Fallacy of excluded choices: Moon or Mars - but what are the other choices?

[PB666]

Well then, let's return to the original topic. What about one of the asteroids in a horseshoe orbit around Earth? The delta-v to get to them while they're near Earth is pretty low, and it would only take a relatively small push to move them into an Earth capture orbit. The advantage of building an asteroid base is that the small size of most asteroids makes landing on one more similar to docking to another spacecraft, but they would still have enough mass to provide a non-negligible amount of radiation shielding. Construction would probably be easier than a Moonbase, since you're not having to haul materials down the Moon's gravity well. In fact, construction could be as basic as hollowing out a section of the rock and coating the walls with a sealant to make them airtight.

I look at asteroids from the point of view of what materials they would provide. The ideal asteroid is one that is a chimera of both rocky and icy materials.

The rocky asteroids for the exact reason that you give, but there is a large future value for any inter-terrestrial space program. The problem is that, in earth orbits, ice sublimates

and in distant orbit there is not enough solar to exact any industries.

There is a Trojan asteroid (the leading variant) sharing earths orbit around the sun right now, but it has been stated that reaching this would actually take more energy. Its orbit is very unstable, in the future they predict it will station behind the sun and then wander somewhere else.

I think the reason for this is that to reach it you would have to run solar retrograde (expensive) or 2 cheaper but taking 20 months, and then expend energy to stop the craft once if got back in earths orbital plane at the same theta as the trojan. For human exploitation we need a craft that can survive at least 2 years without a resupply has alot more dV.

Of course if they can get something like the Cannae drive running they can use the sun energy to push back against w2r and push forward to its station, which might speed things up. I don't hold out hope that it can produce that much thrust no matter how much power you can supply to it. If the drive actually does what they say it does, I believe it has a rapid local space saturation that would be useful for only the smallest loads. If you could get a large scale drive on-line and if you could get a flight path to the F1 or F2 (sun exposed is better for energetic reasons) then that would be the best of all targets.

Other conventional-flight path options include a VASIMR drive or nuclear drive that takes advantage of volatiles liberated from asteroids. The VASMIR however uses argon, which is abundant on some of the outer planet moons, its non-reactive so only incidentally trapped in asteroids.

The Isotope for the nuclear rocket would have to come from earth but the accelerant could be mined from 'roids. The operating temperature would tolerate a wider variety of elements, including boron, sulfur, lithium (although this is prolly too valuable to use as a propellant), beryllium, carbon monoxide, chlorine, etc. The nice thing about an asteroid based nuclear drive is that it would take full advantage of the nuclear potential, versus convential drive where the unspent portion of the fuel is essentially wasted after the propellant is expended. The other good thing about a nuclear drive dedicated to pushing an asteroid is that you can keep the nuclear fuel packaged in graphite until you get to the destination and then unpack it into the engine. This greatly reduces the in-atmospheric transportation risks.

The preliminary science for Asteroids would require a much better space telescopes capable of far better resolution of the surface, the target should be chosen based on best mineralogy and convenience of orbit relative to earth.

[GreenWolf]

Minor Planets like Cruithne with mean motion resonances never get very close to Earth, by definition. It would take several years of phasing to get it here. It's probably easier to find Minor Planets that are already going to make a close approach, even if at flyby it'll have high relative velocity, cause you are going to use high-efficiency solar electric propulsion anyway.

You misunderstand. I was referring to something like 2002 AA29. Cruithne is in such an eccentric orbit that it trying to capture it would be silly.

Edit:

Snipped

If we're going with a nuke, we could use it to power a mass driver. Depending on the type of material you can get from your chosen rock, you could literally use the asteroid (or, rather, pieces of it) to move it into your preferred orbit.

Edited March 13, 2015 by GreenWolf

[PB666]

You misunderstand. I was referring to something like 2002 AA29. Cruithne is in such an eccentric orbit that it trying to capture it would be silly.

Edit:

If we're going with a nuke, we could use it to power a mass driver. Depending on the type of material you can get from your chosen rock, you could literally use the asteroid (or, rather, pieces of it) to move it into your preferred orbit.

An ion drive is essentially a mass driver, I think the goal of a good ion drive is to get the ejection velocities in the 3000 to 100,000 m/s range.

One other thing, here you are wanting to a have an exo-Earth/Moon space program and you are mparting reaction force on micrometeor or larger particles to accelerate your asteroid, so the next calculation is what happens if we throw a few hundred billion meteors into earths orbit around the sun, does that eventually increase catastophic risk for future space flight?

