(2) Expensive insurance policies for the entire mission payload- a 1/3rd failure rate is already calculated into the cost of the Aquarius (whereas even smart boosters occasionally fail- and you have to take out insurance to protect against this). Your insurance policy only needs to be for the dry mass- which means much lower insurance costs (1 ton-payload smart boosters are much cheaper than those that can lift 15 tons to orbit, in this example).

(3) A fleet of super-heavy smart boosters, like the Space Launch System, Saturn V, or Ares V rockets (too bad we didn't figure that out earlier- though it's not too late for the Russians and Chinese who are early in the process of designing their own new super-heavy smart boosters). Any vehicle heavy enough when "wet" (full of fuel) to require a booster of that size can much more cheaply be launched "dry" atop an existing medium-lifter smart booster, and then refueled from the Big Dumb Booster fuel depot (which can be filled up over as many launches as necessary- 3 for each 2 tons of fuel with Aquarius, which yields a cost of $666,666 per metric ton of fuel, or $666 per kg- significantly cheaper than existing launch costs-per-kg. For reference, the Falcon 9 is currently the industry-leader at just over $4,000 per kg)

All in all, a surprisingly intuitive and very cheap system. Why use expensive rockets to transport cheap and easily-replaced fuel? (or consumables for the ISS) Like the designers said "Bread was moved on bread trucks, not on Brinks trucks".

Regards,

Northstar

Edited July 18, 2014 by Northstar1989

[Northstar1989]

I find it hard to imagine that the new technologies will be as cheap or cheaper than established technologies during development, especially if you factor R&D costs in.

No, not once you factor R&D costs in. But you don't have to replace the R&D costs if you lose the prototype, especially if you're planning around there being a high chance of failure (due to the unreliability of BDB's) even if it works perfectly.

But the manufacturing costs for the microwave and heat receivers for a pressure-fed microwave thermal rocket- MUCH less than the manufacturing costs for a turbopump (or even pressure-fed) chemical rocket of similar size (I don't even mention performance, because a microwave thermal rocket engine is capable of MUCH better TWR and ISP with sufficient amounts of beamed power)

I mean, in theory the microwave powered rocket will be cheaper, eventually, once it's a mature technology, once the cost of the microwave emitter has been amortized a bit, etc, etc.

I'm not talking about building a large-scale system. I'm talking about building a 20 MW microwave array (estimated cost $20-40 million US Dollars, this includes power plants and high-energy capacitors at the ground site) and throwing a couple SMALL (the diameter of a thermal rocket in this size range would be less than 1 meter- as a separate rocket, its payload capacity would be measured in fractions of a kg) thermal rockets on the side of a giant ole' Big Dumb Booster as cheap strap-on boosters using experimental technology. The TWR and ISP they get is extremely impressive (up to 1000s in vacuum, and superior thrust to a chemical rocket of the same diameter for less dry mass), so it would be worth the extra mass- and thermal receivers/rockets in this size range are EXTREMELY cheap to manufacture compared to a comparable chemical rocket engine.

Much cheaper and less risky to fully test the engine on the test stand where it doesn't put payloads (cheap or expensive) at risk. Then use it on the higher cost rockets that can afford to pay the R&D costs for increased efficiency.

I'm not arguing against test stands- they're great because they're the ultimate in low-risk. But eventually you need to test the rocket out in flight, and when you do, a Big Dumb Booster is the place to go, once you want to test at higher altitudes than what you can get through drop-tests from planes. You want to start off by putting the CHEAP payloads at risk, not the expensive ones. Once you've got some testing in strapped to the side of a Big Dumb Booster (some of the heavier, Sea Dragon style ones being so powerful that if the 10 MW booster failed, it'd be like a flea on the side of an elephant- it's not going to throw off the thrust vector significantly or weigh it down by much), you graduate to independent rockets relying entirely off the the thermal rockets. There's no need to ever put a much larger smart booster carrying a large and expensive payload at risk anywhere in the process.

