totm nov 2023 SpaceX Discussion Thread

[wumpus]

16 hours ago, Xd the great said:

Farming insects on small scale on earth is totally possible. 

Farming crops in space is harder, but it has been done.

Farming both in a bfr on Mars and in space... this will require intensive caring.

starts imagining worms flying aroubd in 0g...

The catch is that you still have to bring a lot of food and other supplies from Earth.  Biosphere 2 was pretty much a disaster and had essentially an infinite mass budget (compared to anything on Mars).

[MinimumSky5]

You only need about a ton of food per person per year, so you need large crews or very long duration missions to warrant growing your own food.

[DAL59]

19 hours ago, Mad Rocket Scientist said:

Falcon Heavy is surprisingly capable for interplanetary missions.

In fact, it could support manned Mars missions, albeit with smaller crew sizes, in a program proposed by Robert Zubrin called Mars Semi Direct. 

https://www.marssociety.de/files/Medien/Feed Import/2013/11/Mars-Semi-Direct-plan-8-23-2012.pdf

 

On 8/28/2018 at 4:56 AM, Scotius said:

Have you ever ate prawns, crabs or crawfish? They are arthropods. Insects are arthropods too. Therefore you've already technically ate insects. No big deal.

You could eat fish too, as they would be useful for hydroponics.

[DAL59]

3 hours ago, MinimumSky5 said:

You only need about a ton of food per person per year, so you need large crews or very long duration missions to warrant growing your own food.

An MRE weighs 510 to 740 grams, and provides 1,200 calories (so you only need two per day).  I'll use the lower weight, as MRIs contain water and we can freeze dry food for space.  So, about 820 pounds.  

[Ultimate Steve]

3 minutes ago, DAL59 said:

An MRE weighs 510 to 740 grams, and provides 1,200 calories (so you only need two per day).  I'll use the lower weight, as MRIs contain water and we can freeze dry food for space.  So, about 820 pounds.  

With MREs, the problem would quickly become volume unless you severely redesigned the packaging.

[DAL59]

3 minutes ago, Ultimate Steve said:

With MREs, the problem would quickly become volume unless you severely redesigned the packaging.

I wasn't suggesting them, just using them as a comparison mass.  Freeze dried foods would be better.

[totalitor]

Quote

An MRE weighs 510 to 740 grams, and provides 1,200 calories

Do you mean 1200 kilocalories? This is not USA, this is worldwide forum.

[MinimumSky5]

Most English speakers will say "calories" when the mean "kilocalories", mostly because food packaging uses the term incorrectly.

[sh1pman]

35 minutes ago, MinimumSky5 said:

Most English speakers will say "calories" when the mean "kilocalories", mostly because food packaging uses the term incorrectly.

That’s why I prefer kilojoules.

[cubinator]

7 hours ago, sh1pman said:

That’s why I prefer kilojoules.

Multiply by 4000 for mental food calories -> joules conversion.

[Mad Rocket Scientist]

16 hours ago, sh1pman said:

That’s why I prefer kilojoules.

Please. It's best to just measure everything in Hiroshima equivalent. Gasoline (style as "gas" for extra confusion) gallon equivalent is pretty good alternative.

"Nutrition experts recommend a daily food intake of 1.3 nanoHiroshimas"

[Scotius]

Bananas would work best, as they are already radioactive

[Xd the great]

On 8/30/2018 at 3:50 AM, MinimumSky5 said:

You only need about a ton of food per person per year, so you need large crews or very long duration missions to warrant growing your own food.

100 people for 2-3 years of mars? Farms please.

 

[Xd the great]

Since the bfr runs on methaneLox, should a simple laser be sufficient to act as a ignition starter?

[sh1pman]

1 hour ago, Xd the great said:

Since the bfr runs on methaneLox, should a simple laser be sufficient to act as a ignition starter?

Probably, but spark ignition IMO is better for reusability. You'd have to put the laser inside the combustion chamber. And I'm not sure if laser optics are able to survive the pressure of 300 atm and temperature of 3000K inside the Raptor engine without getting cracked, warped or bent.

Edited August 31, 2018 by sh1pman

[MinimumSky5]

7 hours ago, Xd the great said:

100 people for 2-3 years of mars? Farms please.

