The Astronomy Thread

Palum · Jan 20, 2016

Khalan_sl said:
I never said the barges are for Mars. You made the point that they should use the Ocean as a body to catch the rockets but that defeats ONE of the key technologies Musk is trying to develop; reusable rockets that can vertically land.

The Barge landings are a completely different issue and not needed for mars, but they do help by allowing them to create more efficiency in the rockets (Read the article).

Stop making this about the barges they have nothing to do with Mars.

If your primary goal is reusing the rocket, you should ditch and recover. If your primary goal is research you should crash it trying to land vertically at all costs. Seems pretty simple to me?

Palum · Jan 20, 2016

Dandain_sl said:
Two things, ditching a rocket into a bath of salt water is probably as bad as it is for a combustion engine in your car. Perhaps a giant water tight rocket condom would do the trick along with something to slow the fucker down so the impact with the water doesn't hurt anything. Unbuilding/rebuilding such a rocket is probably more of a waste of time than building a new one. Because when you build one from scratch there are built in safeties and quality at every single step, nothing has been used. Every water logged rocket would clearly have different problems, but how complicated is the cleaning process?

Second, "Assuredly losing the vehicle to bad sea swells" is clearly not the case. Did you watch the last landing? That thing was dead center, which means the barge and the rocket were both in precisely the right place. Stabilizing the barge to absorb the impact, making the barge capable of having a near motionless deck in obscene seas, these are all possible solutions that you seem to think are impossible to solve. Just because there are 13 foot seas, doesn't mean the barge deck is pitching like a crab boat.

Well if they can rocket motor down to a platform they can do it to the ocean. NASA recovered and reused the SRBs, so I don't buy the quick salt water bath anathema offhand. Is there something specific to the Falcon which makes it deteriorate more quickly when exposed?

Khalan · Jan 20, 2016

Palum_sl said:
If your primary goal is reusing the rocket, you should ditch and recover. If your primary goal is research you should crash it trying to land vertically at all costs. Seems pretty simple to me?

They are trying to develop the technologies in tandem that is my point. Elon Musk will never do anything the easy way.

Khalan · Jan 20, 2016

Palum_sl said:
Well if they can rocket motor down to a platform they can do it to the ocean. NASA recovered and reused the SRBs, so I don't buy the quick salt water bath anathema offhand. Is there something specific to the Falcon which makes it deteriorate more quickly when exposed?

I think the idea is LOW COST reusable rocket. Im sure they could ditch in the ocean but it would be prohibitively expensive. Musk has stated he wants to be able to relaunch incredible quick i.e within 1-3 days. So an ocean bath is not quite going to work.

Khalan · Jan 20, 2016

Palum_sl said:
Well if they can rocket motor down to a platform they can do it to the ocean. NASA recovered and reused the SRBs, so I don't buy the quick salt water bath anathema offhand. Is there something specific to the Falcon which makes it deteriorate more quickly when exposed?

Also if you do some reading on SRBS, only the steel casing was reused, the rest was basically trashed due to the sea water.

Dandain · Jan 20, 2016

So here is Musk's own words about the topic. 4:36 he talks specifically about recovery.

Ukerric · Jan 20, 2016

LachiusTZ_sl said:
One theory is it happened in 774AD, but was 13k ly from earth, so it just produced a ton of carbon 14. Not sure how that works, and not curious enough to look it up.

Carbon 14 is produced at the top of the atmosphere from cosmic activity, which is why you use carbon 14 for dating fossils of living stuff: plants constantly absorb CO2 which includes that fresh C14, animals eat those plants, and so living creatures tend to have the same C14 balance as the atmosphere, but then they die, and C14 disintegrate without being renewed.

A large increase in cosmic ray leads to a temporary increase in C14 production.

Palum_sl said:
Also lol that this is mars tech. This is Elon being Musky.

Just finished a SF book in which the mars colonists were called Muskies. For the obvious reason.

Dandain · Jan 20, 2016

Signs of second largest black hole in the Milky Way: Possible missing link in black hole evolution

Neph_sl · Jan 20, 2016

Dandain_sl said:
So here is Musk's own words about the topic. 4:36 he talks specifically about recovery.

Thanks (+1). I asked the question about "why water landings" to begin with. But to summarize, the goal is to colonize Mars, and to slow down a rocket there, you have to get good at landing via rockets (and not say wings and wheels like the shuttles, bc there's no landing strips on Mars).

I didn't watch that far, but he didn't mention the trajectories nor velocities that others have pointed out, but that part makes sense. You don't want your trajectories for Earth-based launches to be constrained by where you can land.

However, landing on a barge in swells is still a problem that won't be seen on Mars. But if they can perfect it, then it'll be huge for recovery here on Earth.

Eomer · Jan 20, 2016

Cad_sl said:
Who needs a heavy lift vehicle if you can launch 20 pieces of a large ship cheaply and independently? Why do you have to shoot it up all at once? Assemble in orbit and go from there.

