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

[Guest]

Actually, it is often used for a pressure-fed stage. But that's beside the point. Single stage, expandable rockets with high safety margins and (comparatively) low payloads are the original meaning, and that's a viable approach. Say, two or three engines, made cheaply (by sacrificing efficiency, not reliability), topped by a single, thick-walled tank and a small, solid kick stage. What you get is nearly-SSTO rocket that leaves few debris, uses cheap technology (small solids are cheap) and doesn't cost much. Or just cut the liquid stage altogether and slap a large, dual-nozzle SRB (so that roll control isn't a problem) and a small one together, add fairings and voila! It would likely be even cheaper than anything liquid, SRBs are rather inexpensive.

There is a trend towards things like this. All-solid rockets are the mainstay of American small LV market, so it's just a matter of reducing staging equipment and number of boosters. I think it's just a matter of time before somebody figures out that strapping a Star-48 atop a modified 4-segment RSRM might be a good idea (you can even re-use the RSRM afterwards). It won't carry much, but it could rather cheap.

[Northstar1989]

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

I don't think I ever addressed this point, by the way.

The whole point behind an Aquarius-style Big Dumb Booster (as opposed to a Space Dragon-style BDB, which is entirely different) is that you end up mass-producing the rockets for the CURRENT payload-to-orbit being sent up each year, TODAY AND NOW, rather than needing to increase the annual launch mass (a difficult and expensive proposition) in order to reap the benefits of mass production.

Let's make up some numbers:

Take the fact that an Aquarius is projected to launch 1 ton to orbit per launch.

Compare that to a Smart Booster that might launch say, 12 tons to orbit per launch (there are actual Smart Boosters in this size range)

Let's say that you need to launch 24 tons of low-value consumables to orbit a year. This figure isn't *too far* from the real one: the ISS requires approx. 9.07 metric tons of consumables a year according to a Lockheed Martin article on ISS consumables. Other consumables include station-keeping fuel for fresh satellite launches (you launch the satellite empty on a Smart Booster, and rendezvous with the Aquarius, the Aquarius fuel-depot, or Aquarius tug, in LEO to transfer over the station-keeping fuel), consumables for other space stations, etc...

To launch that with Aquarius-style BDB's, you would need to build 36 rockets a year (3 rockets a month, with a 33% failure rate)- reaping some of the benefits of mass production, as well as reduced ground infrastructure costs (which tend to decrease *SHARPLY* with increasing launch frequency) etc.

To launch that with a 12-ton Smart Booster, you would launch just over 2 rockets per year (with a *very low* failure rate). That leaves your launchpad and production facilities idle most of the year, and drastically drives up the cost of getting these low-value consumables to orbit.

Even with a *much lower* estimate of annual low-value consumables launches of just 12 tons (assuming the vast majority of satellites launch with their station-keeping fuel onboard rather then going for the cheaper option of utilizing Aquarius' orbital consumables-depot system for this purpose, and 75% of all Aquarius payloads utlimately go to the ISS), you still have 18 launches a year vs. just 1 Smart Booster launch a year to orbit this same quantity of supplies.

The economic benefits of an Aquarius-style Big Dumb Booster should be *OBVIOUS*.

Regards,

Northstar

P.S. Please remember that Aquarius' $700 million development budget also included the costs for developing AND launching (atop a separate Smart Booster) a LEO "consumables-depot" where Aquarius launches would accumulate needed consumables ahead-of-need, as well as a small reusable chemical-propelled (non-nuclear) "orbital tug" to move these supplies (in larger increments of maybe 10 or 12 tons at a time- each Aquairus only launches 1 ton at a time) from the depot to the ISS and other destinations as-needed.

Edited August 22, 2014 by Northstar1989

[Kryten]

Let's say that you need to launch 24 tons of low-value consumables to orbit a year. This figure isn't *too far* from the real one: the ISS requires approx. 9.07 metric tons of consumables a year according to a Lockheed Martin article on ISS consumables. Other consumables include station-keeping fuel for fresh satellite launches (you launch the satellite empty on a Smart Booster, and rendezvous with the Aquarius, the Aquarius fuel-depot, or Aquarius tug, in LEO to transfer over the station-keeping fuel), consumables for other space stations, etc...

