Author Topic: Using Carbon Composite tanks for F9/FH Impacts on payload capability  (Read 26970 times)

Online oldAtlas_Eguy

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Here is a thought.

SpaceX is investigating use of carbon composite tanks for ITSy. But what if they changed over to its use on F9/FH prior to the ITSy being operational.

What would that up to 30% weight savings on tank weight do to the F9/FH payload capability?

What would that do to the capability of doing RTLS for a size of payload?

Impacts for life (number of reuse flights)?

Just using a reduction of 1mt of tank weight for example in US that translates directly to a increase of 1mt of payload weight to any orbit. Instead of just 6mt for an EXPD F9 it would be 7mt for a EXPD F9. For FH those TLI and Mars payloads would increase by that same 1mt for example.

By reducing the booster weight the boosters would have more prop and more DV due to the available prop to be able to do RTLS in situations of much larger payloads where now the F9 would have to be ASDS recovered.

Then there is the final item about this is that SpaceX would gain the needed extensive flight data on the reuse of carbon composite tanks. This without the need to do an extensive test program of the ITSy to get this same data set.


Offline yokem55

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Here is a thought.

SpaceX is investigating use of carbon composite tanks for ITSy. But what if they changed over to its use on F9/FH prior to the ITSy being operational.

What would that up to 30% weight savings on tank weight do to the F9/FH payload capability?

What would that do to the capability of doing RTLS for a size of payload?

Impacts for life (number of reuse flights)?

Just using a reduction of 1mt of tank weight for example in US that translates directly to a increase of 1mt of payload weight to any orbit. Instead of just 6mt for an EXPD F9 it would be 7mt for a EXPD F9. For FH those TLI and Mars payloads would increase by that same 1mt for example.

By reducing the booster weight the boosters would have more prop and more DV due to the available prop to be able to do RTLS in situations of much larger payloads where now the F9 would have to be ASDS recovered.

Then there is the final item about this is that SpaceX would gain the needed extensive flight data on the reuse of carbon composite tanks. This without the need to do an extensive test program of the ITSy to get this same data set.
Part of their challenge with carbon fiber tankage is the effects of hot oxygen from autogenous pressurization on the lox tank. If they go linerless, how do they keep the fibers from combusting. If they go with a liner, how do they keep the liner from separating in cryogenic temps.

With Falcon based design, they won't be able to test that aspect out.

Offline ulm_atms

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I've never understood how they were going to keep the LOX in the tank using carbon-composite without a liner.  The COPVs apparently allowed some LOX to go through them at standard LOX tank operating pressures or AMOS-6 would not of happened...and from my understanding, a COPV without the Al liner is basically what they are testing(test tank that had...um...issues)...and are wanting to build just in a much bigger size.  Does anyone know ways to keep the LOX from seeping through the tank without a liner of some sort?  Does RocketLab use a liner?  They are the only ones I know using a carbon composite tank currently.

Now to the original question, it would do everything you say.  I just think that the shear size of ITSy compared to the Falcon series would not be a good gauge for them.  The Falcon series is super skinny and would have a completely different loading profile then ITSy.  Plus, they have so many things going on currently that it's better they just go straight to what they want size wise and learn, then learn at the Falcon size and then find out their time/money would of been better spent elsewhere.  My 2 cents anyways.


Offline john smith 19

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Part of their challenge with carbon fiber tankage is the effects of hot oxygen from autogenous pressurization on the lox tank. If they go linerless, how do they keep the fibers from combusting. If they go with a liner, how do they keep the liner from separating in cryogenic temps.

With Falcon based design, they won't be able to test that aspect out.
This has been discussed by HMX in another thread. (I think specifically to do with the ITS tank)

He said the trick is to start with an inner layer of polymer before moving onto the CF.

How big an issue this warm (or hot) GO2 is depends on the chemistry of the inner tank that it's exposed to. Polymer stability has been creeping up over the decades, to the point you can now buy plastic baking trays good to at least 220c. There are reports of polymers based around benzene rigns good to 400c+

However I'm  not sure how compatible these polymers are with CF construction.

Historically Graphite (in nuclear reactors) has been stable to 450c in air, with fully dense graphite even more stable (but was impossible to make at the time the tests were done).

If high temperature stable polymer linings are not possible there are some mitigation approaches.

The obvious ones are to position the GO2 injector heads along the centreline of the tank and exhaust into the LO2, however this may lower the average density of the mixture to the turbopumps.

Option b would be to dilute high temp GO2 (more likely supercritical O2) with some LO2 from the turbopump inlet to deliver a lower temperature mix.

Tank pressure is one of those easily changed parameters that tempts engineers in a bind to change it. Engine turbo pumps cavitating? Increase inlet pressure.
LV not quite stiff enough? Increase tank pressure a bit more.

But every psi you increase it means more mass that's carried to orbit, although you should relax that pressure after Max Q on the structure.

If you're really concerned about payload to orbit, or you're dealing with SSTO concepts it's something that should be managed very carefully.

Time will tell how serious the issue with warm O2 pressurant really is.  Ideally they run with a stable polymer inner layer and full GO2 temp, allowing minimal mass pressurization of the stage.
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Offline AncientU

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Here is a thought.

SpaceX is investigating use of carbon composite tanks for ITSy. But what if they changed over to its use on F9/FH prior to the ITSy being operational.

What would that up to 30% weight savings on tank weight do to the F9/FH payload capability?

What would that do to the capability of doing RTLS for a size of payload?

Impacts for life (number of reuse flights)?

