Last time I checked the estimates for Kuiper belt combined mass was about E-4 Earth masses. Granted it's hard to spot the stuff that's out there but 5 orders of magnitude is a big gap. I'd expect we'd see much more objects if the number was higher.
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Last time I checked the estimates for Kuiper belt combined mass was about E-4 Earth masses. Granted it's hard to spot the stuff that's out there but 5 orders of magnitude is a big gap. I'd expect we'd see much more objects if the number was higher.
Spoken like a man who deeply lacks understanding of the issues involved.
At least I recognize my own deficiency!
hobbsyoyo
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He's so wrong that he's right though. There is nothing stopping a basic manned Mars mission right now except money and political will. 4 years is super agressive but orders of magnitude less difficult than Apollo was due to 5 decades of experience.
From what I recall, there are only 2 orbital alignments that make sense to get to Mars - one is fast but lots of fuel, the other is slow but takes less fuel. The fast one is every 22 months or so?? Assuming it would have to be a fast trip, is there even an alignment coming up in the time frame required?
Most of what I know about getting to Mars came from reading up about Mars Direct and the SpaceX write up on WaitButWhy.com
Most of what I know about getting to Mars came from reading up about Mars Direct and the SpaceX write up on WaitButWhy.com
I can roughly see how it could be done in 4 years, and I'm not one who would shriek away from supporting such an aggressive output, but it still boggles me how exactly it could be done. The first year would be reorganization and having one team work on this and that, the second a lot of back to back testing, the third the launch basically and the fourth the cruise.
If he had just wanted the launch as he leaves, it extends it to 6 years in reality, giving around four years of development, but his rush would had only given NASA what - two?
If he had just wanted the launch as he leaves, it extends it to 6 years in reality, giving around four years of development, but his rush would had only given NASA what - two?
hobbsyoyo
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Yup, there are orbital alignments roughly every 18 months or so, give or take. Some are more favorable than others.
The trick is that you don't have to wait for an alignment to go, that just makes it easier. This is a problem that can be solved Kerbal-style with the application of MOAR Thrust. I joke but I'm dead serious. Bringing more fuel can open up transfer windows outside of alignments and get you to Mars arbitrarily fast. As it happens, we have spent two decades figuring out how to link up modules in space.
Launching fuel modules into space isn't too much different than building the ISS. This could be done, we could have had astronauts on Mars in 4 years but I doubt they would have been able to make a full round trip in that time.
And it would have been very, very risky, to the point where astronauts would be gambling with their lives. I am not saying it would be easy, cheap or risk-free. I am just saying it is possible given the technology we already have.
The trick is that you don't have to wait for an alignment to go, that just makes it easier. This is a problem that can be solved Kerbal-style with the application of MOAR Thrust. I joke but I'm dead serious. Bringing more fuel can open up transfer windows outside of alignments and get you to Mars arbitrarily fast. As it happens, we have spent two decades figuring out how to link up modules in space.
Launching fuel modules into space isn't too much different than building the ISS. This could be done, we could have had astronauts on Mars in 4 years but I doubt they would have been able to make a full round trip in that time.
And it would have been very, very risky, to the point where astronauts would be gambling with their lives. I am not saying it would be easy, cheap or risk-free. I am just saying it is possible given the technology we already have.
Outside of crew support stuff etc. - what about technologies for getting off Mars back to orbit - do we already have like "give me money and we will build it" or "give me money and we will start to figure out how to do it" technology level?
Thorgalaeg
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Energetic needs to reach Mars low orbit from surface is about a 30% that of Earth, maybe even less having in mind the thin atmosphere. Piece of cake compared to Earth. It is a matter of having enough fuel left.
I don't think we currently have proven and tested fuel manufacturing capabilities for generating on Mars, but I could be wrong. Assuming I am correct, fuel to get from Mars surface back to orbit would have to be landed with the reorbit module. Which means obviously the fuel will have to come from Earth. That's more mass to push from Earth to Mars.
hobbsyoyo
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We're at 'give me money and we will build it'. It wouldn't be an elegant solution - more of a brute force approach. We don't need any new technologies to pull it off at this point. A lot of the work being done to research Mars mission architectures are purely to make the effort more cost efficient, safer and with higher mission capabilities than what we could pull off today.
But if all we care about is getting there and back, we could do it with what we have now, adapted for purpose.
We've had space-storable propellants since the 60's. They are toxic as hell and medium-performance but they get the job done. To speed up the timeline for the mission, they would not design a massive singular spacecraft to do the whole job. They would send one capsule for descent and one capsule (or more!) for the return to orbit. On the way to Mars they'd live in a LOP-G style space station. This space station would be huge but mostly made up of food, fuel and water and would not use fancy electric engines and other exotic technologies.
