Author Topic: Why have no flyback boosters ever ben fielded?  (Read 12103 times)

Offline Nickolai

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Why have no flyback boosters ever ben fielded?
« on: 05/03/2009 12:33 am »
Hi, I'm quite new to this forum and this is my first new topic. I hope people will find my query interesting and maybe someone can provide some insight.

I've been doing some research lately on the idea of a flyback booster. There are a LOT of studies out there ranging from the 1950's to as recently as the 1990's (and who knows, maybe there was an even more recent study that I haven't seen).

These studies have a vast range in their concept designs: there's Vertical-Takeoff-Vertical-Landing (VTVL) variants, Horizontal-Takeoff-Horizontal-Landing(HTHL) variants, air-breathing first stages, SSTO's, TSTO's, fully reusable, partially reusable, and virtually every combination of those factors you can imagine (except perhaps some outlandish ones like HTVL SSTO!)

Virtually every study suggest major cost benefits, yet none have flown. Even as new rockets are desgined and built, no one is fielding a flyback booster. Elon Musk says he'd love to have a flyback booster, but that it's too much of a technical/financial challenge to achieve at the moment. Khrunichev proposed a flyback booster known as Baikal and even built some mock-ups, though it seems that there is not work progressing towards building it.

So my question is, why is there no flyback booster making its way back to an airfield today? Has it been a largely financial/political stumbling block? Or is there a major technical issue with throwing wings, landing gear, and a guidance system onto a booster? It seems like such an obvious thing to do, which is why I'm so curious.

Thanks for listening, and please feel free to comment even if you don't think you have an exact answer to my question.

Note: See http://www.astronautix.com/lvfam/winged.htm for some more info on those previous studies.

Offline Bubbinski

Re: Why have no flyback boosters ever ben fielded?
« Reply #1 on: 05/03/2009 01:40 am »
That's a very good question, I'd be interested in some of the answers myself.  I remember reading about a plan to develop liquid flyback boosters for the space shuttle, there was some talk I was seeing on the web before the Columbia disaster. 

I wonder if a future LFBB would be best used as an SRB replacement or if it would have some utility as a stand alone satellite launcher (perhaps with an upper stage mounted on its back?).
I'll even excitedly look forward to "flags and footprints" and suborbital missions. Just fly...somewhere.

Offline Jim

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Re: Why have no flyback boosters ever ben fielded?
« Reply #2 on: 05/03/2009 02:26 am »
Flight rates don't support the development costs

Offline Lee Jay

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Re: Why have no flyback boosters ever ben fielded?
« Reply #3 on: 05/03/2009 02:31 am »
Flight rates don't support the development costs

Let's say, hypothetically, that the SRBs were never developed and LOX-kero flyback boosters with 2 F1-class engines in each were instead.  Do you think the total cost of the entire STS program would have been significantly different?  If so, in which way?

Offline Nickolai

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Re: Why have no flyback boosters ever ben fielded?
« Reply #4 on: 05/03/2009 02:49 am »
Flight rates don't support the development costs

Naturally your answer would depend on the flight rates, so let me ask you this hypothetical question:

Say one of these concepts, by virtue of its reusability, managed to significantly lower the cost per kg to LEO (consider the just the flight cost with all the reusable hardware already built, so you just have to pay for refurbishment/refueling/expendable parts).

If this happened, wouldn't it drastically increase the launch market, which would then increase the flight rates?

Assuming this were true, the increase in flight rates would certainly change the way people look at those development costs.
« Last Edit: 05/03/2009 02:50 am by ntrgc89 »

Offline Jorge

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Re: Why have no flyback boosters ever ben fielded?
« Reply #5 on: 05/03/2009 03:22 am »
Flight rates don't support the development costs

Naturally your answer would depend on the flight rates, so let me ask you this hypothetical question:

Say one of these concepts, by virtue of its reusability, managed to significantly lower the cost per kg to LEO (consider the just the flight cost with all the reusable hardware already built, so you just have to pay for refurbishment/refueling/expendable parts).

If this happened, wouldn't it drastically increase the launch market, which would then increase the flight rates?

Assuming this were true, the increase in flight rates would certainly change the way people look at those development costs.

