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The problem is that they're already spinning. You need to de-spin them to mine them, enclosure-or-not.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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The first problem is to seal the would be target so that it can be captured. I am wondering if a spray on plastic coating followed by other shells of material would be enough to toughen up the rubble pile in order for it to be towed away.
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None of you will like this, but here's how you mine the smaller dry rubble-pile asteroids:
You approach it at one of the rotation poles, match spin, and touch down. You grab on by means yet-to-be-defined (stakes driven in will not work, described in an earlier post). Drill in and take your deep (10's to 100's of m) core sample (again by means yet-to-be-defined, since if a stake won't work, why expect a drill to work?). If there's nothing there of interest, then forget it. Otherwise you must de-spin the thing to proceed.
To de-spin, I suggest the same kind of light pressure that spins them up in the first place. It needs to be less intense than the gravitational binding, so it can only be a few sun's worth. This will require a robot spacecraft shining this light on the approaching limb of the asteroid, while flying station-keeping alongside for many years. Yep, I said years! There had better be something valuable inside this space junk, because station-keeping for years will be expensive, no matter how you do it. The "years" part is what will drive up costs.
Once de-spun, if it's a small one, enclose it in some kind of net or bag (of material yet to be determined, and probably an "unobtainium" to us right now). Then push on it harder than gravity, probably with a laser and beam-spreader. It will simply fly apart very gradually inside your bag. Tow the bag to your processing plant. You just mined an asteroid.
The ones bound with icy volatiles will be a lot easier. You can push on them much harder to de-spin, in weeks perhaps with intense lasers, or if strong enough, only days with rockets placed strategically. Stakes and drills will likely work much better. No need for a bag around it. Just dig away more-or-less conventionally (as if working in near-zero-gee can be "conventional"). I think these will be larger than the dry loose ones, so a bag would be too big anyway.
Dwarf worlds like Ceres will be the only ones where mining will look it does here at home.
Can't offer any suggestions as to potential spray coatings. There are none that work in vacuum right now. So that's another "unobtainium" material to us at present. But it surely could help with mining these things, if we should ever invent one.
As to the stake and drill technologies that also don't yet exist for the rubble-pile objects, some sort of rocket thrust-balance insertion of a giant hypodermic needle might work. As a stake you inject steam and freeze it to ice, probably with a shot of liquid nitrogen. As a core sample, just close the end and rocket thrust-withdraw it.
For the bag or net, that might be a good application for in-situ-produced basalt fiber. Not sure if it will be very strong, so you have to avoid impact and collision forces of chunks moving around inside. They must be moving very slowly, period.
Absolutely none of these issues and technologies are being addressed in NASA's proposed Asteroid Redirect Mission, by the way. If we can come up with this, how come the supposed experts cannot? Tough question, ain't it?
GW
Last edited by GW Johnson (2014-04-08 10:11:51)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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The spray coat might not be unobtainum as there are some UV hardening sealants for vacuum processes but what you hit on is the why do we want the science of an asteriod, the containantion possibility to what we would want to study and for the other reasons for what we want to do with one. Those are the questions that must be answered....
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My take is that these things are extremely-variable in characteristics, and mostly will prove rather fragile with respect to applied forces. This has enormous impact for both mining and deflection of impact threats. Effective planning for either activity is going to require "ground truth" on a whole bunch of these objects, not just one or two. I'd say several hundred of them, all sizes, all spectral types, all different forms and spin rates.
When you think about the implied costs of doing NASA's ARM with hundreds (not one) small objects redirected to cislunar space, vs the costs of simply developing the long distance manned travel capability needed for any destination out to the main belt, the saner choice is clear. Go for long distance manned travel. It's far more bang for the buck. But it ain't minimum-buck.
Doing the redirect with only one object makes no sense at all. It's just PR, not anything useful. And THAT'S what I object to.
GW
Last edited by GW Johnson (2014-04-10 08:14:08)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Then why is Nasa only setting the goals for just a single mission for plans of the future when the variety of types can be one thing to study....
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You ask why NASA would do nonsensical things? The answer would be too long. Let me shortcut things with two observations about the world which explain much of the nonsense we all see going on all around us. Nonsensical behavior by NASA is just a small part of all the idiocy.
A "law" regarding the behavior of government (and non-government) agencies: the degree of bureaucratic arrogance is inversely proportional to the degree of competence exhibited.