[Technical Ben]

If you have the ability to pick a destination, pick any. With cryo like suspension, then time is the only factor, and you can wait it out. Choose the next nearest Exoplanet and visit it, then return.

[Duxwing]

Money is really the only issue standing in the way of exploration. Technologically we could have gone to Mars in the 80's.

Pffft, had we been lolsokerbal and added moarboosters, we could have gone during the 60s.

-Duxwing

[GreenWolf]

An ion drive is essentially a mass driver,

At the end of the day, all rockets are mass drivers. You throw stuff out the back so that you can go forwards. The difference comes from what you're throwing, and how fast you throw it.

I think the goal of a good ion drive is to get the ejection velocities in the 3000 to 100,000 m/s range.

An ion drive with an exhuast velocity of 3000 m/s would be pitiful. Conventional chemical rockets have exhaust velocities near 3000 m/s, and have far more thrust than an ion drive. Remember, specific impulse (when measure is seconds) is exhaust velocity divided by the acceleration due to gravity at Earth's surface (about 9.81 m/s^2).

One other thing, here you are wanting to a have an exo-Earth/Moon space program and you are mparting reaction force on micrometeor or larger particles to accelerate your asteroid, so the next calculation is what happens if we throw a few hundred billion meteors into earths orbit around the sun, does that eventually increase catastophic risk for future space flight?

I haven't run the numbers, but my (relatively informed) guess is that it would not be significant. As the Hitchhiker's Guide to the Galaxy informs us, space is big. And all that stuff you're throwing out of the back of your mass driver is probably going to end up in highly eccentric orbits. Also, collision avoidance in deep space is a lot easier than in orbit, especially if you've got even basic sensors.

[HopDavid]

I look at asteroids from the point of view of what materials they would provide. The ideal asteroid is one that is a chimera of both rocky and icy materials.

The rocky asteroids for the exact reason that you give, but there is a large future value for any inter-terrestrial space program. The problem is that, in earth orbits, ice sublimates

and in distant orbit there is not enough solar to exact any industries.

There is a Trojan asteroid (the leading variant) sharing earths orbit around the sun right now, but it has been stated that reaching this would actually take more energy. Its orbit is very unstable, in the future they predict it will station behind the sun and then wander somewhere else.

I think the reason for this is that to reach it you would have to run solar retrograde (expensive) or 2 cheaper but taking 20 months, and then expend energy to stop the craft once if got back in earths orbital plane at the same theta as the trojan. For human exploitation we need a craft that can survive at least 2 years without a resupply has alot more dV.

Of course if they can get something like the Cannae drive running they can use the sun energy to push back against w2r and push forward to its station, which might speed things up. I don't hold out hope that it can produce that much thrust no matter how much power you can supply to it. If the drive actually does what they say it does, I believe it has a rapid local space saturation that would be useful for only the smallest loads. If you could get a large scale drive on-line and if you could get a flight path to the F1 or F2 (sun exposed is better for energetic reasons) then that would be the best of all targets.

Other conventional-flight path options include a VASIMR drive or nuclear drive that takes advantage of volatiles liberated from asteroids. The VASMIR however uses argon, which is abundant on some of the outer planet moons, its non-reactive so only incidentally trapped in asteroids.

The Isotope for the nuclear rocket would have to come from earth but the accelerant could be mined from 'roids. The operating temperature would tolerate a wider variety of elements, including boron, sulfur, lithium (although this is prolly too valuable to use as a propellant), beryllium, carbon monoxide, chlorine, etc. The nice thing about an asteroid based nuclear drive is that it would take full advantage of the nuclear potential, versus convential drive where the unspent portion of the fuel is essentially wasted after the propellant is expended. The other good thing about a nuclear drive dedicated to pushing an asteroid is that you can keep the nuclear fuel packaged in graphite until you get to the destination and then unpack it into the engine. This greatly reduces the in-atmospheric transportation risks.

The preliminary science for Asteroids would require a much better space telescopes capable of far better resolution of the surface, the target should be chosen based on best mineralogy and convenience of orbit relative to earth.

To find most retrievable asteroids go to JPL's NEO Close Approaches page, sort by Vinfinity and choose nominal distance <=0.05AU.

I wrote about Catching An Asteroid. If an asteroid is already coming close to the earth, it doesn't take much to nudge it so it passes through earth's sphere of influence. If timed just right, the moon's gravity can remove enough of the hyperbolic excess velocity to trap in the asteroid in an elliptical capture orbit. Then a good place for it would be a Distant Retrograde Orbit (DRO) about the moon.

