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

[Gen3]

Loved the way Elon tried pulling a Steve Jobs and presented city-to-city as "one more thing". Shorter city-to-city travel times are touted as the primary benefit of flying BFR versus the airlines, but there are other, notable selling points:

1. No weather (other than space weather, a potential roadblock at times) at suborbital altitudes. Therefore, no turbulence. Even during the ascent and descent phases through the atmosphere, I'm guessing that passenger comfort will be less affected by weather conditions than on airplane flights.

2. Killer views. Who needs suborbital "space tourist" flights when you can travel with SpaceX on your next overseas trip? I wonder what Sir Richard Branson (Virgin Galactic) is thinking right now. Views will depend on seating configuration, but I'm guessing that every passenger will have at least a sliver of a view.

3. Experience zero gravity. This won't be a selling point for everyone, but many will enjoy being weightless for long enough to savor the experience, and not long enough to have to worry about going to the bathroom or trying to eat.

I'd love to do 0g, but there would likely be a lot of people getting sick

 

[Gen3]

And how many homeless and disadvantaged could be helped and/or rescued with the billions of dollars frittered away in space?

And how many peasants or slaves could have been helped if the European royalty/rich did not explore and settle North America?

 

[Nikxice]

Having just viewed Elon's latest and likely boldest spacefaring proposal, a few early comments.

- I found it difficult to discern the layout pattern for the 31 Raptor engines that make up the first stage booster rocket. As BFR development proceeds, hopefully SpaceX will share more details.
- Elon mentioned the reentry heat shield material would wear like brake pads. Curious to learn more about this ablative
material. Designed for how many flights?
- The Moon and Mars seem to be within reach much sooner than Earth to Earth transport use. Lots of questions here. Just the vertical loading and unloading of hundreds of passengers sounds like a daunting task.
- But hey, heaven can wait, all in for this ride! How about a Tesla type March 31st reservation event? Although maybe keep the deposit low, say 200 bucks, to draw huge numbers. That would still be a fraction (less than .01%) of what Branson collects on his up front full price, now nearly 10 years late with promises of short commercial lobs on Virgin Galactic. Could even work out some preferential dibs for early reservation holders. First seats offered to SpaceX/Tesla employees, followed by existing customers. (In all fairness, if the initial pax flights occur on the US east coast, this time I would expect any ticket rollout offers
to go from east to west)
- The first BFR Mars bound astronauts will certainly be screened for BFRocks! Their return trip to Earth will be contingent on
the ability to successfully manufacture fuel, store it, and eventually refuel the ship for home. Even some routine earthly tasks will be fraught with risks on Mars.

Sincerely hope the multitude of engineering issues facing SpaceX are conquered with timely solutions. Elon isn't alone with his reasons for getting out of bed in the morning.

 

[dhanson865]

Imagining how the "spaceport" ASDS platforms will be designed is an interesting theoretical exercise.

I don't see how the launching and landing rocket exhaust is going to be handled. It will have to be vented away from the platform and into the air. The forces exerted on the platform will be huge. The exhaust can't destabilize or move the platform around.

Why do you say that? The platform is free floating. There is no reason for it to be any different than the existing landing procedure which has exhaust hitting the platform.

The platform has multiple engines for station keeping. It doesn't care if the rocket moves it slightly and the rocket doesn't care either. Both ships know how to adjust for any movement.

 

[ecarfan]

The platform is free floating. There is no reason for it to be any different than the existing landing procedure which has exhaust hitting the platform.

Current F9 ASDS landings involve the exhaust of ONE Merlin engine on an essentially empty first stage hitting the deck for less than 3 seconds (my off the cuff estimate).

That is in no way comparable to THIRTY ONE Raptor engines on the BFR first stage exerting a lift off thrust of 5,400 tons* for over 15 seconds. There is a reason that launch pads are built with massive flame trenches. All the energy needs to go somewhere in a managed fashion.

*5,400 tons of thrust for a BFR going to LEO. For a trans-oceanic ballistic trajectory the lift off thrust will be somewhat less.

 

[ecarfan]

Here's a photo of the flame trench at Cape Canaveral LC39A where the Falcon Heavy will launch this year. It is enormous and wasn't built on a whim, it serves a very important function.

 

[Grendal]

Current F9 ASDS landings involve the exhaust of ONE Merlin engine on an essentially empty first stage hitting the deck for less than 3 seconds (my off the cuff estimate).

That is in no way comparable to THIRTY ONE Raptor engines on the BFR first stage exerting a lift off thrust of 5,400 tons* for over 15 seconds. There is a reason that launch pads are built with massive flame trenches. All the energy needs to go somewhere in a managed fashion.

*5,400 tons of thrust for a BFR going to LEO. For a trans-oceanic ballistic trajectory the lift off thrust will be somewhat less.

