Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

SpaceX BFR [video]

youtube.com

Post reply on HN
Print view View original

241–250 of 277 posts

Re: SpaceX BFR [video]

#241

Post by njarboe »

ryandrake wrote: post #237

Why not instead work on ways to reduce the need to move people from one place on Earth to another, thereby eliminating the cost, hassle and pollution of air travel and hypothetical rocket travel? There's a huge amount of progress that can be made in telepresence technology--it seems silly to get hung up on the assumption that in order to do something or experience something somewhere you need your bag of water and me…

Why don't you start working on Holodecks. Musk wants to get humanity off this rock. Funding the building of a ship designed to land anywhere in the solar system, including Earth, by using it for Earth transport is brilliant. If one can make the trip from New York to Shanghai in 40 minutes, for the same fuel per person and ticket price as an airplane, why not. Having a fully reusable rocket will be amazing.

Once reliability is proven one could even start thinking about nuclear powered rockets and get those CO2 emissions to zero. I'm sure it is on Elon Musk's mind and Mueller has even mentioned looking into nuclear rockets. Solar system travel could really use nuclear rockets to get reasonable travel travel times.

Re: SpaceX BFR [video]

#242

Post by ryandrake »

njarboe wrote: post #241
ryandrake wrote: post #237

Why not instead work on ways to reduce the need to move people from one place on Earth to another, thereby eliminating the cost, hassle and pollution of air travel and hypothetical rocket travel? There's a huge amount of progress that can be made in telepresence technology--it seems silly to get hung up on the assumption that in order to do something or experience something somewhere you need your bag of water and me…

Why don't you start working on Holodecks. Musk wants to get humanity off this rock. Funding the building of a ship designed to land anywhere in the solar system, including Earth, by using it for Earth transport is brilliant. If one can make the trip from New York to Shanghai in 40 minutes, for the same fuel per person and ticket price as an airplane, why not. Having a fully reusable rocket will be amazing. Once relia…

I fully applaud efforts to "get humanity off the rock". To the extent that building a rocket airline helps move humanity toward this goal, great! But, other than as a stepping stone to something bigger, this just seems like a silly distraction.

As for the very HN-ish "why don't you just go make XYZ?" retort, obviously it's because, like most of us (and unlike Elon Musk), I don't have the necessary truckloads of $100 bills necessary to make that happen. I'll get back to you after my windfall from selling PayPal...

Re: SpaceX BFR [video]

#243

Post by njarboe »

jokoon wrote: post #61

Aren't supersonic jets more affordable? I mean I know SpaceX is about changing the world, and I know SpaceX is about rockets, but in terms of market, I think having a new Concorde would better fit the idea of earth to earth travel. I like how SpaceX innovates, but I think this is a "too soon", bad product idea because it will be too expensive at first, and supersonic jets would be a better competitor. Although I have…

Many transportation systems are built using funds from selling land acquired at very low prices and then sold at much higher prices, once the transportation system is in place. Trolley systems in LA in the 1920's or road systems for the famous American suburbs.

Land on Mars is for the taking at the moment. What people will pay to live there is not known yet, but will be in the millions for some.

Re: SpaceX BFR [video]

#244

Post by snrplfth »

stcredzero wrote: post #198
willyt wrote: post #53

Earlier quoted context omitted.

And if it becomes that common, in 150 years time, New York will be under water. I remember reading that the instantaneous power output of one Apollo rocket taking off is roughly the equivalent of the entire average electricity load of the UK. Surely burning a country's worth of rocket fuel every time you want to travel long distance is not sustainable?

And if it becomes that common, in 150 years time, New York will be under water. If it becomes that common, it will be well within the major power's ability to block 1.5% of the sunlight that hits the Earth by posting sunshades at L1. Surely burning a country's worth of rocket fuel every time you want to travel long distance is not sustainable? It doesn't take that many airliner flights to match that power output.

Indeed, a Falcon 9 takes only the amount of fuel used by 2 long-distance 747 flights. BFR might be, say, five to seven times that, though it's a different fuel (natural gas instead of kerosene.)

Re: SpaceX BFR [video]

#245

Post by njarboe »

epaulson wrote: post #218
dzhiurgis wrote: post #169

Earlier quoted context omitted.

Auckland to Vilnius is at least 3 flights and 24+ hours of flight time. Door to door is basically 2 days. Elon please save me.

How often do you think you can find a rocket's worth of people who want to go from Auckland to Vilnius?

Hard to know how many would go at one shot. A few hundred? One could move cargo also. Maybe once a day? For a 40 minute trip, maybe a lot more. Depends on the price. The thing is, the infrastructure a rocket needs might be way less than big airplanes. Super chilled CH4 and O2 and a small pad and tower. Along with doing say 20 flights per day, these things can move around the globe easily and go where the demand is.

Re: SpaceX BFR [video]

#246

Post by Robotbeat »

simplicio wrote: post #234
Robotbeat wrote: post #208

Earlier quoted context omitted.

They're going to get around it because this is a secondary market for BFR. Primary market is launching satellites (especially their constellation). Remember, this point-to-point idea was basically an after-thought. It's decades away, but the rocket will be launching within the next 3-5 years. So they'll have decades to get it right, and the manufacturing line and much of the infrastructure will be paid for. But you'r…

Total orbital rocket flights/yr are usually considerably less than 100 though, so I'm sceptical they'll ever approach airplane reliability with so few flights. Honestly, that's kind of why the BFR idea kind of worries me. It feels like SpaceX analysed the need for orbital space-flights, and realized there was unlikely to ever be the kind demand that would provide the economies of scale needed to do what they want. On…

"Total orbital rocket flights/yr are usually considerably less than 100 though, so I'm sceptical they'll ever approach airplane reliability with so few flights."