To launch that with Aquarius-style BDB's, you would need to build 36 rockets a year (3 rockets a month, with a 33% failure rate)- reaping some of the benefits of mass production, as well as reduced ground infrastructure costs (which tend to decrease *SHARPLY* with increasing launch frequency) etc.

To launch that with a 12-ton Smart Booster, you would launch just over 2 rockets per year (with a *very low* failure rate). That leaves your launchpad and production facilities idle most of the year, and drastically drives up the cost of getting these low-value consumables to orbit.

In reality, the rocket responsible for sending most supplies to the ISS flies about 16 times a year; because it can do the kind of missions aquarius isn't capable of doing; crewed and high-energy ones. Aquarius is restricted to a tiny portion of the actual demand: economies of scale will work against it, not with it.

[Northstar1989]

Not to necro this thread, but this is still an interesting topic worth discussing...

In reality, the rocket responsible for sending most supplies to the ISS flies about 16 times a year; because it can do the kind of missions aquarius isn't capable of doing; crewed and high-energy ones. Aquarius is restricted to a tiny portion of the actual demand: economies of scale will work against it, not with it.

Oh, and that's not right at all. Aquarius benefits from economies of scale by having incredibly low payload-capacity (only 1 metric ton per launch). Thus, even with the limited portion of demand it is restricted to (payloads with low intrinsic value- such as ISS consumables and fuel for missions beyond LEO), it still can be mass-produced (it would take 60-100 launches a year just for ISS consumables).

Of course, it's not the only game in town for low-cost launches relying on mass-production and low payload-capacities. There is also the Microwave Beamed Power approach being developed by Escape Dynamics, for instance, which can easily be scaled-up for manned missions:

http://nextbigfuture.com/2014/02/escape-dynamics-and-microwave-power.html

Ultimately, only one low-cost launch system can succeed. Big Dumb Boosters. Microwave Beamed Power spaceplanes (the much higher ISP makes spaceplanes much more feasible). Conventional spaceplanes. StarTram-style mangetic launch-assist. I just hope ONE of them makes it to operation in the next 20-30 years...

Regards,

Northstar

[magnemoe]

Not to necro this thread, but this is still an interesting topic worth discussing...

Oh, and that's not right at all. Aquarius benefits from economies of scale by having incredibly low payload-capacity (only 1 metric ton per launch). Thus, even with the limited portion of demand it is restricted to (payloads with low intrinsic value- such as ISS consumables and fuel for missions beyond LEO), it still can be mass-produced (it would take 60-100 launches a year just for ISS consumables).

Of course, it's not the only game in town for low-cost launches relying on mass-production and low payload-capacities. There is also the Microwave Beamed Power approach being developed by Escape Dynamics, for instance, which can easily be scaled-up for manned missions:

http://nextbigfuture.com/2014/02/escape-dynamics-and-microwave-power.html

Ultimately, only one low-cost launch system can succeed. Big Dumb Boosters. Microwave Beamed Power spaceplanes (the much higher ISP makes spaceplanes much more feasible). Conventional spaceplanes. StarTram-style mangetic launch-assist. I just hope ONE of them makes it to operation in the next 20-30 years...

Regards,

Northstar

An downside with one ton to LEO is that you would need to dock with IIS so you will need an functional spacecraft capable of doing this, it will cut into your useful payload a lot.

Add the extra work docking all the small crafts.

Also an decent chance the stuff sent up is an mix between life support and stuff needed for experiments, some who are not cheap or easy to replace.

Launching smaller mass produced satellites irdium or gps might work better for an small launcher, they need specific orbits so you only launch that small payload.

[Rakaydos]

Hmm... Elon Munsk's description of BDBs makes me think they would be good for orbital refueling.

Send up a pressure fed stage, dock it with pressure left in the tanks. Pump the excess out to refuel better rockets, and repurpose the tanks as orbital consruction materials. Let anything you dont need decay into earth's atmo.

[Starman4308]

Well, as I see it: if the Big Dumb Booster concept made economic sense, people would be making BDBs. People aren't making BDBs. Therefore, BDBs don't make economic sense.

Part of it I suspect is the tyranny of the rocket equation: a heavy upper stage means a heavier lower stage. It makes a large amount of economic sense to optimize your upper stages. You could apply the BDB concept solely to the first stage, but that means development costs are going into a concept only used for one part of the rocket.

