Author Topic: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)  (Read 609688 times)

Offline Semmel

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #680 on: 11/24/2017 07:41 pm »
The N1 argument comes forward whenever there is no sensible argument left to be made. Just like the shuttle argument for economics of reuses.

Offline Space Ghost 1962

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #681 on: 11/24/2017 09:31 pm »
AFAIK, N-1 never test fired engines until all started at launch.  FH will have fired each core (two of the three have even flown) individually, and the collective will be static fired before launch.

So, how is this like N-1 again?
How are they alike?  N-1 had 30 engines burning at liftoff.  Falcon Heavy will have 27.  Neither was or will be test fired in launch configuration on a ground test stand before launch, leaving uncertainties. 
Bad comparison. Please don't be so silly.

The three component booster are test fired individually. So you have three independent components with large flight history/commonality. In a flight configuration, the flight dynamics are controlled by verified software.

Sorry Ed, your hopes of failure here aren't comparable in the slightest. Closer comparisons are with DIVH and Angara 5.

add:

May I suggest a better line of attack / fear mongering, one that is backed by both examples cited by me? That of the cost/delay/flight frequency of clustered, common core vehicles? They all have pretty bad histories here ...

Oh, and if we're counting engines, the MerlinVac is still a Merlin with commonality, and it must fire for orbit. So that's 28 engines.
« Last Edit: 11/24/2017 09:54 pm by Space Ghost 1962 »

Offline Semmel

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #682 on: 11/24/2017 09:40 pm »
The N1 argument comes forward whenever there is no sensible argument left to be made. Just like the shuttle argument for economics of reuses.
So you think it is a trivial matter to launch using 27 engines?  Elon Musk doesn't seem to agree.  He said "Falcon Heavy requires the simultaneous ignition of 27 orbit-class engines. There's a lot that can go wrong there."

He also said, "I hope it makes it far enough beyond the pad so that it does not cause pad damage. I would consider even that a win, to be honest."

 - Ed Kyle

Please don't put words in my mouth that I didn't voice. I never said it's simple. I just said that the number of engines is not an indicator for the launch vehicle reliability when comparing to the N1. The N1 had many other problems.

Offline Coastal Ron

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #683 on: 11/24/2017 09:42 pm »
So you think it is a trivial matter to launch using 27 engines?

No one said it was trivial. Just that the N-1 is not related enough to modern rocketry to use as a point of comparison.

Like comparing the Tupolev Tu-104 to the Boeing 787 - both twin-jets, and both airliners, but otherwise they are more different than they are alike.
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Offline MATTBLAK

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #684 on: 11/24/2017 09:55 pm »
So you think it is a trivial matter to launch using 27 engines?

No one said it was trivial. Just that the N-1 is not related enough to modern rocketry to use as a point of comparison.

Like comparing the Tupolev Tu-104 to the Boeing 787 - both twin-jets, and both airliners, but otherwise they are more different than they are alike.
Yes; exactly - Boeing 707 and Airbus 340 for comparison: very similar concepts but one design is much more efficient and modern than the other in many ways.
« Last Edit: 11/24/2017 09:56 pm by MATTBLAK »
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Offline Space Ghost 1962

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #685 on: 11/24/2017 10:07 pm »
Quote
How are they alike?  N-1 had 30 engines burning at liftoff.  Falcon Heavy will have 27.  Neither was or will be test fired in launch configuration on a ground test stand before launch, leaving uncertainties. 
Bad comparison. Please don't be so silly.
...
Sorry Ed, your hopes of failure here aren't comparable in the slightest. Closer comparisons are with DIVH and Angara 5.
"Hopes of failure"?  Speaking of putting words in someone's mouth that were never voiced ...
You seem to be going out on a limb. Can only speculate as to why.

Your using it in regards to a BFR thread and number of engines on it.

Another significant issue here is autogenous pressurization. As well as extremely high combustion pressure stage combustion. Such a propulsion system might also compensate by pushing up remaining engines to higher pressure than flight normal as a means to compensate, which both N1 and FH could not do.

