Author Topic: BFR Private Passenger Moonflight - DISCUSSION THREAD  (Read 197228 times)

Offline sanman

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #460 on: 09/16/2018 08:15 am »
Assuming it is an altitude compensating nozzle, it could work like a metal steamer basket. Without other visual cues (drainage holes, etc) it appears o have "gaps" too.

Gee, their stuff doesn't look interleaved - but you may have improved on their design  ;)

(Oh well, I read X-33's linear aerospike used regular lawn sprinkler fixtures, so why not a big steamer basket for this?)

Offline abc2010x

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #461 on: 09/16/2018 08:35 am »
Not saying this is the plan, but would 7 sea level engines give lower gravity losses if launched from earth ssto, making it viable (I know Musk has been negative about it in the past.)

Couldn't find a reference to this in the last several pages so assuming not yet discussed. If it has been then sorry. 

Offline tyrred

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #462 on: 09/16/2018 08:38 am »
Paddles of F119 high-performance, thrust-vectoring jet engines don't interlace:



Exhaust shaping need not be accomplished with purely annular devices. 

Triple duty, including exhaust shaping, thermal radiation, and engine shielding... Sounds quite within the realm of possiblity of something Elon & Co would think up.

Offline KelvinZero

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #463 on: 09/16/2018 08:43 am »
Triple duty, including exhaust shaping, thermal radiation, and engine shielding... Sounds quite within the realm of possiblity of something Elon & Co would think up.
Hey, totally random thought.. If they did all that, maybe you could do away with any swivel mechanism on the 7 engines? (I think I remember some statement about all engines swivelling though)

Offline sanman

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #464 on: 09/16/2018 08:52 am »
Triple duty, including exhaust shaping, thermal radiation, and engine shielding... Sounds quite within the realm of possiblity of something Elon & Co would think up.
Hey, totally random thought.. If they did all that, maybe you could do away with any swivel mechanism on the 7 engines? (I think I remember some statement about all engines swivelling though)

Oh, so you think that with this kind of macro-nozzle thing, then none of the engines would have to gimbal? Could the macro-nozzle thing achieve the required control authority on its own, particularly during landing?
« Last Edit: 09/16/2018 08:59 am by sanman »

Offline KelvinZero

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #465 on: 09/16/2018 09:10 am »
Oh, so you think that with this kind of macro-nozzle thing, then none of the engines would have to gimbal? Could the macro-nozzle thing achieve the required control authority on its own, particularly during landing?
Just a random thought really. I imagine it landing on two engines, giving three symmetrical options in the event of engine out. There seem to be two 'paddles" for each of the outer 6 engines which I think could be enough for left/right, up/down, clockwise/anticlockwise.

It doesn't really look like what is there though, despite the two-per-engine detail. Not really sure what I am looking at. Is this detail drawn rather than rendered? It looks weirdly rounded and thick.

Offline TripleSeven

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #466 on: 09/16/2018 09:13 am »
and no doubt they will continue to get "longer"

I don't see why they would. BFS isn't meant to land like a Space Shuttle, and the leg spread with these surfaces already looks a lot like what Falcon 9 has.

control authority is high mach flight

Like those huge fins the F9 booster has for high Mach flight?

the F9 booster would come completely apart had it to reenter from orbital velocities  as I suspect they have found out the second stage would as well

the comparison is not even remotely relevant
How many vehicles have you seen that re-enter from inter-planetary velocities and have wings?

From mere orbital velocities, we know it can be done either with a large wings or without.

So where is your confidence coming from?

-----
ABCD: Always Be Counting Down

not sure the point you are making here

when one decides to reenter the atmosphere of a planet like the Earth (or to some extent Mars) until we develop the defelector shields that star trek seems to have.. :) you are stuck with two methods

one reenter with one of the ends down, put all the tps there and put the rest in the shadow of the reentry cone developed by the "heat shield"

two of course is to try and "fly ones way" home with a larger reentry protection system and "wings" to allow control authority during that reentry

the velocity only has to do with the entry temps

my "guess" is that watching a lot of FAlcon9 recoveries they have figured out that they are at the velocity end of a recovery phase of one end of a  long cylindrical tube with massive engines at the reentry end and no real TPS

I am assuming that the sims they have run with various second stage recovery methods where they have a TPS system of some sort on the "light end" of a second stage have been "less" in terms of control authority.|I dont know where I have seen them, maybe here but there are a lot of drawings of the second stage using that NASA inflatable system and the second stage reentering with that where the inflatable heat device is on the nose end of the second.  that would put some high demands on control authority with the CG/meta centric height so high.

