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

[sal_vager]

Interesting discussion Northstar, I've stuck this for July

[shynung]

The SATURN V is a example of the wish of the designers to have a cheap rocket with "old" technology. A big good rocket can not be made for our days...

You do know that the SLS is being developed, right?

[Esme]

I don't understand why no-one seems to be considering aerospike engines to make sure they get as much efficiency as possible. (As an aside, I wish that plug-nozzle engine in stock was properly named so, and that we instead had (a) a proper aerospike (where gases from the turbopumps create the pointy bit of the 'spike' and ( that the game allowed aerospike engines in anything other than the 1st stage of a ship. As far as I'm aware, there's no reason this shouldn't be possible (NB: I am not an expert in these matters - for all I know there might be perfectly good reasons why aerospikes aren't actually practical. But as well as more conventional ships, I would also love to build something along these lines: http://www.astronautix.com/craft/pegvtovl.htm. I'v tried, using lots of little radial engines, but I think the way drag works in-game militattes against that being terribly effective. Or maybe I'm jst quite bad at efficient designs!)

[mrfox]

The OTRAG (Orbital Transport und Raketen AG, or Orbital Transport and Rockets, Inc.), was a West German design from the 1970s.

Modular CPRUs (Common Rocket Propulsion Units) - Simple, steel cased pressure-fed rockets with almost no moving parts.

Bundled into clusters of varying sizes, depending on mission payload

And staging requirements

Over 6000 static tests firings were done, with total burning time approaching one million seconds.

And 14 suborbital test flights.

In terms of reliability, the CRPU was human-rated and had a confidence level higher than 6-sigma.

Such a shame it was shut down, mainly due to the political climate of its times.

Edited July 3, 2014 by mrfox

[ZedNova]

-snip-

That looks like a bundle of Chinese fireworks. Seems like a pretty cool concept though

[SUJETO]

[...]

yes but is another try of a lot of trys... like most projects may be more delayed and more costly. That only will be a reality when has his 3th successful launch

[YNM]

The OTRAG (Orbital Transport und Raketen AG, or Orbital Transport and Rockets, Inc.), was a West German design from the 1970s.

Modular CPRUs (Common Rocket Propulsion Units) - Simple, steel cased pressure-fed rockets with almost no moving parts.

http://www.astronautix.com/graphics/z/zotrstg2.jpg

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 ?

[Nibb31]

I don't understand why no-one seems to be considering aerospike engines to make sure they get as much efficiency as possible. (As an aside, I wish that plug-nozzle engine in stock was properly named so, and that we instead had (a) a proper aerospike (where gases from the turbopumps create the pointy bit of the 'spike' and ( that the game allowed aerospike engines in anything other than the 1st stage of a ship. As far as I'm aware, there's no reason this shouldn't be possible (NB: I am not an expert in these matters - for all I know there might be perfectly good reasons why aerospikes aren't actually practical. But as well as more conventional ships, I would also love to build something along these lines: http://www.astronautix.com/craft/pegvtovl.htm. I'v tried, using lots of little radial engines, but I think the way drag works in-game militattes against that being terribly effective. Or maybe I'm jst quite bad at efficient designs!)

An aerospikes is a nozzle design. Their main advantage is that they have the same efficiency at sea-level as in vacuum, which makes them good for SSTO applications. However, because there are no operational SSTO rockets, they have never been used. Aerospikes are usually less efficient that bell nozzles that are each taylored for a specific altitude range, which is actually good because you're staging anyway.

[Nibb31]

Such a shame it was shut down, mainly due to the political climate of its times.

There were all sorts of shady deals involved with OTRAG too, as well as some unfortunate launch site decisions (Zaire in the 70's and Libya in the 80's weren't the most stable places to invest in). The risk of technology proliferation, in addition to it going against Ariane, caused European governments to shut it down.

The idea of mass production of cheap elements rather than reusability of complex elements still has merits. The reusability camp won in the 70's with the Shuttle, but we all know how that turned out.

[shynung]

yes but is another try of a lot of trys... like most projects may be more delayed and more costly. That only will be a reality when has his 3th successful launch

The good thing is, NASA is committed to finishing the SLS (at least for now), so we should expect something useful out of it.

[monstah]

From the start of the game until the end (with mods like KSP interstellar which often needs fairly heavy lifters, and other difficulty/realism mods) I have about 5 designs.

