Elon Musk IAC Mars Speech - Sept. 27, 2016 - DISCUSSION THREAD

[Rocket Science]

How many flights do you need to be confident enough not to have an abort strategy?
How do you get that flight count on a brand new engine and launch system?

I guess you have to retire the risk on each system then the vehicle as a whole and Elon makes the call on what is acceptable since he is running his own space agency here. Now if you ask in light of the recent failures color me a bit skeptical at this point...

Well, I ask given that the answer seems to suggest that the Raptor needs another system to run in in order to "retire the risk" as you say.  You're right, of course, that the recent failures force me to set the bar a little higher than "trust SX", but the thrust of my point was to wonder what that other system is....

I express my "eyebrow raiser" earlier in this thread and that is the use of "all composites" structure and reliable reuse...

[Rocket Science]

It sounds like its the actual tank for the initial ship that they plan on using for testing.

I'm wondering where they will test it. Hawthorne factory probably not best place for exprerimental LOX tank. Could they transport something that big to more safe place?

Also landing legs don't like sturdy enough to hold fully fueled spaceship, even on mars.

Do we know this tank is in hawthorne?

Where are the toolings for it?  It could not have been transported in by road.

Maybe SpaceX has another facility somewhere?

Do we have spies at Michoud?

[RonM]

Do we have any hard data that the Tankers would definitely have/use legs?

It's in the video.

This video is like the reusability video.  It's a very good indication on where they're going, and it's the best source we have right now, but it's not infallible... 

It's sure more than an artists concept (as was the first one!) but don't use it as a bible.

It's the concept as of today. I'm sure it will change, especially the concept of landing the booster in the launch cradle. A unforgiving system that could easily result in the destruction of the pad.

[sanman]

Do we have any hard data that the Tankers would definitely have/use legs?

If landing on a cradle is modus operandi for the Booster, then perhaps is also for the Tankers.  In which case, leave off the legs, and carry more propellant.

Do you really think the booster will be designed to survive the thrust of 3 raptor engines landing on top of it?

I don't think he meant land-the-tanker-on-the-booster, I think he meant land the tanker on its own cradle.

Regarding carrying more propellant on tanker - maybe there's only a certain amount that can be usefully transferred to crewed spaceship? What's the point in taking extra tanker propellant if the crewed vehicle doesn't have the capacity to take it on?


Also - I'd somehow imagined that Bigelow-style inflatables might be used on the journey to-and-fro, and then either be discarded or re-packed before landing.

[rsdavis9]

I bet they will use gaseous o2 and ch4 for the rcs thrusters.

[jpo234]

What do you think is in the spherical tanks? I count one in each tank in the S2 and one in the methane tank in S1.

I thought that this are specially insulated tanks to store fuel and LOX for the landing.

[jpo234]

Do we have any hard data that the Tankers would definitely have/use legs?

[john smith 19]

What if I've severely underestimated his launch rate. What if its many times a day, like aircraft at a airport? Considerably different result - your 50+ days could drop to less than a week.

the quick BOTE I did was as follows.

( 1crew launch + 3-5 prop launches) x 1000
Musk said it's a 20 min RTLS flight.
Assume they have enough tankers to pre fill them. Assume they have a 10 min count down.
So 1/2 hr per launch slot.

At 24/7 on 1 pad that's 105 days worst case (5 propellant loads each) or 83 1/3 with 3 and somewhere in between with a mix. Triple that if they're only allowed to launch in "office hours."

So the first vehicle will have been on orbit for > 3 months assuming very fast launch cadence and 1 pad and no weather delays (or launch delays of any kind).

This suggests a few things.
a) The first fleets won't be 1000 ships. b)You should have at least 2 pads c) Plan for on orbit loiter as it will happen. d) Make the pads far enough apart they cannot be simultaneously affected by weather.

a seems likely, b is prudent (but expensive) c is essential given the math and d is a logistics nightmare but will (baring pad explosion) keep up the launch pace regardless of their being a hurricane in Florida (which is not uncommon).

