Author Topic: TED talk by Gwynne Shotwell (April 2018)  (Read 64823 times)

Offline Dave G

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Re: TED talk by Gwynne Shotwell
« Reply #120 on: 04/26/2018 11:05 am »
Gwynne mentioned the diameter of the fairing being 8 meters for BFR allowing very large sats. Has the BFR stack shrunk in diameter since 2017?
No.

The BFS chomper payload area is smaller than the diameter of the tanks.

Offline Lar

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Re: TED talk by Gwynne Shotwell
« Reply #121 on: 04/26/2018 04:45 pm »
SpaceX showed pictures of BFS's landed in exotic locations like asteroids or Jupiter's moons.  Those would be very hard to get back.  If they fueled in Mars orbit, they could send a probe with another propulsion module off to a much faster trip outbound, but we're still talking about a trip beyond its designed capabilities.
Hard to get back if you're doing a one shot. But that's the wrong way to think about this. Jupiter's moons are just another destination that needs infrastructure emplaced enroute.

Stop thinking flags and footprints, and start thinking about transportation network extension, step by step. Railways managed to get all the way from Omaha to San Francisco, despite locomotives only being able to carry water for maybe 100 miles of travel and fuel for 2-300. At most.  It was done incrementally. As the track was extended, gangs followed behind building wells, dams, water tanks, coaling depots, maintenance facilities, crew lodging, freight depots, and all the rest. All the materials they couldn't ISRU (everything except maybe timbers and rocks and dirt) were brought along, and as facilities were built, it got easier and easier to bring more materials.

(fan to mod transition) Also, the concept of interstellar is not off topic., She mentioned it. But detailed discussion of how to do it in general? Off topic beacuse we have lots of other threads.
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Offline speedevil

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Re: TED talk by Gwynne Shotwell
« Reply #122 on: 04/26/2018 05:14 pm »
Gwynne mentioned the diameter of the fairing being 8 meters for BFR allowing very large sats. Has the BFR stack shrunk in diameter since 2017?

More or less makes sense if it's interior vs exterior diameter.

Offline cppetrie

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Re: TED talk by Gwynne Shotwell
« Reply #123 on: 04/26/2018 05:38 pm »
Gwynne mentioned the diameter of the fairing being 8 meters for BFR allowing very large sats. Has the BFR stack shrunk in diameter since 2017?

More or less makes sense if it's interior vs exterior diameter.
I agree. I think she’s citing an estimate of useable interior diameter not exterior diameter. From a payload perspective that is the relevant measurement.

Offline redskyforge

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Re: TED talk by Gwynne Shotwell
« Reply #124 on: 04/27/2018 08:54 am »
SpaceX showed pictures of BFS's landed in exotic locations like asteroids or Jupiter's moons.  Those would be very hard to get back.  If they fueled in Mars orbit, they could send a probe with another propulsion module off to a much faster trip outbound, but we're still talking about a trip beyond its designed capabilities.
Hard to get back if you're doing a one shot. But that's the wrong way to think about this. Jupiter's moons are just another destination that needs infrastructure emplaced enroute.

Stop thinking flags and footprints, and start thinking about transportation network extension, step by step. Railways managed to get all the way from Omaha to San Francisco, despite locomotives only being able to carry water for maybe 100 miles of travel and fuel for 2-300. At most.  It was done incrementally. As the track was extended, gangs followed behind building wells, dams, water tanks, coaling depots, maintenance facilities, crew lodging, freight depots, and all the rest. All the materials they couldn't ISRU (everything except maybe timbers and rocks and dirt) were brought along, and as facilities were built, it got easier and easier to bring more materials.

(fan to mod transition) Also, the concept of interstellar is not off topic., She mentioned it. But detailed discussion of how to do it in general? Off topic beacuse we have lots of other threads.

I guess this is where companies like Planetary Resources will make money. Deep space refuelling depots and extensive asteroid mining throughout the system to produce propellant and other consumables.

Later maturing into something like the Transport Union of the Expanse series or the Spacing Guild.

Offline Ludus

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Re: TED talk by Gwynne Shotwell
« Reply #125 on: 04/28/2018 05:28 am »
I was impressed at how confident she was about point to point and the numbers she confirmed or mentioned for that. They really are looking at flying it 10X a day, every day. There’s really no difference between that application and orbital transport. I guess they plan to be able to fill the whole thing with propellant and launch in less than 2 hours. Questioned about whether governments will allow it, she said it wouldn’t have seemed likely the USAF would allow F9 boosters to fly back to their property and this is 10 km off shore.