It's like new technological features in cars, they start being offered in high end models at relatively large cost, then as the tech matures and the R&D is paid down it moves downmarket until it reaches the cheapest economy cars. (Lots of examples, ABS, stability control, navigation, etc)

No, it's the OPPOSITE of cars. It's more like new and untested drugs, which actually start off by testing on animals, and then on poor (either economically, or in terms of chance of survival without a novel treatment, i.e. desperate) "volunteers", sometimes even in third-world countries (with some companies, especially the less ethical ones), because there's a chance it could kill them. You NEVER go straight to the high-value customers if there's a chance the new drug could kill them (trust me on this, I'm a biologist in real life). First you do mice, then you do monkeys, then you do healthy but poor volunteers (you need to see how it affects healthy individuals first), then sick volunteers who are desperate for a new option (and whose physicians have thus determined the potential benefit outweighs the potential cost for), and then finally you move to market with the drug. The same basic strategy applies to rockets.

Basically, you can have a cheap BDB, or a new tech BDB, but not both.

I'm not talking about a BDB based on new tech. For the zillionth time, I'm talking about a cheaper TEST PLATFORM. Play 0.24 a bit (like I've been doing for the past several hours), and see all the contracts to test new engines (I assume they've just been developed, within the continuity of KSP) in certain conditions, and then imagine something like that but strapped to the side of a Big Dumb Booster now that we already have tried-and-true chemical rocket designs (though I must point out they WERE NOT so tried-and-true back when the Sea Dragon was proposed in the 1960's...)

Regards,

Northstar

Edited July 18, 2014 by Northstar1989

[78stonewobble]

(3) A fleet of super-heavy smart boosters, like the Space Launch System, Saturn V, or Ares V rockets (too bad we didn't figure that out earlier- though it's not too late for the Russians and Chinese who are early in the process of designing their own new super-heavy smart boosters). Any vehicle heavy enough when "wet" (full of fuel) to require a booster of that size can much more cheaply be launched "dry" atop an existing medium-lifter smart booster, and then refueled from the Big Dumb Booster fuel depot (which can be filled up over as many launches as necessary- 3 for each 2 tons of fuel with Aquarius, which yields a cost of $666,666 per metric ton of fuel, or $666 per kg- significantly cheaper than existing launch costs-per-kg. For reference, the Falcon 9 is currently the industry-leader at just over $4,000 per kg)

I think, that you should make that comparison, between a mass produced Big Dumb Booster and a mass produced "super-heavy smart booster".

Because if noone want's to do stuff in space, or pay for stuff in space, that requires mass production. Then we won't have either rocket mass produced.

On the other hand, if people could and would pay for it. We could have a factory for either doing nothing, but spitting out rockets.

Do you really believe the Big Dumb Booster concept will offer signicant advantages then?

PS: Why is this thread a sticky?

[Sky_walker]

PS: Why is this thread a sticky?

Now that's a good question. It makes exactly zero sense - there are many other equally, if not more, valuable topics - no clue why this one is sticky. Someone wants to promote something he likes? Mods forgot about NPOV principle?

[Red Iron Crown]

Now that's a good question. It makes exactly zero sense - there are many other equally, if not more, valuable topics - no clue why this one is sticky. Someone wants to promote something he likes? Mods forgot about NPOV principle?

It's a thread of the month.

[KASASpace]

The R-7 missile wasn't exactly slapped together, but it wasn't carefully placed and all that. It took good amount of tests before a success, but then the success rate became higher and higher, the rocket evolved, and finally became the legendary Soyuz rocket. It's reliable all right.

This is a legitimate point, though. Why waste so much on a Ferrari just to drive it once? Why not build a jalopy and then drive it off the cliff? It's cheaper to build something quickly. You just need it to work, you don't need it to be over-complicated. This happens too often. Look at the Space Shuttle, it has so much stuff and equipment on just the orbiter. Now, that is more like saving the front of the Ferrari, but you still lose the back side. So, why overcomplicate? Sometimes you just need to design, build, test, repeat.

It would much simpler if we modularized fuel tank pieces. Then you could just order up a certain number of the pieces and put them together.

[Red Iron Crown]

No, not once you factor R&D costs in. But you don't have to replace the R&D costs if you lose the prototype, especially if you're planning around there being a high chance of failure (due to the unreliability of BDB's) even if it works perfectly.

But the manufacturing costs for the microwave and heat receivers for a pressure-fed microwave thermal rocket- MUCH less than the manufacturing costs for a turbopump (or even pressure-fed) chemical rocket of similar size (I don't even mention performance, because a microwave thermal rocket engine is capable of MUCH better TWR and ISP with sufficient amounts of beamed power)

We really don't know what the manufacturing costs will be, given that beamed power is not a solved problem by any stretch. Even if they do turn out to be much lower than conventional chemical rockets, I'd imagine that such propulsion would make its way into both smart boosters and BDBs if economically viable.