"with so few flights" is the operative phrase there.

Current launch market is about 60-100/year.

This is why SpaceX invented its constellation: not only does it allow them to make a lot more money than just doing a few dozen launches per year, but it allows them to generate their own demand for launches to justify these crazy Mars rockets. The constellation is for about 12,000 satellites replaced every 4 years or so. Initially 500kg, but Mueller (rocket guy) recently hinted they could get much larger (so let's say 50-100 tons). Therefore, they'll be able to self-generate between 30 and 3000 annual BFR launches on their own. This point to point thing is another add-on market, could be even larger from a launch volume perspective (but, interestingly, smaller from a addressable-market revenue perspective than the constellation). With 3000 flights per year and margin to spare (and the benefit of post-inspection of the rocket in case of a near-miss), you should be about 100-1000x as reliable as today's crewed rockets just to start. Now add point-to-point, and you can do 50,000 BFR flights per year...

Re: SpaceX BFR [video]

#247

Post by justin66 »

grmarcil wrote: post #219
justin66 wrote: post #207

Earlier quoted context omitted.

An emergency landing on water followed by everyone exiting the vehicle and using their seat cushion as a flotation device seems like the obvious counterexample. That seems survivable enough (I bet that ship would float better than a 747) but you'd want people on hand to help everyone out.

The point is with a rocket, if you can't land at your original destination, you probably don't have the capability to safely land anywhere else. Maybe I'm overlooking a scenario you have in mind, but IMO you're looking at two classes of problems: 1) Problem during launch. There's been one successful use of a launch escape system in rocketry history[1], and such a system has never been developed for a shuttle type cra…

> 1) Problem during launch. There's been one successful use of a launch escape system in rocketry history[1], and such a system has never been developed for a shuttle type craft.

I'm not sure if you're aware, but this is a feature of the latest version of SpaceX's capsules. I'm sure it would exist for their larger vehicles.

edit: although I'm just not sure what you'd do during an abort with all that fuel that larger vehicle holds...

Re: SpaceX BFR [video]

#248

Post by justin66 »

mikeash wrote: post #217
justin66 wrote: post #207

Earlier quoted context omitted.

An emergency landing on water followed by everyone exiting the vehicle and using their seat cushion as a flotation device seems like the obvious counterexample. That seems survivable enough (I bet that ship would float better than a 747) but you'd want people on hand to help everyone out.

I can't come up with a scenario where the BFR ship would make an emergency water landing. (Of course, it could just be that I lack knowledge or imagination.) Airliners can do them because they glide, so water landings are a possibility after fuel exhaustion or engine failure. BFR won't glide well enough to land softly, so it would have to be a propulsive water landing. And if you can land propulsively in the water, s…

> if you can land propulsively in the water, surely you can land propulsively at the landing pad.

I think if you take off and you immediately find that one of the rocket motors isn't gimballing correctly, or something else looks off with the engines, it might be prudent to abort before building up a lot of velocity. (not to mention aborting before something explodes) It's certainly easier.

Re: SpaceX BFR [video]

#249

Post by mikeash »

justin66 wrote: post #247
grmarcil wrote: post #219

Earlier quoted context omitted.

The point is with a rocket, if you can't land at your original destination, you probably don't have the capability to safely land anywhere else. Maybe I'm overlooking a scenario you have in mind, but IMO you're looking at two classes of problems: 1) Problem during launch. There's been one successful use of a launch escape system in rocketry history[1], and such a system has never been developed for a shuttle type cra…

> 1) Problem during launch. There's been one successful use of a launch escape system in rocketry history[1], and such a system has never been developed for a shuttle type craft. I'm not sure if you're aware, but this is a feature of the latest version of SpaceX's capsules. I'm sure it would exist for their larger vehicles. edit: although I'm just not sure what you'd do during an abort with all that fuel that larger…

I'm not so sure. The Dragon 2 integrates a launch escape system by using the same engines that are also intended for propulsive landing (which is now probably off the table for good, but that was the idea). The BFR ship won't have near enough TWR when fully loaded for its landing engines to double as launch escape engines, and I see no evidence of any other engines.

The fact that the BFR ship serves as both second stage and capsule combined, whereas the Dragon 2 is just a capsule with a separate second stage to put it into orbit, makes the problem a lot harder. I bet that the system for the BFR will consist of "don't explode."

Re: SpaceX BFR [video]

#250

Post by mikeash »

justin66 wrote: post #248
mikeash wrote: post #217

Earlier quoted context omitted.

I can't come up with a scenario where the BFR ship would make an emergency water landing. (Of course, it could just be that I lack knowledge or imagination.) Airliners can do them because they glide, so water landings are a possibility after fuel exhaustion or engine failure. BFR won't glide well enough to land softly, so it would have to be a propulsive water landing. And if you can land propulsively in the water, s…

> if you can land propulsively in the water, surely you can land propulsively at the landing pad. I think if you take off and you immediately find that one of the rocket motors isn't gimballing correctly, or something else looks off with the engines, it might be prudent to abort before building up a lot of velocity. (not to mention aborting before something explodes) It's certainly easier.

Land back at the takeoff point then?
Post reply on HN