9/29 2017 IAC - Elon: Interplanetary Plans Pt. 2

[AudubonB]

I'm reasonably familiar with Sabatier process, all of Zubrin's calculations and so forth, but I'm far less comfortable with launch and landing physics, and Mr Musk's presentation of a few minutes ago got me to wondering:

==>Are there significant astrodynamic reasons for performing Martian escape launches from equatorial latitudes? And, for that matter, Martian landings? Because......


why one earth (oops. Should be writing "Why on Mars") can it make sense to extract the necessary CO2 from the Martian atmosphere? Atmospheric density there ranges from 0.3 mbar at the peak of Olympus Mons up to 11.55 mbar in the depths of Hellas Planitia. Assuming that's atmosphere is pure CO2 (it's about 96%, so close enough), that still is so minuscule an amount of carbon dioxide compared to what occurs at the polar regions that there is effectively no comparison.

The winter polar ice caps are effectively pure carbon dioxide - dry ice - which is 790 times as dense as gaseous CO2 at one atmosphere. Introducing the reduced atmospheric multiplier, and I'm getting 69,300 times more dense than what's present at Hellas Planitia, and 2.637 million times more dense than atop Olympus Mons.

So....why not "shovel in" the polar dry ice rather than create atmospheric scrubbers? Can any low latitude astrodynamics outweigh this advantage?

 

[Grendal]

Elon sounded just like he always does. If anything he was smoother than normal. He had more reflective pauses, and tried to let people think about what he said. Cause it was, frankly, all earth shattering. The implications.

It makes all other orbital rockets look like silly toys. It makes the F9 and FH obsolete too once it is built and flown. Using his plane description, F9 is a really good commuter jet. BFR is a true 787 in comparison.

 

[EchoDelta]

... Cause it was, frankly, all earth shattering. The implications.

Bonding, not shattering. Earth bonding.


I honestly wasn’t expecting it. I had always assumed a BFR launch marginal cost would be a few dozen MM, making it hard to compete with private airplane prices, forget about competing w “full fare economy class”

 

[evp]

So....why not "shovel in" the polar dry ice rather than create atmospheric scrubbers? Can any low latitude astrodynamics outweigh this advantage?

Because you can just sit in one place and suck up all the CO2 you can use. It has to be gaseous anyway for the conversion process. The polar ice caps will supply more to wherever your propellant plant is without you having to import a single shovel to Mars.

 

[EchoDelta]

I'm reasonably familiar with Sabatier process, all of Zubrin's calculations and so forth, but I'm far less comfortable with launch and landing physics, and Mr Musk's presentation of a few minutes ago got me to wondering:

==>Are there significant astrodynamic reasons for performing Martian escape launches from equatorial latitudes? And, for that matter, Martian landings? Because......


why one earth (oops. Should be writing "Why on Mars") can it make sense to extract the necessary CO2 from the Martian atmosphere? Atmospheric density there ranges from 0.3 mbar at the peak of Olympus Mons up to 11.55 mbar in the depths of Hellas Planitia. Assuming that's atmosphere is pure CO2 (it's about 96%, so close enough), that still is so minuscule an amount of carbon dioxide compared to what occurs at the polar regions that there is effectively no comparison.

The winter polar ice caps are effectively pure carbon dioxide - dry ice - which is 790 times as dense as gaseous CO2 at one atmosphere. Introducing the reduced atmospheric multiplier, and I'm getting 69,300 times more dense than what's present at Hellas Planitia, and 2.637 million times more dense than atop Olympus Mons.

So....why not "shovel in" the polar dry ice rather than create atmospheric scrubbers? Can any low latitude astrodynamics outweigh this advantage?

Shovel it in and rocket it to where you need it? A boring machine that basically digs it’s own long tank...(being playful haven’t done research to see if it’s a valid approach)

 

[dpeilow]

So I get that Elon wants to use a process of splitting H2 from H2O with an electrolyser and then the Sabatier reaction to make this into methane using atmospheric CO2. That's fine as a concept for refueling on Mars and even a reasonable launch rate from Earth.

However, we all know that making hydrogen in the first step is pretty energy inefficient. Whether the waste heat is something that can be used to drive the Sabatier reaction is something I would need to look at further, but I have a concern that if Elon's vision is everyone flying half way around the world in 30 minutes and this pays for the Mars programme, we need a lot of feedstock hydrogen.

It's then bait for the fossil fuel industry to come along and argue that we may as well just do the same for cars.