Or you could design ITS to launch in a hurricane of course. 

[Cherokee43v6]

After some consideration, there is one key element missing from the plan.

A 'pure play', possibly disposable, cargo transporter.

Reason for the possibly disposable.  Every shot shows the Spaceship landed on its tail, with all the engines and tankage between the cargo and the ground.  This will create serious hardships for the early colonist in removing necessary cargo from the ship to the ground.  It will also limit the size of any specific element of cargo to the maximum capability of whatever crane system were to be incorporated (weight and stability of total stack).

Additionally, to handle the construction of a permanent base, certain heavy machinery would be required on site.  Particularly mars( ) moving equipment and other construction machinery (Cement mixers, cranes, etc).

As such, a cargo ship that lands in a horizontal position would seem to be a necessity.  A ship capable of transporting and landing something probably on the order of a (Mars Optimized) Caterpillar D11 as a maximum single weight item.

[JasonAW3]

Do we have any hard data that the Tankers would definitely have/use legs?

Essentially, Elon stated that teh Tankers would be the same as the Normal ITS, but replacing the passenger and cargo areas with fuel tankage.

[Jim]

  If there is one country who are willing and able to launch a reactor or nuclear fuel into space, it is the French.

Doesn't matter.  Spacex is a US company and falls under US laws and regulations.  So it doesn't matter who provides it.

[john smith 19]

Spark (and torch) ignition for the engines.

Never understood why they didn't go with this from day one. It was the first thing XCOR developed. TEA is nasty, expensive stuff to handle. It baffled me anyone who was serious about reusability would use it.

[jstrout]

I think this talk will turn out to be a key inflection point in history, and here's why.

It outlines a clear BHAG (Big Hairy Audacious Goal), and a surprisingly well-developed plan to get there.

Now the goal itself — colonizing Mars — isn't one I put too much stock in myself.  But after watching yesterday's presentation and digesting it a while, I now realize, that doesn't matter.  It's a goal Musk believes in, and that he can (clearly) get thousands or millions of other people to believe in — and, most importantly, it's big, hairy, and audacious enough to drive a lot of development.

In the process of reaching for this goal, they will be building the biggest, most efficient, and most affordable launch system the world has ever seen.  This creates opportunities in two ways

1. It makes it easier/cheaper to do things that people may want to do for other reasons.  For example, maybe you want to do orbital or lunar tourism, or set up a zero-G or low-G movie studio, or build microchips in a harder vacuum than can be obtained on Earth, etc.  Musk doesn't care about any of that, but if you want to buy/lease/use his launcher system to do it, I'm certain he will be happy to take your money.

2. It creates new needs in space.  For example, he mentioned a lunar propellant depot as a "future optimization," which I read as, "if somebody builds it and it works out cheaper/better for us, we'll be glad to buy their fuel."  The same could be said about an orbital propellant depot, for that matter.  He's laid out a plan that doesn't require a whole ecosystem of support services... but would absolutely benefit from them.

And it's precisely because he has such an ambitious BHAG that this "forcing function" (as he likes to call it) will be so strong.  Musk is not an idiot, and I've long wondered why he seems to have no interest in the Moon, which is so much easier and more obviously the first major site of civilization beyond Earth.  I now suspect that it's simply because the Moon is too easy!  He needs a goal that's ridiculously hard — and then he needs a plan that people can believe in.

He laid out his chosen goal years ago; now he's laid out the plan.

Whether SpaceX succeeds in this ambition almost doesn't matter; it's clear they are going to try.  In so doing they are not only inspiring a new generation of scientists & engineers at a level not seen since Apollo, but they are also going to be creating opportunities in space like we have never seen before.

[DOCinCT]

Do we have any hard data that the Tankers would definitely have/use legs?