I'm not talking about building a large-scale system. I'm talking about building a 20 MW microwave array (estimated cost $20-40 million US Dollars, this includes power plants and high-energy capacitors at the ground site) and throwing a couple SMALL (the diameter of a thermal rocket in this size range would be less than 1 meter- as a separate rocket, its payload capacity would be measured in fractions of a kg) thermal rockets on the side of a giant ole' Big Dumb Booster as cheap strap-on boosters using experimental technology. The TWR and ISP they get is extremely impressive (up to 1000s in vacuum, and superior thrust to a chemical rocket of the same diameter for less dry mass), so it would be worth the extra mass- and thermal receivers/rockets in this size range are EXTREMELY cheap to manufacture compared to a comparable chemical rocket engine.

I find the estimate for the power plant and transmitter assembly wildly optimistic. The power plant alone will cost more than that (power plants have a lot of hidden regulatory costs), let alone the transmitter. What is the capacitor bank for? Capacitor banks are not cheap when trying to build any kind of significant capacity.

No, it's the OPPOSITE of cars. It's more like new and untested drugs, which actually start off by testing on animals, and then on poor (either economically, or in terms of chance of survival without a novel treatment, i.e. desperate) "volunteers", sometimes even in third-world countries (with some companies, especially the less ethical ones), because there's a chance it could kill them. You NEVER go straight to the high-value customers if there's a chance the new drug could kill them (trust me on this, I'm a biologist in real life). First you do mice, then you do monkeys, then you do healthy but poor volunteers (you need to see how it affects healthy individuals first), then sick volunteers who are desperate for a new option (and whose physicians have thus determined the potential benefit outweighs the potential cost for), and then finally you move to market with the drug. The same basic strategy applies to rockets.

Historically, this is not really true. The newest tech gets used on the most sophisticated rockets. The drug analogy is not necessarily a good one either, there are strict regulatory requirements for sufficient testing before bringing new drugs to the mass human market. Before those requirements were in place, new drugs were brought to the human market as quickly as possible with sometimes disastrous results. For that matter, drug companies still race to the human market because that's where the money is, all that testing is due to regulatory requirements and liability mitigation.

I'm not talking about a BDB based on new tech. For the zillionth time, I'm talking about a cheaper TEST PLATFORM. Play 0.24 a bit (like I've been doing for the past several hours), and see all the contracts to test new engines (I assume they've just been developed, within the continuity of KSP) in certain conditions, and then imagine something like that but strapped to the side of a Big Dumb Booster now that we already have tried-and-true chemical rocket designs (though I must point out they WERE NOT so tried-and-true back when the Sea Dragon was proposed in the 1960's...)

Don't use KSP to support real rocket science, it doesn't work. There's no need for a cheaper test platform, new engines are thoroughly tested on the test stand before ever being put on a real rocket. Using the new tech on a different test rocket other than its intended one only increases testing costs, because you still have to have a maiden flight for the full-on smart rocket. Better to launch a payloadless or cheap payloaded expensive launcher to validate the whole design if a test flight is necessary.

[Northstar1989]

We really don't know what the manufacturing costs will be, given that beamed power is not a solved problem by any stretch. Even if they do turn out to be much lower than conventional chemical rockets, I'd imagine that such propulsion would make its way into both smart boosters and BDBs if economically viable.

Beamed Power Thermal Rocketry is far from a "solved problem" in the same way as any other rocket propulsion technology (including chemical rockets)- it's a continuing "Area of Active Research", to borrow a term biologists like to use with still-unsolved problems...

But, it's not for lack of data, expertise, or understanding- only the actual willingness to invest large amounts of money building an entire rocket design on the concept (and this would likely be with a new start-up company, which is always risky no matter how good the idea: consider the example of the electric car company "Project Better Place", for instance- which had a GREAT idea, but crashed-and-burned due to terrible management).

In fact, people have written countless reports, presentations, and even a Doctoral Thesis or two on the subject.