[Fuzzy Dunlop]

I think part of the problem is that while dumb can mean "cheap" big often means "much more expensive than first thought". It's the infrastructure cost as much as anything. I doubt Sea Dragon was meant to launch from the ocean right from the initial inception, but once on the drawing board it grew so huge that there was no economic way to handle it on land.

[NERVAfan]

Well, as I see it: if the Big Dumb Booster concept made economic sense, people would be making BDBs. People aren't making BDBs. Therefore, BDBs don't make economic sense.

I dunno - there have really not been that many orbital launch vehicles, and most of those come from really just 2-3 "traditions". There's plenty of room for cultural biases and historical contingencies to exclude plenty of viable options in a world that small (e.g. the SLS is being built the way it is to use Shuttle heritage, despite the fact that the reasons the Shuttle was designed the way it was don't apply to SLS at all).

New LV makers like SpaceX and India may be starting to change this, but the barrier to entry is so high that we're very far from exploring all viable options.

(And I think there is a strong cultural bias that space stuff is necessarily super-high-standards, super-expensive. Cubesats and SpaceX's vertical integration may be beginning to change this, too, but that will be a long process if it ever happens.)

[Frozen_Heart]

I think that the BDB concept would have been brilliant for quite a long time. However reusable rockets may change that in the future.

I hate the concept of throwing parts of the vehicle away. However carefully designing it with the most high tech stuff possible, and then throwing it away is an even worse way of dong things. BDBs could save a lot of money while doing the same job. Sure it would take more fuel but that is a tiny part of the overall cost.

BDBs vs re usable rockets is something else though. Being able to reuse them may save more than even a very simple expendable rocket.

[John FX]

Very kerbal design IMO... but that's a really modular concept !

Now, who's going to launch Apollo-style Mun mission with just a bunches of S1 SRB-KD25k for launching it into Kerbin orbit ?

Actually, now we have costs in career mode that is exactly how I launch most of my craft. Unless I am going for historical accuracy.

I have a bunch of the largest SRB, a few of the medium and some small ones as the three lifter stages and I tailor the thrust and fuel to get a pretty good orbit so that the last stage burns up and the payload needs minimal fuel to attain orbit.

It`s really cheap.

As far as I know, in RL an SRB is as reliable as any other rocket type. They are human rated anyway.

EDIT :

Hmm... Elon Munsk's description of BDBs makes me think they would be good for orbital refueling.

Send up a pressure fed stage, dock it with pressure left in the tanks. Pump the excess out to refuel better rockets, and repurpose the tanks as orbital consruction materials. Let anything you dont need decay into earth's atmo.

I made a station guide using almost exactly that concept, although I had not heard it until now. You send up a lot of large SSTO which act as your fuel store and they form a station which is a utility base for future missions. Some craft use karbonite for easier gamepley in KSP but most craft are stock and one acts like a refueller.

It`s here if anyone would like a look.

http://forum.kerbalspaceprogram.com/threads/97475-Standard-Utility-Construction-Kit

Edited December 11, 2014 by John FX

[Northstar1989]

Actually, now we have costs in career mode that is exactly how I launch most of my craft. Unless I am going for historical accuracy.

I have a bunch of the largest SRB, a few of the medium and some small ones as the three lifter stages and I tailor the thrust and fuel to get a pretty good orbit so that the last stage burns up and the payload needs minimal fuel to attain orbit.

It`s really cheap.

As far as I know, in RL an SRB is as reliable as any other rocket type. They are human rated anyway.

In KSP, SRB-based lifters are much cheaper than liquid rockets, but still not nearly as cheap as a Space-X style launch using liquid rockets. There is no way to built rockets to looser engineering standards, and accept the necessary hit in payload fraction that entails, opting for just building it bigger instead (which is the entire principle behind a Big Dumb Booster- i.e. that a rocket with 1/3rd the payload-fraction due to looser engineering standards might cost a lot less than 3 times a much per ton of rocket0 and can thus be built bigger/heavier instead...)

What I'd REALLY like to see is a realistic and tweakable relationship between part mass and cost in Procedural Parts mod (so I can use much heavier parts with much lower cost to approximate the Big Dumb Booster concept...)

Regards,

Northstar

P.S. The parts in a Big Dumb Booster aren't *necessarily* heavier in real life- but instead are built to a much wider tolerance of masses and strengths. If a part could be as much as +/- 10% the designed strength, then you need to design it with 10% extra strength in case it ends up on the weaker end, for instance. With the Rocket Equation, even such small extra tolerances rapidly add up into greatly-diminished payload-fraction (but at the benefit of much lower cost-per-kg).