Same with me here. My CommSats (and similar tiny payloads) on LKO are launched from a single long solid booster with a small upper stage running off a Lv-90. Struts? Whazzat?

(...)rarely used, total lagfest on my laptop

That one got me chuckling. I feel you, bro.

[78stonewobble]

I kinda see "space" as the well... ass end of some country. There are ressources and value to be found, but not in amounts that currently makes private enterprise interested. I think it will take government/public investment in infrastructure and access to make anything major happen there.

Personally, if it was up to me and it's not, I'd look into creating some sort of scheduled service to space and places to go.

I wouldn't necessarily call it Big Dumb Boosters... But just imagine what we could create with ie. 4-6 annual launches of a saturn 5 equivalent. Or enough launches to really take advantage from mass production.

As for places to go there. Perhaps some sort of production that benefits from microgravity, spacehotels or if those fails or are not ripe yet, drag a big honking metal asteroid close and mine it.

Let the government(s) handle the basic proof of concepts here (catching asteroids, mining, production in microgravity, living in space) and help with the biggest roadblock (cost of access to space). Then we let private enterprise build on that and do what it does best, find other things to produce in space, stripmine stuff efficiently, sell space tourism or mass production of parts (subcontract the big rocket).

The technology isn't there yet and the motivation to get it isn't there yet, but I have a hard time seeing us getting that technology, unless we as a society choose to get it or we get so desperate that we need it. Waiting til we absolutely need it, seems too risky for my liking.

[Northstar1989]

I think the point is still valid. Just because it's "dumb", made of steel, doesn't mean it isn't reliable, precise, or gets the job done. My wife has a $200 hybrid bike made mostly of steel. I have a $600 "cheap" road bike. Sure, I spend less energy getting from A to B, but I get flats between 2-10 times per year, and the mechanisms need fine tuning at least once a year. My wife's bike had 2 flats in 9 years, and seen a bike shop about as often. Her bike has even been in an accident with another bike (not mine), and not a dent. The other bike's wheel was completely destroyed. If it were a "mission", the steel bike would be able to carry on. The fancy one, not so much.

The point is, you can still get the job done with something simpler. Manage your requirements. Avoid scope creep. In the case of rocketry, I'm guessing fuel isn't the main cost driver. If that's the case, than the question "why bother with efficiency" is certainly pertinent.

Kind of my point- fuel isn't the cost-driver, so why bother with efficiency on the launch vehicles?

Steel (rather than aluminum, advanced alloys, and composites) rockets are cheaper (as steel is easier to machine), and more durable relative to the level of engineering that goes into the rocket- they're just not as efficient. But since efficiency isn't the main cost-driver, why bother using aluminum?

I've known a lot of engineers over the years (in fact, I come from an entire family of engineers- I'm the only non-engineer in the bunch), and they ALL seemed obsessed with efficiency in any design, really just because it's cool...

I've tried pointing out to a number of engineers that a bridge, building, or rocket could be built much more cheaply if less money was spent optimizing the design for efficiency, and just building "quick and dirty" with wide safety margins- but none of them ever seem to listen. I think a big part of the problem is that they don't count the engineering man-hours as part of the cost in their minds, since to them it's more like play than work when they're doing something they love...

Regards,

Northstar

Edited July 6, 2014 by Northstar1989

[Northstar1989]

The guys who build the probes wouldn't want their multi-billion robot to be launched on a rocket that was just slapped together. They want a rocket that can put their rocket on the correct trajectory with high reliability, no matter the cost.

This design could be used for "low-cost" stuff like some resupply missionsa to the ISS. Something that was proposed for the Aquarius rocket. And even then, the 1/3 success rate didn't convince anyone to actually fund the project.

http://upload.wikimedia.org/wikipedia/en/thumb/9/97/Aquarius_rocket.png/270px-Aquarius_rocket.png

The Aquarius was designed to allow a 1/3rd *failure* rate. That's a 2/3rd success rate, not a 1/3rd success rate. And that's not saying 1 in 3 launches WOULD fail- only that the rocket was designed with that considered as an acceptable failure rate:

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

Aquarius was designed for launch of things like fuel and ISS supplies to orbit, *not* probes or satellites- things that would be needed in bulk (necessitating many launches- as the payload capacity was low), and could be cheaply/easily replaced.

"ISS consumables demand alone supported between 17 and 80 metric tons of basic supplies annually, or 20 to 100 Aquarius launches per year."

