SpaceX Tuesday...
Discussion
Eric Mc said:
The motors would only burn for around 15 minutes in total (lift off and landing). Compare that to the hours a jet plane has to burn fuel.
But what a 15 minutes though. It'll be burning fuel at a prodigious rate over that short time.A big jet like a 747 uses around 10 tonnes of fuel per hour, so that's about 70 tonnes to fly between London & New York.
A Falcon 9 would barely get off the ground on 70 tonnes. The second stage alone contains 108 tonnes of RP-1.
The first stage holds another 500 tonnes.
I really can't see inter-city rocket transport as viable. Not with current technology any way. They don't even mention the repeated aborts and technical delays for unmanned rockets that have always plagued the industry. It would be an unworkable nightmare for a time critical business like scheduled passenger transport. As a glorified day trip, then maybe, but perhaps Blue Origin & Virgin have that one sewn up.
The BFR will use around 4400 tons of fuel - thats for a 150t low earth orbit.
Lox/methane isnt a problem from an environmental pov so thats not a worry.
I assume the launch islands wont be 3 kilometers of shore lol..
As for cost, the fuel isnt that expensive but there is a lot of it.
Probably something like 3-4 times the cost of fuelling a 747, will need /most/ of a full load to do any of those flights I suspect.
Lox/methane isnt a problem from an environmental pov so thats not a worry.
I assume the launch islands wont be 3 kilometers of shore lol..
As for cost, the fuel isnt that expensive but there is a lot of it.
Probably something like 3-4 times the cost of fuelling a 747, will need /most/ of a full load to do any of those flights I suspect.
RobDickinson said:
The BFR will use around 4400 tons of fuel - thats for a 150t low earth orbit.
Lox/methane isnt a problem from an environmental pov so thats not a worry.
I assume the launch islands wont be 3 kilometers of shore lol..
As for cost, the fuel isnt that expensive but there is a lot of it.
Probably something like 3-4 times the cost of fuelling a 747, will need /most/ of a full load to do any of those flights I suspect.
how many people could these rockets take though?Lox/methane isnt a problem from an environmental pov so thats not a worry.
I assume the launch islands wont be 3 kilometers of shore lol..
As for cost, the fuel isnt that expensive but there is a lot of it.
Probably something like 3-4 times the cost of fuelling a 747, will need /most/ of a full load to do any of those flights I suspect.
The 747 is taking 500ish passengers.
I'm curious why they'd need the first stage for a sub-orbital flight, 2nd stage with the 1st stage nozzles I would have thought may be enough.
2 stage wouldn't be cost effective, you'd need minimum of 1000 passengers at prices well above conventional aircraft.
Fuel cost on an F9 flight is IRO $200,000, BFR is roughly 10x the size, so 10x the cost minimum.
If it was 100 passengers, You're in the $40-50k range for a ticket when you add associated costs.
There will be some that would take it for the sub-orbital experience, especially if it would render Virgin Galactic dead in the water.
If it was the 2nd stage only with ~£200k fuel, 100 passangers, $4-5k ticket may work.
2 stage wouldn't be cost effective, you'd need minimum of 1000 passengers at prices well above conventional aircraft.
Fuel cost on an F9 flight is IRO $200,000, BFR is roughly 10x the size, so 10x the cost minimum.
If it was 100 passengers, You're in the $40-50k range for a ticket when you add associated costs.
There will be some that would take it for the sub-orbital experience, especially if it would render Virgin Galactic dead in the water.
If it was the 2nd stage only with ~£200k fuel, 100 passangers, $4-5k ticket may work.
Einion Yrth said:
annodomini2 said:
Fuel cost on an F9 flight is IRO $200,000, BFR is roughly 10x the size, so 10x the cost minimum.
Methane is a lot cheaper than RP1.You need a lot more methane for equivalent energy versus RP1.
Another perspective...
'ELON MUSK'S ROCKET TRAVEL PLAN IS DEF POSSIBLE, DEF BANANAS'
https://www.wired.com/story/elon-musk-spacex-rocke...
And a question would also be how does the military view in incoming ballistic projectile.......is it one of Musk's or one of Kim's ?
(just to note Wired place rockets under transportation rather than Science, which is where the subject really belongs)
'ELON MUSK'S ROCKET TRAVEL PLAN IS DEF POSSIBLE, DEF BANANAS'
https://www.wired.com/story/elon-musk-spacex-rocke...
