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

181–190 of 277 posts

Re: SpaceX BFR [video]

#181

Post by baq »

usrusr wrote: post #55
InclinedPlane wrote: post #41

Earlier quoted context omitted.

Maybe. Rockets can actually fly through a variety of rough weather conditions. Indeed, they can even survive being struck by lightning (as Apollo 12 was). However, they are not, as a rule, designed to do so. And because they are multi-million dollar equipment that are only used once before being discarded it's easier to simply avoid launching in weather that might be too severe. However, in practice a rocket could be…

Punching through the atmosphere layer at speeds that are economical when every two extra minutes spent there waste more than one km/s of precious delta-v make every storm look tame. But solving the control problem for the "suicide burn" landing? I would not be so sure about that.

Given enough thrust even pigs can fly, so I'd say it's just a matter of more struts and much bigger RCS. Since we're talking suborbital, mass penalty isn't that bad.

Re: SpaceX BFR [video]

#182

Post by mstade »

simonh wrote: post #138
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…

It’s a really good question. Supersonic jets were always heavily constrained due to noise pollution issues with the sonic boom. They weren’t allowed to fly over land at supersonic speeds, relegating them to trans-oceanic routes. Now yes this system will have such problems on launch, but as they go pretty much straight up out of the atmosphere compared to a jet, the vast majority of the journey is in space where that’…

If people think supersonic jets are loud, they’re in for a treat with rockets. Anyone who’s ever witnessed a launch at KSC (I have) will probably say two things: it’s awesome, and it’s LOUD.

Not ear popping kind of loud, but VERY loud nonetheless, and you feel it too if you’re close enough. (Really recommend a viewing at the LC39 observation gantry, it’s awesome!) I was watching that video and kept thinking that platform isn’t far enough from inhabited land that people won’t go apeshit over how loud it is.

I want this future, and boy do I want to see a rocket launch again, but waking up to that nice sound of rocket fuel burning at 6.30am? Yeah, maybe no. :o)

Re: SpaceX BFR [video]

#183

Post by stcredzero »

pjungwir wrote: post #175

In startups you often have tech that is more general than it needs to be, and you start thinking about all the opportunities, but it can be a mistake. In your go-to-market strategy, you need focus. If you say, "We have 3 business models", it means you don't yet have a business model. I hope Elon the best, but I wonder if that is happening here. SpaceX is going to sell Internet, do fast air travel, do space tourism, .…

In your go-to-market strategy, you need focus. If you say, "We have 3 business models", it means you don't yet have a business model.

It's pretty clear that SpaceX is in the reusable rocket business. By your logic, Boeing didn't have focus, because they built seaplanes, flying boats, fighters, cargo planes, and passenger planes. (This is what they did, in the order that they did it.) They apparently had at least 5 business models. Whoops. I guess they didn't have a business model!

Re: SpaceX BFR [video]

#185

Post by mstade »

InclinedPlane wrote: post #41
ojosilva wrote: post #27

I'm not sure here, but I think weather could play a major role in disrupting launches, greater than with jet liners, right? And not just due to windy conditions (which planes can better withstand up to a certain point), but also rough waters. Another issue is noise. I don't see rockets happening that close to shore in large cities. A long pad-to-city commute, with ship trip included, would be another inconvenience.

Maybe. Rockets can actually fly through a variety of rough weather conditions. Indeed, they can even survive being struck by lightning (as Apollo 12 was). However, they are not, as a rule, designed to do so. And because they are multi-million dollar equipment that are only used once before being discarded it's easier to simply avoid launching in weather that might be too severe. However, in practice a rocket could be…

> sorry fellas, I've overriden your orders, we can't launch today, the weather is too crummy, oh well, better wait until tomorrow, if there is one

This cracked me up! :o)

I can sort of see a Monty Python-esque sketch or something in front of me know. Hilarious, thanks for the laugh!

Re: SpaceX BFR [video]

#186

Post by planteen »

mjamesaustin wrote: post #167
planteen wrote: post #116

Earlier quoted context omitted.