I'd expect your experience to arrive at such considerations as raised here as well, as they aren't particularly deep. So yes I'm calling you on them because you know better and should provider a better foil than you are doing.

Don't mistake the nature of the minor goad to better quality of refutation. You can play at a better level than this. Just hinting at it.

And as to FH risks, we both know its in the structures and system use of them not tearing it apart is where they are. Propulsion and plumbing aren't the issue.

Offline meekGee

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #686 on: 11/24/2017 11:02 pm »
The N1 argument comes forward whenever there is no sensible argument left to be made. Just like the shuttle argument for economics of reuses.
So you think it is a trivial matter to launch using 27 engines?  Elon Musk doesn't seem to agree.  He said "Falcon Heavy requires the simultaneous ignition of 27 orbit-class engines. There's a lot that can go wrong there."

He also said, "I hope it makes it far enough beyond the pad so that it does not cause pad damage. I would consider even that a win, to be honest."

 - Ed Kyle

Please don't put words in my mouth that I didn't voice. I never said it's simple. I just said that the number of engines is not an indicator for the launch vehicle reliability when comparing to the N1. The N1 had many other problems.
You said "there is no sensible argument left to be made", yet Elon himself made one, which is what I was pointing out.

 - Ed Kyle
Nope.  Musk said it was difficult. Not impossible, not similar to N-1.

We're going to go through this every time SpaceX is contemplating a step forward.

We did it with F9.1, with 1.2, with densified propellant...

You're already doing it with FH and with BFR.

You even go as far as distorting facts (e.g. the testability comparison).

What is it with the severe allergic reaction to progress? Makes the lack of progress in the last 30 years seem embarrassing?

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Offline docmordrid

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #687 on: 11/24/2017 11:27 pm »
AFAIK, N-1 never test fired engines until all started at launch.  FH will have fired each core (two of the three have even flown) individually, and the collective will be static fired before launch.

So, how is this like N-1 again?
How are they alike?  N-1 had 30 engines burning at liftoff.  Falcon Heavy will have 27.  Neither was or will be test fired in launch configuration on a ground test stand before launch, leaving uncertainties. 
>
- Ed Kyle

The inevitable FH/BFR pad static fires and BFR/BFS test hops don't count?
« Last Edit: 11/24/2017 11:48 pm by docmordrid »
DM

Offline envy887

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #688 on: 11/24/2017 11:40 pm »
AFAIK, N-1 never test fired engines until all started at launch.  FH will have fired each core (two of the three have even flown) individually, and the collective will be static fired before launch.

So, how is this like N-1 again?
How are they alike?  N-1 had 30 engines burning at liftoff.  Falcon Heavy will have 27.  Neither was or will be test fired in launch configuration on a ground test stand before launch, leaving uncertainties. 
>
- Ed Kyle

The inevitable FH/BFR pad static fires  and BFR/BFS test hops don't count?

Uh, yeah... Falcon Heavy will be test fired in a fully assembled configuration before every launch - probably several times before the first launch. I don't know where this line of argument came from, but it has no basis in reality.

Offline yg1968

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #689 on: 11/25/2017 03:22 am »
What you're really asking is "why isn't Musk agreeing with me that Mars settlement is absurd".
It isn't just me.

 - Ed Kyle

I really like what SpaceX is doing. But I am convinced that SpaceX's objective is to have NASA as a main customer down the road (as an anchor tenant) for their BFR and for their city on Mars. Yes their objective is to have customers other than NASA but they know that it won't be their main source of revenue for the foreseeable future.

This is the same model as other companies (SNC and Bigelow, for example) have had: be ahead of the competition when NASA finally decides to out source some of these services to commercial companies.
« Last Edit: 11/25/2017 03:25 am by yg1968 »

Offline Coastal Ron

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #690 on: 11/25/2017 04:07 am »
I really like what SpaceX is doing. But I am convinced that SpaceX's objective is to have NASA as a main customer down the road (as an anchor tenant) for their BFR and for their city on Mars.

I always feel compelled to remind everyone that NASA does not make it's own decisions. If the U.S. Government has a need to go somewhere in space, then it uses NASA to accomplish that goal. That could include having NASA contract with private firms to accomplish a goal, but the goal is one set by the President and/or Congress - not by NASA.

