SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD (2)

[TomH]

If they are actually able to reach a point of continual reliable reuse of the first stage, I would think that Interstate transport becomes less important. Currently, the ratio of (full transcontinental) transports to launches is 1:1. If each S1 becomes capable of 100 launches, (and retesting can be done at the launch site rather than going back to McGreggor) that ratio becomes 1:100. The cost of the one single transport is now amortized over many launches. The efficiency gains from a wider rocket used 100 times may now become worth the cost of a single transport by barge.

Obviously, they are not at that point. But realization of reusability might make a wider rocket, transported by truck to the CA coast, then by water to Cape Canaveral a viable path to higher efficiency.

Of course, they could always move the manufacturing site to the launch site, or build and launch Falcon at the same place they do ITS.

[Norm38]

Limits that don't need to be explored:
There is no need to to reduce prop loading times by a few minutes to the absolute minimum
Or push He into the vehicle as fast as possible.
Shave a day off pad flow and risk customer's spacecraft.

I grew up with sci-if that had Pan-Am shuttles making routine flights to space. Which is where SpaceX wants to get to.  Go ask United Airlines if they can throw away a day, or an hour, turning around an airliner.
Yes the envelope does need to be pushed, no today's tech is not good enough.  They failed in a way that no one has ever failed before, and I'm fine with that.  So long as it doesn't happen again.
But the future is really long, there are decades ahead of us.  How many planes have crashed in the last 100 years?  How much better are today's planes because of those lessons, because of those envelopes pushed.
Yes, we do need to keep pushing.  Nothing kills an industry like stagnation.

[Jim]

I grew up with sci-if that had Pan-Am shuttles making routine flights to space. Which is where SpaceX wants to get to.  Go ask United Airlines if they can throw away a day, or an hour, turning around an airliner.

Wrong analogy

United Airlines would away a day, or an hour, turning around an airliner, if it were to keep the fleet from standing down for several months.  There is no need for such turnaround at this time.

Yes the envelope does need to be pushed, no today's tech is not good enough. 

That is likely the best that can be.

Nothing kills an industry like stagnation

Nothing kills a company like repeated accidents.

[Jet Black]

1.  Not really worth the effort.  There are other cheaper and easier ways to increase performance for the little benefit it provides.  It is really doesn't follow the Spacex MO since it is complex and PITA method.

I get the feeling that sub cooled Lox is to SpaceX as falcon wing doors are to Tesla.  - looks impressive, but a pain in the backside.

[Norm38]

Yes the envelope does need to be pushed, no today's tech is not good enough. 

That is likely the best that can be.

The only way to know that is to try.  And yes SpaceX will likely have to be more risk adverse now, or experiment differently.  But there is nothing to indicate their first failure was a result of being too aggressive.

Maybe subcooled LOx isn't worth the effort and risk.  Maybe long run it is best to build bigger rockets to fly bigger payloads with reuse. (Which is what they plan to do).  But it's better to lose a small rocket and small payload than a big one.  So they are taking risk the right way, early on.

Failures do kill companies.  But in my experience, companies fail when they fail to innovate, fail to bring new products to market, or to open new markets.

[garidan]

Yes the envelope does need to be pushed, no today's tech is not good enough. 

That is likely the best that can be.

The only way to know that is to try.  And yes SpaceX will likely have to be more risk adverse now, or experiment differently.  But there is nothing to indicate their first failure was a result of being too aggressive.

Maybe subcooled LOx isn't worth the effort and risk.  Maybe long run it is best to build bigger rockets to fly bigger payloads with reuse. (Which is what they plan to do).  But it's better to lose a small rocket and small payload than a big one.  So they are taking risk the right way, early on.

Failures do kill companies.  But in my experience, companies fail when they fail to innovate, fail to bring new products to market, or to open new markets.

Spacex needs more testing, and aggressive testing. This payload could have bene saved, and lessons learnt in a different way. A slowdown in innovation rate is needed

Edit/Lar: Fixed quotes, removed annoying tapatalk banner. Everyone should go into your tapatalk settings and change that.

[fphowell]

Isn't the 1st stage already at the maximum length for Interstate transit?

IMHO, the first stage has already reached the practical limit for "thinness."

I am certainly no expert in that area about how long and thin a rocket can be.  So I would defer to the experts on the board in regards to that.  However I do remember Musk saying that the dimensions of the F9 1st stage when it was stretched for the v1.1 update, was set at the maximum for both length and width that could be transported on Interstates.

Well then can the 2nd stage be stretched?

[Rocket Science]

Why would one need to scale up the current LV when Falcon Heavy is already in the works... Just sayin'

[cscott]

1.  Not really worth the effort.  There are other cheaper and easier ways to increase performance for the little benefit it provides.  It is really doesn't follow the Spacex MO since it is complex and PITA method.

I get the feeling that sub cooled Lox is to SpaceX as falcon wing doors are to Tesla.  - looks impressive, but a pain in the backside.

As someone in the target demographic for the model X -- a dad with two young kids in car seats -- let me just say that the falcon wing doors are definitely worth it.  If you're not in that demo, I can see why you'd think them frivolous.

I think the analogy holds for subcooled propellant.  For what SpaceX is trying to do, the supercooled propellants are important, as is the learning that is part of the process.  From the outside its easy to second-guess, but your goals and priorities are probably not aligned with SpaceX's.

Let's wait until the full report comes out.  There's some reason why this problem didn't show up in all of the developmental work with subcooled propellant and chose to show up in a "normal" static fire instead.  As with most incident reports, it was probably a chain of failures which led to this bad day.  Let's be careful about claiming that SpaceX's entire approach to development and testing needs to change until we know more precisely what really happened, and whether carelessness or a speedy dev cycle was actually involved.