You still have a chicken and egg problem. The dramatic increase in flight rates would not occur until after the flyback booster starts flying, but you still have the high upfront development costs.
JRF

Offline Nickolai

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Re: Why have no flyback boosters ever ben fielded?
« Reply #6 on: 05/03/2009 03:46 am »
Flight rates don't support the development costs

Naturally your answer would depend on the flight rates, so let me ask you this hypothetical question:

Say one of these concepts, by virtue of its reusability, managed to significantly lower the cost per kg to LEO (consider the just the flight cost with all the reusable hardware already built, so you just have to pay for refurbishment/refueling/expendable parts).

If this happened, wouldn't it drastically increase the launch market, which would then increase the flight rates?

Assuming this were true, the increase in flight rates would certainly change the way people look at those development costs.

You still have a chicken and egg problem. The dramatic increase in flight rates would not occur until after the flyback booster starts flying, but you still have the high upfront development costs.

Well yea, that's the point. I do agree, the logic is somewhat self-serving, but if we can agree that a significantly reduced cost/kg to LEO would increase the launch market then you still have the same effect of spreading out the development costs more quickly.

So really you have two hypothetical questions here:

1) Can a flyback booster significant reduce launch costs?

2) Would a significantly reduced launch cost cause more people to want to launch things into space?

I contend that the answer to both questions is yes. To the first one because mutliple studies point to it, and to the second one because you're lowering the barrier to entry for a wide range of audiences. You could fly a lot more educational and amateur payloads, let alone capturing launches from other companies with your reduced rates.

Offline Jorge

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Re: Why have no flyback boosters ever ben fielded?
« Reply #7 on: 05/03/2009 03:57 am »
Flight rates don't support the development costs

Naturally your answer would depend on the flight rates, so let me ask you this hypothetical question:

Say one of these concepts, by virtue of its reusability, managed to significantly lower the cost per kg to LEO (consider the just the flight cost with all the reusable hardware already built, so you just have to pay for refurbishment/refueling/expendable parts).

If this happened, wouldn't it drastically increase the launch market, which would then increase the flight rates?

Assuming this were true, the increase in flight rates would certainly change the way people look at those development costs.

You still have a chicken and egg problem. The dramatic increase in flight rates would not occur until after the flyback booster starts flying, but you still have the high upfront development costs.

Well yea, that's the point. I do agree, the logic is somewhat self-serving, but if we can agree that a significantly reduced cost/kg to LEO would increase the launch market then you still have the same effect of spreading out the development costs more quickly.

So really you have two hypothetical questions here:

1) Can a flyback booster significant reduce launch costs?

2) Would a significantly reduced launch cost cause more people to want to launch things into space?

I contend that the answer to both questions is yes. To the first one because mutliple studies point to it, and to the second one because you're lowering the barrier to entry for a wide range of audiences. You could fly a lot more educational and amateur payloads, let alone capturing launches from other companies with your reduced rates.

I contend that the answer to the first is "maybe" until actually proven. It is probably true but until one is actually built and flying, investing money in developing one is a risky proposition. That is why it has not been done.
JRF

Offline MATTBLAK

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Re: Why have no flyback boosters ever ben fielded?
« Reply #8 on: 05/03/2009 04:03 am »
$$$$$$$$$$$$$$$$$$$:

No bucks, no Buck Rogers... :(
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Offline Nickolai

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Re: Why have no flyback boosters ever ben fielded?
« Reply #9 on: 05/03/2009 04:45 am »
I contend that the answer to the first is "maybe" until actually proven. It is probably true but until one is actually built and flying, investing money in developing one is a risky proposition. That is why it has not been done.

OK, I'll buy that, but is that really the reason this design has never flown? Technical risk?

There have been plenty riskier developments with goal of achieving low cost to orbit (think: any multi-billion dollar project that NASA has been involved with over the last 30 years), so why hasn't flyback been considered more seriously?

I feel like that concept makes a lot of sense, and that there must be some large factor as to why it hasn't been flown.

I mean, how technically risky is it really? For a HTHL booster, you're pretty much just talking about making an airplane (ok so it's more complex than that but there's still a lot of comonality, right?)

Offline simonbp

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Re: Why have no flyback boosters ever ben fielded?
« Reply #10 on: 05/03/2009 05:21 am »
Flyback boosters only make sense to aeronautical engineers who failed economics...