A "law" explaining why nonsensical things happen in any society: HA >>>> H, where H is the number of horses, and HA is the number of horses' asses.
GW
Last edited by GW Johnson (2014-04-11 09:11:02)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Then why is Nasa only setting the goals for just a single mission for plans of the future when the variety of types can be one thing to study....
Bolden Says ARM Is About Planetary Defense But Not Protecting Earth with a sticker shock of $3 Billion + ARM. A Multibillion Mission with ARM spacecraft is $1.25B - plus a SLS launch - plus a crew launch on another SLS? Ya ouch....
http://nasawatch.com/archives/2015/01/t … unche.html
http://www.lpi.usra.edu/sbag/meetings/j … ohnson.pdf
One thing to consider: NASA is supposed to consider commercial launch alternatives unless there are compelling performance or technical reasons not to. Delta IV is mentioned, but no consideration seems to have been given to Falcon Heavy or the new Atlas that has been proposed. Of course, you can expect NASA to tweak things such that only SLS can meet the requirements because they have to.
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Bolden wants to waste some more money on another impossible task that requires technology we don't even have prototypes tested for yet so we won't have money to go to Mars or achieve any other worthwhile science and exploration goals.
Planetary defense? We can't stop dumping billions of tonnes of carbon into our atmosphere every year, but we're going to "defend the planet" from space rocks? While we're at it, let's use warp drive to get there faster. Seriously though, I want some of whatever these guys are smoking.
Maybe an astronaut can determine what kinds of space suits make the best snow angels on one of these dust clods.
Has anyone else noticed that Orion is always docked to Battlestar Galactica near Mars, like some sort of hood ornament, in every one of these PR brochures, but Mars is always in the corner, just out of reach?
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The asteroid re-direct mission is a mission for Orion/SLS to go and do with humans, nothing but a reason-to-exist. It is a mission that falls within what Orion/SLS can actually do, which is inherently restricted to cis-lunar space and no more than 2-3 weeks cooped up inside a capsule. Scientifically, it makes little, but not non-zero sense: a way to get lots of samples from one body, but not a way to sample representatively an excruciatingly-diverse family of bodies. That second choice is what you really want to do. It supports both asteroid mining and asteroid deflection. Orion/SLS cannot ever do that as a one-rocket/one-mission shot, which is the mission model Congress seems hung up on.
Anything that could successfully take men to an NEO in-situ could take men to Mars. Mission times and velocity requirements are quite similar, and way, way beyond what Orion/SLS can do in single shots. (Used as a launcher for a transport to be assembled in LEO, Orion/SLS could make sense if it could be launched for commercial prices, but it cannot and never will be.) The difference between those missions is a lander for Mars (why go all that way and not land?). Sampling multiple NEO's in-situ, which is what should be done first, is more properly an unmanned mission, because the flight times are too long for human crews (one example only: Ceres-Vesta probe). That kind of things gets smaller samples, but identifies where men should go to explore and get lots of samples.
GW
Last edited by GW Johnson (2015-01-16 12:04:13)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Bolden wants to waste some more money on another impossible task that requires technology we don't even have prototypes tested for yet so we won't have money to go to Mars or achieve any other worthwhile science and exploration goals.
Your channeling Zubrin's 'Mars or Bust' mentality which is dead-wrong. We don't have the financial or technical ability to go to Mars now, interim missions of SOME kind need to happen to build a Mars capability. If Asteroid visitation is a good/bad interim mission is another topic, and I'd argue that it is simply the only interim mission the the current SLS/Orion combination is capable of doing, so if we don't want to do it we should just cancel both vehicles right now.
I think the development and validation of a large SEP vehicle is essential for deep space exploration as that's the technology with the long term promise of high mass fraction delivery, shorter transit times and ultimately some chance at reusability in space. ARM mission thus looks to couple the 2 wasteful elements that Congress has mandated with something that's actually useful in the long run for any destination, could we have that SEP vehicle without SLS/Orion, sure a F9H sized SEP would easily validate the engineering, but this shotgun-weeding may be the only way it can happen.
