totm nov 2023 SpaceX Discussion Thread

[mikegarrison]

1 hour ago, Dale Christopher said:

I’m sure solar will be a big piece of a Mars power solution but I don’t think it will be the whole picture. Nuclear would be nice but probably impractical to think every outpost will be able to have nuclear reactors. I haven’t looked into the cost but I’m sure they’re not cheap or easy to make, in contrast to solar panels which are both.

Going to Mars is not going to be either "cheap" or "easy". We already know that probes powered by RTGs are less affected by the weather and the seasons than probes powered by solar, but both solutions have worked OK. The problems are going to come with scaling up either type of power.

[tater]

2 minutes ago, mikegarrison said:

Going to Mars is not going to be either "cheap" or "easy". We already know that probes powered by RTGs are less affected by the weather and the seasons than probes powered by solar, but both solutions have worked OK. The problems are going to come with scaling up either type of power.

Yeah, for human missions RTGs sorta barely get the job done, I think something like kilopower makes more sense (actual reactors vs RTGs).

[sh1pman]

3 minutes ago, tater said:

I think something like kilopower makes more sense (actual reactors vs RTGs).

For 100+ ppl colony something like "megapower" makes even more sense.

https://en.wikipedia.org/wiki/TEM_(nuclear_propulsion)

Maybe Rosatom can sell one TEM reactor to SpaceX, it'll fit perfectly for the job.

Quote

• Coolant: 78% helium/22% xenon.
• Heat power: 3.8 MW
• Electric power: 1 MW
•  
• Mass: 20,290 kg 

 

Edited February 13, 2020 by sh1pman

[mikegarrison]

Russian nuclear reactors don't have the greatest of history. (Of course, neither do Solar City roofs.)

[kerbiloid]

7 minutes ago, mikegarrison said:

Russian nuclear reactors don't have the greatest of history.

Can you pick any other reactor history having same great amount of books, movies, series, and games dedicated to?

Edited February 13, 2020 by kerbiloid

[sh1pman]

5 minutes ago, mikegarrison said:

(Of course, neither do Solar City roofs.)

Or Starships. Or Mars colonies. 

[StrandedonEarth]

Hmm, This sounds to simple to actually work, but what if those first few expendable lunar Cargo SSs were sliced open down the side, unrolled,  and use that steel as the pad (properly secured, of course). Depends on how the steel holds up to the exhaust plume, and how much it warps with that much localized heat....

[zolotiyeruki]

Semi-trailer-sized walk-away-safe nuclear reactors are very much possible, but I imagine SpaceX would have to outsource that to someone with more experience/expertise at the technology, not to mention the regulatory issues.  Given SpaceX's rapid development pace, and the glacial pace of anything related to nuclear fission, I don't see it working out.  Maybe if they somehow separated various parts until they get away from Earth, they could bypass some of the regulatory hurdles?

[ThatGuyWithALongUsername]

Well... this is a very complicated design idea for a niche purpose, but what if we got around the plume interaction by mounting a pair of superdraco-style engine pods near the top of the vehicle, maybe under the front flaps? While a plain superdraco would obviously not be powerful enough, you only need about 110,000 lbf of thrust (490 kN) for a fully fuelled Starship to lift off in lunar gravity. A single Merlin engije would be more than ebough for that, although for this design you would want that power divided into 4 engines.

 

I'm not saying it's a good idea (it would involve SpaceX developing a whole new engine and making various difficult structural design changes to fit them in for a variant of Starship that becomes useless the second a pre-prepared pad is set up) but hey, it would work at least

 

(Fingers crossed that simulations show plume interactions being less of a problem then they may seem)

 

Another thing... maybe the legs are designed this way (with a narrow base) for better shock absorption, potentially letting them shut off the engine early and just fall the last few meters to the lunar surface... how long are they?

Edited February 13, 2020 by ThatGuyWithALongUsername

[tater]

A vac optimized Super Draco could totally work in this regard.

 

 

[CatastrophicFailure]

2 hours ago, zolotiyeruki said:

Given SpaceX's rapid development pace, and the glacial pace of anything related to nuclear fission, I don't see it working out. 

This is why solar makes so much more sense for them (not to mention they’re about to get a ton of experience with it thru Tesla Energy). A purpose built solar farm on Mars would have one huge advantage poor Oppy never did: the solar panels can be cleaned, whether by robots or colonists. If they’ve got multiple football-fields worth of panels for making fuel, then that’s still probably enough to power the colony thru a month-long dust storm if they suspend fuel production during that time. 

[tater]

6 minutes ago, CatastrophicFailure said:

This is why solar makes so much more sense for them (not to mention they’re about to get a ton of experience with it thru Tesla Energy). A purpose built solar farm on Mars would have one huge advantage poor Oppy never did: the solar panels can be cleaned, whether by robots or colonists. If they’ve got multiple football-fields worth of panels for making fuel, then that’s still probably enough to power the colony thru a month-long dust storm if they suspend fuel production during that time. 

They must already be working on automated clearing, albeit for a much smaller area—Tesla cars need to have something that can keep the cameras clean 100% of the time, or self-driving in winter is a non-starter.

[ThatGuyWithALongUsername]

1 minute ago, tater said:

They must already be working on automated clearing, albeit for a much smaller area—Tesla cars need to have something that can keep the cameras clean 100% of the time, or self-driving in winter is a non-starter.