If you dont go "one end first"  one needs "lifting devices" to get the vehicle through the heavy temperature phase of the reentry until you can "tip over" and do the technique that they have learned so well with the first stage.  but from reentry at any velocity to tip over, the vast majority of the kinetic dissipation is going to be done by the TPS.

this is particularly true since the CG on the vehicle changes " a lot" as fuel is burned, tanked over to other vehicles, cargo is dropped out.  but to "me" at least the design speaks of a nose first entry (notice how they tried to shape the nose) with tps on the bottom and sides...although "I guess" (not the high speed personhere) that I would expect the shape to get more "Oval" as time goes on

they are a long way in my view from a final design.

I am not the high speed aero guy/gal and I will take this up with my friend who is...but a thought came to me this morning while riding my bike...and just musing here while having my coffee

one wonders if they are going to try and come up with some "feather" system where as they reenter at high angles of attack with the two "wings" essentially in a feather holding control authority during the worst of the temps with rocket engines...but eventually transtioning the wings from deep stall into and then as the RCS became less effective transition into flight

Langley looked at this a long long time ago for both high speed reentry and slow speed flight (the latter of which has nothing to do with reentry ) but the former was in terms of getting into Martian atmosphere.  we were testing the electric ailerons on the new 757 they had while they were doing this.  there was as I recall a popular science or mechanics article on something like "deepstalling to Mars" ...

I recall that they did it but nothing much else (just to long ago)

but I would add two points

first any reentry scenario which is not blunt end first is going to make the structure of the "body" far stronger than it is now....and second the TPS system is going to be "interesting"

if you dont want much cross range you dont need much wing...but if you put the long cylinder down for reentry you need "something" that flies.
« Last Edit: 09/16/2018 09:25 am by TripleSeven »

Offline Star One

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #467 on: 09/16/2018 09:39 am »
So money is not a big concern as long as new investments are under $1B per year. With investments only needed when revenue and profits are not enough to cover development costs in that year. This paid for flight will likely produce some profit or be at cost where SpaceX is gaining flight experience in a new regime.

It's not the size of the investment that would be of concern, but when the investment would pay off. Google has the luxury of investing in things that don't pay off for a long time, but normal Venture Capital funds manage funds that expect a payoff within 10 years.

That said there are likely a lot of sources for $1B or more where the investors have the luxury of being patient, but at some point there needs to be a liquidity event. Would that be pre-Mars colonization, or post-Mars colonization?

With all their spare cash I am kind of surprised Apple haven’t already invested in them.

Offline IRobot

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #468 on: 09/16/2018 09:43 am »
What I meant by that is "if something goes wrong". We take orbital docking for granted these days on account of how many times it gets done successfully, and routinely, on the ISS. The truth is it's extremely hard, and the ISS docking is nothing compared to what lining up fueling ports on two spacecraft this size is going to be like. To me it add's complexity and risk because now you have much tighter tolerances on not just roll, any irregular body rates are going to have to be perfectly controlled or you either won't get a solid connection on your fueling ports, or you will tap fins or both.
Really? Harder than landing on a barge? Come on!

Offline RotoSequence

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #469 on: 09/16/2018 09:45 am »
What I meant by that is "if something goes wrong". We take orbital docking for granted these days on account of how many times it gets done successfully, and routinely, on the ISS. The truth is it's extremely hard, and the ISS docking is nothing compared to what lining up fueling ports on two spacecraft this size is going to be like. To me it add's complexity and risk because now you have much tighter tolerances on not just roll, any irregular body rates are going to have to be perfectly controlled or you either won't get a solid connection on your fueling ports, or you will tap fins or both.
Really? Harder than landing on a barge? Come on!

And like they aren't already addressing how to do it with Dragon 2, which features automated docking capabilities!

Offline IRobot

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #470 on: 09/16/2018 10:00 am »
With all their spare cash I am kind of surprised Apple haven’t already invested in them.
Apple is not that type of company. They are solely focused on year to year profit.
They focus an incredible amount of R&D on their current success products and even dry up on the marginal products like macOS.
Apple is also known to be a not so nice company to work in. Burnout is common. Paranoia is common. Retention of talent is difficult. As soon as they get their stock options after the 4th year, a lot of people leave. This is not good for a long term project, it only works for their year on year projects.

Offline speedevil

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #471 on: 09/16/2018 10:17 am »
As far as landing on unimproved landing sites... a thought...
Suggest we consider the Moons ~1/6 and Mars ~1/3 gravity and the possibility a one Raptor engine final landing burn could maybe throttle down low enough to hover a loaded BFS and slowly land... sci-fi style...
10+ seconds of blasting a site clear of it's loosest material before sticking the landing gear and lower fins into the debris flying zone may mitigate much of the issue.. At the cost of some prop reserve while sucking up the gravity loss while hovering at say 6m up...
Just a wild thought on subtopic...