Just using a reduction of 1mt of tank weight for example in US that translates directly to a increase of 1mt of payload weight to any orbit. Instead of just 6mt for an EXPD F9 it would be 7mt for a EXPD F9. For FH those TLI and Mars payloads would increase by that same 1mt for example.

By reducing the booster weight the boosters would have more prop and more DV due to the available prop to be able to do RTLS in situations of much larger payloads where now the F9 would have to be ASDS recovered.

Then there is the final item about this is that SpaceX would gain the needed extensive flight data on the reuse of carbon composite tanks. This without the need to do an extensive test program of the ITSy to get this same data set.

Their revenue source is the rising launch rate of F9, especially after Block 5 starts flying. Doubt that GS would support R&D on their breadwinner.  ConnX isn't going anywhere without F9 high flight rate, ITSy discussions and possibilities notwithstanding.

If they want to test carbon composite tankage, they can do it many other ways on 'Test Articles' -- when one fails, testing and operational flights are uninterrupted.
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Offline Robotbeat

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They explicitly said that they'd stop major revisions of Falcon family after Block 5. So no. Lock thread?
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Offline Jimmy Murdok

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They explicitly said that they'd stop major revisions of Falcon family after Block 5. So no. Lock thread?

I guess it worth to keep it open until question from title (Impact on payload capability) and from 1st post are reasonably estimated and answered. I find it interesting.

- What would that up to 30% weight savings on tank weight do to the F9/FH payload capability?
- What would that do to the capability of doing RTLS for a size of payload?
- Impacts for life (number of reuse flights)?

Offline john smith 19

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Their revenue source is the rising launch rate of F9, especially after Block 5 starts flying. Doubt that GS would support R&D on their breadwinner.  ConnX isn't going anywhere without F9 high flight rate, ITSy discussions and possibilities notwithstanding.

If they want to test carbon composite tankage, they can do it many other ways on 'Test Articles' -- when one fails, testing and operational flights are uninterrupted.
If we're specifically talking about applying composites to F9 tank construction then it's a non starter due to all the knock on effects.
F9 is affected
F9/Dragon is affected
FH is affected

Which is essentially all of SX's current, and potential revenue earning business.  :(

Carbon fiber <> Aluminum. It would invalidate a huge amount of test data. We know that SX has carried out a continuing programme of upgrades, tests and mods to its LV's practically since F1 but something this fundamental would really be for a completely new LV, which ITS (or mini-ITS or ITS-Lite, whatever flies) will be.

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Offline john smith 19

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I guess it worth to keep it open until question from title (Impact on payload capability) and from 1st post are reasonably estimated and answered. I find it interesting.
- Impacts for life (number of reuse flights)?
That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.

Note that the interstage and fairings are both large or largish composite structures but the interstage is a single use object and the fairings are planned to be recovered without slamming them into the ground, or a pitching deck.  Obviously the landing legs should absorb quite a lock of the initial shock loading but it's unclear if that would be enough to prevent tank damage if the tanks were composite.

So you could get a situation where what  you gained on the tank mass you lost on the leg weight and/or the stage life in terms of how many flights it could do. Heavier legs could substantially reduce any increases in payload due to the switch to composite tanks, but shortened life expectancy (compared to Aluminum tanks) would probably be an even worse issue.  :(
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Offline Nomadd

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 Since when is the interstage a single use object?
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Offline MP99

A composite F9 could conceivably use autogenous pressurization on its LOX, but at the expense of Merlin changes to generate hot GOX.

However, the RP1 would need to continue with GHe pressurization, with the COPVs embedded in the LOX. Would there be an issue with needing penetrations to the LOX tanks to support the COPV struts?

Cheers, Martin

Online wannamoonbase

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Here is a thought.

SpaceX is investigating use of carbon composite tanks for ITSy. But what if they changed over to its use on F9/FH prior to the ITSy being operational.

What would that up to 30% weight savings on tank weight do to the F9/FH payload capability?

What would that do to the capability of doing RTLS for a size of payload?

Impacts for life (number of reuse flights)?

Just using a reduction of 1mt of tank weight for example in US that translates directly to a increase of 1mt of payload weight to any orbit....

If they were to pursue carbon composites on the F9/FH perhaps it makes sense on the US. 

The weight savings could produce enough weight savings to enable US reuse technology. 

Allowing the development and flight experience of both technologies.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline envy887

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Since when is the interstage a single use object?

It is most definitely not a single use object.

Offline john smith 19

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Since when is the interstage a single use object?

It is most definitely not a single use object.
It was my understanding it separated from the first stage to let the US go free.
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Offline Ictogan

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It was my understanding it separated from the first stage to let the US go free.
No, it stays attached to the first stage until landing.

Offline AncientU

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It was my understanding it separated from the first stage to let the US go free.
No, it stays attached to the first stage until landing.

The 'sport' interstage houses the grid fins and reaction control system... booster wouldn't make it back if it was separated.
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Offline Lars-J

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Since when is the interstage a single use object?

It is most definitely not a single use object.
It was my understanding it separated from the first stage to let the US go free.

I suspect you have watched too much Apollo footage. Take another look at stage separation for any F9 mission - or practically any modern rocket. No, for F9 the interstage is always attached to the first stage, it has the nitrogen thrusters and grid fins which are necessary for landing.
« Last Edit: 08/08/2017 07:21 pm by Lars-J »

Offline spacenut

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EM said they are working on second stage reusability.  So, carbon fiber on second stage may be used.  I thought Block 5 was only for the first stage upgrades. 