[Lee Jay]

I think the analogy holds for subcooled propellant.  For what SpaceX is trying to do, the supercooled propellants are important, as is the learning that is part of the process. 

There is a massive difference between subcooled and supercooled.  These are subcooled (below the boiling point) not supercooled (below the freezing point but not frozen).

[edkyle99]

Well then can the 2nd stage be stretched?

The rocket equation shows that there is a point at which a heavier second stage starts to reduce payload, especially to higher energy orbits.  Falcon 9 v1.2 may already be using close to the optimum sized second stage.

Abandoning first stage recovery would allow better design margins on the stages, especially on the second stage.  It might be possible then to abandon the entire extra cooling idea that imposes the hazardous late-loading restrictions.

 - Ed Kyle

[spacenut]

From what I've read, the helium is in the kerosene tank on the first stage, and it hasn't had any major problems except landings.  The second stage might have to not use supercooled lox, since the helium is in the lox tank, and it may restrict total payloads to LEO and GSO or GTO.  The first stage seems to be well designed and has reached it's limits.  I say they should leave it alone except for some minor improvements.  Second stage, well, two failures, seems like for whatever works safely, they should leave well enough alone for now, then complete the FH, then work on ITS.  Seems like reliability is more important than  2 extra tons of payload.   

[Jet Black]

The only way to know that is to try.  And yes SpaceX will likely have to be more risk adverse now, or experiment differently.  But there is nothing to indicate their first failure was a result of being too aggressive.

aggressive on price.

[woods170]

Liquid helium? I thought it was cold gaseous He at high pressure.

That was assumed to be the case. But it has been suspected for some time now that SpaceX has been messing around with partially liquified helium in loading their COPV's to prevent having a large, and potentially problematic, thermal gradient between the LOX touching the outside of the COPV's and the gaseous Helium inside the COPV's.

[TomH]

Well then can the 2nd stage be stretched?

The rocket equation shows that there is a point at which a heavier second stage starts to reduce payload, especially to higher energy orbits.  Falcon 9 v1.2 may already be using close to the optimum sized second stage. - Ed Kyle

Welcome to the forum. Ed is correct. Let me try to put this in simpler terms for someone who may not have studied physics or rocket science. By making the 2nd stage larger, you make it heavier. Now the first stage engines are struggling to push that heavier second stage up, burning and wasting a lot of stage 1's fuel and oxidizer. The first stage burns up all that propellant at a lower velocity and altitude than it normally would have. Now the second stage kicks in. Its engine is optimized to operate in a vacuum by having a huge expansion nozzle, but due to the lower altitude, it is now firing with some atmospheric pressure pushing back against its escaping exhaust gasses. This reduces its efficiency. Also, the weight of the second stage burdens its one engine even more than it did the first stage engines. You wind up getting less mass into space than you would have had you just left the design the way it was. Upper stages need to be designed to match what the first stage can do. Too big or too small and you don't get optimum performance. There is a sweet spot in upper stage design that matches what the first stage can provide.

[matthewkantar]

That is likely the best that can be

This is the kind of thinking that propels buggy whip companies all over the world into collapse. Seriously? The way we do it is the best way possible? Are you even listening to yourself? There is always a better way.

Matthew

[Proponent]

Liquid helium? I thought it was cold gaseous He at high pressure.

That was assumed to be the case. But it has been suspected for some time now that SpaceX has been messing around with partially liquified helium in loading their COPV's to prevent having a large, and potentially problematic, thermal gradient between the LOX touching the outside of the COPV's and the gaseous Helium inside the COPV's.

Given that helium's critical temperature is 5.2 K, I don't see how it could be anything other than a supercritical fluid at the pressures (~30 MPa) involved.  Surely it can't be cold enough to be liquid.

[Roy_H]

So am I correct in assuming that the fix is to load the helium first then the oxygen? Even loading the helium while the LOX level is below the level of the COPV tanks but still being filled would be risky as LOX could splash on the COPV tanks so don't do both simultaneously at all.

[matthewkantar]

Musk is quoted as saying there was liquid helium involved, either that is a misquote, or a misspeak, or they were pumping liquid He into the COPV. How else could there be liquid Helium? At ambient pressure, it is only a few degrees above absolute zero.

Matthew

[Remes]

This is the kind of thinking that propels buggy whip companies all over the world into collapse. Seriously? The way we do it is the best way possible? Are you even listening to yourself? There is always a better way.

Theoretically there is always a better way. Practically there are constraints (we don't have time for the best way, we need to make money so take what we have, ...) and what is much more important: There are so many variables and parameters in such a complex system like a rocket that no one can exactly predict what will turn out as the best way.

Putting a copv into lox? Saving weight, increasing performance, increasing risk? No one could have predicted that this event would happen. But everyone can predict that as newer the design, as higher the innovation, as higher the rate of change, as higher the risk will be that something goes wrong. In the aftermath we are always more clever: no, copv in lox didn't pay out. Whatever the performance win was, it's eaten up by the cost off one rocket and one satellite and all the other damage done.

I know, it's boring to say there are lessons learned in the last decades about complex systems, the rate of change, the probability of loss of mission, etc. and how often a rocket failed because of a small failure or change or .... But still the same lessons seems to be (at least to me) valid. SpaceX is driving fast. Looking at their launch manifest for next year on wikipedia with 31 launches (no simple prediction, really real rockets with real customers) I would say this can't work.