Author Topic: SpaceX Falcon Heavy Discussion (Thread 6)  (Read 533263 times)

Offline Lars-J

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #60 on: 07/19/2017 07:30 pm »
ChrisGebhardt's transcript of Musk's answer to a question about FH deserves to be in this thread:

Complete text of Elon's comments on Falcon Heavy:

First of all I should say that Falcon Heavy requires the simultaneous ignition of 27 orbital class engines. There's a lot that could go wrong there. And I encourage people to come down to the Cape and see the first Falcon Heavy mission. It's guaranteed to be exciting.  But it's one of those things that's really difficult to test on the ground. We can fire the engines on the ground and try to simulate the dynamics of having 27 orbital booster engines and the airflow as it goes transonic. It's going to see heavy transonic buffeting. It's behavior at Max Q, there's a lot of risks associated with Falcon Heavy.  Real good chance that that first vehicle doesn't make it to orbit. So I want to make sure to set expectations accordingly. I hope it makes it far enough away from the pad that it's not going to cause damage. I would consider that a win, honestly. And yeah. Major pucker factor is the only way to describe it. I think Falcon Heavy is going to be a great vehicle. There's just a lot that's impossible to test on the ground. And we'll do our best. And it ended up being way harder to do Falcon Heavy than we thought. Because at first it sounds really easy to just stick to first stages on as strap-on side boosters. But then everything changes. The loads change, the air dynamics totally change. You triple the vibration and acoustics. So you break the qualification levels and so much of the hardware. The amount of load you’re putting through that center core is crazy because you have two super powerful boosters also shoving that center core. So we had to redesign the whole center-core airframe on the Falcon 9 because it’s going to take so much load. And then you’ve got the separation systems... and, yeah, it just ended up being way way more difficult than we originally thought. We were pretty naive about that. But the next thing is that we're going to fully optimize it.  It has about 2.5 times the payload capacity of the Falcon 9. We’re well over 100,000 lb to LEO payload capability. And then it has enough thrust performance to put us in a loop with Dragon 2 around the moon. And Dragon itself, the heat shield is designed with a huge amount of margin. So it has enough margin to handle a lunar reentry. But no question, whoever is on the first flight, brave.

Offline gongora

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #61 on: 07/19/2017 07:35 pm »
A new generation of giant rockets is about to blast off
http://www.latimes.com/business/la-fi-heavy-lift-rockets-20170716-htmlstory.html

A couple FH related quotes from the article:

Quote
“There is a part of the commercial market that requires Falcon Heavy,” said Gwynne Shotwell, president of SpaceX. “It’s there, and it’s going to be consistent, but it’s much smaller than we thought.”
...
Shotwell said the company is currently working to see if it can bring the side boosters back to land, which would require overhauling its landing zone at Cape Canaveral. SpaceX may also need to build more droneships if the company chooses to land the side boosters at sea, she said.

Offline ChrisGebhardt

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #62 on: 07/19/2017 09:30 pm »
Thought I remember reading somewhere that there's a possibility of Falcon Heavy going through more than one static fire on 39A before the actual launch count.  Am I making that up, so can someone point me to where I ready that?
« Last Edit: 07/19/2017 11:24 pm by ChrisGebhardt »

Offline Ictogan

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #63 on: 07/19/2017 09:39 pm »
Thought I remember reading somewhere that there's a possibility of Falcon Heavy going through more than one static fire on 39A before the actual launch count.  Am I making that up, so can someone point me to where I ready that?
I think this is what you are thinking of:
https://twitter.com/elonmusk/status/867667009839931393
Quote
There will be a combined booster static fire. Maybe a few.

Offline ChrisGebhardt

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #64 on: 07/19/2017 09:40 pm »
Thought I remember reading somewhere that there's a possibility of Falcon Heavy going through more than one static fire on 39A before the actual launch count.  Am I making that up, so can someone point me to where I ready that?
I think this is what you are thinking of:
https://twitter.com/elonmusk/status/867667009839931393
Quote
There will be a combined booster static fire. Maybe a few.