If carbon fiber tanks on the second stage helps 30%, then the heat shielding, landing legs, and either parachutes or landing thrusters could be enough to offset the weight savings and still keep the same payload capability. 

If they decide to use and expendable carbon fiber second stage on say a multiple used first stage to improve GTO performance, would it be worth going to carbon fiber?


Online wannamoonbase

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If they decide to use and expendable carbon fiber second stage on say a multiple used first stage to improve GTO performance, would it be worth going to carbon fiber?

Potential FH market would get smaller yet again.  Not that there is anything wrong with that.
« Last Edit: 08/08/2017 10:18 pm by wannamoonbase »
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline speedevil

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That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.
I wonder on birdstrikes.

Online wannamoonbase

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That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.
I wonder on birdstrikes.

Birdstrike would be a minor splat.
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Offline john smith 19

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That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.
I wonder on birdstrikes.

Birdstrike would be a minor splat.
Not so minor.

The NAO report on crewed Dragon stated this is an issue with why certification is taking so long.  :(

That would be a serious delay as NASA looked at the LV for Dragon 2 all over again, unless SX ran 2 separate mfg lines for "A" F9 and "C" F9. We know SX don't like to retain inventory or capability unnecessarily IE F1.  :(
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Offline Owlon

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The thread title says "impacts on payload capacity." We can consider the question as a theoretical exercise and ignore the practical certification issues.

Assuming 25000 kg 1st stage, 5000 kg 2nd stage, half of the mass of each stage is tank, 30% tank weight savings, and 1/7 ratio of first stage mass reduction to payload gain (a number I have seen thrown around often): 25000*.5*.3/7 + 5000*.5*.3 =  1285.71 kg. I suspect some of my assumptions lead to an optimistic number.

Anyone have a rough idea of how much of the mass in each stage is actually tankage?

Offline Robotbeat

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That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.
I wonder on birdstrikes.

Birdstrike would be a minor splat.
Not so minor.

The NAO report on crewed Dragon stated this is an issue with why certification is taking so long.  :(

That would be a serious delay as NASA looked at the LV for Dragon 2 all over again, unless SX ran 2 separate mfg lines for "A" F9 and "C" F9. We know SX don't like to retain inventory or capability unnecessarily IE F1.  :(
"The NAO report on crewed Dragon stated this is an issue with why certification is taking so long."
and
"Birdstrike would be a minor splat"

...are not incompatible with one another.
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Offline Req

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Isn't it intuitively obvious that a bird strike on the second stage is far less serious than a bird strike on Dragon due to the possible angles involved?

Offline Jim

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That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.
I wonder on birdstrikes.

Birdstrike would be a minor splat.
Not so minor.

The NAO report on crewed Dragon stated this is an issue with why certification is taking so long.  :(

That would be a serious delay as NASA looked at the LV for Dragon 2 all over again, unless SX ran 2 separate mfg lines for "A" F9 and "C" F9. We know SX don't like to retain inventory or capability unnecessarily IE F1.  :(

What is NAO?

Offline jpo234

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That's an interesting one.  Impact tests on composite tanks have show a 30% reduction in maximum load before failure but without visual signs of impact damage.
I wonder on birdstrikes.

Birdstrike would be a minor splat.
Not so minor.

The NAO report on crewed Dragon stated this is an issue with why certification is taking so long.  :(

That would be a serious delay as NASA looked at the LV for Dragon 2 all over again, unless SX ran 2 separate mfg lines for "A" F9 and "C" F9. We know SX don't like to retain inventory or capability unnecessarily IE F1.  :(

What is NAO?

That one: https://www.nao.org.uk/report/the-red-dragon-project/ ??????

Or did you get your Government watchdogs mixed up and meant that one: http://www.gao.gov/products/GAO-17-137 ?
« Last Edit: 08/10/2017 07:48 am by jpo234 »
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Offline envy887

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The thread title says "impacts on payload capacity." We can consider the question as a theoretical exercise and ignore the practical certification issues.

Assuming 25000 kg 1st stage, 5000 kg 2nd stage, half of the mass of each stage is tank, 30% tank weight savings, and 1/7 ratio of first stage mass reduction to payload gain (a number I have seen thrown around often): 25000*.5*.3/7 + 5000*.5*.3 =  1285.71 kg. I suspect some of my assumptions lead to an optimistic number.

Anyone have a rough idea of how much of the mass in each stage is actually tankage?

Based on size (37 x 3.7 meter near-cylinder) and thickness (4.75 mm) the booster tanks walls are around 5800 kg. But the tank has internal stringers that also will contribute some mass.

The Merlins only mass 4230 kg including TVC, so the octaweb must mass quite a bit - and it could also be replaced with composites.

The interstage, legs, and COPVs are already composites, and the grid fins, RCS, TPS, avionics, and plumbing either can't use composites or don't mass much anyway.

Online oldAtlas_Eguy

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For the booster there are secondary gains due to lighter stage, meaning less return prop needed (Boost back and reentry burns), lower landing prop needed (lower mass means a lower terminal velocity needing less prop to perform landing). This means more prop available for larger payloads (higher delta V from stage for given GLOW). So the payload gains for the booster are not just for its way up but also the impacts on its way back.

Offline speedevil

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Isn't it intuitively obvious that a bird strike on the second stage is far less serious than a bird strike on Dragon due to the possible angles involved?

To clarify, I meant on a returning second stage, with a CF tank, one of the variants that has been suggested to have significant sideways velocity in the low atmosphere.