Latest claim: "elonmusk Fly to most places on Earth in under 30 mins and anywhere in under 60. Cost per seat should be about the same as full fare economy in an aircraft. Forgot to mention that." https://www.instagram.com/p/BZnVfWxgdLe/ What's a NYC to SHA full fare one way, about $800? I wonder if he is also getting into the fuel business? So if this rocket holds 200 people, that only gives him $160k in revenue. Fue…

In the presentation he mentions that the payload volume is larger than an A380, which seats 525 passengers in a standard configuration or over 800 passengers in an all-economy configuration. So we're looking at more like $400-$600k revenue per launch. And honestly, if prices came in at 50% more than traditional airlines, you're looking at a hell of a great deal to cut your travel time dramatically.

So say we boost things to 1,000 passengers, cost of full fare is $5000 so people are willing to pay $10,000. Assume passengers and luggage average out to 200 lbs/passenger. You are looking at a revenue per launch of $50/lb. Sure, this is suborbital, but that is nearly 50x cheaper than what it costs to get to LEO using SpaceX right now.

Re: SpaceX BFR [video]

#187

Post by jessriedel »

usrusr wrote: post #55
InclinedPlane wrote: post #41

Earlier quoted context omitted.

Maybe. Rockets can actually fly through a variety of rough weather conditions. Indeed, they can even survive being struck by lightning (as Apollo 12 was). However, they are not, as a rule, designed to do so. And because they are multi-million dollar equipment that are only used once before being discarded it's easier to simply avoid launching in weather that might be too severe. However, in practice a rocket could be…

Punching through the atmosphere layer at speeds that are economical when every two extra minutes spent there waste more than one km/s of precious delta-v make every storm look tame. But solving the control problem for the "suicide burn" landing? I would not be so sure about that.

I don't think it's a suicide burn. The upper stage of the BFG has separate engines for vacuum (4) and atmosphere (2). The two atmospheric engines are only used for landing so, unlike the Falcon 9/Heavy, they can probably be throttled down far enough so the thrust equals the weight. The suborbital earth transport rocket (which is super hypothetical at this point) would presumably have these features too.

Another way to say this is that suborbital flight requires sufficiently less Delta v that you can afford to have engine diversity.

Re: SpaceX BFR [video]

#188

Post by jessriedel »

fludlight wrote: post #48
InclinedPlane wrote: post #41

Earlier quoted context omitted.

Maybe. Rockets can actually fly through a variety of rough weather conditions. Indeed, they can even survive being struck by lightning (as Apollo 12 was). However, they are not, as a rule, designed to do so. And because they are multi-million dollar equipment that are only used once before being discarded it's easier to simply avoid launching in weather that might be too severe. However, in practice a rocket could be…

ICBMs also typically launch from underground, which helps a bit with the noise and maybe even the weather. Also, you'd have to dig a pretty wide hole to make it land-able and reusable.

Plenty of ICBMs launch above ground, e.g., Russia's rail-mounted arsenal.

Re: SpaceX BFR [video]

#189

Post by justin66 »

planteen wrote: post #179
justin66 wrote: post #168

Earlier quoted context omitted.

> the loss rate for rockets I wonder how you constructed that comparison such that it seemed meaningful. I'm pretty sure the lesson when you look at the data would be "fly on a man-rated Soyuz, not a Space Shuttle."

Are you looking at failures per mission or fatalities per person-trip? I thought the shuttle and Soyuz were very close on the fatalities per person-trip metric.

I'm surprised by that. They haven't lost a Soyuz crew since 1971, and they've flown quite a few.

(Soyuz capsules have had one or two pretty hard landings that I'm aware of. That's a failure mode that the newer capsules probably won't have.)

Re: SpaceX BFR [video]

#190

Post by nradov »

sillysaurus3 wrote: post #161
thesash wrote: post #157

Earlier quoted context omitted.

Yes, totally, I get that they have a plan to make it safer -- my point is that a 20,000x increase in saftey is a massive leap, and that will be the limiting factor for this technology.

Well, your comparison isn't too fair. It seems like you're using the loss rates for modern aircraft capabilities. This is roughly like comparing the crash rates of modern OS's to early Unix. To put it another way, it seems likely that the safety will increase by that much. Before airplanes, hang gliders were one of the most popular ways to fly, along with balloons. Gliders were incredibly unsafe, because pilots were…

Fair has nothing to do with it. Civilians aren't going to pay for tickets on a rocket that they perceive as unsafe just to save a few hours. Those rockets will have to go years carrying cargo (or maybe military personnel) with zero crashes before the FAA will be willing to certify them for carrying paying commercial passengers.
Post reply on HN