It's a very good point and one that will need to be addressed if and when SpaceX actually attempts Earth to Earth transport. The big first step is to build a BFR & BFS and launch them. If and when that happens then they'll probably have plenty of reserved launches for other things. That will be a lengthy testing period to determine the efficiencies and capabilities of their rocket. I expect to see BFR and BFS go through a number of iterations just as F9 has done before the company finalizes the design. I expect to see significant improvements to everything as we've seen with F9 too. Once the rocket flies once successfully, then the floodgates will be open for what can be done with the system. Space stations, a Moon Base, really big satellites, vast numbers of small satellites, exploration systems, robotic factories, tourist trips, orbital junk cleanup, and space fuel depots are all possible with a system like Elon presented. Earth to Earth transport is a great idea but as many have already pointed out, it would need to overcome a lot of drawbacks. I expect that once the rocket is shown that it works then projects for the rocket to do will be plentiful. Money should not be an issue and Earth to Earth transport can be a nice money making fallback if it becomes necessary. If they do move forward with it actively then I'm sure all of the issues will be addressed.

The long term goal is Mars. Elon will not let that drop. I expect that part of his being emotional at this presentation is that he knows it will take a long time to achieve and he wants to see and know that it will actually happen. Elon saw, as a lot of us did, the exploration of space and humanities expansion, slow and almost come to a complete halt. He is smart enough to know that if it happens again that humanity may never recover. There are currently real world examples of humanity working against its best interests. To Elon it is just what needs to be done for the greater good and for the future. Because that is true, you do it. That is Elon's philosophy. His viewpoint is more rare than he would like to admit. I think he sees that more and more as he gets older. I think that is why he was emotional. JMHO.

Having just viewed Elon's latest and likely boldest spacefaring proposal, a few early comments.

- I found it difficult to discern the layout pattern for the 31 Raptor engines that make up the first stage booster rocket. As BFR development proceeds, hopefully SpaceX will share more details.

No doubt they will

- Elon mentioned the reentry heat shield material would wear like brake pads. Curious to learn more about this ablative material. Designed for how many flights?

SpaceX has the most advanced PICA material in the world: PICA-X I'm sure we'll get more information on it since it will be used a lot more than it is now.

- The Moon and Mars seem to be within reach much sooner than Earth to Earth transport use. Lots of questions here. Just the vertical loading and unloading of hundreds of passengers sounds like a daunting task.

As I responded above, I agree that there will be a lot of other things happening long before Earth to Earth transport happens.

- But hey, heaven can wait, all in for this ride! How about a Tesla type March 31st reservation event? Although maybe keep the deposit low, say 200 bucks, to draw huge numbers. That would still be a fraction (less than .01%) of what Branson collects on his up front full price, now nearly 10 years late with promises of short commercial lobs on Virgin Galactic. Could even work out some preferential dibs for early reservation holders. First seats offered to SpaceX/Tesla employees, followed by existing customers. (In all fairness, if the initial pax flights occur on the US east coast, this time I would expect any ticket rollout offer to go from east to west)

I expect New Shepard to launch customers long before VG gets their system working.

- The first BFR Mars bound astronauts will certainly be screened for BFRocks! Their return trip to Earth will be contingent on the ability to successfully manufacture fuel, store it, and eventually refuel the ship for home. Even some routine earthly tasks will be fraught with risks on Mars.

Actually colonizing Mars is going to an unbelievably daunting task. Getting there and back with BFR/BFS is only the first step. There are a lot of people already trying to figure this out though.

Sincerely hope the multitude of engineering issues facing SpaceX are conquered with timely solutions. Elon isn't alone with his reasons for getting out of bed in the morning.

You got that right. Elon has set very difficult goals. They are goals worth fighting for though.

 

[woof]

Here's a photo of the flame trench at Cape Canaveral LC39A where the Falcon Heavy will launch this year. It is enormous and wasn't built on a whim, it serves a very important function.

Indeed--that's where the Unicorns dance!
Reference:
Musk Calls Out Blue Origin, ULA for ‘Phony Blocking Tactic’ on Shuttle Pad Lease - SpaceNews.com

 

[dpeilow]

And that would be fine, as long as everything is extraterrestrially fusion reactor fueled, as Elon said. The fact Toyota sucks now doesn't mean their failed approach won't be one way to process energy in the future. By then, we can look at whatever options we have at that time.

I'm not talking about the Mars plan. That's fine - go ahead and make all the methane you want.

However if you want nuclear reactors - or as Elon said solar panels - making the stuff here on Earth, then the waste of energy argument doesn't go away.

 

[Yggdrasill]

Current F9 ASDS landings involve the exhaust of ONE Merlin engine on an essentially empty first stage hitting the deck for less than 3 seconds (my off the cuff estimate).