Offline Robotbeat

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Not a concern. If they lose one out of every 100,000 to a bird strike (unlikely), then who cares?
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Offline deruch

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IIRC, the length of the upper stage was limited by the vehicle's bending moment.  i.e. In the change to F9v1.2, SpaceX would have liked to lengthen the upper stage even more than they did, based on thrust/power, but were limited by shear/bending.  Could a switch to carbon composite tanks allow them to go back and stretch the vehicle even more?  Given all the thrust increases they've eked out of the Merlin, such a move is probably even more attractive today than it was during the last update.  That's really the only situation where I could see them making the swap.  Otherwise, IMO, the potential gains aren't worth all the work.
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Offline john smith 19

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Not a concern. If they lose one out of every 100,000 to a bird strike (unlikely), then who cares?
If only that were true. :(

It was cited as one of the reasons neither contractor can make the NASA goal (LOC in 1 in 270 flights IIRC).

TBH I'd never thought bird strike was even applicable to VTO rocket systems at all. I can only presume it would have to be something like the bird hitting one of the windows and crashing through it.  :(
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Offline John Santos

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Not a concern. If they lose one out of every 100,000 to a bird strike (unlikely), then who cares?
If only that were true. :(

It was cited as one of the reasons neither contractor can make the NASA goal (LOC in 1 in 270 flights IIRC).

TBH I'd never thought bird strike was even applicable to VTO rocket systems at all. I can only presume it would have to be something like the bird hitting one of the windows and crashing through it.  :(
I thought the topic was carbon composite tanks for the Falcon 9, not the Dragon, and the particular topic you are replying to is the vulnerability of a carbon composite 2nd stage to bird strikes during re-entry and landing.  I don't see how LOC possibly enters into it.  Worst case, you lose a 2nd stage that you otherwise might have recovered.

A bird strike on the 2nd stage during launch would have to be from the side, which would either be low-velocity (while the rocket was still moving slowly and the bird could fly into it) or extremely unlikely due to the geometry, when the rocket has accelerated significantly.  A bird in the path of the rocket would be far more likely to hit the nose cone (or Dragon) than the 2nd stage.


As far as I know, the Dragon is made out of aluminum honeycomb, not carbon composite.

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Not honeycomb. Solid aluminum isogrid type structure.

John

Offline Nomadd

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 I've heard more like a 10% payload benefit for 1st stage weight reduction. In any case, they're not going to build a whole different rocket for a few hundred kilos extra payload. The 2nd stage might be different, but still no chance it's in the cards.
« Last Edit: 08/14/2017 07:21 pm by Nomadd »
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Offline tdperk

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Not a concern. If they lose one out of every 100,000 to a bird strike (unlikely), then who cares?
If only that were true. :(

It was cited as one of the reasons neither contractor can make the NASA goal (LOC in 1 in 270 flights IIRC).

TBH I'd never thought bird strike was even applicable to VTO rocket systems at all. I can only presume it would have to be something like the bird hitting one of the windows and crashing through it.  :(

My gut tells me that as a grotesque over-reaction to the foam strike on an RCC leading edge loss of a Shuttle, that NASA has baked into their requirements some quite unrealistic assumptions.  Are the engineering justifications for that requirement as written available?

Are there any recorded birdstrikes in launch vehicle history?

How many launches have there been?
« Last Edit: 08/15/2017 06:18 pm by tdperk »

Offline Norm38

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Regarding high temp auto-pressurization: 
How thick does a layer of epoxy have to be to prevent reaction to LOx?  Is a linerless tank simply lined with extra epoxy from the molding process?

Offline Robotbeat

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Epoxy burns in LOx, too.
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Offline Eric Hedman

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Not a concern. If they lose one out of every 100,000 to a bird strike (unlikely), then who cares?
If only that were true. :(

It was cited as one of the reasons neither contractor can make the NASA goal (LOC in 1 in 270 flights IIRC).

TBH I'd never thought bird strike was even applicable to VTO rocket systems at all. I can only presume it would have to be something like the bird hitting one of the windows and crashing through it.  :(
Which begs the question of how big a bird and at what altitude are they typically distributed at.  A couple of weeks ago I was listening to a Q&A by the Blue Angels pilots.  They said their F-18s can handle strikes of small birds up to around 700 mph including on their canopies.  Bigger birds have been known to punch holes in their aircraft.  The solutions are making the top surfaces including windows tougher, chasing the birds away, or detecting if the birds are flying above the launch pad and only launching if there is a clear path.  One of the three has to be possible.  I could see drones chasing birds away as one solution.

Offline john smith 19

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Regarding high temp auto-pressurization: 
How thick does a layer of epoxy have to be to prevent reaction to LOx?  Is a linerless tank simply lined with extra epoxy from the molding process?
I think it's a bit more subtle than that.

You've got competing processes between the "hot" GO2 (400F, 205c in the case of the Aerojet Orbital tug dual expander drive concept of 1994) and the mixing with the existing tank ullage contents before hitting the walls. Assuming the GO2 is still hot enough to react it then depends how much thermal mass is in the polymer layer and how cold it is wheather it can quench the GO2 faster than the GO2 can start it burning, either across the surface or at hotspots caused by a rough surface layer before the heat of the reaction diffuses into the rest of the layer and shuts it down.

This is clearly a job for CFD. Fortunately what's available for a given price has improved a lot in 25 years.

So thick enough, smooth enough and cold enough (and not placing the tank inlets too near the walls) and the gas could be pretty warm without an issue.

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Offline john smith 19

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My gut tells me that as a grotesque over-reaction to the foam strike on an RCC leading edge loss of a Shuttle, that NASA has baked into their requirements some quite unrealistic assumptions.  Are the engineering justifications for that requirement as written available?
Possible.  :(

It depends if they date from the Shuttle days or if they go back much further.

