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.
They explicitly said that they'd stop major revisions of Falcon family after Block 5. So no. Lock thread?
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.
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)?
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....
Since when is the interstage a single use object?
Quote from: Nomadd on 08/08/2017 03:41 pm 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.
Quote from: john smith 19 on 08/08/2017 04:14 pmIt 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.
Quote from: envy887 on 08/08/2017 04:03 pmQuote from: Nomadd on 08/08/2017 03:41 pm 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.
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?
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.
Quote from: john smith 19 on 08/08/2017 03:25 pmThat'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.
Quote from: speedevil on 08/08/2017 11:42 pmQuote from: john smith 19 on 08/08/2017 03:25 pmThat'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.
Quote from: wannamoonbase on 08/09/2017 04:17 amQuote from: speedevil on 08/08/2017 11:42 pmQuote from: john smith 19 on 08/08/2017 03:25 pmThat'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.
Quote from: john smith 19 on 08/09/2017 06:57 amQuote from: wannamoonbase on 08/09/2017 04:17 amQuote from: speedevil on 08/08/2017 11:42 pmQuote from: john smith 19 on 08/08/2017 03:25 pmThat'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?
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?
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?
Not a concern. If they lose one out of every 100,000 to a bird strike (unlikely), then who cares?
Quote from: Robotbeat on 08/11/2017 06:01 pmNot 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.
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?
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?
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?
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.
Quote from: tdperk on 08/15/2017 01:49 pmAre there any recorded birdstrikes in launch vehicle history?
Quote from: Jim on 08/17/2017 10:32 amQuote from: tdperk on 08/15/2017 01:49 pmAre 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.
Quote from: tdperk on 08/15/2017 01:49 pmAre there any recorded birdstrikes in launch vehicle history?[ duplicative video deleted ]
Still about, what, two seconds from launch it was doing 30mph? No visible change in the foam.
Quote from: tdperk on 08/17/2017 06:48 pmStill about, what, two seconds from launch it was doing 30mph? No visible change in the foam.That is Columbia type thinking.
Quote from: Jim on 08/17/2017 07:03 pmQuote from: tdperk on 08/17/2017 06:48 pmStill 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.
Quote from: tdperk on 08/17/2017 07:17 pmQuote from: Jim on 08/17/2017 07:03 pmQuote from: tdperk on 08/17/2017 06:48 pmStill 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?
Quote from: tdperk on 08/17/2017 08:32 pmNo, 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.
Quote from: Eric Hedman on 08/17/2017 05:41 am 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
<snip>The fact a material as well characterized as the foam on the ET was, <snip>
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.
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.
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?
The fact a material as well characterized as the foam on the ET was,
Quote from: TomH on 08/18/2017 07:05 amDo 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.
Quote from: tdperk on 08/17/2017 08:32 pmThe 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.
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.
Quote from: Jim on 08/20/2017 02:15 pmQuote from: tdperk on 08/17/2017 08:32 pmThe 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.
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 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....
Quote from: tdperk on 08/21/2017 12:28 amQuote from: Jim on 08/20/2017 02:15 pmQuote from: tdperk on 08/17/2017 08:32 pmThe 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.
Quote from: john smith 19 on 08/21/2017 07:34 amQuote from: TomH on 08/21/2017 12:30 am... 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.
Quote from: TomH on 08/21/2017 12:30 am... 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?
Sorry about the improper redaction. What tanks are we talking about? John
Quote from: livingjw on 08/21/2017 06:55 pmSorry about the improper redaction. What tanks are we talking about? JohnThe reactant tanks that sored reactants for the Fuel Cell electrical system.