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SpaceX BFR [video]

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Re: SpaceX BFR [video]

#171

Post by thesash »

justin66 wrote: post #168
thesash wrote: post #151

There are three things that would factor into my decision about whether to strap myself to a rocket rather than fly in a plane: time, cost, and safety. Musk & SpaceX are talking a lot about time and cost, but safety is obviously a lot more important. Based on data I found on the internet (so it must be true!) the loss rate for rockets is 20k - 165k higher than the fatal crash rate for airplanes over the past 20 years…

> 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."

Loss rate for Space Shuttle program was 1.5%

135 missions, 2 lost.

http://www.popularmechanics.com/space/a6611/us-space-shuttle...

Re: SpaceX BFR [video]

#172

Post by thesash »

ncallaway wrote: post #162
thesash wrote: post #155

Earlier quoted context omitted.

The loss rate for manned space launches over the past 20 years has been 0.79%. What you're pointing out (only once every few decades) is a factor of the small number of manned launches per year. Actual loss rate is very high. 1/130 chance of loss.

> is a factor of the small number of manned launches per year That's true, but the person you're replying to spent most of their comment directly addressing that fact.

What am I missing that addresses the math?

Re: SpaceX BFR [video]

#173

Post by thesash »

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…

Again, I'm not saying it's not possible I'm saying that it's going to be really, really hard and that saftey is the critical path to making this viable. I'm sure they are spending all of their time and resources devoted to improving saftey. I'm just pointing out the ridiculousness of focusing the PR on time savings and cost parity when the saftey deficit is currently massive.

Re: SpaceX BFR [video]

#174

Post by willyt »

skykooler wrote: post #117
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?

This was brought up in the presentation as well - they have plans to eventually use the same technology they will use on Mars, on Earth as well, to take CO2 out of the air and combine it with water to create methane and oxygen. If it happens, the rockets would be carbon-neutral.

Ah ok, that's not in the linked video, but in the following one that autoplays afterwards.

Re: SpaceX BFR [video]

#175

Post by pjungwir »

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, . . . . Same with Tesla: we aren't just a car company, we're a battery company! There is a hyperloop and a digging company and solar rooftops. I think it's true there are many opportunities, and history has had its conglomerates like GE, but there is risk in losing your focus.

Still, I'm thrilled he is pushing us forward!

Re: SpaceX BFR [video]

#176

Post by grinich »

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’…

After the Concord was built, NASA did some research into reducing sonic booms (the Shaped Sonic Boom Experiment) which showed you could modify the fuselage to reduce the noise shock by about 30%. This would have brought the Concord below the acceptable noise threshold. Unfortunately it was never built-out commercially and we now have legislation banning supersonic flight over land.

https://en.wikipedia.org/wiki/Shaped_Sonic_Boom_Demonstratio...

Re: SpaceX BFR [video]

#177

Post by justin66 »

thesash wrote: post #171
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."

Loss rate for Space Shuttle program was 1.5% 135 missions, 2 lost. http://www.popularmechanics.com/space/a6611/us-space-shuttle...

Do you see that as an indictment of the safety of manned space flight, or the safety of that vehicle? (you do understand that the modern Soyuz is quite safe, right? One can expect SpaceX's stuff to be safer.)

Re: SpaceX BFR [video]

#178

Post by Shank »

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, .…

These are all related to the core business though. If you can launch rockets, you can launch sats. If you can discount sat launches, you can launch a lot of sats.

If you can launch rockets capable of re-entry and reuse and need to finance building rockets to go to Mars, you can build rockets for cross-continental travel.

It's not like SpaceX is building a smartphone. They're building in their core competencies.

Re: SpaceX BFR [video]

#179

Post by planteen »

justin66 wrote: post #168
thesash wrote: post #151

There are three things that would factor into my decision about whether to strap myself to a rocket rather than fly in a plane: time, cost, and safety. Musk & SpaceX are talking a lot about time and cost, but safety is obviously a lot more important. Based on data I found on the internet (so it must be true!) the loss rate for rockets is 20k - 165k higher than the fatal crash rate for airplanes over the past 20 years…

> 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.

Re: SpaceX BFR [video]

#180

Post by Cerium »

thesash wrote: post #172
ncallaway wrote: post #162

Earlier quoted context omitted.

> is a factor of the small number of manned launches per year That's true, but the person you're replying to spent most of their comment directly addressing that fact.

What am I missing that addresses the math?

That you will always have at least single digit failures. Sometimes things have to go wrong before we can correct them. We got where we are today with airplanes not because the first million flights didn't have a single accident, but because we paid careful attention to every failure and did our best to keep it from ever happening again.

Take a look at this report on Boeing crash history: http://www.boeing.com/resources/boeingdotcom/company/about_b... In particular, take a look at page 17 (slide 16) which shows the crash rate over time. We have gone from about 40 hull losses per million departures in the 50's to about 0.6 to 1 (depending on how you count) per million departures today.

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