I'd never heard of bird strike as an issue. That said didn't Mercury and Gemini ride inside fairings?
 Apollo had the "eyelid" due to concerns about exhaust from the emergency escape system motors cutting visibility after they fired on separation and covered the windows?
Quote from: tdperk
Are there any recorded birdstrikes in launch vehicle history?
It does sound like it would the sort of thing that would stick in your mind but I can't recall one.
Quote from: tdperk
How many launches have there been?
Globally since 1956 10 000+? 20 000?

However some of them may have failed without a final root cause being established, so a bird strike could be lurking in the data somewhere (y'know, absence of evidence <> evidence of absence  :( )
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Offline Jim

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Are there any recorded birdstrikes in launch vehicle history?



Offline Jim

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That said didn't Mercury and Gemini ride inside fairings.

No


 Apollo had the "eyelid" due to concerns about exhaust from the emergency escape system motors cutting visibility after they fired on separation and covered the windows?

No, Apollo had a Boost Protective Cover that was jettison with the LES

http://www.collectspace.com/resources/reviews/model/saturn_v_04.jpg

Offline Jim

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or detecting if the birds are flying above the launch pad and only launching if there is a clear path.  One of the three has to be possible.  I could see drones chasing birds away as one solution.

https://www.nasa.gov/mission_pages/shuttle/behindscenes/avian_radar.html

Offline Lars-J

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Are there any recorded birdstrikes in launch vehicle history?




Wow, I had not seen that before. I imagine the sound basically disabled them (full on panic), but they were dead anyway... The radiant heat of the SRB's would have fried them even if they tried to fly away at full speed.

Offline tdperk

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Are there any recorded birdstrikes in launch vehicle history?

[ duplicative video deleted ]

Wow, I had not seen that before. I imagine the sound basically disabled them (full on panic), but they were dead anyway... The radiant heat of the SRB's would have fried them even if they tried to fly away at full speed.

Gotta tell you, if I'd seen that I wouldn't be worried about the bird.

Still about, what, two seconds from launch it was doing 30mph?  No visible change in the foam.

I have to believe a CC tank would be far more resistant to damage.

I cannot find any engineering justification for the problematic birdstrike resistance requirement, or even yet what that requirement is.
« Last Edit: 08/17/2017 07:15 pm by tdperk »

Offline Jim

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Still about, what, two seconds from launch it was doing 30mph?  No visible change in the foam.

That is Columbia type thinking.

Offline tdperk

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Still about, what, two seconds from launch it was doing 30mph?  No visible change in the foam.

That is Columbia type thinking.

No, the Columbia type thinking is seeing damage and imagining it is not relevant, because it has not been yet.

Observing that birdstrikes at that speed cause no damage is the beginning of an engineering assessment as to what is a hazard, putting a lower bound to the issue with respect to a structure which is no longer in use.

Burdening Commercial Crew with excuseless requirements which NASA itself does not intend to meet with it's own vehicles is politics. 

I cannot find any engineering justification for the problematic birdstrike resistance requirement, or even yet what that requirement is.
« Last Edit: 08/17/2017 07:20 pm by tdperk »

Offline Jim

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Still about, what, two seconds from launch it was doing 30mph?  No visible change in the foam.

That is Columbia type thinking.

No, the Columbia type thinking is seeing damage and imagining it is not relevant, because it has not been yet.

Observing that birdstrikes at that speed cause no damage is the beginning of an engineering assessment as to what is a hazard, putting a lower bound to the issue with respect to a structure which is no longer in use.


Just wrong.  Columbia type thinking is seeing an impact and  hand waving it away just as you did.
« Last Edit: 08/17/2017 07:35 pm by Jim »

Offline tdperk

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Still about, what, two seconds from launch it was doing 30mph?  No visible change in the foam.

That is Columbia type thinking.

No, the Columbia type thinking is seeing damage and imagining it is not relevant, because it has not been yet.

Observing that birdstrikes at that speed cause no damage is the beginning of an engineering assessment as to what is a hazard, putting a lower bound to the issue with respect to a structure which is no longer in use.


Just wrong.  Columbia type thinking is seeing an impact and  hand waving it away just as you did.

No, you are just wrong.  The history of NASA's mismanagement of it's human spaceflight program is of seeing actual damage and ignoring it.  Observing no damage is a very different thing.

For O-rings to ice to presumably damage to tiles caused by shed foam, NASA ignored actual damage caused by it's piss poor engineering, and carried on as before in spite of that observed damage and the plausibility that the damage could be far worse later.

Observing no damage /= observing damage.

But imagining "no damage" = "damage"...that is the sort of paralysis by meaningless and endless analysis (and I mean that two ways, endless by being indefinite and endless by way of having no point) which will prevent NASA from getting anything done worthwhile if it is allowed to continue even if it is given twice it's current budget.  You can always spend all the money and time you have making something metriclessly "more safe".

And it may be "safe" for a government bureaucrat pretending to be an engineer to do just that, the Iron Laws of Bureaucracy being what they are.

The fact a material as well characterized as the foam on the ET was, sustains no damage from a birdstrike at about 30mph provides good info as to what kind of hazard a birdstrike poses to a CF structure. Where is the evidence the birdstrike requirement spoken of in this thread is driven by engineering? What is that requirement, exactly?