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Oddly, I am supportive of the asteroid capture notion. In addition to what Impaler has spoken, it may indicate what potential there could be for harvesting asteroids for economic purposes. I also do think that this is much like working out at a gym. The path to not being too wimpy to go to Mars, is to practice lesser tasks, hopefully that can still have some use, and we would hope build up the stamina in abilities to actually do Mars eventually.
Done.
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Your channeling Zubrin's 'Mars or Bust' mentality which is dead-wrong. We don't have the financial or technical ability to go to Mars now, interim missions of SOME kind need to happen to build a Mars capability. If Asteroid visitation is a good/bad interim mission is another topic, and I'd argue that it is simply the only interim mission the the current SLS/Orion combination is capable of doing, so if we don't want to do it we should just cancel both vehicles right now.
Of course we don't have the financing or tech, Impaler. When you keep throwing billions of dollars at programs that won't directly assist with achieving the objective, you wind up with lots of program cancellations, congressional micromanagement, and no money.
Who in their right mind would, and unfortunately this necessarily excludes almost everyone in the Congress and Senate, keep forking over money to NASA's manned space program without producing a result?
Look, I like all space exploration, even exploration of asteroids. That said, the space nuclear power and propulsion program was cancelled decades ago, it's currently not being funded to the level it needs to be, and there's no non-nuclear propulsion system that could realistically retrieve an asteroid of any substantial size. If we're going to retrieve samples from a variety of small space rocks, let's use robots to do that. Set the horse before the cart.
Orion isn't a space exploration vehicle, it's a small short duration crew transfer vehicle that's every bit as expensive as the Space Shuttle and redundant. The Apollo/LEM combination could at least land on the moon. Orion isn't going to land anywhere except an ocean on Earth. If TPTB had elected to cancel Orion and fund Altair, I would have supported that decision and whatever amount of money it took to create a reliable multi-mission capable lander. A Dragon, Soyuz, or Space Shuttle could have transferred the crew to Altair and the EDS/Altair combination could have transported the crew to their destination.
I think the development and validation of a large SEP vehicle is essential for deep space exploration as that's the technology with the long term promise of high mass fraction delivery, shorter transit times and ultimately some chance at reusability in space. ARM mission thus looks to couple the 2 wasteful elements that Congress has mandated with something that's actually useful in the long run for any destination, could we have that SEP vehicle without SLS/Orion, sure a F9H sized SEP would easily validate the engineering, but this shotgun-weeding may be the only way it can happen.
Test SEP powered tugs? Sure, let's do that in LEO first. We can start by retrieving all the satellite and rocket parts strewn all over the place and moving them to an orbital manufacturing facility aboard ISS to repurpose the parts into useful hardware.
Please explain how grabbing a space rock is useful for landing on a planet. There's no atmosphere on an asteroid and we don't have any program to produce flight hardware to land on one anyway, irrespective of whether or not it was useful.
Yes, if we're going to launch a SEP powered tug then let's not break the bank doing it with SLS.
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Has Nasa narrowed down its selection so as to design for that mission such as the max distance or for the mass extreme that we might try for?
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I guess for my part I will leave it up to them, since they say it's what they wanted to do.
The original plan was to go to the Moon, muscle up, and then go to Mars.
That got altered by a new entity. I can give two major speculations on their objectives. One is honorable, and one is wicked.
It might be supposed that the powers that be have done well fostering SpaceX and others. I see it that way at least for now.
So their plan in that case seems good.
They got forced to take a very hard challenge with insufficient provision. They were forced to not do the Moon. They found something that they could do, that might help them to muscle up.
The concerns are these. Either wise planning was done where they hope that NASA will only exist as a skeleton, and other entities will cling to it like muscles, or we have been infiltrated by an entity which does not like who we are, and hopes to contribute to keeping us captive. There is such a social system that thinks that way.
Done.
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It was in another thread somewhere on these forums that I described the fundamental change between the NASA of 1958, and the NASA of today. But I’ll repeat it here, because that’s what the most recent conversations in this thread seem to be about.
NASA was originally formed to put man in orbit, and carry out science and aeronautics, too. But the “prime show” or “front-burner project” was manned spaceflight. 3 years later, the mission got upgraded to the far more demanding man-on-the-moon, which really energized the little agency.
In those days, NASA was rather small, very heavy on engineering talent, had a definite front-burner mission, money was no object, and no one told them how to do their jobs. They got to figure that all out themselves. And, miss-steps notwithstanding, it worked quite well. It was 8 years from assigning the moon-as-mission to the agency, until two men first walked there.
