BFR Private Passenger Moonflight - DISCUSSION THREAD

[sanman]

Egress would not be problem in space. The hatches are inline if dropping from one hatch to the other in gravity while facing nose upward.

In space there is no surface to go to. It's not that the hatch is actually blocked, it's that the way to the surface would be blocked.

Okay, fair enough - so is there no scenario where you might want to deploy the built-in solar array on the ground? If it's an extended stay on the surface, you might want make use of those solar arrays.

Or why can't they eventually make use of all that surface area on the fins to put some solar PV cells there? At least then you don't need moving mechanisms to deploy your solar power.

[clongton]

I would be more worried about EDL. There is no escape system when you come in from deep space. EDL works or you leave either a puff of smoke or a crater.

Either you got them or you don't.

[Ludus]

Elon’s casually tweeting that yes, what the heck, let’s land BFS on the Moon before landing on Mars, would probably have gotten more attention if so much else wasn’t going on.

[moreno7798]

Couldn't that be said about every rocket?

Not if they have a LES

If you have a LES you still rely on a dangerous system and hope nothing goes wrong with it in case of a failure...

How about margins, reducing failure points and redundancy?

How about stop being overtly risk averse?

[sanman]

Elon’s casually tweeting that yes, what the heck, let’s land BFS on the Moon before landing on Mars, would probably have gotten more attention if so much else wasn’t going on.

So, a moon-landing it is then, eh? Sounds like a plan. Better to test your off-world landing capability on the nearby Moon, before journeying all the way to Mars.

If BFS is going to be landed on the Moon, what would it likely take with it besides passengers?

[Tulse]

So, a moon-landing it is then, eh? Sounds like a plan. Better to test your off-world landing capability on the nearby Moon, before journeying all the way to Mars.

But the way a BFS would land on Mars is radically different from the way it would have to land on the Moon.  BFS is designed to use atmosphere to bleed off velocity for a Mars landing.  Landing on the Moon wouldn't tell us much about how things would work on Mars.

[sanman]

So, a moon-landing it is then, eh? Sounds like a plan. Better to test your off-world landing capability on the nearby Moon, before journeying all the way to Mars.

But the way a BFS would land on Mars is radically different from the way it would have to land on the Moon.  BFS is designed to use atmosphere to bleed off velocity for a Mars landing.  Landing on the Moon wouldn't tell us much about how things would work on Mars.

Fair enough, Moon is airless and Mars EDL is famously more challenging. But you've got to walk before you can run.

I wonder what the timeline would be for a moon-landing attempt?

[speedevil]

A note about reentry to help inform the discussion.  The 2017 animation showed the intended sequence (which of course could have changed by now).  Most of the animation was sped up considerably.  The reentry starts nose DOWN, with some slight changes in angle-of-attack  After bleeding off sufficient velocity, the ship yaws to a nose up attitude during an over-two-minute period and then lofts several kilometers UP.  As the descent becomes steeper, the ship the rotates further and brings engines into play.  None of the maneuvers seem abrupt or jerky.  Reality may differ, of course!

For reference: https://www.youtube.com/watch?v=tdUX3ypDVwI?t=35m35s

As mentioned earlier this may be misleading for most uses of BFS and is an artifact of showing a high speed reentry

The entry into Mars atmosphere is at a speed which is double that of a circular orbit, so it has to thrust down.
Entry from LEO certainly won't do the 'enter upside down' as it is an excellent way to die.

The shuttle was in a near circular orbit most of the time, and the vertical entry velocity was only 80m/s, and it was also pointed up at entry and had no 'bouncing off' issue.

For entry at lunar speeds it's different 11km/s - 1.4* LEO. You are going to need -1G aerodynamically, if you want to maintain the altitude you entered at. This is not to stop 'bouncing off' the atmosphere, it's to stop continuing on in the orbit you would be in anyway without an atmosphere.

This may mean an initial 'upside down' (heatshield up) reentry, with aerodynamic lift of 1G, and drag of around probably 2G.
This phase lasts around three minutes, and then you're in the same state you would be in if you had just entered from LEO, and need to flip the other way up in order to keep your altitude high and not do a ~20G reentry into a fireball.

[Nibb31]

With no handrails and no robotic arm, there will be no fixing stuff through EVA. There are no user serviceable parts outside anyway.

This is one additional reason why the solar panels should unfold from the bottom of the cargo/crew area: you could design a backup mechanical system to manually override automatic deployment/retraction from the inside.

[intrepidpursuit]

My predictions before tomorrow.