When arriving at it, did they remember to thaw the bird?
« Last Edit: 08/17/2017 08:45 pm by tdperk »

Offline Ictogan

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No, you are just wrong.  The history of NASA's mismanagement of it's human spaceflight program is of seeing actual damage and ignoring it.  Observing no damage is a very different thing.

For O-rings to ice to presumably damage to tiles caused by shed foam, NASA ignored actual damage caused by it's piss poor engineering, and carried on as before in spite of that observed damage and the plausibility that the damage could be far worse later.

Observing no damage /= observing damage.

But imagining "no damage" = "damage"...that is the sort of paralysis by meaningless and endless analysis (and I mean that two ways, endless by being indefinite and endless by way of having no point) which will prevent NASA from getting anything done worthwhile if it is allowed to continue even if it is given twice it's current budget.  You can always spend all the money and time you have making something metriclessly "more safe".

And it may be "safe" for a government bureaucrat pretending to be an engineer to do just that, the Iron Laws of Bureaucracy being what they are.

The fact a material as well characterized as the foam on the ET was, sustains no damage from a birdstrike at about 30mph provides good info as to what kind of hazard a birdstrike poses to a CF structure. Where is the evidence the birdstrike requirement spoken of in this thread is driven by engineering? What is that requirement, exactly?

When arriving at it, did they remember to thaw the bird?
So you are concluding that bird strikes are safe for all vehicles from a single video where a bird strike did not do visually obvious damage to one vehicle. Right.

Columbia type thinking is seeing potential issues, but just handwaving them away because they happened before without any actual failure.

Offline tdperk

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No, you are just wrong.  The history of NASA's mismanagement of it's human spaceflight program is of seeing actual damage and ignoring it.  Observing no damage is a very different thing.

For O-rings to ice to presumably damage to tiles caused by shed foam, NASA ignored actual damage caused by it's piss poor engineering, and carried on as before in spite of that observed damage and the plausibility that the damage could be far worse later.

Observing no damage /= observing damage.

But imagining "no damage" = "damage"...that is the sort of paralysis by meaningless and endless analysis (and I mean that two ways, endless by being indefinite and endless by way of having no point) which will prevent NASA from getting anything done worthwhile if it is allowed to continue even if it is given twice it's current budget.  You can always spend all the money and time you have making something metriclessly "more safe".

And it may be "safe" for a government bureaucrat pretending to be an engineer to do just that, the Iron Laws of Bureaucracy being what they are.

The fact a material as well characterized as the foam on the ET was, sustains no damage from a birdstrike at about 30mph provides good info as to what kind of hazard a birdstrike poses to a CF structure. Where is the evidence the birdstrike requirement spoken of in this thread is driven by engineering? What is that requirement, exactly?

When arriving at it, did they remember to thaw the bird?
So you are concluding that bird strikes are safe for all vehicles from a single video where a bird strike did not do visually obvious damage to one vehicle. Right.

No, I've said nothing like that.  That is a data point however.

Columbia type thinking is seeing potential issues, but just handwaving them away because they happened before without any actual failure.

And the issues seen were actual damage which was waived away.  Not hypothetical damage for which there was not merely no evidence, but in fact evidence there was no damage.

Obviously Jim disagrees but I do not think the point is one without distinction.

Now if a train of thought descending from this imagery had resulted in examination of what would happen with hits higher and faster, and the "shotgun" effect of a bird hitting the foamed ET had been extrapolated to the worst case of a single foam piece, maybe with adhered ice, hitting a stressed RCC leading edge in conjunction with the fact foam pieces were regularly falling off throughout the flight in the regular launch profile...then that could have been productive.

But it is still true that the knowledge that foam was regularly falling off throughout the flight in the regular launch profile was generally known and not followed up, even though damage to tiles was seen.  Was all the damage to tiles always traced to a definite cause?  No way to know now how much was from foam strikes, and probably no point either.  The Shuttle can no longer be improved.

But the birdstrike requirement giving delay to Commercial crew can be looked at for pertinency.
« Last Edit: 08/17/2017 09:46 pm by tdperk »

Offline Eric Hedman

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or detecting if the birds are flying above the launch pad and only launching if there is a clear path.  One of the three has to be possible.  I could see drones chasing birds away as one solution.

https://www.nasa.gov/mission_pages/shuttle/behindscenes/avian_radar.html
Interesting line from this link: "If the test proves successful, the unit's location will allow it to monitor either of the launch pads at Launch Complex 39 during future space shuttle launches, providing a new margin of safety for astronaut crews."
Does anyone know how well this worked?

Online oldAtlas_Eguy

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This has wandered away from the point of the tread. Which is how a carbon composite tank affects the payload and operations such as recovery of boosters. Bird strikes is not any more of a concern by a carbon composite tank than for other LV designs.

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<snip>
The fact a material as well characterized as the foam on the ET was, <snip>
This is a flaw in your thinking.

The foam on the ET was NOT well characterized, nor was it well understood. It kept surprising the engineers (both NASA and non-NASA) and NASA management until the very last shuttle flight.
One of the prime lessons from the shuttle program is that you do NOT expose your vehicle's TPS to ill-characterized, ill-understood, debris-shedding, elements of the launch vehicle. Or haven't you noticed how NASA has made a very big deal of hardening Orion's backshell and completely encasing Orion's primary TPS in the CMA? Not to mention putting the spacecraft on top of the launch vehicle in stead of side-mounting it.