That is in no way comparable to THIRTY ONE Raptor engines on the BFR first stage exerting a lift off thrust of 5,400 tons* for over 15 seconds. There is a reason that launch pads are built with massive flame trenches. All the energy needs to go somewhere in a managed fashion.

*5,400 tons of thrust for a BFR going to LEO. For a trans-oceanic ballistic trajectory the lift off thrust will be somewhat less.

I think you could probably make it work by suspending the rocket above the sea, and just let the exhaust go into the sea. This worked for Sea Launch. (It could potentially just be a hole in the platform.) I'm not entirely sure how high above the water you would need to suspend the rocket, though.

And regarding the platform; I assumed this platform would be affixed to the sea bottom. Either a tension-leg platform, or a gravity-based structure. These kinds of structures can be expected to be quite stable.

 

[dpeilow]

Current F9 ASDS landings involve the exhaust of ONE Merlin engine on an essentially empty first stage hitting the deck for less than 3 seconds (my off the cuff estimate).

That is in no way comparable to THIRTY ONE Raptor engines on the BFR first stage exerting a lift off thrust of 5,400 tons* for over 15 seconds. There is a reason that launch pads are built with massive flame trenches. All the energy needs to go somewhere in a managed fashion.

*5,400 tons of thrust for a BFR going to LEO. For a trans-oceanic ballistic trajectory the lift off thrust will be somewhat less.

Also, there's a reason why thousands of gallons of water are dumped into the flame trench as the rocket lifts off and that is to deaden the acoustic shock from the engines from bouncing back up and hitting the vehicle.

So the problem is not only the landing on the barge for Earth-Earth launches but also this...

When Apollo did it they left behind the the launch platform. It had a lot less thrust too.

 

[TLej]

Good discussion here. Other questions I had during the presentation that I have not seen discussed:

- all well and good to launch the rocket, but no details on radiation protection for the journey (other than the solar storm shelter) nor those lucky enough to go to Mars while they're there. Pictures of domes are awesome, but descriptions like in the Red Mars trilogy or The Expanse books of initial colonization being underground seem more realistic than the Mars city pictured. Health threat from cosmic rays - Wikipedia

- looking forward to plans for artificial gravity (spin up the Ship to .5g?) during the voyage, and expected effects on those who make the trip. A year on the ISS in freefall doesn't seem to have a huge number of health effects other than the initial few weeks after return to Earth, but a couple years at .4g combined with a few months each way of transit at maybe 0g seems like it might be a little more harsh on the old bod

- my first thought was that SpaceX is working on developing an ICBM that can deliver a 150-ton payload anywhere on Earth in an hour. Can't make governments all over the world too comfortable; not okay for Iran or North Korea to do it, but go ahead, Elon. Sure, in the hands of a benevolent capitalist all is well, but in the wrong hands.... It will be interesting to see how this part plays out, if it was intended to be serious...

I realize Elon's presentation was more about revealing a concept than a plan - much work to be done and details to be shared (spin-off from SpaceX to build Mars/Moon habs? Partnership with Bigelow? Private development or is that where the gov't money comes in?) but the fact the discussion is even being had and inspiring engineers, scientists, and regular folks to help make it happen is a great thing that I'm excited to be alive for. The timeline of the concept means the plan needs to be close behind.

 

[dhanson865]

I don't see how the launching and landing rocket exhaust is going to be handled. It will have to be vented away from the platform and into the air. The forces exerted on the platform will be huge.

Current F9 ASDS landings involve the exhaust of ONE Merlin engine on an essentially empty first stage hitting the deck for less than 3 seconds (my off the cuff estimate).

That is in no way comparable to THIRTY ONE Raptor engines on the BFR first stage exerting a lift off thrust of 5,400 tons* for over 15 seconds. There is a reason that launch pads are built with massive flame trenches. All the energy needs to go somewhere in a managed fashion.

*5,400 tons of thrust for a BFR going to LEO. For a trans-oceanic ballistic trajectory the lift off thrust will be somewhat less.

now the second post makes more sense. What confused me was mentioning landing in the first post. Landing is currently handled and doesn't need anything new done to handle it.

Launch is more heat, a trench would be needed but I think of a trench as down and "into the air" as up. So your first post had me imagining some weird funnel to redirect launch flames into the air above the launch platform. Thank you for expanding and helping me see your original intent.

I could see them venting below the platform directly towards the sea surface or at an angle out to the side of the platform but still pointed down generally towards the sea.

Whatever they do for a launch trench solution it'll be new as the ASDS doesn't have any such structure now. I'm sure even if the launch platform could handle the direct flame it'd ruin the "rhoomba" and it's storage area. And I'm not sure that the current landing surface wouldn't melt under the power of a full thrust liftoff. As in I have no idea what it's temperature rating is and I have no hard number for how hot it'd get after a launch if there was no trench.