It might have taken perhaps 3 extra years to do this, had budgets been a problem, but that basic approach of assigning the mission and then “stand back and let them do it” works really well either way.
All that changed in the middle of the moon landings in 1972 (there should have been missions through Apollo 22, not 17), when Apollo got cancelled early and all manned flight outside Earth orbit forbidden by presidential order. NASA has never had a front-burner mission, an agency reason-to-be, ever since. They have only had major projects mandated upon them mostly by Congress, with some from the various presidents. Projects like Space Shuttle, like ISS, like X-30, like X-33, etc.
Science and aeronautics are still small-time background, but by dint of the successes of the probes (derived from being left mostly alone by Congress), the planetary probe program kind-of falls in-between in that spectrum. Some of these projects, like the Mars landers and Hubble, turn out to be quite popular with the public, too popular to kill, even though Congress often tries.
Two of these mandated projects flew men in space, the rest didn’t. There were some tests as exceptions that never led anywhere. None of these were actually managed in an overall sense by the agency. Instead, the project, its detailed objectives, how it would be done, and where things would be built (by that I mean in whose districts) were all mandated by Congress. That’s exactly what Constellation was, and what its resurrected form Orion/SLS is. There is no one in Congress at all competent to do any of this work, which is precisely why their mandated management plans are so egregiously ineffective and nonsensical.
Meanwhile the agency has grown to enormous size, trying to be “everything to everybody” in lieu of a front-burner mission / reason-to-be. Once an organization gets too large, it gets very inefficient, worrying more about preserving departments, people, and budgets than actually doing anything real anymore. NASA is no exception. There’s more managers and support functions at NASA these days than there are real engineers. That’s not a good recipe to get anything major, actually done. Not in industry, not in government.
When you add bureaucratic inertia to mandated-but-nonsensical-projects to be done, you have what we see now: no man has flown beyond Earth orbit, or explored anything off-world, in person, since 1972. And with the projects they have to do sopping-up most of the available money, we’re having a hard time not spending trillions just to go back to moon, the same moon that we visited over 4 decades ago! None of the stuff they are doing now (with the serious money) can take a crew to Mars alive, much less land there.
I’m talking about Orion/SLS. The PR about that is nothing but lies. And everybody who knows much at all about these things knows it. Most within the agency are too afraid to tell the emperor that he has no clothes, though. And as an agency, NASA is afraid to tell Congress that it too has no clothes.
There are small groups within NASA that are working on the right kinds of things for men to go beyond Earth orbit again. But these are not funded with any serious money. Some of these groups are better managed than others. Some of these groups have better talent than others. So, their ideas and plans vary considerably in practicality and feasibility. That should not be unexpected, given the situation. But until these things get the money and attention to perfect them, they will take no one anywhere. That, you can count on.
That’s fundamentally why what is funded seriously often makes no sense. A lot of you on these forums seem to have noticed that. Nothing about that situation will change, until the operating model for NASA-as-an-agency goes back to that 1958 version. They need a front burner mission as a reason-to-be, and they need to be left alone to accomplish it. Period.
Unfortunately, Congress craves ever-more control, not less. Ergo, no change is forseeable.
GW
Last edited by GW Johnson (2015-01-17 12:43:04)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Hopefully you will not respond.
Some of my hobbies have lead me to believe that our nation will transition from a defunct aquisitioner nation (Which served us well until it got senile), to a warlord nation.
That is scary. But I witnessed the funeral of a somewhat distant cousin who had military honors. It was quite touching. In the past, lets say the Viet Nam era, we endured situations where our blood was spilled (not mine), but those who were better than me, for the desires of aquisitioner objectives.
The military, if not prompted to waste human life foolishly, may be a good template for the future rather than the money people.
Done.
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If we're really interested in studying some space rocks, there's this planet that's even closer than the main belt that has these two giant space rocks orbiting it named Phobos and Deimos. Taking some samples from either of those rocks might be interesting. I can't speak to the feasibility of putting either of them into lunar orbit, but I'm pretty sure that they're fine where they are.