 

You'd be surprised how heavy hydroponics systems are, and remember the weight of the power generating equipment to light and run the farm. (even at earth's distance to the sun, in space you need some supplemental lighting, because the colours in the light aren't the same as at the earth's surface.)

[AVaughan]

6 hours ago, Xd the great said:

100 people for 2-3 years of mars? Farms please.

Personally, I'd be surprised if the first manned BFR Mars mission carries a crew of 100.  I'd expect more like 12-20 per BFR for the first mission.   Possible even lower, especially if they decide to add a detachable capsule (think something similar to a re-entry capsule, with integrated abort thrusters) as a LES/landing escape system.  I know that's not in the announced plans,  but having some sort of abort capability if something goes catastrophically wrong during launch or landing seems to sensible, at least for the first few manned missions.

[tater]

Any first crew mission to Mars on BFR will be nothing remotely close to 100 people. It would in fact be the minimum number required to accomplish the task.

A LES for a crew version makes little sense WRT to Mars. It's added mass. Better to send crew on Dragon, or a LEO variant with LES, since LES buys you nothing at Mars, the spacecraft works, or you're dead.

[MinimumSky5]

I thought that the first BFR crew varients to Mars were going to be unmanned, and used as permanent habitats?

[AVaughan]

TBH, I'm more concerned with the landing on Earth.  If something goes wrong with the transition from re-entry to vertical landing, then it's potentially going to be fatal for any crew members.  Ejection might be feasibly, for some of the flight envelope,  but making the control/crew cabin detachable, with integrated launch abort thrusters and parachutes for landing can get you both launch escape functionality, and similar landing escape functionality.  (Again only intended for use on Earth, I agree that it isn't going to help at Mars, and I'm not talking about a capsule big enough for 100 people, just 12 or so crew, and only on the first few manned BFRs).  

BFR has a huge payload capacity to and from Mars.  Using afew of tons of that payload capacity for a detachable crew capsule, in the case of a problem during earth ascent/landing might be worthwhile.   One thing we learnt (or at least should have learnt) from Columbia and Challenger, is that vehicle and mission designers should consider the possibility of an unanticipated and potentially catastrophic failure, and as much as is feasible design the vehicle/mission so that the crew still has the best chance of survival as is feasible.   (Yeah, you could transfer crew in LEO after the ascent.  If you get things right, aero-capturing into Earth orbit and transfering crew in Earth orbit might also be possible at mission end, but if you anything goes wrong during that aero-capture, then what's the plan B ?).  

 

[Spaceception]

1 hour ago, MinimumSky5 said:

I thought that the first BFR crew varients to Mars were going to be unmanned, and used as permanent habitats?

The plan so far, afaik, is to launch 2 uncrewed BFR's stocked with supplies and stuff that can be used to set up a propellant depot, habitats, recycling, etc. Ideally in 2022. Seeing as that's just 4 years away, I don't see how they can do that (I can see 2024-28 personally). But that's besides the point: If both ships land alright, then 2 years later, 4 BFR's will launch; 2 cargo, 2 crew/some cargo. And like @tater said, they will likely be the minimum number needed. I don't expect them to be sending hordes of people to Mars until some habitats are up, farms are running, and solar collectors are doing their thing.

 

On a side note: SpaceX has stated they only plan to be the transportation company. And they'll let others take care of the life support and such instead. But I doubt there's any company on Earth who is willing to do this in just the next few years, so SpaceX will almost certainly need to R&D the life support/habitats/etc themselves if they intend to keep on a fast timeline. Is there any information of them doing this?

Edited August 31, 2018 by Spaceception

[tater]

Yeah, the linchpin on any colonization or permanent settlement on Mars is some economic reason to do it. Short of that transport capability is meaningless. There are better places to homestead all over the Earth that are so harsh no one wants to live there (northern Alaska/Canada, for example), and they're all better than any spot on Mars will ever be, even in the most unlikely terraformed fantasy.

[55delta]

I found this video from the International Mars Society Convention. Warning: sections of low volume and general stammering.

https://www.youtube.com/watch?v=C1Cz6vF4ONE

 

Mostly a re-iteration of what we knew of SpaceX's plans, with a few 'new' details on selecting landing sites and general plans.

[Spaceception]

Well, after I sent that reply earlier, I started wondering about it, so I sent a tweet out. Let's see if I get any response  

 

[tater]