But I'm not concerned about the force of the thrust as much as I am the temperature of the exhaust. That was the other thing that confused me why you thought a super large ASDS would be moved away.

The take of is vertical and by the time the rocket tilts any noticeable amount it's airborne and far enough away that it won't move the platform. So long as the platform doesn't sink below the surface of the water I'm not concerned about lateral forces. They just have to have the new larger ASDS to be able to support the weight of 2x the BFR + equipment on the deck and likely Musk is thinking big and would make the new ASDS big enough to handle the ship to come not just this one.

 

[dhanson865]

Specifically on the down thrust at takeoff that is limited by the max output of the engines and is commonly compared to the max weight of the BFR before takeoff in the form of Thrust vs Weight aka TTW

Thrust-to-weight ratio - Wikipedia

I'm going by memory but I do believe in elon's presentation it was stated as a roughly 5:4 ratio at launch. So the force is simply launch weight x 1.25. Not that much more than the force applied by the rocket sitting there waiting to take off.

I might take the trouble to watch again and do a screenshot of the relevant spot in the video if I can find it.

 

[ecarfan]

looking forward to plans for artificial gravity (spin up the Ship to .5g?) during the voyage, and expected effects on those who make the trip

There has never been any indication from Elon that the Mars ships will have any "artificial gravity". I'm not expecting it.

A year on the ISS in freefall doesn't seem to have a huge number of health effects other than the initial few weeks after return to Earth, but a couple years at .4g combined with a few months each way of transit at maybe 0g seems like it might be a little more harsh on the old bod

Yes, those who go to Mars and decide to return to Earth (I think many will not choose to do so) will have a lengthy period of re-adapting to terrestrial gravity, but I am confident it is doable.

But I'm not concerned about the force of the thrust as much as I am the temperature of the exhaust. That was the other thing that confused me why you thought a super large ASDS would be moved away.

You may not be concerned, but I am. And I did not say that the barge would be forced out of position by the launch. I was simply pointing out that the force exerted on the launch platform during a BFR launch is vastly greater than what the F9 1st stage exerts during landing.

The exhaust generated by a BFR launch will have to be managed in some way, it can't simply hit a solid deck a few feet away, the acoustic forces created and the high temperature blow back would destroy the rocket.

 

[ecarfan]

While Elon's "one more thing" E2E BFR flights have captured a lot of attention (including mine) that was not the point of his presentation. The "realization", as he put it, that by resizing the BFR so that it could replace all the current SpaceX launch vehicles, enabling the entire company to focus on a single vehicle, while generating a lot of revenue from commercial launches, is the big news.

I think the reason Elon appeared to be so emotional during his presentation was because the prospect of actually getting to Mars within a decade was becoming very real to him. At the same time, he was publicly noting that SpaceX's first successful launch was only 9 years ago: how far the company has come in that time!

Just imagine where SpaceX will be in another 9 years...

 

[dhanson865]

You may not be concerned, but I am. And I did not say that the barge would be forced out of position by the launch. I was simply pointing out that the force exerted on the launch platform during a BFR launch is vastly greater than what the F9 1st stage exerts during landing.

The exhaust generated by a BFR launch will have to be managed in some way, it can't simply hit a solid deck a few feet away, the acoustic forces created and the high temperature blow back would destroy the rocket.

I wasn't concerned in the sense that your original post implied (you didn't think it was confusing, but to me it was), we seem to have done the back and forth enough now to be in violent agreement.

Renewing the famous Flame Trench, one brick at a time | NASASpaceFlight.com
Fire brick - Wikipedia (aka refactory brick)

The flame trench – 571 feet long, 58 feet wide and 42 feet high – is built with concrete and refractory brick

This will allow the north side of the flame trench to withstand temperatures of up to 2000 degrees Fahrenheit at launch.

Heat and sonic forces are nothing to ignore. I look forward to see how they handle a flame trench on a sea platform. I'm expecting BFR to put out just as much if not more than SLS (if only by the factor that SLS may never see practical use).

 

[evp]

Here's an analysis of Elons presentation: The Space Review: SpaceX prepares to eat its young

Best quote: "SLS is now certifiably toast."

 

[Grendal]

Here's an analysis of Elons presentation: The Space Review: SpaceX prepares to eat its young

Best quote: "SLS is now certifiably toast."

Sadly no. SLS will have a life past the creation of BFR/BFS. Once it flies a few times then SLS is toast. So figure three or four more years. It will take the media making a huge fuss over the insane cost of SLS compared to the minimal cost of BFR/BFS. Then you can expect the various contractors for SLS to use the ULA playbook and say that there needs to be a "backup" system. With ULA there is a reasonable argument for two major contractors. For SLS? Definitely not.

 

[Electroman]

I know what BFR is. What is BFS?