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We don't have the financial or technical ability to go to Mars now
Yes we do. Read these discussion threads:
update of Mars Direct: Light weight nuclear reactor, updating Mars Direct
alternate mission architecture: Yet another Mars architecture
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Ok, I gave this a second thought and now I have a proposal that's a slight modification of NASA's ARM. I was angry at first because the mission isn't going to Mars, but I got over myself.
My proposal is a taxing two year deep space mission to 433 Eros that validates that we have the right stuff to make the journey to and from Mars before we devote money to expensive landing hardware.
We can't retrieve this asteroid due to its size, but we can take samples and use a SEP powered satellite to map its surface and any debris surrounding it caused by its orbit, rotation, or sublimation to mitigate the danger of maneuvering a manned spacecraft so close to an object that could and probably does have smaller objects surrounding it that could potentially damage a spacecraft.
At its closest, 433 Eros is less than half the distance between Earth and Mars, but it's still far enough away and the mission duration commensurate with an interplanetary mission. This particular space rock is large enough that a spacecraft of sufficient mass could orbit it, but gravity is also weak enough that a full blown purpose built lander like Altair is not required. Orion could easily have its service module modified with lightweight landing support struts to permit a surface visit.
Here's what we get from this mission:
The meat - 433 Eros is thought to contain an enormous quantity of alumina and rare earth metals, based on data collected in 1998. Our samples will either confirm our suppositions about the composition of this body or demonstrate that we don't know what we think we know about asteroid composition and hopefully improve future sampling missions to accurately infer what certain asteroids are comprised of.
The potatoes - The astronauts on this mission will be exposed to SPE's, GCR's, micrometeoroids, thermal extremes worse than anywhere on the surface of Mars, and will spend a significant portion of their mission in deep space. Make no mistake, this is a severe test of the capabilities of our Orion spacecraft, transit habitats, and propulsion systems where even small mistakes have extreme consequences. The more I think about this, the more I like it. Everything from mission planning, software and sensors for flight maneuvers necessary to perform course corrections and debris avoidance, closed cycle life support, astronaut endurance, and even the use of a small nuclear power device to keep Orion and the space habitat livable would be included.
The gravy - Virtually everything but an atmospheric descent/ascent is accomplished if this mission is successful. I think we've already proven that we can do atmospheric descent/ascent fairly well.
Bonus - If it turns out that this particular space rock is, in fact, rich in metal ores required for the construction of spacecraft then all those smart young high school and college kids are going to have their chance to submit proposals to NASA to design and construct an asteroid mining setup that proves our ability to complete complex industrial processes in deep space.
This mission is basically an economical way to demonstrate deep space transit capability required for interplanetary missions and has a valuable scientific return that could have future implications for the use of space-based resources.
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Instead of wasting money going on a joy ride around the moon for the first manned Orion mission, this is what our return to deep space using Orion will involve:
1. A Bigelow Aerospace rotating transit habitat, based on the mark 1 model 0 wheel, capable of spinning up to provide 1G, will be launched into space on the maiden flight of SLS and injected into lunar orbit using EDS (or ICPS or whatever, I don't care how the hardware gets to where it's going as long as it gets there). If the launch is successful, then further aspects of the mission proceed. If the launch is not successful, then no Orion capsule is lost.
The J-2X test stand will finally have a reason to exist. There's nothing like getting some bang for your bucks.
We all know that a deep space habitat is a requirement for space exploration, so the first launch sends equipment for the upcoming mission rather than Orion. NASA should not hazard an expensive Orion capsule on an untested launch system when an object of suitable mass and lesser cost can be utilized that would also enable a follow on mission.
2. The second unmanned test flight of Orion will use the Delta IV Heavy or Falcon 9 Heavy, preferably F9H so an upper stage can push Orion to the moon. No more of this "We must use capsule X with launcher X and capsule Y with launcher Y." If we have major issues with any of our launch systems, that should not prevent our spacecraft from using a different launch system until we can determine the cause of the problem. For normal operations, Orion uses SLS. For the SLS flight test phase, we're using proven rockets.
3. Orion will be injected into lunar orbit by the second SLS/EDS flight, the first manned flight of SLS. I want that transit habitat to sit there in lunar orbit for two years between launches to prove its durability and thus suitability for manned space exploration. Most of the current NASA Mars DRM's that I've seen use inflatable transit habitats, presumably provided by Bigelow Aerospace. Well, we're going to determine in no uncertain terms whether or not the things work as advertised.