Most notable surprise-moments from shuttle:
- When a seemingly "harmless" suitcase-sized piece of ET foam managed to put an 16" by 16" hole in an RCC panel during one of the CAIB tests. That result quite literally dropped the jaws on a boatload of engineers and management and proved to be the "smoking-gun" evidence for what happened to Columbia.
- When the supposedly "fixed" foam-loss problem turned out to be very much NOT fixed on STS-114 (the first Return To Flight mission after Columbia). It initiated a "Take 2" on fixing the ET foam loss problem and yet another stand-down for the space shuttle.
- Every monitored shuttle mission since STS-114 observed multiple instances of ET foam loss, despite the problem now supposedly having been fixed... Twice... Fortunately, most of those pieces were very small.
« Last Edit: 08/18/2017 12:20 pm by woods170 »

Offline TomH

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Do I infer correctly that if the radar spots the vultures just before launch that it is scrubbed? Or can the same radar target a focused sonic weapon, shotgun, etc? Do the environmental protections in place prohibit those?

Offline john smith 19

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This has wandered away from the point of the tread. Which is how a carbon composite tank affects the payload and operations such as recovery of boosters. Bird strikes is not any more of a concern by a carbon composite tank than for other LV designs.
I can think of a couple of points.
1) It depends on the "exchange rate" between stage mass and payload to orbit. IIRC this is quite high for a first stage (13 to 1?). This is good news for recovery hardware as you can put 13 (lbs, Kgs, bananas) of hardware on the booster and loose 1 in payload to orbit.

But this leverage is not so good for mass reduction. You have to lose a lot of stage mass to make it worthwhile to (this was a key discovery of Arthur Schnitlers design to cost studies, which lead to the "Sea Dragon" chain of thinking).  :(

Then you've got composite structure reuse. NDE for flight damage and failure modes which are different from metal tanks. Yes H2 COPVs flew dozens of times on the Shuttle so we know it's possible, but is it desirable??

Composite tanks are like 3D printing. You can duplicate existing structures with it but that does not play to the strengths of the technology.

That suggests you're looking at clean sheet design for the stage, and once you've done that you're looking at doing the US as well. You're also looking at scrapping the FSW technology they've used so far for a completely different materials and mfg approach. That has serious cost implications.

Given SX seems more focused on costs than other LV mfgs. This does not seem worth the gain for the massive stand down. F9 is not broke, why fix it?
« Last Edit: 08/18/2017 08:18 am by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline john smith 19

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Most notable surprise-moments from shuttle:
- When a seemingly "harmless" suitcase-sized piece of ET foam managed to put an 18" by 18" hole in an RCC panel during one of the CAIB tests. That result quite literally dropped the jaws on a boatload of engineers and management and proved to be the "smoking-gun" evidence for what happened to Columbia.
- When the supposedly "fixed" foam-loss problem turned out to be very much NOT fixed on STS-114 (the first Return To Flight mission after Columbia). It initiated a "Take 2" on fixing the ET foam loss problem and yet another stand-down for the space shuttle.
- Every monitored shuttle mission since STS-114 observed multiple instances of ET foam loss, despite the problem now supposedly having been fixed... Twice... Fortunately, most of those pieces were very small.
Note however that AFAIK this occurred after H&S concerns about some of chemicals used to make and spray the foam lead to a change in the mixture.  I think this was ruled a "minor" change, so did not require the full battery of tests the original formulation had passed acceptably.

However this was compounded by programme officials who did not believe that something with the consistency of a ceiling tile could do any damage to something as strong and rigid as RCC.

Except things change when what you're being hit by is traveling at Mach 2.  :( I guess they'd never heard the UL about the wood splinter found embedded in the side of an armored car after a hurricane (which is odd given how many hurricanes blow through Florida  :( )

I'll note that in conventional aviation they'd settle this by using a "bird gun" to fire a standard sized (defrosted) bird into the rocket, or capsule, at whatever angle or bird weight they were concerned about, as they do with jet engine ingestion tests.

The real problem would be what to do if the orbiter failed the test (or rather how to fund what to do about it  :(  )

I think it's time to close this discussion and re-focus on the title of this thread.
« Last Edit: 08/19/2017 07:10 am by john smith 19 »
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Offline RoboGoofers

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Do I infer correctly that if the radar spots the vultures just before launch that it is scrubbed? Or can the same radar target a focused sonic weapon, shotgun, etc? Do the environmental protections in place prohibit those?

I'm not sure those are great options around a rocket prepped for flight.

Offline docmordrid

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Propane cannons etc. have been used around airports and other installations for years. So long as you don't mount one on the pad....

example news story...
« Last Edit: 08/18/2017 07:49 pm by docmordrid »
DM

Offline john smith 19

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Hmm.

Perhaps a poll of people who think it would be a good idea to go to a composite F9 booster, a full composite F9 or stay as it is?

I think I can guess the outcome but I don't want to say to avoid prejudicing it one way or the other, so I could be wrong.
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Offline Jim

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The fact a material as well characterized as the foam on the ET was,

There is no such fact.  Just another case where anonymous posters choose items to make as fact to support their claims.

Offline TomH

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Do I infer correctly that if the radar spots the vultures just before launch that it is scrubbed? Or can the same radar target a focused sonic weapon, shotgun, etc? Do the environmental protections in place prohibit those?

I'm not sure those are great options around a rocket prepped for flight.

Their acoustic energy would be far < that of the engines and they would be mounted such that none could point directly @ the LV, prop storage tanks, lines, etc.

Offline tdperk

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The fact a material as well characterized as the foam on the ET was,

There is no such fact.  Just another case where anonymous posters choose items to make as fact to support their claims.

And as a different poster mentioned, it was well characterized until changed.

A poster no more anonymous than you are, Jack.