Quote
Yes their objective is to have customers other than NASA but they know that it won't be their main source of revenue for the foreseeable future.

From a recent SpaceNews article, where Gwynne Shotwell said:
Quote
“I do anticipate that there is residual capability of that system that the government will be interested in,” she said. “I do see that we would likely get some funding from the government for BFR and BFS.” She added, though, that work on the vehicles was not contingent on receiving government funding.

So yes, would love to have NASA as a customer, but aren't waiting for them.

Quote
This is the same model as other companies (SNC and Bigelow, for example) have had: be ahead of the competition when NASA finally decides to out source some of these services to commercial companies.

Another perspective is that showing that they are ready for the responsibility means that it's less of a risk for NASA to try out commercial service providers for things that the U.S. Government used to do themselves. And at this point in history I think the assumptions are that the private sector is able to, in some ways, rival NASA is what they can do.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline woods170

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #691 on: 11/25/2017 09:05 am »
The N1 argument comes forward whenever there is no sensible argument left to be made. Just like the shuttle argument for economics of reuses.
So you think it is a trivial matter to launch using 27 engines?  Elon Musk doesn't seem to agree.  He said "Falcon Heavy requires the simultaneous ignition of 27 orbit-class engines. There's a lot that can go wrong there."

He also said, "I hope it makes it far enough beyond the pad so that it does not cause pad damage. I would consider even that a win, to be honest."

 - Ed Kyle
You are grasping for straws. Elon is well-known for purposely down-playing expectations of "firsts". He did the same thing for Falcon 9 v1.0, Falcon 9 V1.1, booster landing attempts, Grasshopper missions, and Cargo Dragon.

Offline Lar

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #692 on: 11/25/2017 10:35 am »
FH and especially N1 are off topic.

The Ed Kyle vs everyone else show was on display in this thread a month ago and had died down. It seems to have started up again. Stop.
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Offline AncientU

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #693 on: 11/25/2017 01:52 pm »
What you're really asking is "why isn't Musk agreeing with me that Mars settlement is absurd".
It isn't just me.

 - Ed Kyle

I really like what SpaceX is doing. But I am convinced that SpaceX's objective is to have NASA as a main customer down the road (as an anchor tenant) for their BFR and for their city on Mars. Yes their objective is to have customers other than NASA but they know that it won't be their main source of revenue for the foreseeable future.

This is the same model as other companies (SNC and Bigelow, for example) have had: be ahead of the competition when NASA finally decides to out source some of these services to commercial companies.

And actually allow NASA to use a launch vehicle that will get them to Mars (and the Moon thrown in) on a budget?
Weird.
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Offline yg1968

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #694 on: 11/25/2017 05:25 pm »
I agree that this is a good thing. But I hate it when people assume that SpaceX doesn't need NASA's money. BFR and the city on Mars needs NASA as a customer.  SpaceX is spending about $80 million per year on BFR, not $1B per year. 

Offline Hauerg

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #695 on: 11/25/2017 06:08 pm »
I agree that this is a good thing. But I hate it when people assume that SpaceX doesn't need NASA's money. BFR and the city on Mars needs NASA as a customer.  SpaceX is spending about $80 million per year on BFR, not $1B per year.
That will definitely change next year.

Offline AncientU

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #696 on: 11/25/2017 07:16 pm »
I agree that this is a good thing. But I hate it when people assume that SpaceX doesn't need NASA's money. BFR and the city on Mars needs NASA as a customer.  SpaceX is spending about $80 million per year on BFR, not $1B per year.

As a taxpayer, I'd be satisfied if we'd just get somewhere for the $4B per year we are spending... so, taking some of NASA's money (actually, mine and other taxpayers' money), and allowing NASA to actually explore, would be a good thing. 
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Offline john smith 19

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #697 on: 11/25/2017 09:19 pm »

Falcon Heavy will be an interesting test of a rocket that won't be test fired in a fully assembled condition until it reaches the launch pad.  That is a big step, though not unprecedented.  Shuttle and the big Titans and Energia did the same.  But so did the Soviet's N-1.
IIRC the Titan and Titan II missile s both had test programmes that were astonishing by modern standards. Something like 50-60 firings. Energia worked fine and N-1 was handicapped by several very-high-risk ideas that didn't work out well  on a programme which does not seem to have been well funded to start with and would have been high profile.