Heavy lift vehicles tend to also have lower launch costs per pound, because of economies of scale etc. And if we're talking about building colonies, it's entirely possible that some components are simply too big to fit on a smaller rocket and assembling them in space isn't feasible or optimal.

Palum_sl said:
NASA recovered and reused the SRBs, so I don't buy the quick salt water bath anathema offhand. Is there something specific to the Falcon which makes it deteriorate more quickly when exposed?

First off, you might want to look in to the differences in complexity for solid and liquid fueled rockets. Wee bit of a difference there in terms of the complexity of the rockets, components, etc etc. Solid rockets are simple as fuck and have next to no moving parts. Liquid fueled rockets, not so much. And has been mentioned, apparently only the casing of the SRB's was reused.

Neph_sl said:
(and not say wings and wheels like the shuttles, bc there's no landing strips on Mars)

It's not the lack of landing strips. It's how thin Mars' atmosphere is. Parachutes, wings, and other lift generating designs simply don't generate enough lift to handle anything other than extremely light loads. That's why the first small Mars rovers used parachutes then giant air bags to bounce around with, while the latest, heaviest ones have to use retro rockets. They can't make an airbag strong enough to handle the high velocities that happen with heavy loads and parachutes.

Agraza · Jan 20, 2016

They could cluster bomb parachute the components, but it adds a ton of complexity. Landing one vehicle is the most promising solution.

Cad · Jan 20, 2016

Eomer_sl said:
Heavy lift vehicles tend to also have lower launch costs per pound, because of economies of scale etc. And if we're talking about building colonies, it's entirely possible that some components are simply too big to fit on a smaller rocket and assembling them in space isn't feasible or optimal.

Ok, then how come nobody is building them? I did some analysis from cost per launch and payload that I found and the new Falcon 9 is cheaper per pound (barely) than the Saturn V. Granted there's 50 years of tech separating those, but still. If F9 can be reused like they plan, that would greatly decrease the cost as well.

meStevo · Jan 20, 2016

New evidence suggests a ninth planet lurking at the edge of the solar system - The Washington Post

Agraza · Jan 20, 2016

That's the A.I. monitor. As soon as our species is advanced enough to detect it, it arms, and once we arrive at it, it detonates our star. Organic life is too dangerous to be allowed to spread.

Khalan · Jan 20, 2016

Cad_sl said:
Ok, then how come nobody is building them? I did some analysis from cost per launch and payload that I found and the new Falcon 9 is cheaper per pound (barely) than the Saturn V. Granted there's 50 years of tech separating those, but still. If F9 can be reused like they plan, that would greatly decrease the cost as well.

I would assume the goal would be to be building the smallest craft capable of reaching LEO. I think most satellites they put into LEO/Geo orbit are around the same size and only need X amount of thrust to get them up there, so building massive rockets for short missions when they are not needed is a bit of a waste. We aren't building a space station or getting people to the moon/mars so massive rockets arent really needed I would assume.

Eomer · Jan 20, 2016

Cad_sl said:
Ok, then how come nobody is building them? I did some analysis from cost per launch and payload that I found and the new Falcon 9 is cheaper per pound (barely) than the Saturn V. Granted there's 50 years of tech separating those, but still. If F9 can be reused like they plan, that would greatly decrease the cost as well.

The US is building the Space Launch System, which is heavy lift. But there's really very little commercial viability for a privately developed and funded heavy lift vehicle. Very, very few satellites are big enough or need to go in to a high enough orbit that a heavy lift platform is required. And just because you have two or four times the lift capacity doesn't mean you can combine several Falcon 9 launches in to a single Heavy launch, because the orbits etc are probably going to be very different. That being said, SpaceX is developing the Falcon Heavy and they do already have half a dozen or so launches on their manifest. One is for the DOD, the rest are private.

Falcon Heavy - Wikipedia, the free encyclopedia

Musk has stated that he thinks he can get launch costs to LEO down to $500/lb with the Heavy. I think that the Falcon 9 is somewhere around $1,000-$1,500 right now. I'm not clear if he needs reusability of the lower stages on the Falcon Heavy to meet that target.

Big Phoenix · Jan 20, 2016

Cad_sl said:
Who needs a heavy lift vehicle if you can launch 20 pieces of a large ship cheaply and independently? Why do you have to shoot it up all at once? Assemble in orbit and go from there.

Working in space is expensive.

Draegan_sl · Jan 20, 2016

Is musk the real life version of this series?
Firestar: An Epic of Science Fiction for the Twenty-First Century: Michael Flynn: 9780312855253: Amazon.com: Books

Itzena_sl · Jan 21, 2016

meStevo_sl said:
New evidence suggests a ninth planet lurking at the edge of the solar system - The Washington Post

That's areallyweird orbit if it's real. Wonder if it was an extrasolar planet captured by the Sun?

meStevo · Jan 21, 2016

Thought all the suspected bodies like that in the outer solar system were believed to have been evicted from the inner solar system by Jupiter or something.

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