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The BFR “EP2P” (Earth Point-to-Point) turnaround time goal, per Gwynne Shotwell

Discussion in 'SpaceX' started by ecarfan, Apr 12, 2018.

  1. ecarfan

    ecarfan Well-Known Member

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    I think everyone participating in this SpaceX forum is familiar with the idea that Elon sprung on us at the end of his IAC presentation last year on the revised BFR plan; using it for transporting large numbers of people from one point on earth to another, or what I call “EP2P”. If you don’t know what I’m referring to, go to the 41 minute point in the video on this page Mars .

    In this article, SpaceX’s president says we’ll be able to take a rocket to Shanghai — or Mars — ‘within a decade’ , a startling claim caught my eye. From the article, quote: “How could travel by rocket cost so little? Shotwell said the efficiency would come from being fast enough to be able to operate a route a dozen or so times a day, whereas a long-haul airplane often only does one flight per day.”

    If she really said “a dozen or so times a day” and that means using the same rocket on that route, that seemed impossible to me simply because of the time needed for refueling. Then I realized that a newly fueled 1st stage will be ready at the landing site. The 2nd stage will have used only a small amount of fuel for landing but probably not used any fuel earlier in the flight; the 1st stage will do all the work needed to achieve the needed suborbital trajectory. So perhaps starting the day with a fully fueled 2nd stage it won’t need to be refueled until it has been used for a dozen or more landings?

    So to accomplish 12 flights a day using a single BFR, it has to land, disembark the passengers, and load new passengers in just two hours. I can imagine that is achievable.
     
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  2. RDoc

    RDoc S85D

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    I don't get why this is still being discussed. There is no way I can see that SpaceX can get an FAA certificate for the BFR/BFS, nor do I see how they can avoid the noise limits.

    Perhaps some people might be willing to take such a flight, but I'm pretty sure that there will be a lot of people, and a lot of insurance companies, who won't.
     
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  3. TEG

    TEG TMC Moderator

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    Whenever I see these stories about rocket EP2P travel, I think back to all those Popular Science covers I saw at the newstands over the years...

    [​IMG]
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  4. dhanson865

    dhanson865 Active Member

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    It'll only take an hour or less to refuel, think of paired first stages

    London to Tokyo and Tokyo to London. Both first stages Return To Landing Site (RTLS) both ships proceed to destination swapping places.

    in between flights you refuel 2x stage 1 and 2x ship, all 4 pieces get refueled every flight. But since you can do the refueling in 45 minutes or so and deal with incidentals along the way you can fly 12+ times a day.

    The downtime comes in the roughly 8 hour window that is early/late in both time zones and sees little travel. Otherwise if you get tickets sold you just keep flying and can do more than 12 a day.
     
  5. ecarfan

    ecarfan Well-Known Member

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    You are welcome to your opinion. But this is certainly a legitimate topic for discussion. Laws and regulations change over time to accommodate new technology, and the technology improves to overcome obstacles that people previously thought were insurmountable.

    In 1910 no one imagined that just 45 years later high-speed transoceanic flight would be routine.
     
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  6. Brando

    Brando Member

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    #6 Brando, Apr 13, 2018
    Last edited: Apr 13, 2018
    rocket launches off-shore from barge
    rocket lands off-shore onto barge
    far enough off-shore to meet sound limits for launch and landing
    once 15 Km up no one will hear - and no sound at 115 Km up which is probably min. cruise altitude
    No doubt they will optimize fuel weight (just like we currently do for planes - enough fuel + safety margin.
    (no need to carry dead weight - better to carry paying people and freight)

    IF falcon heavy style - boosters land and refuel - perhaps no need for 2nd stage? don't need orbital velocity. Just fuel for landing. Perhaps a single stage??

    I think SpaceX can figure it out.

    Maximum charge would be $200,000 - $250,000 as that is the Virgin Galactic charge for edge of space visit. This a much better deal.

    Consider 160,000 Kg for $90 Million [Falcon Heavy Prices] $560/Kg => $56,000 for 100 Kg person.
    So that is all in for Falcon Heavy currrent charges.

    I think Elon has said, Falcon 9 uses about $500,000 of fuel?? So Falcon Heavy about $1.5 million fuel => $9.50/Kg for one way fuel => $950 fuel for 100 Kg person one way.
    Hardware costs + barges, boats + rocket hardware - these est. above my pay scale - anyone care to
    estimate?

    Note: check prices for Falcon 9 vs Falcon Heavy - as Elon has pointed out, bigger is always cheaper. That is why cargo ships are so big.
    (Elon also compared Twin Turbo prop purchase to 747 charter trip half way around the world US- Australia.)

    OH, I just had an idea. HyperLoop to the launching/landing barges/islands.
    China to Middle East. All those rich people visiting each other.

    What an imagination - Elon has no doubt thought thru the details much better than my lame attempt.
     
  7. ecarfan

    ecarfan Well-Known Member

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    The Earth P2P flights that we are discussing here will be done using the BFR design that Elon introduced at the 2016 IAC and then presented a revised design for at the 2017 IAC. Look at the video of that presentation, which specifically shows quite clearly the basics how the Earth P2P flights will be done. For those flights, the vehicle consists of a first stage, the booster rocket, and a second stage with rockets and a large volume for people and cargo.
     