We've tested in situ systems on Earth and the baseline chemical technologies themselves are pretty normal as far as that goes. It's really the whole, 'do that thing you know how to do but on Mars' factor that makes it seem exotic. But I wouldn't bother with that, I'd just use hydrazine and dinitrogen tetroxide and lots of it.
so let's toss some numbers around?
How much mass would you need, ballpark, for a module to get from the Martian surface back to orbit? 1000kg? 2000? And how much of that toxic stuff would it take to make the re-orbit trip?
In Europa Report one of the astronauts gets some Hydrazine on his suit, and then (i think?) on his skin. I'm assuming it's not as nasty as they made it out to be? (assuming of course that you've seen the movie)
hobbsyoyo
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About 7,000 metric tonnes, give or take. This works out to around 100 Falcon Heavy flights and $30 billion dollars. *napkin math alert*
(2) 13,000 per lander (mass of Dragon 2)
(1) 10,000 transit habitat (engineering estimate)
(3) 2,000 kg food per person (googled how much food a person needs for a year)
(3) 1,000 kg water per person (same method)
16 km/s Delta-V there for full stack (quora/wikipedia/NASA)
16 km/s Delta-V back for the transit habitat and half the food/water (same method)
339 s specific impulse hydrazine/nto (NASA)
This got me to 114 Falcon Heavy flights. This is the brute force, ugly as hell way to do it. I'm not even counting on water recyclers of the kind already deployed on the ISS, though I haven't accounted for breathing air as a separate line item so it's probably in the wash. I did work out that in just oxygen, the astronauts would need about 600 kg for a year long journey. I actually double-counted the mass of the transit habitat because it was easier than mathing it out.
Now, if the transfer stage is sent from Earth with hydrogen/oxygen fuel like the Centaur and Delta IV upper stage uses (isp=465 s), the total flights of Falcon Heavy equivalent falls to less than 30. This would assume much better insulation technologies than are ready off the shelf at the moment - hydrogen would boil off faster than they could launch it with today's technology. However, this is an active area of research by multiple space agencies and independent companies. It's not a particularly demanding challenge, it comes down to using sun shades made of mylar (like on James Webb Space Telescope) and active refrigeration. I am assuming hydrazine fuel for the return trip due to the really long transit times - I think we can develop hydrolox to get this stack to Mars in a couple years but not to get there and all the way back too.
With infinite money it could be figured out in time but I went with the more conservative answer to show how reasonable (if expensive and downright ugly, from a technical perspective) this is.
Falcon Heavies go for $90 million each so launching 100 of them costs $9 billion. Let's add $20 billion more for spooling up production capacity.
So for about $30 billion dollars (about 1/3 more than NASA's current budget or 5% of the Pentagon's), you could put three astronauts on Mars and bring them back with today's technology.
This method does require hohmann transfers to work but one opens up in 2020 - which is why they are calling Curiosity's follow-on Mars 2020 as it launches that year. In any case, more fuel = longer transfer windows = more launch options. It all comes back to MOAR Thrust!
That scene in Europa report was downright silly. Hydrazine is not that bad as much as I joke about it and even if it were, they had tons of ways to deal with it.
Edit: He didn't even get it on his skin. That whole scenario was really dumb.
(2) 13,000 per lander (mass of Dragon 2)
(1) 10,000 transit habitat (engineering estimate)
(3) 2,000 kg food per person (googled how much food a person needs for a year)
(3) 1,000 kg water per person (same method)
16 km/s Delta-V there for full stack (quora/wikipedia/NASA)
16 km/s Delta-V back for the transit habitat and half the food/water (same method)
339 s specific impulse hydrazine/nto (NASA)
This got me to 114 Falcon Heavy flights. This is the brute force, ugly as hell way to do it. I'm not even counting on water recyclers of the kind already deployed on the ISS, though I haven't accounted for breathing air as a separate line item so it's probably in the wash. I did work out that in just oxygen, the astronauts would need about 600 kg for a year long journey. I actually double-counted the mass of the transit habitat because it was easier than mathing it out.
Now, if the transfer stage is sent from Earth with hydrogen/oxygen fuel like the Centaur and Delta IV upper stage uses (isp=465 s), the total flights of Falcon Heavy equivalent falls to less than 30. This would assume much better insulation technologies than are ready off the shelf at the moment - hydrogen would boil off faster than they could launch it with today's technology. However, this is an active area of research by multiple space agencies and independent companies. It's not a particularly demanding challenge, it comes down to using sun shades made of mylar (like on James Webb Space Telescope) and active refrigeration. I am assuming hydrazine fuel for the return trip due to the really long transit times - I think we can develop hydrolox to get this stack to Mars in a couple years but not to get there and all the way back too.
With infinite money it could be figured out in time but I went with the more conservative answer to show how reasonable (if expensive and downright ugly, from a technical perspective) this is.