The event will give us at least a high level update on BFR capability, design, and progress. The "petals" do not actuate except for access. They are radiators and double as access hatches to what must be a service area in a ring around the engines. The engine bells are a compromise design like the SSME; if they needed to add one more engine for one of the modes, the weight of another engine would have overcome the savings gained by vacuum optimized engines, plus a single engine greatly simplifies the design. Solar is still the big fan shapes, we can see the doors in the first rendering.

Now let's see what happens at the event and on twitter and reddit afterward. (an NSF AMA would be stellar)

Let me add that I think they will be announcing landing on the moon as well as doing a flyby. Probably one after the other rather than going all in on the first try. Just re-announcing what was announced years ago but with a new ship isn't worth a press event.

Once BFR is built and flying people, refueling and EDL will already be well practiced. Landing on the moon is (I know, I hear me saying this too) easy once the steps required to get humans up and back down on BFS are mastered. Only technology missing will be a moon EVA suit, which I'd guess will not be a huge leap by that point considering their assumed need of deep space and mars EVA suits. (no way you'd go to the moon and not go outside)

So yes, I think they will be announcing an aspirational goal of landing tourists on the moon.

[speedevil]

So, a moon-landing it is then, eh? Sounds like a plan. Better to test your off-world landing capability on the nearby Moon, before journeying all the way to Mars.

But the way a BFS would land on Mars is radically different from the way it would have to land on the Moon.  BFS is designed to use atmosphere to bleed off velocity for a Mars landing.  Landing on the Moon wouldn't tell us much about how things would work on Mars.

It would tell you about the landing hardware being good, and your crane/... working properly.
At the right time of day, the thermal environments are broadly comparable, and the atmosphere being 0% instead of 1% does not really matter for much stuff, as martian wind is usually close to negligible.

It is also essentially free to do, if you are doing tests of multiple tanker loads into one BFS.
Other than the risk of landing/taking off, there is if not zero cost, very close to zero cost.

And - well - obviously possibly negative cost if you sell first tourist on the moon.

[niwax]

@elonmusk on twitter
https://twitter.com/elonmusk/status/1041766343769387008

Btw, can’t emphasize enough how @SpaceX would not be where it is today without @NASA. Thank you.

This might be an indication that they are getting to the stage where not stepping on SLS' toes is no longer possible. Seems that there is some softening to SLS politically so the timing might be good for that.

Upcoming implication from presentation:

"Love you NASA, but my rocket can do everything yours' can better for less money"

Looks like Shotwell still thinks it might even fly before SLS:

@jackiewattles
Gwynne Shotwell: Hope to be flying BFR hop tests next year (reiterating Elon), and first orbital flight in 2020.

[meekGee]

Another issue. In the 3-fold geometry the crew hatch is directly above the solar panel hatch. Therefore, deployment of the solar panel on the Mars would prevent the crew to access the surface.

I really doubt that the solar arrays on the BFS have the structural strength to be deployed anywhere outside zero gravity. SpaceX Mars renderings show fields of solar panels, but never a deployed BFS solar array at the surface.

What if you deploy the solar panels in space and they get stuck - and now your crew can't get out of their hatch to do an EVA to fix the problem?

You take the crane down half way and jump on them until they fall off.

Welcome to Mars. 

[sanman]

It would tell you about the landing hardware being good, and your crane/... working properly.
At the right time of day, the thermal environments are broadly comparable, and the atmosphere being 0% instead of 1% does not really matter for much stuff, as martian wind is usually close to negligible.

It is also essentially free to do, if you are doing tests of multiple tanker loads into one BFS.
Other than the risk of landing/taking off, there is if not zero cost, very close to zero cost.

And - well - obviously possibly negative cost if you sell first tourist on the moon.

Once that first BFR tourist sets foot on the Moon and the precedent is set, then it'll set off a huge stampede - a gold rush - and Musk will have to beat off those billionaires with a stick.

Even if Musk himself isn't among the initial passengers, he'd probably get there soon enough.

Will the Moon - a very fascinating destination in its own right - take SpaceX on a detour?

[kdhilliard]

My prediction, based on them announcing a customer so far in advance (what, 4 to 5 years?) is that the buyer is paying a very large sum up-front (perhaps approaching $1B, but secured against SpaceX stock and refundable if the flight doesn’t happen by a given date) which will help fund BFR development in exchange for exclusive rights to the first crewed lunar flight.  The buyer will go on to sell additional seats on the flight as well as create television shows about training and preparation, and if legalities can be worked out, even have a contest or lottery to fill some seats.