BINGO.  That's it.  Thanks.

Offline Herb Schaltegger

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #65 on: 07/19/2017 09:45 pm »
Yeah, fast-loading that much LOX and RP1 is gonna be a hell of a GSE challenge. No doubt they'll solve it but I'd expect some hiccups.
Ad astra per aspirin ...

Offline Khadgars

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #66 on: 07/19/2017 09:47 pm »
They're setting expectations for FH to be really low, I understood it to be a difficult task but they've clearly run into more issues than expected.
Evil triumphs when good men do nothing - Thomas Jefferson

Offline SpacemanSpliff

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #67 on: 07/19/2017 10:15 pm »
They're setting expectations for FH to be really low, I understood it to be a difficult task but they've clearly run into more issues than expected.
Yeah, I'm surprised how heavily Elon is caveating the first launch.

And I'm even more surprised how severely SpaceX underestimated FH challenges per the Chris Gebhardt quote. Or perhaps, how much Elon underestimated things? I'd be shocked if many of the engineers didn't know how complicated things were going to get. I know that former Boeing/ULA engineers worked on Delta IV Heavy went on to SpaceX, so at the very least those people knew what was coming ...
« Last Edit: 07/19/2017 10:19 pm by SpacemanSpliff »

Offline whitelancer64

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #68 on: 07/19/2017 10:38 pm »
They're setting expectations for FH to be really low, I understood it to be a difficult task but they've clearly run into more issues than expected.
Yeah, I'm surprised how heavily Elon is caveating the first launch.

And I'm even more surprised how severely SpaceX underestimated FH challenges per the Chris Gebhardt quote. Or perhaps, how much Elon underestimated things? I'd be shocked if many of the engineers didn't know how complicated things were going to get. I know that former Boeing/ULA engineers worked on Delta IV Heavy went on to SpaceX, so at the very least those people knew what was coming ...

I'm not. He put really low odds on landings that turned out to be successful. He just knows of everything, everything that can possibly go wrong.

People entering into a complex challenge always underestimate its complexity. Kinda like Trump saying "Who knew how complex healthcare was?" Well, the experts know. But most people don't realize just how deep the rabbit hole goes for any given field. See the Dunning-Kruger Effect for more details.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline Krankenhausen

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #69 on: 07/19/2017 10:46 pm »
But if you think about it, they do have to have some confidence that it'd work to some extent right? I mean, it wouldn't be good if it went boom since 39A is sort off vital to commercial crew. Would they seriously risk that?

Offline whitelancer64

Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #70 on: 07/19/2017 10:54 pm »
But if you think about it, they do have to have some confidence that it'd work to some extent right? I mean, it wouldn't be good if it went boom since 39A is sort off vital to commercial crew. Would they seriously risk that?

you're right, but there are, of course, limitations as to what you can determine by testing and simulations. They are probably reasonably confident it won't blow up on the pad - but the first flight may very well not be successful.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline Lars-J

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #71 on: 07/19/2017 11:08 pm »
But if you think about it, they do have to have some confidence that it'd work to some extent right? I mean, it wouldn't be good if it went boom since 39A is sort off vital to commercial crew. Would they seriously risk that?

Have you ever heard of the concept of "managing expectations"? This is what Elon does. He routinely low-balls the chances of success whenever something new is tried for the first time. (and even after that too)

FH won't launch until SpaceX is very confident it will hold together enough to clear 39A and beyond.

Offline ChrisGebhardt

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #72 on: 07/19/2017 11:10 pm »
But if you think about it, they do have to have some confidence that it'd work to some extent right? I mean, it wouldn't be good if it went boom since 39A is sort off vital to commercial crew. Would they seriously risk that?

Have you ever heard of the concept of "managing expectations"? This is what Elon does. He routinely low-balls the chances of success whenever something new is tried for the first time. (and even after that too)

FH won't launch until SpaceX is very confident it will hold together enough to clear 39A and beyond.