Falcon Heavies go for $90 million each so launching 100 of them costs $9 billion. Let's add $20 billion more for spooling up production capacity.
So for about $30 billion dollars (about 1/3 more than NASA's current budget or 5% of the Pentagon's), you could put three astronauts on Mars and bring them back with today's technology.
This method does require hohmann transfers to work but one opens up in 2020 - which is why they are calling Curiosity's follow-on Mars 2020 as it launches that year. In any case, more fuel = longer transfer windows = more launch options. It all comes back to MOAR Thrust!
That scene in Europa report was downright silly. Hydrazine is not that bad as much as I joke about it and even if it were, they had tons of ways to deal with it.
Edit: He didn't even get it on his skin. That whole scenario was really dumb.
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hobbsyoyo
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I just used Falcons as a reference. You can launch that mass with any mix of rockets.
Edit: And if you did use electric propulsion for the mission, you could probably get the total number of launches down below 10 or 20. Transit time will make getting there before the 2020 pretty iffy given how low thrust they are.
Edit: And if you did use electric propulsion for the mission, you could probably get the total number of launches down below 10 or 20. Transit time will make getting there before the 2020 pretty iffy given how low thrust they are.
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Daunting indeed.
I love the inspiration and accomplishment of manned space missions, but seeing all this life support crap really reinforces some of the advantages to robotic missions.
I love the inspiration and accomplishment of manned space missions, but seeing all this life support crap really reinforces some of the advantages to robotic missions.
hobbsyoyo
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Watching billion dollar rovers fail because there's no one to wipe off the dirt on their solar cells or knowing that none of the billion dollar rovers we've sent over has been able to turn over a rock and smash it open with a hammer like any field geologist can is the counterargument.
They have a role to play for sure in space exploration but I think it will be a few more decades before we can send robots that make adequate substitutes for people. We've only just now, a decade in, driven our Martian rovers for a distance that is further than a human could cover in a single day. They are sophisticated for sure and we should keep sending them but the amount of science they can return pales in comparison to what a few boots on the ground could do.
Broken_Erika
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Not to mention, Trump would have probably insisted that the spacecraft must be powered by coal.
hobbsyoyo
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@peter grimes
I'm still thinking about that scene in Europa Report. Like I said before, hydrazine is bad but it's not the worst thing in the world. Dinitrogen Tetroxide (commonly called NTO) is that bad and is the worst thing in the world. If he had gotten that all over himself then it would have been a real crisis. They still could have (and would have, in reality) solved the problem but it would have been a much more serious situation if he had been covered in NTO versus hydrazine. With NTO, he probably would have exploded into flames (NTO is an oxidizer so potent that everything is a fuel for it) and if he hadn't, the fumes from bringing it into the habitat would have gotten into the air filters and sickened everyone and began to melt the insides of the spacecraft.
If he had hydrazine on him, they could have just squirted him with IPA in an airlock, vented the air and then brought him inside.
NTO is an oxidizer used with hydrazine for in-space propulsion. Hydrazine is often used by itself but it's extremely low performance and adding NTO to it makes it more feasible. For a mission all the way out to Europa they would have needed every bit of performance they could out of their craft so they would have had it in the ship and the writers could have used that as the big bad plot device.
But they didn't so yeah, it was a really dumb scene.
I'm still thinking about that scene in Europa Report. Like I said before, hydrazine is bad but it's not the worst thing in the world. Dinitrogen Tetroxide (commonly called NTO) is that bad and is the worst thing in the world. If he had gotten that all over himself then it would have been a real crisis. They still could have (and would have, in reality) solved the problem but it would have been a much more serious situation if he had been covered in NTO versus hydrazine. With NTO, he probably would have exploded into flames (NTO is an oxidizer so potent that everything is a fuel for it) and if he hadn't, the fumes from bringing it into the habitat would have gotten into the air filters and sickened everyone and began to melt the insides of the spacecraft.
If he had hydrazine on him, they could have just squirted him with IPA in an airlock, vented the air and then brought him inside.
NTO is an oxidizer used with hydrazine for in-space propulsion. Hydrazine is often used by itself but it's extremely low performance and adding NTO to it makes it more feasible. For a mission all the way out to Europa they would have needed every bit of performance they could out of their craft so they would have had it in the ship and the writers could have used that as the big bad plot device.
But they didn't so yeah, it was a really dumb scene.
Glad I didn't know that stuff before I saw the film :haha:
Did anyone read anything non-sensational about that radio signal that was people were so quick to say "it's not aliens"? I thought for sure Phil Plait would have written about it by now, but he hasn't. He's pretty much my go-to for debunkings.
Did anyone read anything non-sensational about that radio signal that was people were so quick to say "it's not aliens"? I thought for sure Phil Plait would have written about it by now, but he hasn't. He's pretty much my go-to for debunkings.