Over the course of four or five dozen small launches like that (over the course of 1-2 years), the 1/3rd failure rate would have averaged out to statistical noise, and the overall cost-per-kg to orbit would have been extraordinarily low.

At $1,000/kg and $1 million/launch, with the rated 1000 kg/launch payload capacity, you could launch more than thirty 1000-kg payloads to LEO on an Aquarius (with an average of 20 payloads reaching LEO) for less than HALF the $61.2 million cost of a Falcon 9 v1.1 launch, which can lift 13,150 kg to LEO in each launch (http://en.wikipedia.org/wiki/Falcon_9_v1.1)

Aquarius could also be used to launch fuel for interplanetary missions (the mission profile called for automated docking and fuel transfer). The mission vehicles would be launched dry, and fueled up with Aquarius launches. Thus, the low-cost, easily-replaced component of missions (the fuel) would be launched on low-reliability vehicles, while the high-cost difficult-to-replace mission vehicles (probe missions, manned vehicles, etc.) would be launched on other high-reliability launch vehicles.

In fact, of the $700 million proposed development cost, only $150 million was for the Aquarius launch vehicle itself, the remainder was for the development AND launch of two unmanned orbital tugs (which would act as unmanned fuel tankers for fuel payloads) and a high-tech cryogenic-storage fuel depot. In summary, the designers made this historical analogy:

"Bread was delivered by a bread truck, not a Brinks truck"

All-in-all, a great example of another "Big Dumb Booster" design (so-called not for its payload capacity, but its low efficiency and cheap construction) that was rejected without very good reasons.

Regards,

Northstar

P.S. It's also worth mentioning that Aquarius was a SSTO design (reaching a very low 200 x 200 km orbit), utilizing LH2/LOX from the launchpad- meaning it had quite a bit of launch-vehicle dry mass that would also reach orbit with the payload. If the launch stages were towed to "graveyard" orbits by orbital tugs, instead of de-orbited as planned, then you would have a substantial basis for an orbital-scrapping operation some day in the future...

Each Aquarius was planned to have a dry mass (after disposing of all propellant, RCS propellant, and tank pressurant) of 10.0 tons (with a 0.5 ton margin). Meaning each launch really nets you a 1.0 ton payload, and a separate 10.0 ton piece of scrap material- some components of which you could eventually (with further developments in orbital infrastructure) recycle to build things in orbit...

Edited July 6, 2014 by Northstar1989

[Claw]

You raise a lot of good points, and I'm not necessarily arguing one side or the other. I have an engineering background and and I understand the efficiency thing. Although I think your analogy of the bridge might be a little oversimplifying the problem. Also consider if every bridge, building, car, ship, and anything else was simply looked at as "eh, good enough" and double engineered, there would be half as much steel and other resources available.

If you have to spend the time to engineer the bridge, you might as well design to the needs.

However, I still see your point. I agree that it would be nice if we could pump out cheap rockets. It's not really so much about enginering efficiency, is that people in general cannot stomach the thought of failure (I guess I can only speak to this from an American perspective). If someone were to propose to congress (and ask for money for) a rocket that will fail 1 out of 3 times, I think they would be unimpressed even if it was incredibly cheap. And the American public would probably feel like their space program was in shambles, even if it was sending up 100s of successful launches each year. Unfortunately perceptions and impressions are a real motivator.

"ISS consumables demand alone supported between 17 and 80 metric tons of basic supplies annually, or 20 to 100 Aquarius launches per year."

At $1,000/kg and $1 million/launch, with the rated 1000 kg/launch payload capacity, you could launch more than thirty 1000-kg payloads to LEO on an Aquarius (with an average of 20 payloads reaching LEO) for less than HALF the $61.2 million cost of a Falcon 9 v1.1 launch, which can lift 13,150 kg to LEO in each launch

I think one of the fallicies here is to first believe that the launches would cost exactly what is predicted. I know of very few government projects of this scale of undertaking that comes in on budget. Just a side note.

The other thing to consider is that 100 launches per year means the space station would be receiving a ship every three days. I would argue you would probably need a person on board whose sole purpose would be to track incoming and outgoing ships, manage docking operations, and do all of the logistics movement. Not to mention that the station's docking system would have to be pretty heavy duty to absorb that much use.

That's compared to something like the Falcon example you used, at 13t per launch. So now it's at 7 or 8 launches per year. Once every six weeks and less than one-tenth the wear on the station for docking. I'm sure we could do a back-and-forth about how much work the crew does moving supplies, but also consider you're exposing them to one-tenth the docking risks.