That's one of the option the Keck folks proposed anyway. They want to use Hall ion thrusters which a 30 km/s exhaust velocity.

[Stargate525]

If you have the ability to pick a destination, pick any. With cryo like suspension, then time is the only factor, and you can wait it out. Choose the next nearest Exoplanet and visit it, then return.

Can't wait THAT long. At the speed's we're capable of, the only people able to debrief the astronauts when they return would be a professor of dead languages.

[Sillychris]

I think that in the very near future the benefits of human astronauts will begin to disappear... What I am talking about is better robots and post singularity.

A human body is better at walking around on a surface and collecting rocks, doing science, etc. A robot is better at being cheap to send and expendable.

What if we had true androids that could accomplish human tasks?... their creative thinking would obviously be limited, so we'd still need to communicate.

I think that the argument "humans do better science" will melt in our lifetime.

However, manned spaceflight is absolutely crucial for long term colonization purposes. Unless we are willing to accept the inevitable extinction of all life on Earth, it is absolutely critical to escape the confines of our current rock and star.

[GreenWolf]

I think that in the very near future the benefits of human astronauts will begin to disappear... What I am talking about is better robots and post singularity.

A human body is better at walking around on a surface and collecting rocks, doing science, etc. A robot is better at being cheap to send and expendable.

What if we had true androids that could accomplish human tasks?... their creative thinking would obviously be limited, so we'd still need to communicate.

I think that the argument "humans do better science" will melt in our lifetime.

However, manned spaceflight is absolutely crucial for long term colonization purposes. Unless we are willing to accept the inevitable extinction of all life on Earth, it is absolutely critical to escape the confines of our current rock and star.

See what I bolded right there? That's the limitation in robotics right now. The appeal of using humans isn't because they're better at doing stuff than robots, it's because they are actually autonomous. The lightspeed delay between Earth and Mars varies between 4 and 20 minutes depending on distance, and averages at around 10. Ever try driving a car on a ten minute delay? The reason the Mars rovers are so slow isn't because they can't go faster (just look at Lunakhod. Thing went 40 kilometers in a few weeks!). It's because driving them with a 10 minute delay requires you to go very slowly, even with the incredibly advanced pathfinding software that the rovers have.

[PB666]

I think that in the very near future the benefits of human astronauts will begin to disappear... What I am talking about is better robots and post singularity.

A human body is better at walking around on a surface and collecting rocks, doing science, etc. A robot is better at being cheap to send and expendable.

What if we had true androids that could accomplish human tasks?... their creative thinking would obviously be limited, so we'd still need to communicate.

I think that the argument "humans do better science" will melt in our lifetime.

However, manned spaceflight is absolutely crucial for long term colonization purposes. Unless we are willing to accept the inevitable extinction of all life on Earth, it is absolutely critical to escape the confines of our current rock and star.

Im not going to knock unmanned space flight, I want more of it also, I am amazed at the Voyager missions, they are still producing cutting edge science. We need really great roboticized telescopes with the ability for them to repair themselves in space (with the occasional supply mission). While Kepler is still going wouldn't it be great if we could repair it and recharge it with liquid Helium. But I really would like to see a manned observatory with a large capacity to do cutting edge science on the space station.

But if you look at what human accomplished 40 years ago (with 40 year old technology) in 1 moon mission. It all revolves around bringing samples back! So this is why I started this thread, why would you send humans to a place you already have samples, or to a place where you could not bring samples back. If they want to make a Polar lunar landing and do polar science, I have no problem with that, and if they want to practice a future Mars landing, I have no problem in combining the missions. But if your mission is not about the science, you really don't belong in space, because it is simply a waste of dV to go there and not gather preparatory information.

Look at Hayabusa 1, it suffered ghastly luck, just the worst possible fate, and yet it made its way back to Earth. The reason it could do that is because the gravity of asteroids is very forgiving. If that luck happened on Mars, not only would you have stranded (or killed, the fate is the same) the astronaut, you would have stranded your sample. Lets talk about sending humans to places where they can easily bring samples back, and when we have the skill to perform a moon landing like success on Mars, we will be ready. The gravity of Phobos is also very forgiving and a great place to wet ones whistle.