And a question would also be how does the military view in incoming ballistic projectile.......is it one of Musk's or one of Kim's ?
(just to note Wired place rockets under transportation rather than Science, which is where the subject really belongs)
Edited by Toaster on Monday 2nd October 17:59
annodomini2 said:
Cheaper per litre, possibly, but it is cheaper per Joule?
You need a lot more methane for equivalent energy versus RP1.
"An Airbus A380 carries up to 271 tons of fuel. BFR's takeoff weight is quoted as 4400 tons - 2nd stage dry mass is 85 tons, payload 150 tons, propellant 1100 tons; this leaves 3065 tons for the fully-fueled first stage - assuming an optimistic propellant fraction of 95%, this gives another 2900 tons of propellant, for a total of 4000 tons. At the ratio listed in the propellant numbers for second stage, this comes out to 900 tons of methane and 3100 tons of oxygen. Jet-A costs a dollar per kg. Google says natural gas cost for electricity producers is $2.99 per thousand cubic feet - there's about 19.45kg of methane in there unless my math is off, so the lower bound cost for methane is about 15 cents a kilogram, or 150 dollars a ton; let's say purifying and liquefying it will double the cost. Top Google search result for liquid oxygen cost gives an old (2001) NASA figure of 16 cents a kilogram, but whatever, let's go with that. $464k for oxygen and $270k for methane to fuel a BFR compared to $270k to fuel an A380."You need a lot more methane for equivalent energy versus RP1.
BFR and A380 have about the same volume/capacity.
And personally i dont think you would mistake a spacex BFR stage 2 for a small icbm nuke.. Especially with published schedules etc
RobDickinson said:
And personally i dont think you would mistake a spacex BFR stage 2 for a small icbm nuke.. Especially with published schedules etc
Well I guess the military have never made that type of mistake with aircraft on Scheduled flights!"In the history of commercial aviation, there have been many airliner shootdown incidents which have been caused intentionally or by accident. This is a chronologically ordered list meant to document instances where airliners have been brought down by gunfire or missile attacks, including wartime incidents, rather than terrorist bombings or sabotage".
https://en.wikipedia.org/wiki/List_of_airliner_sho...
http://www.latimes.com/world/europe/la-fg-ukraine-...
Toaster said:
Well I guess the military have never made that type of mistake with aircraft on Scheduled flights!
"In the history of commercial aviation, there have been many airliner shootdown incidents which have been caused intentionally or by accident. This is a chronologically ordered list meant to document instances where airliners have been brought down by gunfire or missile attacks, including wartime incidents, rather than terrorist bombings or sabotage".
https://en.wikipedia.org/wiki/List_of_airliner_sho...
http://www.latimes.com/world/europe/la-fg-ukraine-...
This won't be flying through contested air space.. "In the history of commercial aviation, there have been many airliner shootdown incidents which have been caused intentionally or by accident. This is a chronologically ordered list meant to document instances where airliners have been brought down by gunfire or missile attacks, including wartime incidents, rather than terrorist bombings or sabotage".
https://en.wikipedia.org/wiki/List_of_airliner_sho...
http://www.latimes.com/world/europe/la-fg-ukraine-...
It'll only be in air space of the launching and landing countries, the rest of the time it'll be in orbit.
Shooting down something in orbit is pretty f
kin hard only the USA and probably Russia could at the moment and it wouldn't happen by accident America & Russia have both shot down passenger airliners in the past, accidentally on purpose of course.
Anyway, it's a non-starter and Musk knows it. But, like the showman he is, he knew it'd get clueless journalists wet and sure enough, it made the TV news.
So while we won't see rocket transport like this anytime soon, the hype will help promote what is actually possible and what he really wants to do - Mars.
Anyway, it's a non-starter and Musk knows it. But, like the showman he is, he knew it'd get clueless journalists wet and sure enough, it made the TV news.
So while we won't see rocket transport like this anytime soon, the hype will help promote what is actually possible and what he really wants to do - Mars.
Beati Dogu said:
Anyway, it's a non-starter and Musk knows it. But, like the showman he is, he knew it'd get clueless journalists wet and sure enough, it made the TV news.
Getting non-starters up and running is kind of his thing though. And given he has rockets that land themselves and a contract to get people in them I think that's a pretty good start.Gassing Station | Science! | Top of Page | What's New | My Stuff