Half of me thinks, “Hey, what ever it takes to fund development of this thing.”, while the other half worries about it being turned into a circus.  I just don't think SpaceX would enter into a lunar flyby passenger deal so far in advance unless they were being offered a lot up-front  The buyer, by contributing early when development funds are most needed, could view it not just as a hugely expensive adventure vacation, but as a contribution to the development of human space travel for which the lunar trip itself is simply a premium or reward.

The deal may also include a right of first refusal for the first crewed lunar landing mission.  SpaceX could start entertaining offers on that in a year's time or so, to continue funding development.

[intrepidpursuit]

It would tell you about the landing hardware being good, and your crane/... working properly.
At the right time of day, the thermal environments are broadly comparable, and the atmosphere being 0% instead of 1% does not really matter for much stuff, as martian wind is usually close to negligible.

It is also essentially free to do, if you are doing tests of multiple tanker loads into one BFS.
Other than the risk of landing/taking off, there is if not zero cost, very close to zero cost.

And - well - obviously possibly negative cost if you sell first tourist on the moon.

Once that first BFR tourist sets foot on the Moon and the precedent is set, then it'll set off a huge stampede - a gold rush - and Musk will have to beat off those billionaires with a stick.

Even if Musk himself isn't among the initial passengers, he'd probably get there soon enough.

Will the Moon - a very fascinating destination in its own right - take SpaceX on a detour?

It isn't a detour if it pays for and builds experience using the hardware that will go to mars. They can really only launch to mars every two years, so might as well do a moon flight a month in between.

[Johnnyhinbos]

Okay - low value post here. But hope it lives!

To show how much I’m looking forward to SpaceX’s, er, update tonight, this is my night...

Due to predicted weather, Amy (my wife) and I have found ourselves in Cuttyhunk Island on our boat Sequel (aka, middle of nowhere). There is basically zero cell service here. Zero. So I am dinghy-ing to shore to hike up the to the top hill at of the center of the island at 9:00 PM in the pitch black to hunker down in the howling wind and cold to pick up (I hope) enough radio waves to watch.

Amy thinks I’m nuts - but I think folks here get it...

[envy887]

Another issue. In the 3-fold geometry the crew hatch is directly above the solar panel hatch. Therefore, deployment of the solar panel on the Mars would prevent the crew to access the surface.

I really doubt that the solar arrays on the BFS have the structural strength to be deployed anywhere outside zero gravity. SpaceX Mars renderings show fields of solar panels, but never a deployed BFS solar array at the surface.

What if you deploy the solar panels in space and they get stuck - and now your crew can't get out of their hatch to do an EVA to fix the problem?

You take the crane down half way and jump on them until they fall off.

Welcome to Mars. 

They would have to be jettisoned before reentry in the even that refurling fails. NASA specs pyro bolts that would work great for this, or SpaceX can use their old standby: pneumatic latches and pushers.

[speedevil]

Looks like Shotwell still thinks it might even fly before SLS:

@jackiewattles
Gwynne Shotwell: Hope to be flying BFR hop tests next year (reiterating Elon), and first orbital flight in 2020.

And, of course, EM2 (first mission with crew around the moon) is currently scheduled for June 2022, with EM3 roughly pencilled in for 2024.

Other deadlines that might apply - CLPS is Dec 2021, for landing a payload of at least 10kg on the moon.
This would be a notable push-forward of the schedule of needing to get everything working by Sep 2022 to hit the window for Mars.

[meekGee]

Another issue. In the 3-fold geometry the crew hatch is directly above the solar panel hatch. Therefore, deployment of the solar panel on the Mars would prevent the crew to access the surface.

I really doubt that the solar arrays on the BFS have the structural strength to be deployed anywhere outside zero gravity. SpaceX Mars renderings show fields of solar panels, but never a deployed BFS solar array at the surface.

What if you deploy the solar panels in space and they get stuck - and now your crew can't get out of their hatch to do an EVA to fix the problem?

You take the crane down half way and jump on them until they fall off.

Welcome to Mars. 

They would have to be jettisoned before reentry in the even that refurling fails. NASA specs pyro bolts that would work great for this, or SpaceX can use their old standby: pneumatic latches and pushers.

Sure, but the more subtle point is that Mars-life will not be anything like the scripted and choreographed activities on ISS.

The plans will survive, at best, until the moment the rockets touch down.

Starting then, things will predictably not work as expected, and the crew will have to have general tools and general knowledge to deal with things.