Author Topic: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 1 (Pre-and-During Speech)  (Read 156032 times)

Offline su27k

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AMOS-6. Vehicle exploded because they had no idea how to handle super dense cryogenics and despite being warned multiple times that composites don't play nice with cryogenics they ignored the warnings. People WITHIN SPACEX giving these warnings by the way. They had previous buckling with helium tanks prior to this.

This is survival bias, you're picking one example where they were wrong while people giving advice were right, you're ignoring the countless times when they were right while people giving advice were wrong. Hell if Musk listened to his friends' advice to stay out of launch market, there would never be a SpaceX.

Offline su27k

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There is absolutely no way this vehicle will exist and fly by 2022. Carve it in stone it's not going to happen. They can't even solve the problems they already have and now they just want to throw out all their existing systems? More importantly it should tell you alot when this thing is so expensive they would have NO CHOICE but to throw out their existing systems to build it

They are shooting themselves in the foot with this. Big time. And you will almost certainly see them lose contracts over this idea if they insist on it. Nobody wants to take that amount of risk.

If you haven't noticed, a lot of existing launch vehicles are being thrown out: Ariane 5, H2, Delta IV, probably Atlas V too. And their replacements all have fairly aggressive timeline with first launch in 2019/2020. Their customers are not panicking, there's an orderly transition planned for each one, why do you think SpaceX wouldn't plan something similar?

And what risk? You do realize for a fully reusable vehicle it can afford to fly several test flights before taking any customer payload? And we already have commsat customer signing up to New Glenn even though Blue Origin hasn't orbit anything and New Glenn is about 35x of the size of their current vehicle, the customers are not as risk averse as you think.

As for solving their current problems: That's what they're doing right now, but you need to plan for the next step before the current step is done, that's just common sense, especially for space projects where it takes a long time to start anything. What do you want them to do? Just don't plan anything until they got all the current problems solved? Why do you think NASA is planning DSG when they haven't get SLS/Orion flying yet?
« Last Edit: 09/29/2017 12:38 PM by su27k »

Offline jebbo

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There's been much discussion of the BFR, but it strikes me that with a (optimistically) launch only 5 years away, and 7 for people, there's been no discussion of other aspects.

For example for the 2022 launch, the goals are:
- confirm water resources.
- identify hazards
- Land power, mining and life support infrastructure

Which implies all sorts of things: choice of site, design of equipment, etc.

Is there a thread that discusses such things?

--- Tony

Offline OneSpeed

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So no, changing the engines is a bad bad idea. With that said however, how a 31 engine cluster on a 9 meter vehicle will perform, particularly with engines that operate at higher pressures than anything ever seen before in the history of liquid rocketry, how that will behave is a big series of questions.

The RD-180 chamber pressure is 26.7 MPa, higher than the 25 MPa proposed for the first flight of the Raptor. The RD-180 has been quite successful.

And to here and say "oh its still less complex than the a vehicle that is built out of flight proven hardware and engines (FH)" is absolutely ludicrous.

The problem with FH is not just its complexity, but the untestable interaction between the three booster stages in flight. The BFR design has no such dynamic mode.

Offline Ekramer

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I would think DOD is his most likely customer for this  150 tonnes plus anywhere on earth in under 60 mins. If DOD had 10 such craft they could  have 5000 men and equipment at any base on earth within a day. Got to be appealing to some military types. I personally doubt this is ever used in regular flights tourist type flight between spots on earth but I expect space tourism would get a huge boost. What about 300 people spending $40,000 for a trip of a lifetime spending 4 earth orbits in space. That's 120 mill in revenue. I think u could fill that once a week for many years. You would take off and land in the same spot. That's $6 bill in revenue right there with no satellites etc. Plenty of potential revenue from different sources without putting Boeing, airbus and all the airlines out of business, which for all sorts of reasons is never going to happen.

You can't land "anywhere on earth" unless you are prepared to leave the ship behind. You need a booster and a pad at the other end to get home.

For some military situations this may be a price worth paying.  How do costs compare to building or capturing and then defending airstrips/ports/roads needed to deliver troops and supplies to where it is needed?  But I also wonder if, once the military situation is resolved, it could be refuelled by trucks to do a short hop to the nearest floating platform which has been moved into position in the meantime.  I think pentagon war gamers have a new scenario to add to their calculations.

Offline woods170

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And to here and say "oh its still less complex than the a vehicle that is built out of flight proven hardware and engines (FH)" is absolutely ludicrous.

