Outer Space Thread

[AdmiralKird]

Hyperloop is plausible technology if someone like Musk would actually fund its development, but it's stagnant. It's already near impossible to get governments in the U.S. to fund high speed rail let alone a hyperloop system. I think Musk is just sitting on it in case someone comes calling. I don't think he wants to fund it because your development cycle for a loop is too long and if that one line is bust - it's game over.

Going to mars would be like going back to the 1920s at best. In a [expletive] hole climate and landscape. [expletive] that.

But it beats extinction if it ever came to that.

Mars would be way worse than the 1920's. You can't go outside without a pressure suit. If you do, you'll have dust all over you in minutes. It's freezng cold. You get dowsed in radiation unless you're underground. Want to talk to someone on the phone? skype? zoom? use the internet? Can't, can't, can't, and barely. Round-trip communication with Earth is on a 6-12min lag, depending on the distance between the planets. Click the link and come back in 10min and maybe it will have loaded. Also bandwidth to Mars is not a great priority so far. Perseverance, the latest rover, can download a small size 4.7GB DVD in just over 5 hours. Good luck sharing that bandwidth with 100 homesick people.

The closest experience to living on Mars you can get on Earth would be a two and a half year prison sentence. The only people that would actually get something out of Mars would be trained scientists who would be able to constantly perform science, make discoveries, and write papers.

If you're worried about being a multi-planetary species, then Breakthrough Starshot is the way to go. As much as its amazing that we appear to have won the billion in one lottery to evolve into intelligent life, we may not have another habitable planet around for ~20 light years, if that, which really sucks. The closest star system that appears to share a lot of the same traits as our star and system is Delta Pavonis which is 20 light years away. It would take a hundred and twenty years just to survey it with Starshot under optimistic scenarios. Who knows if local dust-disc systems like Tau Ceti and Epsilon Eridani have anything. I'm leery of putting so much faith in planets in the habitable zones of red dwarfs just because we're not around a red dwarf. There is probably a larger chance of an earth-like planet around one of those though than Delta Pavonis having anything, which even if its got something in the habitable zone might just be more Mars or Venus bs.

Edit: On the plus side, five hundred years to get humans to another planet is nothing on the cosmological timescale to where we should be existentially afraid for earth's habitability due to external factors.

[Arthur Dent]

Hyperloop is plausible technology if someone like Musk would actually fund its development, but it's stagnant. It's already near impossible to get governments in the U.S. to fund high speed rail let alone a hyperloop system. I think Musk is just sitting on it in case someone comes calling. I don't think he wants to fund it because your development cycle for a loop is too long and if that one line is bust - it's game over.

I would rank hyperloop as less ridiculous than the ballistic missile based transport idea, but it’s not especially realistic. The infrastructure costs would be extremely high, and the track would have to be ultra-straight leaving little flexibility to acquire a possible route. Again, there is an actually existing technology, high speed rail, that actually works but has limited deployment. Would a much higher-end transport system that doesn’t integrate with existing rail networks, stations, etc be viable for some routes someday? Maybe, but it’s not that great a sell. You’d lose much of what makes train travel compelling: easy access to stations in the urban core where you can just hop on and dump your bag in a rack and ride in a nice comfy environment enjoying the countryside, etc.

[Arthur Dent]

[ghostrunner]

I wonder why this was so important. Not sure if the lack of a flame trench was the only issue but that seems to be the primary suspect based on what I’m reading.

Expense? Time?

[AdmiralKird]

Flame diverters and trenches need maintenance after every launch. The water table there is very shallow so it would have been challenging to build one. They thought raising the entire rocket up would be cheaper and still mostly effective, but someone or someones miscalculated the height required to completely replace the need of having a flame diverter and trench system.

Edit:



This is also much larger problem with the upper stage of Starship and the feasibility of taking off from Mars. If you put large tri- or tetr- pod landing gear on that giant heavy body to lift it further off the ground it's going to greatly increase the weight. If you put the engines higher up on the side it'll shoot heat into the body that will lower its re-usability and greatly increase aerodynamic drag. The Mars sample return mission is solving this by tossing the return rocket up into the air by using submarine spring pods designed to release Tomahawks and ICBMs before firing their main engines. You can't do that with Starship. They' need to have a launchpad on Mars to get it off the ground.

[Arthur Dent]

I thought this was a good and fair rundown of the aggressive/scrappy vs reckless/crappy views of the test.

https://thenext30trips.com/p/scrappy-special-edition

Nuking the launchpad, blasting engines completely off and sending off huge chunks of uncontrolled debris everywhere does seem to be the kind of egregious misconduct that is likely to cost them.