Im sure when we finally get geologist/astronauts on Mars, we are going to be able to bag lots and lots of really useful geology, the number of samples will prolly exceed the weight of astronauts, but we have to be able to get them back to Earth. It looks like a great place to do science also much better than the moon, but we have to be able to get back. Suicide missions offer no scientific benefit (Unless you are going to land a 30 ton geology lab complete with a mass accelerator/isotope detector, a wet chemistry lab, electron microscope, etc. (i'de like to see Mars power up a TEM), of course isolation for TEM, and since they are wasting all the dV*Mass give it a jack and some wheels, and a complimentary backhoe for digging graves of all the geologist that land and use it. But then again if you can send 30 tons of lab you can also send food and water on one of those bouncy bally and feed and water that astronaut until he either dies of natural causes or can be returned to earth.

[magnemoe]

I think that in the very near future the benefits of human astronauts will begin to disappear... What I am talking about is better robots and post singularity.

A human body is better at walking around on a surface and collecting rocks, doing science, etc. A robot is better at being cheap to send and expendable.

What if we had true androids that could accomplish human tasks?... their creative thinking would obviously be limited, so we'd still need to communicate.

I think that the argument "humans do better science" will melt in our lifetime.

However, manned spaceflight is absolutely crucial for long term colonization purposes. Unless we are willing to accept the inevitable extinction of all life on Earth, it is absolutely critical to escape the confines of our current rock and star.

Well in the future probe rovers might get able to drive by themselves and not get stuck.

However have fun trying to get packs of 20 un IC work for years on Mars, fun how Asimov predicted that radiation was more dangerous for robots than humans.

No I would not do an manned mars mission even if I had the money as i would send a lot more probes first,

[tater]

Regarding sample return, humans did so well not because they were autonomous, but because the craft that got them there had the capacity to carry many kg of samples largely by design, but possible because a manned craft has to have some excess capacity. I think it is unfair to compare robotic vs manned sample returns given the entirely different parameters and budgets.

If the sole goal of Apollo had been placing X science instruments, and returning X hundred kg of samples, I think it could have been done remotely with no real difference in scientific outcomes. I cannot imagine that it would not have been so much less expensive that many more missions could have been done as well, so perhaps smaller sample quantitates, but from many more sites, with a net gain in data.

I've very much a "manned spaceflight" person, but science is not the reason, remote/robots are superior if cost is a consideration at all. What they just don't engender is the same level of inspiration or adventure. I think that that is valuable all by itself.

[HopDavid]

I think that in the very near future the benefits of human astronauts will begin to disappear... What I am talking about is better robots and post singularity.

A human body is better at walking around on a surface and collecting rocks, doing science, etc. A robot is better at being cheap to send and expendable.

What if we had true androids that could accomplish human tasks?... their creative thinking would obviously be limited, so we'd still need to communicate.

I think that the argument "humans do better science" will melt in our lifetime.

However, manned spaceflight is absolutely crucial for long term colonization purposes. Unless we are willing to accept the inevitable extinction of all life on Earth, it is absolutely critical to escape the confines of our current rock and star.

Robots vs humans is a false dichotomy.

Robots will make plausible a sustained human presence on another body. If robots can establish infrastructure to extract water, Tsiolkovsky's rocket equation becomes much less of an obstacle. Life support becomes more doable.

Humans nearby eliminates light lag latency. On-site humans can also maintain robots.

A combo of robots and humans is more able than either alone.

[Kibble]

Robots vs humans is a false dichotomy.

Robots will make plausible a sustained human presence on another body. If robots can establish infrastructure to extract water, Tsiolkovsky's rocket equation becomes much less of an obstacle. Life support becomes more doable.

Humans nearby eliminates light lag latency. On-site humans can also maintain robots.

A combo of robots and humans is more able than either alone.

Omg the legendary Hop David! I didn't even know you were on this forum <3

I completely agree that astronauts working in conjunction with robotic probes makes them both more effective!

[magnemoe]

Omg the legendary Hop David! I didn't even know you were on this forum <3

I completely agree that astronauts working in conjunction with robotic probes makes them both more effective!

I agree, I would send the robots first to do the initial mapping, then do an manned missions, note that for many missions humans who are able to swap burned out circuit boards and blow dust off solar panels will help. More fun if you run into more fussy equipment like an drilling rig, an drill where an astronaut add more drill pipes would be far lighter and more reliable than something totally automated.

Say something of kerbal engineers who need multiple missions for repairing tires.

[HopDavid]

Omg the legendary Hop David! I didn't even know you were on this forum <3

I completely agree that astronauts working in conjunction with robotic probes makes them both more effective!

"legendary"? Well, maybe I'm a legend in my own mind. Thanks for the warm welcome.