Besides the video, the tanker is basically a variant on the passenger version (typical manufacturing economies) AND it has to land via retro-propulsion, thus landing legs.

[Lars-J]

For people who wonder how they plan on squeezing 100 people like sardines into the spaceship - They won't.

Look at the the SpaceX PDF presentation ( http://www.spacex.com/sites/spacex/files/mars_presentation.pdf ) - page 36. At the bottom it says this: (emphasis is mine)

"Long term goal of 100+ passengers/ship"

So 100 passengers is for a future (larger) version of the system, it seems.

[dnavas]

I express my "eyebrow raiser" earlier in this thread and that is the use of "all composites" structure and reliable reuse...

Wasn't the composite structure also used in the booster, which was going to be a "trivial" size-up from Falcon?  I also want to see how the O2 self-pressurizes.  There are many things that can go wrong here.  Sure, no He valves knocking about, just pure O2 gas coursing through composite carbon structures.

Well, at least there's no H2O2, but I do want to see the test plan for this stuff.  It's going to be ... interesting, for sure.

[Lars-J]

Do we have any hard data that the Tankers would definitely have/use legs?

Besides the video, the tanker is basically a variant on the passenger version (typical manufacturing economies) AND it has to land via retro-propulsion, thus landing legs.

Yes, and it makes sense for both the tanker and crewed version to have the same system, to build confidence in the landing system.

-----

BTW, I'm still surprised by the cradle landing of the booster, but it does have a MAJOR benefit. All the suspension and dampening for landing can be built into the pad, so you don't need to bring any mass for that on the booster. And while propellant tanks scale well with size, landing legs do not, I imagine.

All you need to make sure is that the bottom fins are structurally strong.

[Lars-J]

I express my "eyebrow raiser" earlier in this thread and that is the use of "all composites" structure and reliable reuse...

Wasn't the composite structure also used in the booster, which was going to be a "trivial" size-up from Falcon?  I also want to see how the O2 self-pressurizes. There are many things that can go wrong here. 

Isn't that what STS did?

[Nibb31]

I'd also like to see what kind of docking system they plan to use. In the video, the ITS and the tanker seem to be docked side by side, but that makes no sense, because of the 3-fin geometry and because the underside is a (supposedly flat) heatshield. There seems to be some fishy 3D clipping in that shot.

I would really expect a properly sized IDS docking ring, to at least provide some means of cargo transfer (getting some spare parts onto a stranded ship) or crew rescue. At a minimum, there must be some sort of extensible fueling probe coming out of a hatch somewhere. If they dock side by side, then all this equipment must be extensible, hidden behind a hatch somewhere, but we don't see any of that in the cutout diagrams. How easy is it to design an airtight extensible docking mechanism ?

The same goes for those huge solar arrays. There is no way they can fold into the tiny space between the tank and Raptor nozzles as shown in the video. It simply doesn't add up.

Also, no radiators ? No antennas ? No airlock ?

[Lars-J]

I'd also like to see what kind of docking system they plan to use. In the video, the ITS and the tanker seem to be docked side by side, but that makes no sense, because of the 3-fin geometry and because the underside is a (supposedly flat) heatshield. There seems to be some fishy 3D clipping in that shot.

I would really expect a properly sized IDS docking ring, to at least provide some means of cargo transfer (getting some spare parts onto a stranded ship) or crew rescue. At a minimum, there must be some sort of extensible fueling probe coming out of a hatch somewhere. If they dock side by side, then all this equipment must be extensible, hidden behind a hatch somewhere, but we don't see any of that in the cutout diagrams. How easy is it to design an airtight extensible docking mechanism ?

The same goes for those huge solar arrays. There is no way they can fold into the tiny space between the tank and Raptor nozzles as shown in the video. It simply doesn't add up.

Also, no radiators ? No antennas ? No airlock ?

Those details will surely be fleshed out in the future. I don't think they have forgotten about them.