Simon ;)

Offline Jorge

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Re: Why have no flyback boosters ever ben fielded?
« Reply #11 on: 05/03/2009 06:05 am »
I contend that the answer to the first is "maybe" until actually proven. It is probably true but until one is actually built and flying, investing money in developing one is a risky proposition. That is why it has not been done.

OK, I'll buy that, but is that really the reason this design has never flown? Technical risk?

Not just that. Also market risk, basically "what if you build it and they don't come?" So far, demand in the launch market has not shown much price elasticity. That is, when launch prices have gone down, customers have not bought more launches - they just pocket the savings instead. That creates a strong disincentive for established players to invest in flyback boosters; they'd just be spending a lot of money in order to wind up making less. So the only players likely to invest would be startups. And the only way the startups can build a business case is to postulate that, below a certain price, the demand curve will start showing some price elasticity (i.e. new customers will emerge who could not have afforded launches at the old higher prices). Otherwise they're screwed.
JRF

Offline Kaputnik

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Re: Why have no flyback boosters ever ben fielded?
« Reply #12 on: 05/03/2009 11:15 am »
A long idea ago I asked something similar, not specifically on flyback boosters, but just reusing first stages.
The best candidate other than the shuttle SRB and the Ariane-V SRBs, which are often recovered, would be Zenit. In it's role as an Energia strap-on it was designed to be recoverable- hence large lockers visible on the exterior of the stage, carrying parachutes and airbags. The RD170 engine was designed for ten reuses and has achieved twenty in tests.
Zenit is operated on a purely commercial basis. I'm sure that Boeing would love to pay the Ukraine less by reusing the stages. For a company like Sealaunch, they could even diversify into stage recovery quite conceivably.

Yet they have never attempted to go down this avenue. This, to me, is all the evidence you need that it is nothing but simple economics at work.
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Offline butters

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Re: Why have no flyback boosters ever ben fielded?
« Reply #13 on: 05/03/2009 12:32 pm »
It's a demand-side issue.  The market hasn't suggested the purchase intent to launch more payload for the same cost.  They won't pay for more space launches at a lower price unless they stand to profit.


The demand for space launches has never really spread beyond national defense/pride and communications.  The commercial interest in creating a market for space tourism is a testament to the failure of the profit motive to capitalize space as productive property.


The economy doesn't necessarily reward ambition or inspiration, progress or discovery.  It rewards those who are able to most efficiently provide the mundane banality of basic human needs and outward manifestations of social status.


This is why the most promising emerging business model for space is to sell the opportunity for the elite leisure class to brag at cocktail parties about their six minutes of weightlessness in space.


It's also why the most sensible strategy for launch vehicle design is cheap and simple, expendable and extensible.
« Last Edit: 05/03/2009 12:33 pm by butters »

Offline MKremer

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Re: Why have no flyback boosters ever ben fielded?
« Reply #14 on: 05/03/2009 02:24 pm »
I think if you closely examine the cost-benefit figures in most of those early studies they will either explain the savings based on projections of fast turnaround and large numbers of flights per year, or worse, rather unrealistic R&D and construction costs on top of unrealistic turnaround times and flight rates.

I think there are many people who still don't grasp just how much time, effort, and costs are involved with turnaround processing for reusable LVs. (Especially ones that are designed to haul another large vehicle into the upper atmosphere and then serve as its launch platform.)
They still persist in comparing them to passenger and cargo airplane servicing, and the realities are totally different.
« Last Edit: 05/03/2009 02:26 pm by MKremer »

Offline mlorrey

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Re: Why have no flyback boosters ever ben fielded?
« Reply #15 on: 05/04/2009 03:31 am »
In short: you can't influence the market by the availability of RLV technologies because the small increment on return isn't enough to bootstrap more development that radically improves such economics, such that it becomes a dominant trend. Absent that, the subsidy runs out, and then everybody points fingers over how stupid it was to be suckered by the RLV, when all along the ELV netted out cheaper.

Applied to Shuttle: the govt LV market was forced through Shuttle to artificially increase demand/flight rate. Instead of reducing costs it increased costs, so there was no increment on return, and so no justification to refine Shuttle to increase its "RLV effect", e.g.you weren't going to make it up on volume.