  8. e-FTW

    e-FTW New electron smell

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    Right, forgot about cargo: is FedEx/Amazon interested?
     
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  9. ecarfan

    ecarfan Well-Known Member

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    My statement was poorly phrased. A clearer explanation would be; The BFR vehicle consists of a first stage (the booster rocket) and a second stage with rockets and a large volume for people and cargo.

    The 2017 IAC video, starting at the 41 minute point, shows that the BFR first stage is used to life the vehicle to space on a sub-orbital trajectory. The BFR second stage — with the people and cargo — uses its engines for the retropropulsive landing.

    So what I’m interested in is how quickly SpaceX could turn around a landed BFR second stage. Would it start off the day’s flight itinerary with enough fuel to do Gywnne’s “dozen” flights without refueling? Maybe so. And at each landing, a fueld up BFR first stage would be ready to go. Which means maybe it would be possible for a BFR second stage to do a dozen flights within 24 hours.

    And if that is possible, that is a major cost reduction driver. As Gywnne pointed out, current long distance (trans-Pacific, for example) commercial jets only get used once every 24 hours or so.

    Of course you need a travel route that can provide enough demand for seats to fill 12 EP2P flights per day. And that demand will depend upon the price and whether or not people are going to accept this radically new form of transportation; radically new compared to current commercial jets. I think enough people will accept it so that it will be commercially viable and if it is priced as Gywnne indicated: somewhere between an economy and a business class ticket.
     
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  10. PhantomX

    PhantomX Member

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    It'll be interesting to see how life cycle is addressed for a BFR that flies a dozen time a day. It'll need to take into consideration of structure life cycle limits like commercial airplanes, and also various backups in case of engine failures, structures issues, equipment malfunctions, etc. Think of the logistics of flying an A380 that needs to plot compatible backup airports along the way, or a 787 that needs to have fly within range of alternate airports due to its ETOPS requirements.

    The one thing I am also very curious of is how they'll address the life of TPS. As far as I know, there are no known TPS that is meant to be cycled at this rate without rework or rebuild. Anyone know how they are addressing this?
     
  11. Brando

    Brando Member

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  12. ICUDoc

    ICUDoc Member

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    Can anyone outline the relative pollution caused by an A380 flying 500 people 12000km compared to BFR flying them the same distance?
     
  13. Grendal

    Grendal SpaceX Moderator

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    I have not seen the numbers officially run but I've heard a number of times that a BFR is the equivalent of a jumbo jet pollution flying internationally. The difference being that all the fuel is burned in two and a half minutes instead of eight or ten hours. That makes sense to me. The burning of fuel is burning of fuel. RP-1 is supposed to be pretty similar to jet fuel, if I remember correctly.
     
  14. hmcgregoraz

    hmcgregoraz Member

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    The BFR won't be using RP-1, it will be a Methalox Engine, and a fair amount cleaner.

    -Harry
     
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  15. Grendal

    Grendal SpaceX Moderator

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    Duh. I knew that. Thanks for correcting me. I had originally thought I'd comment on the F9 then I switched to BFR but didn't change the fuel. Methalox will be cleaner than RP1. Does anyone know how much cleaner?
     
  16. PhantomX

    PhantomX Member

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    Assuming max fuel of 85471 gallons of fuel to fly 8595 miles between LAX and DXB, and a full load of 489 passengers (not including crews), that comes out to .02 gallons of fuel per mile per passenger. If BFR can carry 100 passengers per trip and perform the same flight, then it needs to fuel burn to 17478 lb in order to match A380 efficiency. I know it'll take a sightly longer route due to its trajectory, but I don't it'll change the number to match in order to match efficiency of A380. And this doesn't take into account of the new twin jets like 787 or A350, which are much more efficient per seat mile than just about anything out there. Rocket transport will be good for speed, but I really doubt it'll be better for the environment.
     
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  17. sandpiper

    sandpiper Active Member

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    No to be particular but I think you missed a conversion. A 100 passenger BFR would need to burn 17478 gallons or roughly 108,000# of kerosene to match the A380. Given that the F9 carries about 900,000# of fuel, I'd say that that's highly unlikely.
     
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  18. ggr

    ggr Roadster R80 537, SigS P85 29

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    Methane has a higher Hydrogen : Carbon ratio than kerosene, so less of the exhaust (proportionally) is CO2. Also because there are no long-chain molecules at all, there are no particulate emissions (smoke...).
     
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  19. PhantomX

    PhantomX Member

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    You are right. Thanks for helping the conversion!
     
  20. Ben W

    Ben W P85 #61, Roadster #108

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    F9 1.1 first stage uses 276,000kg LOX and 119,000kg (262,000#) RP-1. (I couldn't find exact figures for F9 FT.) The LOX doesn't count for comparison purposes; the A380 simply uses oxygen already in the atmosphere for combustion. (In other words, only the fuel counts, not the oxidizer.) So a F9-based EP2P that carried 100 people would be about 2.5x worse in terms of emissions than the A380.

    However, as pointed out, BFR uses Methalox, which burns more cleanly than RP-1. Furthermore, both methane and LOX can be produced renewably using just electricity, water, and CO2. (Split water into O2 and hydrogen via electrolysis, then use the Sabatier process to produce methane from hydrogen and CO2.) If done this way, using renewable electricity, the net CO2 output will be zero. By contrast, renewable jet fuel is much, much harder to create.
     

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