The problem with FH is not just its complexity, but the untestable interaction between the three booster stages in flight. The BFR design has no such dynamic mode.
Indeed.
Let's consider the booster part of BFR for example. Basically that is a hugely scaled-up F9 booster stage. A set of two tanks (propellant and oxidizer), feeding multiple engines (~ 3.5 times the number of engines on F9), equipped with it's own avionics and grid fins to do RTLS landings. SpaceX has plenty of experience designing and flying multi-engine booster stages. Other than having more engines and being considerably bigger there is nothing that SpaceX hasn't already tackled. And proportionally speaking not more complex than FH due to it's single-stick design.


The spaceship part of BFR is different however. Essentially that is a second stage and spacecraft in one. But again, tankage and engines are nothing new. SpaceX knows how to do those. Same for the avionics, heatshield, propulsive landing. The challenges will be in the new stuff on BFR. All-carbon fiber structures for example. Autogenous pressurization of propellant tanks. Long duration reliability of spacecraft systems.

Offline Star One

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I bet New Armstrong when itís announced, Bezos being the Saturn V that he is, will go down the fewer but much bigger engine route as the better way to go.

Offline woods170

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Quote
Don't you just love it when just two or three concern trolls manage to fill an entire page on this thread with sticking feathers up each others *ss?

Technical reality is not concern trolling.
Don't you just love when some folks claim to know better than the folks that are actually working on BFR?   

And donít you just love it when constructive commentary is dismissed out of hand by those drinking the Space X Kool-Aid.
I'll be blunt. There was, IMO, nothing constructive about those concern posts. There is nothing constructive in immediately dismissing concepts (such as BFR) simply because folks here can't think outside the box.
Statements like "never going to work" or "not gonna happen" are completely unfounded IMO. That's because a bunch of arm-chair engineers/concern trolls, that don't actually work for SpaceX, nor know all the details of the BFR design, have absolutely no clue what they are talking about.

I called those concern trolls out on that. Not because I supposedly drink SpaceX Kool-Aid (which I don't btw) but because SpaceX has a track-record of trying to make the supposedly "impossible" a reality. And guess what: they have been very successful at some of it.
In stead of dismissing BFR (as currently conceived) straight away the concern trolls would have been best-adviced to give SpaceX the benefit of the doubt.
« Last Edit: 09/29/2017 01:20 PM by woods170 »

Offline CuddlyRocket

So, what is Elon not telling us? :)

I think he gave us just enough to make development of the system and its financing plausible to most people. Enough to bring in external financing, perhaps? But I bet he hasn't told us every revenue opportunity he foresees or relatively straightforward developments of the initial system that enable other mission scenarios.

The obvious lacunae is tourism. A thing about point to point travel is that the point of departure can be the same as the point of landing! Start sub-orbital. Then you might want to have more than one launch pad (East/West coast, or operate from an ITAR-compliant friendly country - Australia, UK, Japan etc). Then you consider flying between them - sell two tickets per passenger instead of one. People might stagger the journeys; put in a tourist trip between. Others might then take advantage of the service to travel quickly!

Laughter at the size of the upper stage next to the ISS; those saying they'll never let it near the ISS. They're missing that it is big compared to the ISS - it is a space station! Designed to go to Mars and back, how long can it loiter in Earth orbit? A station that can come back, be inspected and updated or re-tasked for another purpose. And an orbital hotel is one kind of space station. Perhaps later, a modified upper stage for a more permanent structure; combine elements together?

Refuelling tankers suggest refuelling depots in LEO; maybe beyond?

No mention of lunar ISRU. Not needed, but useful. Given power, oxygen can be produced from regolith anywhere on the Moon. And oxygen is 75% by mass of the propellant. (Also needed for breathing. Add a source of hydrogen, get water without all the mining, purification etc.) Bring some back as cargo for for your refuelling depots?

What else?

Online Chris Bergin

OK, so possibly my mistake for saying we'd leave this thread open for a while longer as it seems four people took it upon themselves to have a pie throwing contest amid the majority of good discussion.

As regulars know, I've got zero tolerance for pie throwing and those poor quality posts (and posts insisting on quoting them) have been trimmed from the thread. May have missed one or two, so report to mod if a crap post still exists.

And with that we'll start the promised second thread, and trust me, anyone throwing pies on that one will be kicked off the site. It always happens, the more active a site gets, the more people on it, the bigger chance of people will butt heads. I don't care how big we get, we'll never let it get out of hand. If you don't like that, you're on the wrong site and I suggest you find another one.

Thanks :)


New thread:
https://forum.nasaspaceflight.com/index.php?topic=43851.0
« Last Edit: 09/29/2017 03:25 PM by Chris Bergin »

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