So before Shuttle, which BTW started with a S1C flyback booster approach that already had worse than Shuttle economics (you were reusing a low-pressure, low efficency, not too reusable F1 engines), the bar was set high (perhaps still not high enough) for RLV. This is why Shuttle didn't get flyback replacements for the RSRB's.

X-33 was a long shot last ditch approach to "change the RLV recipe". It was a disaster because it didn't/couldn't follow the X vehicle success strategy. The idea was to start again from the ground up and shoot for economics much better than Shuttle, including vehicle turn around costs/time which are a large part of the standing army needed for Shuttle (that just having flyback boosters doesn't get you).

It is hard to see how this could have been different, because the demands of the time forced the approach. Most wished X-33/VentureStar hadn't happened. I go back and forth on if a smaller X project (like the subscale X-40 of the X-38) might have been better, but it gets ridiculous after a while.  You needed 1) an aerospike that gave better performance/less weight than possible, you needed much lower mass fraction than possible, and you needed more durable/lower weight TPS than possible - three strikes and you're  out!

The big problem has always been the demand to have both RLV and SSTO, and in the worst proposals, wings because they are cool.

Lets take it one goal at a time:

a) RLV TSTO/1.5STO: STS was nearly there but its technologies were too nonrugged (TPS and main engines maintenance needs destroyed the sortie rate, and the tank foam...). The goal of NASA since STS went online SHOULD HAVE BEEN to design Shuttle II that eliminated these design weaknesses and enabled high sortie rates.

b) SSTO: Goal is economics and risk reduction. Total reusability has IMHO been a false goal. Fuel tanks, in and of themselves, are cheap to make and not worth recovering unless you have a very very high sortie rate. Make a recoverable engine pod, put a cheap (STS external tanks true production cost is somewhere about $750,000.00) tank set over it, and a payload cowling above that. This should be the easiest to achieve.

c) Wings: Thats Buck Rogers. Its possible, but you are going to have to pull some other rabbits out of your hat, particularly high density/high Isp propellants that don't make the EPA shut you down, master the art of utilizing atmospheric O2 as oxidant. GTX, Skylon, NASP, X-106, etc...
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Offline DerekL

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Re: Why have no flyback boosters ever ben fielded?
« Reply #16 on: 05/04/2009 09:57 pm »
I think there are many people who still don't grasp just how much time, effort, and costs are involved with turnaround processing for reusable LVs. (Especially ones that are designed to haul another large vehicle into the upper atmosphere and then serve as its launch platform.)
They still persist in comparing them to passenger and cargo airplane servicing, and the realities are totally different.

There are also many people who mistakenly persist on believing the status quo is as stable as a continent.

Offline joema

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Re: Why have no flyback boosters ever ben fielded?
« Reply #17 on: 05/10/2009 01:14 am »
...there are many people who still don't grasp just how much time, effort, and costs are involved with turnaround processing for reusable LVs. (Especially ones that are designed to haul another large vehicle into the upper atmosphere and then serve as its launch platform.)They still persist in comparing them to passenger and cargo airplane servicing, and the realities are totally different.
That is a key point. Just because a flyback booster looks sort of like an airplane doesn't equate  with airline-like operating costs.

Flyback boosters have been dreamed of for decades.

Unfortunately when serious, realistic calculations are done, a fully-reusable shuttle with a flyback booster entails immense development cost and technical risk.

The optimal staging velocity producing the best overall two-vehicle mass is typically around 12,000 ft/sec. Imagine something like the current orbiter but with internal propellant. It would probably weigh 350,000 lb or more. A 747 couldn't even lift it off the ground. What kind of flyback booster would be required?

The flyback booster to lift an external 350,000 lb payload to 12,000 ft/sec would be mind-boggling. Something like the X-30 NASP but 3x or 4x the takeoff weight. Alternately a hypersonic Antonov-225. Even if using airbreathing scramjets, it would probably weigh over 1 million pounds, maybe a lot more. If pure rocket it would weigh even more.

Aerospace development cost is closely related to gross takeoff weight, so it would be expensive.

"Flyback booster" can also mean strap-on liquid boosters instead of the current shuttle SRBs. Those have been considered several times. Unlike the big winged single booster, they are technically very achievable. However even the modest development cost for those isn't useful given the current flight rate. The main advantage would be performance and improved abort options, not operational costs.

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