 

[ecarfan]

Wow. 30 minutes around the world, we’ll maybe 50 minutes tops. And they are going to junk falcon 9, falcon heavy, dragon 1 and 2 relatively soon too, like in a few years. Balls, man. Giant balls. Space balls!!

Exactly.

I was so impressed with the fact that Elon is willing to obsolete his own products (F9, FH, Dragon), products that are way ahead of the competition by the way, to move on to a much better product. Embrace the future, don't be afraid of it! That is the mark of a fearless genius.

I had a hard time sleeping after watching the presentation. Woke up at 3:30AM.

 

[Skotty]

Last year was pie in the sky. This year's revised plan looks risky in some ways (retiring proven existing hardware), but far more realistic, and I think some folks who were initially saddened by humans just flying around in little capsules again will be pleased to see a bigger more futuristic craft in the works.

Using it for Earth-domestic flights is a fascinating idea. Can costs per passenger be economical enough? He didn't hazard a guess on what a ticket might cost. But if it's possible, I'm sure many world travelers would be delighted by the idea of a 30 minute flight instead of 8+ hours. It would probably kill off any idea of another supersonic commercial aircraft. And it would be a brand new reason for Boeing to feel uncomfortable about SpaceX. Probably made a shiver run down the spine of the folks over at Boeing.

Note they talked about not needing landing legs, but they WILL still need landing legs in at least a few cases. The first flights to new worlds will require landing legs until landing pads are built.

Also, I would recommend to Elon and SpaceX to heavily document and save all data on Falcon 9 if it goes into retirement. Always bugged me seeing stories of how knowledge about the Saturn V engineering and manufacturing has been lost.

 

[Yggdrasill]

I was surprised they would use the booster for earth transportation. Anyone know how far and how fast the spacecraft alone would be able to get?

With potentially 6 sea-level raptors it could do around 1050 tons of thrust. That's less than the fully fueled spacecraft at around 1335 tons, but they could probably dispense with some of the 150 tons of cargo, and they wouldn't have to fully fuel it. I was thinking maybe a variant would be able to get across the atlantic or something like that.

 

[mikevbf]

Using it for Earth-domestic flights is a fascinating idea. Can costs per passenger be economical enough? He didn't hazard a guess on what a ticket might cost.

He predicts same as full fare economy air travel:

Instagram post by Elon Musk • Sep 29, 2017 at 6:19am UTC

 

[Skotty]

He predicts same as full fare economy air travel:

Instagram post by Elon Musk • Sep 29, 2017 at 6:19am UTC

I see that now. Thanks for the correction.

Reading around on some discussions at other places, my personal feeling on the viability of city to city use is that the biggest obstacles will be noise level and safety concerns having a large rocket fly over/near populated areas. While the rocket for interplanetary use and satellite launch has gone from pie in the sky to realistic, this city to city thing is the new pie in the sky; might be more marketing than serious business at the moment. But you have to at least give some second thoughts to the idea of reducing a long range flight time from half a day to half an hour.

 

[mikevbf]

While the rocket for interplanetary use and satellite launch has gone from pie in the sky to realistic, this city to city thing is the new pie in the sky

Your statement makes it painfully obvious how different a league Elon Musk is in to lets say automotive companies coming out with one electric self driving concept after another which are mostly vaporware. Elon Musk's "vaporware" is in a little different category.

 

[Zaxxon]

Last year was pie in the sky. This year's revised plan looks risky in some ways (retiring proven existing hardware), but far more realistic

This was one of my big takeaways, too. In one year this went from 'even I don't believe it' (as a pretty big Tesla/SpaceX/Musk fan) to 'now we're talking.'

What reaction will next year's update garner?

 

[e-FTW]

Throughout the presentation, I could not help but think about the (internal) reactions of the engineers at SpaceX. What are they thinking as he tells the world about these plans, about ISS, moon base, Mars? How much of what he said is aspirational, and some of the engineers are thinking “no way Elon, orbital refueling can't work like that, but I know you'll make me do it, and we will be successful”.
I hope we get to hear those reactions one day.

Then he got to the planetary transport, and my oh my, how much I would have paid to be in a Boeing/Airbus/airline board room to see their reactions. Am sure they are all blowing this off as impossible bluster.
Maybe it is, maybe it is. But what if it isn't? See Tesla.

 

[Zaxxon]

Am sure they are all blowing this off as impossible bluster. Maybe it is, maybe it is. But what if it isn't? See Tesla.

Or, you know, SpaceX.