Alternatively, you can go the way of Aquarius and combine the extra mass/strength variance with slim engineering margins for a high failure rate overall (as much as 1 in 3 for the Aquarius rocket). But that's not really a Big Dumb Booster in the truest sense of the word- as it is not necessarily any larger than a comparable-capacity "Smart Booster", only dumber to bring down costs...

[Bill Phil]

I think that if there were bigger margins on launch vehicles, then they could be made cheaper. For example, if everything is running less than its full potential, and one engine fails, you can proportionally increase the thrust of the others to help account for that.

[meve12]

Hmm... Elon Munsk's description of BDBs makes me think they would be good for orbital refueling.

Send up a pressure fed stage, dock it with pressure left in the tanks. Pump the excess out to refuel better rockets, and repurpose the tanks as orbital consruction materials. Let anything you dont need decay into earth's atmo.

I dunno about this whole BDB aproach to refueling.

I mean, there's asteroids (And Deimos and Phobos) up there with water ice already. Might as well use Kuck mosquitos to refuel your depot.

(You'll need a chemical plant to synthesize hydrogen peroxide for propellant, of course. Plus enough power for that and to electrolyze the ice.)

Initial cost'll be steep, though. At least three superheavy launches I think, one for the Mosquito, one for the chemical plant+solar panels, and one big dumb tank for an ice depot. After that, though, it practically pays for itself.

[Exoscientist]

The NASA developed Morpheus lander now makes easy suborbital spaceflight since NASA has opened up NASA developed technology to commercial licensing:

NASA Technology Transfer for suborbital and air-launched orbital launchers.

I don't think NASA fully appreciates the usefulness of the Morpheus development. Here I'll show how the Morpheus itself can be used to produce suborbital launchers, and also the stages for orbital launchers. For instance the Morpheus can be used to provide the solution to DARPA's ALASA air launched, small orbital system.

http://exoscientist.blogspot.com/2015/01/nasa-technology-transfer-for-suborbital.html

Bob Clark

Edited January 24, 2015 by Exoscientist

[Nibb31]

The NASA developed Morpheus lander now makes easy suborbital spaceflight since NASA has opened up NASA developed technology to commercial licensing:

NASA Technology Transfer for suborbital and air-launched orbital launchers.

I don't think NASA fully appreciates the usefulness of the Morpheus development. Here I'll show how the Morpheus itself can be used to produce suborbital launchers, and also the stages for orbital launchers. For instance the Morpheus can be used to provide the solution to DARPA's ALASA air launched, small orbital system.

http://exoscientist.blogspot.com/2015/01/nasa-technology-transfer-for-suborbital.html

Bob Clark

That blog post has been removed. But what has Morpheus got to do with Big Dumb Boosters ?

Edited January 22, 2015 by Nibb31

[Louella]

I think large, simple rockets have a role to play in space, but the requirement for that role has not as yet arisen.

they make sense for large, cheap payloads, with losses being acceptable.

This makes them suitable for doing several things, such as for supply missions for colonisation of Mars. Not for Mars exploration, but for colonisation. Launch a few thousand big cheap rockets, with supplies, with the understanding that not all of the supplies will reach Mars.

There is a comparison, or a couple of them, from the 2nd world war. The British Sten gun, designed when the threat of invasion was highest, could be made by almost any workshop, with as little as 5 man-hours of work, instead of by the specialised firearms manufacturers, who were under pressure. The early models were very basic, while later models, produced after the threat of invasion had diminished, were higher standard.

The more relevant comparison, is I think, the Liberty ship. These ships, built from standardised parts, could be built by all sorts of engineering fabricators, not just shipyards. They were cheap and quick to build. They were not the most finely built ships in use, but they did the job, and were a large factor in the outcome of the war.

Big Dumb Boosters would be the rocketry equivalent of the Liberty Ship. Simple, cheap, and can be built by manufacturers other than rocketry builders.

For when you need a lot of stuff put into space, at as cheap a cost as possible, with the understanding that not all of them will succeed.

However, we currently don't live in a situation where space exploration/exploitation/colonisation needs a Liberty Ship equivalent. For better or worse.