It makes sense as an important part of driving reusability harder than any conventional space application. It wouldn’t really matter to SpaceX if they can make money at it, as long as they don’t lose too much and it subsidizes the perfection of gas and go reusability for space launch.


Offline speedevil

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Re: TED talk by Gwynne Shotwell
« Reply #126 on: 04/28/2018 08:56 am »
I guess they plan to be able to fill the whole thing with propellant and launch in less than 2 hours.
The main phase of filling the propellant in F9 and launching takes under half an hour, with most completed in 15 minutes.
It starts only about an hour and twenty minutes before launch.

Offline Dave G

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Re: TED talk by Gwynne Shotwell
« Reply #127 on: 04/28/2018 12:50 pm »
Questioned about whether governments will allow it, she said it wouldn’t have seemed likely the USAF would allow F9 boosters to fly back to their property and this is 10 km off shore.

By the way, this is the first time we've gotten any numbers from SpaceX as to how far offshore the BFR launch pad will be.  Gwynne actually mentioned both 5km and 10km as possibilities.

So that's a range of 3.1 to 6.2 miles offshore.  Previously, I'd speculated somewhere around 5 miles offshore, so that seems to be about right.

Re: TED talk by Gwynne Shotwell
« Reply #128 on: 04/28/2018 01:09 pm »
I've read sound propagates better over water. Are there any calculations on the acoustic pollution produced by a BFR 5-10km offshore a major city?
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Offline philw1776

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Re: TED talk by Gwynne Shotwell
« Reply #129 on: 04/28/2018 01:14 pm »
I've read sound propagates better over water. Are there any calculations on the acoustic pollution produced by a BFR 5-10km offshore a major city?

Yes it does propagate well.  I am very familiar with the Isle of Shoals ~6 miles off the NH coast and city of Portsmouth. I would be seriously surprised if any commercial passenger launch site outside a major city, assuming any are ever built, is less than 10 miles or 16Km offshore.  These are very big rockets.

Re: TED talk by Gwynne Shotwell
« Reply #130 on: 04/28/2018 01:27 pm »
I've read sound propagates better over water. Are there any calculations on the acoustic pollution produced by a BFR 5-10km offshore a major city?

Yes it does propagate well.  I am very familiar with the Isle of Shoals ~6 miles off the NH coast and city of Portsmouth. I would be seriously surprised if any commercial passenger launch site outside a major city, assuming any are ever built, is less than 10 miles or 16Km offshore.  These are very big rockets.

Well even 16km is not that bad. With an hydrofoil it's a 15min ride.
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Offline Ludus

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Re: TED talk by Gwynne Shotwell
« Reply #131 on: 04/29/2018 07:16 am »
I guess they plan to be able to fill the whole thing with propellant and launch in less than 2 hours.
The main phase of filling the propellant in F9 and launching takes under half an hour, with most completed in 15 minutes.
It starts only about an hour and twenty minutes before launch.

That’s impressive. That makes 2 hour turn around plausible at least as far as refilling.

Offline Ludus

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Re: TED talk by Gwynne Shotwell
« Reply #132 on: 04/29/2018 07:23 am »
I've read sound propagates better over water. Are there any calculations on the acoustic pollution produced by a BFR 5-10km offshore a major city?

Yes it does propagate well.  I am very familiar with the Isle of Shoals ~6 miles off the NH coast and city of Portsmouth. I would be seriously surprised if any commercial passenger launch site outside a major city, assuming any are ever built, is less than 10 miles or 16Km offshore.  These are very big rockets.

I wonder if there are sound suppression techniques that might apply to this situation. I understand that the water systems used at some pads are for this. If it’s a pad at sea there might be new approaches to suppressing sound in the direction of the city.

Offline Dave G

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Re: TED talk by Gwynne Shotwell
« Reply #133 on: 04/29/2018 09:37 am »
The President and Chief Operating Officer of SpaceX said 5-10km offshore.  She wouldn't have said that unless SpaceX had analyzed all aspects of the offshore pad at those distances, including sound.

In the absence of any information, speculation is fine. It's part of what makes this a great forum.

But when we have it straight from the horse's mouth, speculation otherwise seems pointless.