[Joe Shlabotnik]

I thought this was a good and fair rundown of the aggressive/scrappy vs reckless/crappy views of the test.

https://thenext30trips.com/p/scrappy-special-edition

Nuking the launchpad, blasting engines completely off and sending off huge chunks of uncontrolled debris everywhere does seem to be the kind of egregious misconduct that is likely to cost them.

Typical libertarians. Don't Tread On Me while I piss on your head and tell you its raining!

[AWvsCBsteeeerike3]

I thought this was a good and fair rundown of the aggressive/scrappy vs reckless/crappy views of the test.

https://thenext30trips.com/p/scrappy-special-edition

Nuking the launchpad, blasting engines completely off and sending off huge chunks of uncontrolled debris everywhere does seem to be the kind of egregious misconduct that is likely to cost them.

Very informative, thanks for posting.

Don't know much about anything from a technical perspective or what is required to get approval for launch. But, I'm surprised they were allowed to store their fuel (I imagine that is what is in those big white silos/tanks) that close to the launchpad. Forget about debris from tearing up the launch pad, what about if the whole thing just blew to smitherines? Would they have been able to withstand that? Perhaps they would have and blasting off with however many thousands of tons of thrust propelling concrete into the abyss was more damaging than a catastrophic bang sending the energy everywhere instead of being focused on a small area. Who knows.

But, yeah, making it rain concrete a mile or so away seems to be a bit more of an oopsie that should be written off, even if the videos of it landing in the water are freaking awesome. Of all things, protecting the launch site seems to be among the most mundane of details. Obviously there are precedents there that were simply ignored...and concrete, even with all the admixtures available, is among the most researched material in the world.

No idea how they calc thrust but if you take it as pressure*area then pressure is thrust/area. Run of the mill concrete has a compressive strength ~4K psi or ~2tons/in^2. If starship has a thrust of 8500 tons distributed evenly over it's 30' diameter, the pressure would be a miniscule ~0.1 tons/in^2. But I have no idea how much pressure was actually on the pad under starship or how to calc it for rockets. If it was a hydraulic press or something like that, the pressure seems to check back of napkin calcs. I've spent the last hour trying to figure this out and am going to give up...for now.

Regardless, concretes strength comes from breaking cylinders in a lab by putting it into compression until it deforms enough to break in tension. And, it has little tensile or shear strength. That's not the number you'd use to see what a slab could actually withstand because it ignores tension and shear. Certainly wouldn't use it for a launch pad because it's not a static environement either. Curious to see what the report generates, but I wouldn't be the least bit surprised to see that there was insufficient strength below the concrete to prevent deformation to the point of cracking and then failure. And, I'm curious as to what role the rapid heating played in the process. I know it's high heat concrete or whatever, and they use it or something similar to cover the steel diverter plates. Guess time will tell.

Apples to oranges here, but to design roads, the amount of axels equivalent to 9 tons are calcd and then used to come up with a structural number. The higher tha tnumber, the thicker the pavement. Even small structural numbers result in 4" of concrete. Repetitive loading vs single loads and superior concrete be damned. If yo u need 4" concrete (plus compacted base plus compacted subgrade) to withstand the forces created by a truck, I can only imagine what would be needed for a rocket.

Crazy. Awesome but crazy. That video of debris raining down in the ocean is wild.

[Arthur Dent]

I’m way outside my area here, but I read that it is not compressive stress that’s the issue with the pad concrete. Apparently, the massive amount of gas pressure will make its way through pores and cracks all the way through to the earth, and then produce a huge lifting pressure underneath. The heat loading helps cracks form and more cracks mean more pressure gets through, and you get a run away positive feedback. Though not exactly the kind of concrete physics that goes into your average building design, this is apparently well known, and their engineers were almost certainly aware that this was likely to happen. Musk claims that they they decided it was ok based on the short half throttle static fire test, which sounds exactly like the type management [expletive] I’ve encountered before.

Regarding the fuel tanks close to the pad, that does seem crazy. I would have thought that a the rocket detonating on the pad or only lifting off a short distance before coming crashing back down on the pad would be a more likely failure mode than the one they had. Maybe the theory is that this type of failure would be so bad, that the bit of extra fuel in the tanks is a “who care” afterthought?

Some close up photos of the debris cloud:

[Arthur Dent]

If you zoom in to the engines at around 12:20 on this video, you can [expletive] flapping around in the wind and breaking off.