'cost of some prop reserve'.
This can be really quite high.

If you believe BFS launch costs of $5M, if you have three BFS, you can in principle do utterly insane things like for the cost of eight launches or so, and one tanker in low lunar orbit, for around the cost of the profit of one F9 launch, descend to 100m, and fly tight flat spirals over the proposed landing area to brush it clean at up to pulses of >3G for five minutes, before having another couple of minutes to think about if you want to land or not.
Even using only one BFS, and a tanker, refuelling in high earth orbit gives you another couple of minutes of hover time.



And then there is this thing.
Might dropping this out at 20m or so, with the outer ring partially filled with water for ballast, and then simply waiting a minute for it to inflate, to anchor a debris mitigation surface to the moon be useful?

Even if not this particular thing,  50 tons of equipment for landing dropped, and then ten minutes to setup offers perhaps many options.

Consider also the price of having a shot at having a damn good shot at being remembered in a few hundred years - at least by some.
This might be one reason for SpaceX to just drop stuff on the moon to prepare for a crewed landing.

I would be very surprised if most people even here could name the three Apollo 8 astronauts who flew round the moon. Or the second space tourist.

There are very few 'firsts' that will be remembered - first space tourist on the moon may be one of them, especially if it was combined with 'First person to land on the moon in a private spacecraft'.

This of course raises the possibility that someone might pay a significant sum to be the first human on Mars.
That's not something that'd be forgotten.


Offline mikelepage

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #472 on: 09/16/2018 10:18 am »
Earlier in this thread - because of Elon's Japanese flag tweet - Yusaku Maezawa's name was thrown about as the potential SpaceX moon traveler.  I followed his twitter account, and have since seen a series of tweets I find very interesting.

Quote
Yusaku Maezawa 前澤友作 Aug 31
I will start tweets not only in Japanese but also in English from today.

Quote
Yusaku Maezawa 前澤友作 Sep 1
Big announcement here soon. Please follow me and stay tuned!!!

Quote
When will be schedule to be announced?

Yusaku Maezawa 前澤友作 Retweeted T.H Sep 1
about mid September

And today... he's put up a cryptic tweet with a picture of his watch here:
https://twitter.com/yousuck2020/status/1041135281653465088



Note the date/time.  0946 hrs on September the 19th... which if you account for the timezone difference, is 46 minutes after the SpaceX event is due to start.  Time for Elon to give a presentation on how BFS now works, and then introduce the customer :)

Offline pcostabel

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #473 on: 09/16/2018 10:40 am »
tuesday is september 18. the first september 19 that falls on a tuesday is 2023...

Offline IRobot

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #474 on: 09/16/2018 10:48 am »
BTW, that Patek Philippe Grand Complications costs around US$140.000!! So his moon shot costs 1000x his watch.
« Last Edit: 09/16/2018 10:48 am by IRobot »

Offline mikelepage

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #475 on: 09/16/2018 10:55 am »
tuesday is september 18. the first september 19 that falls on a tuesday is 2023...

Well I’ll just show myself out then  :P
Got all excited for a minute there.

Offline ncb1397

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #476 on: 09/16/2018 11:20 am »
The moon does seem to feature randomly in the guy's twitter account this year. One tweet on July 4th has the earth and the moon replacing the Os in ZOLO and another in January just has a random photo of the moon linking to research.starttoday.jp that as far as I can tell has nothing to do with the moon.
« Last Edit: 09/16/2018 11:21 am by ncb1397 »

Offline arnezami

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #477 on: 09/16/2018 11:30 am »
What I find Interesting is their choice of mission: a fly-around the moon.

They can do that without refueling in orbit, right?

Offline su27k

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #478 on: 09/16/2018 11:31 am »
tuesday is september 18. the first september 19 that falls on a tuesday is 2023...

True, but the day of week window does show "TUE", which is Tuesday.

On a separate note, Japan's timezone is GMT+9, so 0946 on September 18 in Japanese time is 14 minutes before the webcast starts.

Offline speedevil

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Re: BFR Private Passenger Moonflight - DISCUSSION THREAD
« Reply #479 on: 09/16/2018 12:14 pm »
What I find Interesting is their choice of mission: a fly-around the moon.

They can do that without refueling in orbit, right?
Barely.
The IAC2017 numbers lead to it being doable or not quite doable, depending on numbers we don't know well enough.
One refueling is certainly enough, and may be barely enough to do entry and exit to lunar orbit too.

Note that a refueling may not be just a just a refueling, it is also a system test, that can be used to raise launches on your vehicle and gain assurance.
If I was going to the moon, I would feel a lot happier if the vehicle I was going in had first hauled 7 tanker-loads to orbit. (which may enable landing)

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