[Bryce Ring]

Bob that link had some garbage at the end of the link address.

%EF%BB%BF

http://exoscientist.blogspot.com.au/2015/01/nasa-technology-transfer-for-suborbital.html%EF%BB%BF

this one worked.

http://exoscientist.blogspot.com.au/2015/01/nasa-technology-transfer-for-suborbital.html

[Kruleworld]

I do agree there is a lot of 'elitism' in the rocketry fields.

[Exoscientist]

Bob that link had some garbage at the end of the link address.

%EF%BB%BF

http://exoscientist.blogspot.com.au/2015/01/nasa-technology-transfer-for-suborbital.html%EF%BB%BF

this one worked.

http://exoscientist.blogspot.com.au/2015/01/nasa-technology-transfer-for-suborbital.html

Thanks for noticing the garbled link. I corrected the link in that prior post.

Bob Clark

- - - Updated - - -

Big dumb boosters are supposed to be very simple designs. For one thing they use the much simpler pressure-fed engines rather than turbopumps. Indeed, about the complexities of developing turbopump-powered rocket engines, a saying among rocket engineers is "orbital systems are turbopump developments with rockets attached."

The simplicty of pressure-fed engines has allowed many amateurs to build such engines in their backyards. More advanced amateurs have used them to also launch rockets. The Morpheus lander uses pressure-fed engines and is suborbital capable. That NASA is now allowing commercial licensing of their technology means the many amateur and commercial concerns building pressure-fed rockets can now actually accomplish suborbital launches.

Big dumb boosters though are thought of as orbital systems. However, with staging suborbital rockets can be used to produce orbital rockets.

Bob Clark

Edited January 25, 2015 by Exoscientist

[Pds314]

You've gotta run the numbers to see if it works out. Lets say that your budding space program is building a rocket to land on the moon, and you have the option of using solid motors and hybrid solid-liquid ones, at 250 ISP, or Hydrogen, at 450 ISP.

18 km/s is what you need in delta-v. Let's assume that in each design, each stage is 5% non-fuel, and that the hydrogen rocket has 5 stages. The final one that returns being 5 tonnes dry.

Each stage has 3.6 km/s of delta-v.

So the rocket would weigh 430 tonnes at launch. Note that these numbers are optimistic, as in reality, the dry mass of the landing stage will be much higher. If the stages took 15% of the mass, we'd see a rocket at something like 900-1000 tonnes. Realistically, spent stages have quite significant masses, and low altitude performance is low.

Now if we have solids at 5% mass, we have 9 stages... And a whopping 15000 tonnes of booster. Remember, this is with the same formula that gave hydrogen boosters 430 tonnes for the same mission.

And 15% basically becomes madness. 53000 tonnes of MOAR BOOSTERS to accomplish the same task as 1000 of efficient rocket, and scaling solid motors to where the bottom stage weighs 30,000 tonnes wouldn't be simple or cheap to do.

At some point, a clever economist might ask why not go to orbit using gunpowder in an iron keg at 150 ISP? Why not is because having 9 stages, each almost twice as big as the last, ends up making a rocket with 10000 tonnes of boom barrel for every tonne of payload to LEO. Sure, it might be technically possible, but it's really not a good idea when modern hydrogen vehicles can get payload fractions of almost 4%. There is no way that making a reliable rocket out of iron boom barrels is 400 times cheaper per kg than modern rocketry.

- - - Updated - - -

As has been mentioned elsewhere, any rocket with an ISP lower than around 1/6th it's mission delta-v is probably cost-prohibitively massive. There are places and times for big dumb boosters with low payload fractions, but they aren't particularly affordable for trying to reach orbit or beyond in real life, due to the tyranny of the rocket equation.

Edited January 25, 2015 by Pds314

[Kryten]

The Morpheus lander uses pressure-fed engines and is suborbital capable.

This is nonsense. It barely hits 200m.

[Pds314]

This is nonsense. It barely hits 200m.

Technically, I believe that does qualify as a suborbital trajectory.

[sgt_flyer]

Technically, I believe that does qualify as a suborbital trajectory.

i think you need to hit the karman line (100km) before getting back on earth to qualify as suborbital

[Newt]

Well, while it was a trajectory that was definitely not an orbit, it was not suborbital spaceflight. That is what we are talking about here, and space is defined as that which is beyond Karman line.