See this page (and the thread at large) for additional reading on beamed power thermal rocketry:

http://forum.kerbalspaceprogram.com/threads/81147-Next-Generation-launch-technologies-achievable-with-CURRENT-technology?p=1210983&viewfull=1#post1210983

Of course, to get back to the subject of Big Dumb Boosters- since BDB's don't have to have a high success-rate, it enables you to utilize new, experimental technologies in them. The chance of failure of the experimental system factors into the overall chance of failure of the rocket, and if the cost of the experimental system is low to begin with (as with Microwave Thermal Rocketry- if you built an entire line of Big Dumb Booster off of them), then you can much more easily build a Big Dumb Booster with the experimental tech than you can a modern "smart booster" with the technology...

My other sub-point is that we should be utilizing Big Dumb Boosters built off cheaply-made experimental technologies to test out new propulsive systems, rather than smart boosters. If the cost of the payload is low and easily replaced (as with fuel.consumables), and the rocket is made to looser engineering standards to begin with (and thus has a high chance of failure WITHOUT the experimental tech not working), then it's much less of a big deal if the prototypes crash-and-burn. Especially if the experimental tech was also built to relatively loose engineering standards (and thus was built cheaply).

I find the estimate for the power plant and transmitter assembly wildly optimistic. The power plant alone will cost more than that (power plants have a lot of hidden regulatory costs), let alone the transmitter. What is the capacitor bank for? Capacitor banks are not cheap when trying to build any kind of significant capacity.

The capacitors/batteries are due to the fact that the power usage is intermittent- you only run the transmitters when you're actively launching a rocket, and spend the rest of the time charging up for the next launch- meaning you don't have to be able to produce at 10 or 20 or 100 MW continuously- a 2 MW plant charging 200 MW of capacitors will work just as well... Which is also why the costs *ARE* accurate for the power plant- you're talking about building a power plant at the nominal capacity, I'm talking about build a cheap (probably Natural Gas) power plant at a much lower nominal capacity and charging up capacitors for intermittent usage...

Historically, this is not really true. The newest tech gets used on the most sophisticated rockets. The drug analogy is not necessarily a good one either, there are strict regulatory requirements for sufficient testing before bringing new drugs to the mass human market. Before those requirements were in place, new drugs were brought to the human market as quickly as possible with sometimes disastrous results. For that matter, drug companies still race to the human market because that's where the money is, all that testing is due to regulatory requirements and liability mitigation.

When's the last time we've had "newer tech" in rocketry in any meaningful sense since the 1970's? Aside from incremental advances in composites and materials, the only company that has built anything that can in any sense of the word be called "innovative" in Space-X, with their work on low-cost reusable rockets. And they actually went back to OLDER Kerosene-LOX technology for that, due to its lower cost and greater simplicity than LH2/LOX (they're also looking at Meth/LOX for interplanetary stages, which is more expensive than both, but doesn't have any of the coking problems of Kerosene, or boil-off problems of LH2...)

Don't use KSP to support real rocket science, it doesn't work. There's no need for a cheaper test platform, new engines are thoroughly tested on the test stand before ever being put on a real rocket. Using the new tech on a different test rocket other than its intended one only increases testing costs, because you still have to have a maiden flight for the full-on smart rocket. Better to launch a payloadless or cheap payloaded expensive launcher to validate the whole design if a test flight is necessary.

Sometimes it does. KSP is designed to mimic real life rocket science, after all. Most of us wouldn't know half of what we do, or be having this discussion right now, if not for KSP.

There are times when it's best to perform ground-tests, and times where you really need to test a propulsive system in orbit. For the latter of those, it's better to strap a risky experimental technology to a Big Dumb Booster carrying a cheap payload than to a Smart Booster carrying an expensive payload (and, as the whole point of this thread goes- there's no reason to ever launch a cheap payload on a Smart Booster, when you could launch it on a Big Dumb Booster instead...)

Regards,

Northstar

Edited July 22, 2014 by Northstar1989

[cantab]

The capacitors/batteries are due to the fact that the power usage is intermittent- you only run the transmitters when you're actively launching a rocket, and spend the rest of the time charging up for the next launch- meaning you don't have to be able to produce at 10 or 20 or 100 MW continuously- a 2 MW plant charging 200 MW of capacitors will work just as well...

I'd like to see the capacitor bank that can sustain 200 megawatts for the duration of a rocket launch.

[Northstar1989]

I'd like to see the capacitor bank that can sustain 200 megawatts for the duration of a rocket launch.

You can always "Build It Bigger".