Maybe something like a wiper on rails sweeping across a row of solar panels? Would that work?

 

Eventually, the track would get clogged with dust. But, again, there are people here.

[magnemoe]

1 minute ago, tater said:

They must already be working on automated clearing, albeit for a much smaller area—Tesla cars need to have something that can keep the cameras clean 100% of the time, or self-driving in winter is a non-starter.

You can clean dusty solar panels with compressed air, modern cars uses high pressure water with an mostly glycerol cleaning  and anti freeze agent to keep the front light clean. My previous car, an Volvo had wipers for the lights but they moved away from it. 
 

[StrandedonEarth]

5 minutes ago, ThatGuyWithALongUsername said:

Maybe something like a wiper on rails sweeping across a row of solar panels? Would that work?

 

Eventually, the track would get clogged with dust. But, again, there are people here.

Compressed Martian air to blow dust off

[CatastrophicFailure]

28 minutes ago, tater said:

They must already be working on automated clearing, albeit for a much smaller area—Tesla cars need to have something that can keep the cameras clean 100% of the time, or self-driving in winter is a non-starter.

I recall Musk saying that the new Solarglass panels are largely self-cleaning or dust-repellent or some such. But given what else he’s up to, a Martian Roomba couldn’t be that difficult. 

No, really... flat, contiguous field of Solarglass tiles and some robot periodically cleaning it, both with brushes and compressed Martian air. 

Probably light years easier than getting regulatory approval to launch a nuclear reactor to another planet by a private company, since such regulations don’t really exist, and the only thing more contentious than changing existing regulations is making new ones. 
 

 

Hmm... thought occurs to me... Solarglass is supposed to be really durable... wonder if they could just use that for the landing pad..? 

Edited February 13, 2020 by CatastrophicFailure

[tater]

 

[tater]

Note that we have no idea what the actual turn around time was., we just know that it's at worst 61 days. For all we know it sat around and got actually turned around in 61 hours. The only way we'll know is if they tell us at some point, or we see a core get reused in a substantially shorter time period.

[Shpaget]

1 hour ago, tater said:

The only way we'll know

Well, we could ask Elon himself. He does tend to reply to technical questions fairly often and seems open and honest about stuff like this.

Also, I am still convinced that he lurks on these forums, so yeah, Elon, if' you are reading this, please give us the knowledge. We have cookies.

[Akela]

3 hours ago, tater said:

Note that we have no idea what the actual turn around time was., we just know that it's at worst 61 days. For all we know it sat around and got actually turned around in 61 hours. The only way we'll know is if they tell us at some point, or we see a core get reused in a substantially shorter time period.

That leaked(?) talk that was released a few weeks ago mentioned that booster turnaround time was around 30 days. Cost of a reused booster is apparently now down to $30m as well.

Source: https://forum.nasaspaceflight.com/index.php?topic=43154.360

[tater]

Shotwell said that while they could do an IPO, it wouldn't be for several years. The TL;DR of the story is that they should be at the most capital intense period right now, so if they are not seeking money (the point of an IPO), they must be really confident (and their costs under control).

[Guest]

13 hours ago, mikegarrison said:

Going to Mars is not going to be either "cheap" or "easy". We already know that probes powered by RTGs are less affected by the weather and the seasons than probes powered by solar, but both solutions have worked OK. The problems are going to come with scaling up either type of power.

Well you aren’t going to power crewed bases of any real scale or much industrial activity with RTGs and rather than scaling them up and running into issues such as uncertain access to sufficient quantities of radioisotopes, you would be looking at using the in development Kilopower reactors for those types of applications.

Yer, Mars isn’t going to be cheap easy, so it makes sense to use the simplest, most cost effective, serviceable and scalable solutions possible right? Kilopower reactors and one use/ one way trip Starships may be the best initial steps required to get a foothold on Mars but factors such as reusability, sustainability, cost efficiencies, engineering considerations and local manufacturing capabilities mean they aren’t practical solutions for putting 1million people on Mars.

Edited February 14, 2020 by Guest

[tater]

I still find it hard to wrap my head around the fact that he takes this colonization thing seriously. Very seriously. I see Starship (ie: any inexpensive, 100% operationally reusable LEO LV) as transformative minus the Mars stuff... interesting times.

[mikegarrison]

1 hour ago, Dale Christopher said:

Well you aren’t going to power crewed bases of any real scale or much industrial activity with RTGs

I guess I wasn't clear enough. I assumed people would understand I meant "nuclear reactor v. solar farm", not that I thought they would build a house-sized RTG.

[Shpaget]

3 hours ago, tater said:

Shotwell said that while they could do an IPO, it wouldn't be for several years. The TL;DR of the story is that they should be at the most capital intense period right now, so if they are not seeking money (the point of an IPO), they must be really confident (and their costs under control).

Or they could have a private investor footing the bill. The genius part about satellite internet, if it proves to be viable, is that once the sats are up there is virtually not additional cost tosign up a new customer. There is no infrastructure to build, no trenches to dig for underground cables... etc. only a small and probably very cheap satellite dish and receiver. With just ten million subscribers (which is not a lot considering worldwide market) they could bring in billions in yearly revenue, so it's very interesting for investors. I sure would buy some shares.