Also, if the system relies on using the launch pad every three days, what happens if one of those failures wipes out the pad? Sure, that's always a risk with any launch platform. So you'd need a backup. But now we also have to consider the frequency of the launches as well as the failure rates. That's more risk to the pad, not to mention the resulting cleanup and rebuild. Extra launch pads and infrastructure aren't free.

I suppose that all sounds like I'm arguing against cheap vehicles. I don't mean to sound overly negative about them because personally I think we should be willing to back down from "top of the line, state of the art" from time to time. That philosophy itself becomes crippling. Hopefully I was just bringing forward some other things to think about. Efficiency isn't always about "the cheapest thing," but also about the stuff that surrounds it. The bits I mention above are just a few of those things.

[Winter Man]

At $1,000/kg and $1 million/launch, with the rated 1000 kg/launch payload capacity, you could launch more than thirty 1000-kg payloads to LEO on an Aquarius (with an average of 20 payloads reaching LEO) for less than HALF the $61.2 million cost of a Falcon 9 v1.1 launch, which can lift 13,150 kg to LEO in each launch (http://en.wikipedia.org/wiki/Falcon_9_v1.1)

Doesn't stack too well against the 9-R though, does it. $7m a launch for a 13 tonne payload blows Aquarius out the water.

[shynung]

Doesn't stack too well against the 9-R though, does it. $7m a launch for a 13 tonne payload blows Aquarius out the water.

I didn't know Elon has let out F9R price tags lately. Where did you read it?

[Kryten]

Doesn't stack too well against the 9-R though, does it. $7m a launch for a 13 tonne payload blows Aquarius out the water.

Remember that SpaceX initially gave Falcon 9 price at $27 million; it ultimately cost at least twice that. If that's the best they can do for a pretty conventional vehicle, I wouldn't pay any attentions to their predictions for reusable ones.

[maccollo]

Doesn't stack too well against the 9-R though, does it. $7m a launch for a 13 tonne payload blows Aquarius out the water.

F9R wont have the the full payload capacity of the expendable version. If I remember right Elon said he thinks the payload capacity would be cut by about 30-40%.

[R0cketC0der]

F9R wont have the the full payload capacity of the expendable version. If I remember right Elon said he thinks the payload capacity would be cut by about 30-40%.

The 13 tons that they are currently offering are already 30% lower than what the expandable version would be capable of so SpaceX can do their tests for the reusable version.

[shynung]

-snip-

There's more about Aquarius here.

[Javster]

The whole concept of Keep It Simple Stupid is what made that idea happen, IMO. I don't know if that applies today.

[Northstar1989]

You raise a lot of good points, and I'm not necessarily arguing one side or the other. I have an engineering background and and I understand the efficiency thing. Although I think your analogy of the bridge might be a little oversimplifying the problem.

Oversimplifying, perhaps- but it cuts to the heart of the issue.

Also consider if every bridge, building, car, ship, and anything else was simply looked at as "eh, good enough" and double engineered, there would be half as much steel and other resources available.

The answer to that is simple supply/demand/price economics. Engineers would usually take the double engineered "good enough" approach until rising steel/resource/labor prices made the finely-engineered approach cost-competitive. At which point, an equilibrium would be reached, with engineers making use of each approach some percentage of the time (or competing firms making use of both approaches), with fluctuations in the balance commensurate with fluctuations in steel prices...

True, rising steel prices would place pressure on others sectors of the economy- but there would also be economic benefits from the increased availability of engineering labor (which would otherwise be spent more carefully designing infrastructure), increased employment of manual/menial laborers (who tend to have difficulty finding jobs- cheaper infrastructure means more infrastructure will be built and more construction jobs as a result), increased infrastructure (lower prices means more would be built), increased mining/steel-making revenues, and reduced failure rates of infrastructure (counter-intuitively, double engineered infrastructure tends to fail LESS often due to its wider safety margins).

If you have to spend the time to engineer the bridge, you might as well design to the needs.

But you DON'T have to spend the time to finely engineer the bridge, or the rocket- at least not most of the time.

However, I still see your point. I agree that it would be nice if we could pump out cheap rockets. It's not really so much about enginering efficiency, is that people in general cannot stomach the thought of failure (I guess I can only speak to this from an American perspective). If someone were to propose to congress (and ask for money for) a rocket that will fail 1 out of 3 times, I think they would be unimpressed even if it was incredibly cheap.