You have to remember we're not talking just one individual capacitor- at that scale we're talking rows and rows and rows of capacitors in an underground complex. We do that kind of thing all the time for the largest particle-colliders... (and for experiments into fusion power- the National Ignition Facility was used as the set for the warp core of the Starship Enterprise in Star Trek: Into Darkness, for instance)

Regards,

Northstar

Edited July 26, 2014 by Northstar1989

[KASASpace]

Okay, okay. So basically........ the best system is the one that's not there? Like, for example, if I had a launch vehicle capable of orbiting 10 tons and someone else had one that could orbit 15 tons, but mine was much more simple, then mine is the superior one?

This is kind of like the Saturn I. It's my favorite of all "classic" launch vehicles and was barely used for operational payloads. Now, the design used off the shelf components, like the Redstone tanks and the Jupiter tanks, plus the H-1s, which were based on a previously designed and built engine. So, the S-I stage is kind of a big dumb booster. But it wasn't extremely mass produced. But it was very reliable............

I actually like this concept. Perhaps by putting together multiple sounding rockets, we could have a first stage? But then again, we should probably used something like the Angara rocket family. It's basically a rocket, with the ability to add more boosters (identical to the core) to the side of the core. Only one core stage would be needed for the whole family, and then the rockets would overall be cheaper.

Would you consider arches to be easy to build and thus cheap? I don't why, but I have a strange affection towards arches, they're strong structures and quite simple to construct. The ROMANS built them, for aqueducts, for monuments, the Coliseum, etc. Perhaps alternating arches, made of steel? Wrapping around the first stage.

Now, another thing about boosters, did you know the structure of boosters was moved inside the tanks? This made the rockets lighter, but also a bit harder to produce, as you have to design the tanks to support it. So, perhaps, going back to the not so famous "corset" of the V-2/A-4, we could make rockets even cheaper.

On the reliability note:

Just test it and test it and test it and iron out every bug over a long period of time, get 99+% reliability, because they were only test launches.

Edited July 26, 2014 by KASASpace

[shynung]

Why waste so much on a Ferrari just to drive it once? Why not build a jalopy and then drive it off the cliff? It's cheaper to build something quickly. You just need it to work, you don't need it to be over-complicated. This happens too often. Look at the Space Shuttle, it has so much stuff and equipment on just the orbiter. Now, that is more like saving the front of the Ferrari, but you still lose the back side.

Most of the Shuttle orbiter's parts are designed to be used several times from the onset, including the heat shield. Compared to the orbiter itself, the external tank and solid rocket boosters are mere dumb aluminium tanks. So, it's more like losing some of the body panels every time the Ferrari is driven.

Unfortunately, true to the analogy, a Ferrari is still a Ferrari. Replacement parts for the orbiter are expensive, especially the individually-installed, specially-arranged heat shield (some of them even have odd shapes), along with the SSMEs. In the end, that keeps the launch costs of the Shuttle high, despite being reusable.

Edited July 29, 2014 by shynung

[Northstar1989]

Alright guys, so it was an awesome run as a Thread of the Month for July, and I thank everybody who posted on it.

Since I expect discussion to considerably die down from here, I figure I'd sum up the issue as I see it.

Basically, it boils down to this. Rockets that can carry things to space are big, EXPENSIVE machines due to their very precise engineering margins- despite there being no inherently high cost in the actual technology they involve (rocket engines, for instance, are actually CHEAPER, lighter, and more powerful than jet engines built to the same level of precision of a comparable size).

This leaves 2 solutions to get large total payloads to Low Earth Orbit:

(1) Build an EVEN BIGGER rocket, with lower precision in construction but much greater safety margins, to get the same payload to orbit much less efficiently. I.e. like the Sea Dragon- which would have been SEVERAL times the size of the Saturn V, but the payload to Low Earth Orbit was relatively much smaller due to the much larger safety margins. Such rockets are actually more reliable than traditional "Smart Boosters" due to the higher safety margins, and the potential to utilize large rocket engine clusters (think 21 nozzles of thrust- 3 of which could fail on any given launch) or just a single huge rocket engine with enormous safety margins. This is the "classic" Big Dumb Booster approach.