Exactly.  How many times in the past few missions have we been cautioned that "the booster probably won't land on the ASDS"... only to have it standing tall on the ship?

It's managing expectations, not actually predicting a failure.

Offline SpacemanSpliff

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #73 on: 07/20/2017 02:46 am »


People entering into a complex challenge always underestimate its complexity. Kinda like Trump saying "Who knew how complex healthcare was?" Well, the experts know. But most people don't realize just how deep the rabbit hole goes for any given field. See the Dunning-Kruger Effect for more details.

thanks, while I was all too aware of the phenomenon and its corollary I never knew there was a name for it. Perhaps I have given Elon too much credit regarding his genius -- I always thought Elon knew he was making ridiculous schedule claims as a way of drumming up hype and pushing his workforce, but perhaps he really does believe the dates he puts out and really does underestimate the challenges. I'd reckon the truth is probably somewhere in the middle...
« Last Edit: 07/20/2017 02:51 am by SpacemanSpliff »

Offline Robotbeat

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #74 on: 07/20/2017 02:55 am »


People entering into a complex challenge always underestimate its complexity. Kinda like Trump saying "Who knew how complex healthcare was?" Well, the experts know. But most people don't realize just how deep the rabbit hole goes for any given field. See the Dunning-Kruger Effect for more details.

thanks, while I was all too aware of the phenomena and its corollary I never knew there was a name for it. Perhaps I have given Elon too much credit regarding his genius -- I always thought Elon knew he was making ridiculous schedule claims as a way of drumming up hype and pushing his workforce, but perhaps he really does believe the dates he puts out. The truth is probably somewhere in the middle...
He really does believe it.

The most outrageous schedule claims are made when he knows the least about the actual schedule. But this should be expected: he characteristically gives the very earliest possible date given the information he knows about, and so logically the less he knows about something the more likely he is to give an early date.

In other words, always keep in mind that when Musk gives a NET date, he's answering this (kind of silly) question: "What is the earliest date such that you're certain you literally couldn't possibly do any earlier?"

...keeping that in mind will save you a lot of disappointment.

...but this helps push himself as well. Thinking in this way can help identify obstacles to rapid development. It's also terrible for any kind of realistic projection.
« Last Edit: 07/20/2017 03:04 am by Robotbeat »
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Offline Robotbeat

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #75 on: 07/20/2017 03:04 am »
There's a side effect of this:
Dragon propulsive landing now looks really hard because their information on it is now high. Their information on ITS is still relatively low, therefore Musk's usual timeline shows they could get it done in almost the same amount of time, so why even bother? The grass always looks greener on the other side of the TRL graph.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline wannamoonbase

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #76 on: 07/20/2017 04:00 am »
Rockets are hard, ones that launch 100,000+ pounds are harder.

I've criticized the FH schedule, it's been a crazy long time coming but the F9 base vehicle has evolved so much in that time.  It was hard for FH to really get a good start.

The lessons learned on FH will help them going forward with the next generation of vehicle.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline sunbingfa

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #77 on: 07/20/2017 04:33 am »
So can anyone share a little bit about the development of Delta IV Heavy? Thanks.

Offline Proponent

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #78 on: 07/20/2017 08:44 am »
What do we think the odds are that, doing it all over again, SpaceX would not attempt a tri-core launch vehicle?

Offline Proponent

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Re: SpaceX Falcon Heavy Discussion (Thread 6)
« Reply #79 on: 07/20/2017 08:50 am »
So can anyone share a little bit about the development of Delta IV Heavy?

One thing we know about Delta IV is that it has, IIRC, four different versions of core:  single-stick medium core, heavy core, left booster core and right booster core.  That makes it more expensive than it ought to be.  The plan was for just three cores, with the heavy core flying as the medium core, but performance shortfalls meant that the medium core had to be lightened, making it a separate variant.  It sounds like the Falcon family has at most three cores, because the left and right heavy boosters are identical.

 

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