Offline TomH

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Gotta tell you, if I'd seen that I wouldn't be worried about the bird.

Still about, what, two seconds from launch it was doing 30mph?  No visible change in the foam.

I have to believe a CC tank would be far more resistant to damage.

I cannot find any engineering justification for the problematic birdstrike resistance requirement, or even yet what that requirement is.

This IS the kind of thinking that led to both STS disasters. Wanting something to be true doesn't make it true.

No VISIBLE change in the foam?.........From a distant poor quality video? The strike could easily have induced fractures in the foam that caused it to tear apart during MaxQ or Max drag. Even a dent could cause an eddy in the airflow that would eat the foam away.

You BELIEVE the CC tank is more resistant? This is Rocket SCIENCE, not Rocket Faith. Belief ignores facts. In science, belief can be invoked no farther than hypothesis. Rocket science involves rigorous scientific testing and verification. Belief is what got 17 astronauts killed.

Look, I've disagreed with Jim before, too. But you better have some scientific and mathematical justification to do so. This is NOT the forum in which to argue things based on belief.

« Last Edit: 08/21/2017 12:51 am by TomH »

Offline TomH

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The fact a material as well characterized as the foam on the ET was,

There is no such fact.  Just another case where anonymous posters choose items to make as fact to support their claims.

And as a different poster mentioned, it was well characterized until changed.

A poster no more anonymous than you are, Jack.

Ummmm. He's NOT anonymous. Most people here know that he has a PhD in Aeronautical Engineering/Rocket Science and has worked for NASA for decades.
« Last Edit: 08/21/2017 12:35 am by TomH »

Offline john smith 19

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This IS the kind of thinking that led to both STS disasters. Wanting something to be true doesn't make it true.

No VISIBLE change in the foam?.........From a distant poor quality video? The strike could easily have induced fractures in the foam that caused it to tear apart during MaxQ or Max drag. Even a dent could cause an eddy in the airflow that would eat the foam away.

You BELIEVE the CC tank is more resistant? This is Rocket SCIENCE, not Rocket Faith. Belief ignores facts. In science, belief can be invoked no farther than hypothesis. Rocket science involves rigorous scientific testing and verification. Belief is what got 17 astronauts killed.

Look, I've disagreed with Jim before, too. But you better have some scientific and mathematical justification to do so. This is NOT the forum in which to argue things based on belief.
I've mentioned before that NASA has tested impact damage to COPV's and found a 30% loss in strength with no visible damage. This was a deliberate test and historically COPV's operate at much higher pressure s than LV main tanks and have much higher safety factors (IIRC more like 6x the standard operating pressure) while human rated LV's have an SF of 1.4.

Unfortunately that 30% on an LV tank (SF = 1.4) would put it to 98% of full standard operating pressure.:(

Caveat Main LV tank <> COPV but this does suggest that impact damage can be an issue with coposite structures in a way they wouldn't with Aluminum alloy.

The reverse argument is that the F9 interstages are both composites and AFAIK there have been no issues with damage. OTOH they are not pressurized structures. OT I had not realized (till I'd seen it happen) that birds will fly into window glass without realizing it's there, breaking their necks in the process. Why they would fly straight into the side of a LV tank is another matter, as the contrast with the sky seems quite clear.   :(

I will note that the tanks supplying supercritical H2 and O2 on all the Shuttles were (AFAIK) original equipment, installed when they were built. So they survived the whole life of the Shuttles they were on.

These are the only data points I have. It would depend on how big an impact you'd need to hit an LV sized composite main tank. Something which on a small tank would cause a 30% loss in strength would not have the same event (you can't say "It wouldn't leave a dent,"  because neither would, which is the problem   :( )

That said acoustic monitoring, with multiple sensors to triangulate sources feeding modern processors, should be able to match any damage signatures with images from monitoring cameras on the pad.

But I wouldn't like to be a passenger on a composite main tanked LV if that was the first flight of such a vehicle.  :( 
« Last Edit: 08/21/2017 07:39 am by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline livingjw

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... I will note that the tanks supplying supercritical H2 and O2 on all the Shuttles were (AFAIK) original equipment, installed when they were built. So they survived the whole life of the Shuttles they were on....



??? What tanks are we talking about?
« Last Edit: 08/21/2017 06:52 pm by livingjw »

Offline tdperk

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The fact a material as well characterized as the foam on the ET was,

There is no such fact.  Just another case where anonymous posters choose items to make as fact to support their claims.

And as a different poster mentioned, it was well characterized until changed.

A poster no more anonymous than you are, Jack.

Ummmm. He's NOT anonymous. Most people here know that he has a PhD in Aeronautical Engineering/Rocket Science and has worked for NASA for decades.

The several who have met him, yes.  I suspect they cannot verify his identity here for the rest of us.

Offline TomH

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... I will note that the tanks supplying supercritical H2 and O2 on all the Shuttles were (AFAIK) original equipment, installed when they were built. So they survived the whole life of the Shuttles they were on....



??? What tanks are we talking about?

You have copied and redacted incorrectly. I did not write that. Please go back, edit, and correct your mistakes.

Offline livingjw

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Sorry about the improper redaction. What tanks are we talking about?

John

Offline john smith 19

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Sorry about the improper redaction. What tanks are we talking about?

John
The reactant tanks that stored reactants for the Fuel Cell electrical system.
« Last Edit: 08/21/2017 08:34 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Jim

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Sorry about the improper redaction. What tanks are we talking about?

John
The reactant tanks that sored reactants for the Fuel Cell electrical system.

They were not COPVs

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