airsurfer

Today at 12:30 ET (no idea what timezone that is, probably Ephemeris Time which is actually UTC) Elon Musk had a presentation about settlement on Mars but he ended by telling 'the same rockets we can use to displace people between two places on Earth.

This clip shows JFK-PVG in 39 minutes

https://www.theguardian.com/technolo...lon-musk-video

but other long haul flight in less than an hour, even on the opposite side of the world.

I like that, but problems arise to expose passenger so many G acceleration.

What are your ideas ?

invisible

Oh boy...

OK, this was his 'there is one more thing' moment. Now from purely practical perspective there are SO many questions in term of implementation of the concept that...

- You need to have booster (stage 1) at landing site too, so the ship is going fly back/to other destination. I means that you need to build spaceport to launch BRF at every place where the ship is going to land. How much each spaceport/infrastructure will cost?

- Considering size and how much fuel the booster and ship will carry, you can't have spaceports at the places or similar vicinity where airports are - too dangerous to fly 5000 tons of liquid oxygen and methane on top of your home.

- Reusability of the ship: to make it practical, it should be able to do minimum hundred such space flights without major refurbishments. Nothing like this has been done before. I don't even know if materials exist to withheld such pressure and are useful to build such spaceship. Space Shuttle comes to mind and it cost billions of dollars to build and operate.

- Already mentioned Gs - most likely it will be in the range of 3-4. While it is the range one will get at roller coaster, there it last seconds. In case of BFR it will be minutes. How many ordinary people can take such loads?

- Money... this will cost no less than $5b to build, my estimation. Unless you ask Apple to finance it, there are no other companies having that amount of money, forget about government financing.

and so many other questions.

But I think humanity should give Musk a credit - this guy alone is dragging us into future...

CPRich

Roughly 0.9g constant acceleration then deceleration to do JFK-PVG in 39 minutes. Not near human limits, but significantly more than in a plane today. (0.2g is a typical limit for trains, elevators, etc., but that involves standing. Hyperloop's working assumption seems to be 0.5g max - "this is deemed the maximum inertial acceleration that can be comfortably sustained by humans for short periods.").

At a minimum, I would expect some type of seat that can swing 180 degrees half way through the flight. Being pressed into the back of you seat for 20 minutes might be bearable. Straining forward against just a lap-belt, or even a 5-point harness wouldn't be.

I can't see any type of in-flight service - just a 40 minute ride with small roller coaster level forces.

trooper

And a VERTICAL tail first landing at the destination? So carrying not only the fuel to get there..but the fuel for THAT? In Earths gravity?

Has he heard of the "Rocket Equation"?? How much fuel needed...just to carry the fuel needed? (Which becomes an apparently endless cycle of increase)

Diversion possibilities?..or is it "make it or crash?" How does the reusable booster get recovered and transported back to a/the launch site?

It sounds a bit fantastic to me.....in the original sense of the word!

84fiero

The vertical rocket landing is already being tested with the unmanned Falcon 9 rockets, with a dozen successful tests I think, and of course some failures, which isn't unexpected at this point. So that's not a technical barrier in itself.
Whether people would want to ride on something like that, or whether the economics would make sense for using that type of rocket for point-to-point Earth travel, would have to be worked out obviously.

We've known for 56 years that humans can handle the G forces of rocket launches. But so far said humans have been known to be in good health prior to launch. I would think this concept wouldn't be feasible for some people with health conditions, certain body injuries, etc. Yet just because not everyone could handle it, doesn't mean it couldn't be available for those who can.

It does seem less likely to be feasible than some other concepts for very high-speed point-to-point Earth travel such as hypersonic planes. There has to be demand for such a service to begin with and then a business case for providing it.

Still, if someone like Musk wants to explore the possibility I'm all for it, even if it doesn't ultimately pan out. Lots of great ideas come out of trying and failing. And I think we have too few visionaries at a time when humanity might need them more than ever.

frobozzelectric

I like my time in F and the G forces would probably kill or injure me anyway.

timfountain

Given the awful fatality statistics for space related activities (ok small sample size but a high %) since the space race began, I'm going to say not for me, thanks! It will also be astronomically expensive so again, not for me.

roberino

Airplane fuel is $6 a gallon. An A380 carries about 80k gallons, so it costs $480k to fuel one for a long haul journey.

NASA used to spend $1.5m in hydrogen and oxygen to get a space shuttle to orbital flight. A point-to-point flight will use less than that.

As a very rough guess I’d say that the fuel cost for a rocket flight would be around double that of an A380. Then take into account that a rocket uses the same fuel load whether it flies from JFK to EWR as it would from LHR to SYD, making longer haul journeys more economical.

The BFR should take up 150 metric tons as cargo, so matching the passenger load of an A380 shouldn’t be an issue.

Maybe someone more schooled in aeronautical engineering that me can pick apart my guesswork but I don’t see why, once the business model has been established, that this shouldn’t be accessible to anyone used to buying a J ticket.

invisible

Well, people already made rough estimations and it comes profitable around US $10K per seat, with the current price of CH4/LOX fuel, plus service/etc. This does not account any costs for the vehicle itself which most likely will be north of $1B (just for one, excluding all development costs). And we are not talking infrastructure costs....

I am big fan of Musk, but I really can't see how it can fly (pun intended), even when all safety concerns are taken care of.

airsurfer

CH4 / LOX or H2 / LOX and a spark ... => B O O M !!!!
And many victims and lots of damage at the spaceport, much more than a fire happening in a fully loaded A380, as it is MUCH more explosive than kerosene / air !
A lot has to be done to minimize this risk.

tmiw

All-J services haven't done well in the past, IIRC. The better comparison, IMO, would likely be with private jet services.

invisible

5400 tons of fuel is like mini-Hiroshima in case of explosion. Soviet's N1 moon rocket explosion on pad was 6kt - the biggest non-nuclear explosion in history.

Agree, unfortunately, physics, specifically - gravity is a .... and we have not yet discovered or invented viable means of transport in air/space without requiring explosive chemical reactions...

chrisl137

Because launch vehicle failure rates are still astronomical compared to aircraft - as in 1 to 3%. For the foreseeable future you'll probably has as much chance of getting blown up as of making the highest frequent flyer status.

trooper

Umm.. no they won't....unless you plan on it freefalling to the ground which sort of defeats the purpose... its going to take at LEAST as much fuel to decelerate and land the thing as it did to launch it... suborbital or not.....

The only suborbital rocket stats I can find are from the Mercury-Redstone... For it to put 1800kgs up on a suborbital path the whole thing weighed 30,000kg...AND it burnt ALL its fuel going UP.

A payload of 150, 000 kg is going to need...well..a whole shitload of fuel... half (or more) of which has to be carried most of the way...thus the actual payload at launch is that claimed 150,000 kg PLUS the entire weight of the descent fuel...... Would be a LOT more realistic IMO idf the plan involved aerobraking and parachutes...or a shuttle type glider.....

I just don't see how it would be possible...let alone economic.

WorldLux

Musk has a few brilliant ideas but a lot of unrealistic ones. This one goes (along with the propositions of building huge tunnel systems under LA) into the latter category.

If the economic data doesn't stop this idea, then the people probably will. When Concorde was launched, dozens of airlines ordered it. After protests everywhere, most nations banned Concorde from flying supersonic over land and thus eliminating the selling point for most airlines.

Musk would probably be better off building a quiet Concorde (There are a couple of design being tested by several companies). I could see those on ULH routes where some premium passenger would certainly be willing to cut of a couple of flight hours.