I don't know- money talks. Especially when you make the case to the Congressmen about all the tax rebates for corporations/their constituents (I think we all know which they care about more these days...) they could fund with the cost-savings to NASA (assuming reduced launch costs were coupled with budget cuts...)

And the American public would probably feel like their space program was in shambles, even if it was sending up 100s of successful launches each year. Unfortunately perceptions and impressions are a real motivator.

But our space program IS in shambles- at least compared to where it was 40 years ago. We are, as has been repeatedly pointed out, the only country to ever WILLINGLY give up the ability to go the the Moon... (the Soviets gave it up as well- but not willingly. Their economy was in shambles, and we had several high-ranking government officials on the CIA payroll, trying to destabilize the USSR from the inside- as was recently declassified...)

I think one of the fallicies here is to first believe that the launches would cost exactly what is predicted. I know of very few government projects of this scale of undertaking that comes in on budget. Just a side note.

True- but a cheap launch program that comes in over-budget is still likely going to be a lot cheaper than an expensive launch program that comes in over-budget...

The other thing to consider is that 100 launches per year means the space station would be receiving a ship every three days. I would argue you would probably need a person on board whose sole purpose would be to track incoming and outgoing ships, manage docking operations, and do all of the logistics movement. Not to mention that the station's docking system would have to be pretty heavy duty to absorb that much use.

The International Space Station actually already does get quite a bit of traffic- most of the time there are at least two other vessels docked to it, one of them almost always a resupply ship.

And the astronauts already share the responsibility of unloading cargo pretty evenly as part of their current duties- the total amount of cargo to unload wouldn't change.

But the biggest problem with what you say is that this isn't actually how Aquarius would have worked- the $700 million development proposal called for the development of a LEO consumables depot (for not only fuel, but food) at which the supplies would be consolidated. From there, larger but more infrequent trips would have been made by a space tug to carry the cargo to the International Space Station in larger payload packets...

The depot could have apparently been designed explicitly for the high docking frequency- and it would have been unmanned (so no crew member would be required to oversee docking operations).

That's compared to something like the Falcon example you used, at 13t per launch. So now it's at 7 or 8 launches per year. Once every six weeks and less than one-tenth the wear on the station for docking. I'm sure we could do a back-and-forth about how much work the crew does moving supplies, but also consider you're exposing them to one-tenth the docking risks.

Somebody already thought of this. With the Aquarius' space tug, which was part of the (very reasonable) $700 million development proposal, you could have actually delivered LARGER cargo packets than 13 tons, at reduced frequency, for reduced wear and docking risks to the station.

Also, if the system relies on using the launch pad every three days, what happens if one of those failures wipes out the pad? Sure, that's always a risk with any launch platform. So you'd need a backup. But now we also have to consider the frequency of the launches as well as the failure rates. That's more risk to the pad, not to mention the resulting cleanup and rebuild. Extra launch pads and infrastructure aren't free.

I think you might need to review the description of Aquarius again. It doesn't launch from a launchpad- it makes use of sea-based launches (and the consumables would be scheduled to launch "ahead of need" to the LEO depot- so a handful of launch failures in a row wouldn't deprive the ISS of needed consumables). The ocean is the Aquarius' launchpad, much like the Sea Dragon. Now how are you going to break THAT launchpad?

I suppose that all sounds like I'm arguing against cheap vehicles. I don't mean to sound overly negative about them because personally I think we should be willing to back down from "top of the line, state of the art" from time to time. That philosophy itself becomes crippling. Hopefully I was just bringing forward some other things to think about. Efficiency isn't always about "the cheapest thing," but also about the stuff that surrounds it. The bits I mention above are just a few of those things.

All of the potential issues for an Aquarius-style Big Dumb Booster you brought up are valid- but were already addressed, and satisfactorily resolved, years before I ever created this thread. Aquatic launches and a LEO consumables depot deals with most of the issues of high launch frequency and small payload packet-size, for instance.

Regards,

Northstar

[Northstar1989]

The whole concept of Keep It Simple Stupid is what made that idea happen, IMO. I don't know if that applies today.

Aquarius was less than 10 years ago (proposed for a 2005/2006 initial launch). And Sea Dragon, though older, should still work perfectly well with today's technology.

How could the golden, beautiful rule of KISS (Keep It Simple Stupid) possibly ever become outdated???

Regards,

Northstar

[Whirligig Girl]

I wrote a blog post about the BDB.