 

[N5329K]

I wonder if the number of people who will (sooner rather than later) physically need to travel long distances (global scale, not Hyperloop scale) can justify the huge upfront infrastructure costs. Concorde was totally reusable, too.
Robin

 

[NCAviator]

Can't wait to see the response of NASA leadership that are wasting billions of our tax payer dollars on STS. SpaceX is not asking for any of our tax dollars for their development. I also would have loved to see Wernher von Braun reaction if still alive. The refueling idea is brilliant. The difference in engineering concept between SpaceX and the NASA brain trust is very telling. NASA engineers are not allowed to think BIG and NEW. ULA just lost their business.

President Trump asked NASA for a mission to Mars before his term is up. They said no way. SpaceX just said we can do it and we don't want any of your money.

 

[ccutrer]

I wonder if the number of people who will (sooner rather than later) physically need to travel long distances (global scale, not Hyperloop scale) can justify the huge upfront infrastructure costs. Concorde was totally reusable, too.
Robin

Yup, this is my concern. That and the regulatory hurdles. I would love to see a future where rockets hop around the planet, and can be turned in a matter of hours just like airplanes. It's the getting there from here that I don't see the path. Sure the fuel cost for a flight may split up to a couple thousand per passenger. But you have to amortize the cost of the launch pad, operations, lobbying efforts to get it approved. So many hurdles. If the only available flight is NYC to Hong Kong, once a week, there just won't be enough customers for it. Having a full, busy, flight schedule in order to be flexible enough for average use just multiplies the capital costs.

But if anyone has proven himself capable of doing the impossible, it's Elon Musk. When he was introduced as chief designer or whatever of SpaceX I thought "oh, that's a nice honorary title". I know he loves to get into the nitty-gritty details... but then he was talking about not being able to hire any rocket engineers, so he had to become one. Wow, just wow.

I also noticed Elon was more flustered than normal. He's never been a great public speaker, but this was a step beyond. Like, he couldn't even remember what was coming next in the presentation. I chalked it up as being severely jet-lagged, though. Maybe if he could have hopped down to Australia on a BFR, he wouldn't be worn out from traveling

 

[AudubonB]

Because you can just sit in one place and suck up all the CO2 you can use. It has to be gaseous anyway for the conversion process. The polar ice caps will supply more to wherever your propellant plant is without you having to import a single shovel to Mars.

MMmmmmm......the miner in me says that when choosing between a deposit that is between 70,000 and 1 million or so times richer than the other deposit (polar solids vs. atmospheric gases), you have to do better - an awful lot better - than the above to convince me not to use the former.

ALSO - the other resource needed to create the rocket fuel is H2O, and the richest source on Mars for that also is going to be the polar deposits.


So....it seems to me that in order for the polar option not to be optimal, you have to demonstrate that:

• the two other inputs also needed - TIME & ENERGY - are of sufficient quantity to permit the inefficient resource base to be utilized:
  • TIME: are recycle trip times more a function of Earth<-->Mars locations, OR are they a function of the time needed to create Mars-based fuels? The answer to that weighs heavily on choosing which of these diametrically different fuel-factory locations.
  • ENERGY: this is a resource that is
    • reasonably constant at low-latitude sites (solar insolation varies little thoughout the year, vs.
    • highly variable AND inversely proportional to the availability of the solid CO2 and H2O that I'm championing at polar latitudes: sublimation to the atmosphere during each pole's summers occurs at the times when insolation permits solar energy to be utilized.
• the astrodynamics I mentioned in my prior post:
  • Is there a difference in Martian launching/landing as f(latitude)?
  • If so, by how much and do the above factors counter those differences sufficiently to outweigh them?

By the by, "...need to be gaseous anyway..." is a non-issue. There's never a problem turning CO2 or H20 into the appropriate state.

More: as both Mr Musk last night AND other SpaceX pronouncements AND other Martian propounders have stated, there is an absolute necessity to locate water ice deposits.
HOWEVER: Ice will NOT be just anywhere on Mars - surface or underground - other than at polar latitudes. The "Oh, we'll just go dig around that shaded area over there" type of approach will no more work for finding water on Mars than it would for finding {fill in the blank with whatever element or compound you desire} on Earth. The specific counterexample to the prior statement is that in this one specific situation, "anywhere" does work for CO2 - bless you, Boyle's Law of Gases - but that juicy rich polar deposit that has been the crux of my posts still holds all the Aces, I'm thinking....

 

[mongo]

I also noticed Elon was more flustered than normal. He's never been a great public speaker, but this was a step beyond. Like, he couldn't even remember what was coming next in the presentation. I chalked it up as being severely jet-lagged, though.

I chalked it up to the audience. It seemed like a few of the pauses were where he would normally get a response from the group he was speaking to, but this crowd was mostly silent throughout.