Offline niwax

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Re: TED talk by Gwynne Shotwell
« Reply #134 on: 04/29/2018 12:57 pm »
I've read sound propagates better over water. Are there any calculations on the acoustic pollution produced by a BFR 5-10km offshore a major city?

Yes it does propagate well.  I am very familiar with the Isle of Shoals ~6 miles off the NH coast and city of Portsmouth. I would be seriously surprised if any commercial passenger launch site outside a major city, assuming any are ever built, is less than 10 miles or 16Km offshore.  These are very big rockets.

I wonder if there are sound suppression techniques that might apply to this situation. I understand that the water systems used at some pads are for this. If it’s a pad at sea there might be new approaches to suppressing sound in the direction of the city.

Sound travels well over water because it's a perfectly flat surface. Maybe some installation around the pad to deflect the sound waves slightly upwards?
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Offline nacnud

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Re: TED talk by Gwynne Shotwell
« Reply #135 on: 04/29/2018 01:15 pm »
Sound travels well over water because it's a perfectly flat surface. Maybe some installation around the pad to deflect the sound waves slightly upwards?

The rocket travels upwards too, quite a long way up. I can't think how you could shield from that.
« Last Edit: 04/29/2018 01:15 pm by nacnud »

Offline philw1776

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Re: TED talk by Gwynne Shotwell
« Reply #136 on: 04/29/2018 01:38 pm »
The President and Chief Operating Officer of SpaceX said 5-10km offshore.  She wouldn't have said that unless SpaceX had analyzed all aspects of the offshore pad at those distances, including sound.

In the absence of any information, speculation is fine. It's part of what makes this a great forum.

But when we have it straight from the horse's mouth, speculation otherwise seems pointless.

For example, many of us here speculated that BFR specs from horses mouth at IAC 2016 would change.  They did. 
When far off plans meet reality, especially when they are not engineering constrained, but regulatory, they have an even greater risk of change. 
SpaceX statements are not stone tablets to be worshiped without question, but current plans subject to change over the many years before possible fruition.  I had thought SpaceX was notable for its ability to change course on the fly to adapt to reality intrusions and opportunities previously unknown or not sufficiently vetted.  I doubt that BFR P2P is sufficiently vetted as of 2017.
« Last Edit: 04/29/2018 01:41 pm by philw1776 »
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Offline deruch

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Re: TED talk by Gwynne Shotwell
« Reply #137 on: 04/29/2018 03:28 pm »
Sound travels well over water because it's a perfectly flat surface. Maybe some installation around the pad to deflect the sound waves slightly upwards?

The rocket travels upwards too, quite a long way up. I can't think how you could shield from that.

The issue, if there is one, is going to be less about the sound of the rockets as the vehicles leave and more about incoming vehicles creating very large sonic booms.
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Offline CapitalistOppressor

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Re: TED talk by Gwynne Shotwell
« Reply #138 on: 04/30/2018 02:42 am »
A more mundane possibility: Asking about stuff that would happen 20/35/50 years from now is a bit ridiculous from Gwynnes perspective. She is responsible for the economic success of SpaceX. She has necessarily a horizon of maybe 5 years or some more in some long term development projects. From her perspective, talking about stuff that is 4 to 10 times her current time horizon, there is no way she can give a sensible answer. So she gives intentionally a ridiculous one.

I live in LA and run across SpaceX people all the time, including propulsion types. 

I've had, and overheard, multiple conversations that imply, or flat out state, that these guys expect to be working on advanced propulsion as soon as they finish Raptor/BFR. 

Some were actually bored with Raptor development, which they think is not really that advanced of a propulsion concept.  Just highly necessary, and better than anything else available.


Offline Robotbeat

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Re: TED talk by Gwynne Shotwell
« Reply #139 on: 04/30/2018 03:13 am »
If you're doing point-to-point transport using a highly reusable system and fuel that is produced via electrolysis (indirectly for methane), then the fuel energy costs ends up being a driver of the overall system costs.

Besides the usual performance improvements like higher chamber pressure, thrust-to-weight, etc, that drives you to playing with mixture ratios and using hydrogen instead of methane. Again, if you're making the fuel electrically.

Nuclear thermal only really helps much for high speed beyond-LEO orbits. Anything else just ends up being suboptimal, energy-wise.

So although SpaceX has not pursued hydrogen for a while, I expect them to return to it eventually. And yeah, nuclear thermal probably, too, in order to reduce Mars transit times to below 40 days.
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