If you mean Titan as LV,s with the honking great SRB's on the sides I'd agree that is the configuration FH most resembles. However unlike SRB's if anything goes wrong post ignition all engines can be shut down, unlike any large SRB based design (and when 90% of GTOW thrust is from the SRB's, as Shuttle was, it is very definitely based on them working perfectly).

That's why I think FH is useful intermediate step to BFR/BFS
How are they alike?  N-1 had 30 engines burning at liftoff.  Falcon Heavy will have 27.  Neither was or will be test fired in launch configuration on a ground test stand before launch, leaving uncertainties. 
And until something actually happens it always will.

But there are doubters and skeptics.

Skeptics have doubts that can be reasoned with. As elements of the design are proved out their skepticism drops as the TRL of the systems rise.

Doubters just doubt.  They will always doubt. They will not explain their doubts. They cannot be reasoned with. If it succeeds they will complain about how long and how much it took.

They should just be ignored. They are a waste of time.

I think you have to decide what your attitude to risk is. I commented on the FH being a good intermediate step because there are unknowns. FH will either retire some of those or show there is more work to do. But worst case no one is going to get killed doing so.  Anything less starts down the road of "paralysis by analysis," of endless efforts to reduce that last 0.1% of uncertainty that is removable by analysis when the simplest path is just to run the actual test.

Let's contrast that with NASA's former and current attitude to risk. Mercury, Gemini and Apollo were all uncrewed for their first flights and IIRC all eventually flew with escape rockets and all had engines that could all be shut down.

Shuttle in contrast had engines that could not be shut down and no escape system, and required (as part of the design contract) to be crewed. 

It would seem Shuttle was a programme that would tolerate any level of risk to human lives.
The inevitable FH/BFR pad static fires and BFR/BFS test hops don't count?
That's a very good point.  Wheather or not a short firing on the pad will be SOP it seems a very logical thing to do as part of a test programme.
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Offline meekGee

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #698 on: 11/25/2017 10:05 pm »
What you're really asking is "why isn't Musk agreeing with me that Mars settlement is absurd".
It isn't just me.

 - Ed Kyle

I really like what SpaceX is doing. But I am convinced that SpaceX's objective is to have NASA as a main customer down the road (as an anchor tenant) for their BFR and for their city on Mars. Yes their objective is to have customers other than NASA but they know that it won't be their main source of revenue for the foreseeable future.

This is the same model as other companies (SNC and Bigelow, for example) have had: be ahead of the competition when NASA finally decides to out source some of these services to commercial companies.

If that was the case, why the giant (and risky) effort to develop other sources of revenue, such as BFC and P2P travel?  Neither of these are "on the way to Mars", except if you consider revenue generation.

If either of them works, SpaceX will have more income than they can ever hope to get from NASA.

Your statement also stands in contrast with everything they said to date...

So... what is it based on?
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Offline speedevil

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Re: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 3 (Post Speech)
« Reply #699 on: 11/25/2017 10:16 pm »
If that was the case, why the giant (and risky) effort to develop other sources of revenue, such as BFC and P2P travel?  Neither of these are "on the way to Mars", except if you consider revenue generation.

If either of them works, SpaceX will have more income than they can ever hope to get from NASA.

P2P also has the nice feature that it can (indeed, must) dramatically build up the fleet, and may even be able to do things like 'retiring' operational craft onto mars, after a thousand flights perhaps, dramatically reducing the need for ISPP.

If you can credibly without impacting your schedules for commercial flight much give each mars-borne BFS a dozen or two extra tanker flights, you can also reduce the trip time a fair bit. (playing the annoying bridge-crossing game to get them all home).
This, and not caring about ISPP for any but returning crew, may be really interesting.

It makes the trades very, very odd.


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