(2) Build a CHEAPER rocket- one in which the precision of engineering is low (allowing these rockets to fit the "dumb" part of "Big Dumb Booster" despite their small size), but the safety margins are similar to a "Smart Booster". This will lead to FREQUENT launch-failures, but unlike the Sea Dragon, you only use this style of rocket to lift payloads with low inherent value- like fuel, food, and toothpaste for astronauts. This is the "Bread Trucks were used to move Bread, not Brinks Trucks" approach to rocketry. You still need an alternative style of high-reliability rocket, such as Big Dumb Boosters styled after the Sea Dragon, to lift high-value payloads: such as live astronauts, valuable scientific instruments, and EMPTY interplanetary vessels or probes (you lift the fuel on Cheap-O-Fail rockets like the ones just described). The classic rocket in this category is the Aquarius- which would have amortized the launch failure rate approaching 1 in 3 over many launches through a small payload capacity of only 1-ton-to-orbit, and avoided risking damage to ground launch facilities or space infrastructure through sea-launches and a specialized depot to collect the supplies of multiple launches in orbit (before transferring them over to more expensive space stations like the ISS via orbital tug).

Both styles of Big Dumb Booster had much lower cost-per-kg to orbit that "traditional" Smart Boosters. Both would have had their own unique niches where they performed best (Aquarius for launch of consumables and fuel; Sea Dragon for launch of heavy, expensive payloads that you simply can't afford to lose- it would have been more reliable than a "Smart Booster"). Both would have had drawbacks- a high designed launch failure rate (and thus bad PR) for the Aquarius, a low mass-ratio for the Sea Dragon (a rocket several times the size of Saturn V, yet much cheaper and with only slightly larger payload capacity). Though, IMHO, the drawbacks of either would be well worth the benefits- as these rockets would be BY FAR the cheapest way to get mass to orbit, even today with the days of Space-X reusable rockets rapidly approaching.

Regards,

Northstar

P.S. For those interested, somebody actually made a working Sea Dragon mode for 0.23.5

http://forum.kerbalspaceprogram.com/threads/84810-Official-release-of-my-SeaDragon-mod!

Edited August 3, 2014 by Northstar1989

[Caroliano]

Just wanted to leave here an Elon Musk quote about this topic:

'Big Dumb Booster' usually refers to a pressure-fed stage. It usually means, minus the turbopump. I think that is actually not a good way to go. You want the turbopump, otherwise your rocket is just too heavy, because if you go with a pressure fed stage, your entire stage has to operate something like the chamber pressure, and you'll have a ton of pressure left there at the end of the flight. So it's just not a great way to go. Turbopumps are hard, but they're not that hard. They're just a spinning centripetal pump, that's tricky, but they're not that tricky. The hard thing about a rocket engine is just getting those last incremental seconds of ISP. That's where it's really quite difficult, and those last seconds of ISP matter a lot for something that's going to go beyond Earth orbit, where just every little tiny bit of ISP is important. So I really do think you just have to push everything to the limit in terms of advanced materials, smart design of everything, high efficiency engines, everything, it's all got to be pushed to the limit. What you don't want to do though is have insufficient margin in your engines and structure such that you have to rebuild them after returning them. That's, I think, an error that was made with the Shuttle. The SSMEs were just really difficult to reuse. They required a lot of inspection and parts replacement between flights. So I think we may need to back off a little bit on our chamber pressure, still aim for a high combustion efficiency but back off a little bit on chamber pressure.

He is really more a fan of re usability, and for that they need all the performance they can get reasonably

[Northstar1989]

Just wanted to leave here an Elon Musk quote about this topic:

He is really more a fan of re usability, and for that they need all the performance they can get reasonably

I respect and admire a lot of Elon Musk's work, bu what he's doing here is constructing a "Straw Man" argument to tear apart.

"Big Dumb Booster" doesn't necessarily equate to "no turbopump". though that's often the case due to the difficulties in constructing a space-grade turbopump (that is, onew that gets those "last few seconds of ISP").

The WHOLE IDEA behind a Big Bumb Booster is to use wide margins and throw away the whole approach of squeezing out those last few seconds of ISP. Your payload fraction plummets, but you get a MUCH CHEAPER cost per kg to orbit, at the cost of efficiency and reliability. As repeatedly stated, it doesn't work for ALL payloads, but it does work for cheap, easily-replaced payloads like fuel of space station consumables.

Big Dumb Boosters can in theory also be re-used, although they payoff for doing so is much less.

Regards,

Northstar