4. Orion docks with the transit habitat and a 1 year occupation of the habitat follows to test the life support systems and to train the crew to patch holes in the space habitat and repair systems so that whereupon testing has been completed, NASA has some experience for the upcoming two year mission to 433 Eros. If there are issues with Orion or the habitat, then if Orion is disabled the habitat keeps the crew alive until a rescue mission can be attempted. If the habitat is disabled, then the crew can use Orion to return to Earth.
5. So as to provide at least a minimal science return, this habitat will be outfitted with instrumentation to record the effects of radiation over the duration of the mission.
This mission will be filled with tests and drills to prepare NASA for the challenge of spending a couple years on a large asteroid in deep space. Basically, this is the shakedown mission. If anything fails here, there's a much better chance of the crew coming home alive.
While all of this mission prep/test takes place, NASA and LANL get hot on flight rating a small nuclear reactor based on LANL's new spacecraft power design to provide heat and power. We simply must have more than one power source for our asteroid intercept mission. We're going to take both systems with us. If either is damaged or fails, then we have redundancy in the form of a completely different system that has different failure modes.
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Apparently, a Eugene Smith from Northrop Space Laboratories already thought about a mission to Eros in 1966 as a way to prep for interplanetary space travel. I guess I should have done some more googling and then I would have known that. Better late than never, I guess. All I did was look at space debris that was reasonably close to Earth but far enough to simulate a Mars transit, solid enough to land on, and supposedly rich in ores that could be mined.
Anyhow, it's solid or relatively solid and apparently the NEAR Shoemaker probe mapped and landed on it- didn't know that, either, but once again, Google is your friend. I still think another probe is required to confirm and to determine the existence of any other debris that might interfere with the mission, but with money tight I'll concede that that's probably not necessary.
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Any asteroid mission is *NOT* any sort of preparation for Mars. Remember Mars requires less propellant to reach than the Moon. That's because direct atmospheric entry and landing requires a lot less propellant. If you want to stop in Mars orbit, then aerobraking. The Moon has no atmosphere, so full propulsive landing is the only option. Mars has gravity, so no body degredation due to zero-G/microgravity while on the Red Planet. The atmosphere means no micrometeoroids. And the bulk of the planet shields against radiation for half the sphere surrounding, and atmosphere greatly reduces radiation from overhead. Mars has ready resources to produce propellant, and can be used as backup for air and water. Yes, you can make oxygen from the CO2 atmosphere, and soil permafrost can be melted/filtered. The surface of Mars is the safest place in our solar system, second only to Earth.
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Any asteroid mission is *NOT* any sort of preparation for Mars. Remember Mars requires less propellant to reach than the Moon. That's because direct atmospheric entry and landing requires a lot less propellant. If you want to stop in Mars orbit, then aerobraking. The Moon has no atmosphere, so full propulsive landing is the only option. Mars has gravity, so no body degredation due to zero-G/microgravity while on the Red Planet. The atmosphere means no micrometeoroids. And the bulk of the planet shields against radiation for half the sphere surrounding, and atmosphere greatly reduces radiation from overhead. Mars has ready resources to produce propellant, and can be used as backup for air and water. Yes, you can make oxygen from the CO2 atmosphere, and soil permafrost can be melted/filtered. The surface of Mars is the safest place in our solar system, second only to Earth.
Rob,
We've been given lemons and I'm trying to make lemonade.
If NASA can prove that humans can live in lunar orbit for a year and then in deep space for two years on or near the surface of an asteroid, then we've accomplished everything but living on Mars, ostensibly a far easier than living on a space rock for an equivalent length of time.
Yes, the propellant requirements are different. The technology to make the transit is the same. The technology for going to/from and living on the surface of Mars is obviously different. Once Red Dragon is man rated, we'll have spacecraft capable of making the landing. NASA has no money in their budget to develop a lander, but SpaceX does. Give SpaceX some time.
A lot of engineering is required for landers and there is no serious effort at NASA to develop the capability. In the interim, if NASA takes the asteroid mission seriously, the feasibility of deep space transit is proven.
Aerobraking requires heavier heat shields than propulsive capture. If NASA develops GCNR's, then the risks involved with aerobraking and the weight penalty associated with a heavier heat shield won't make sense. Assuming fuel efficient GCNR's are available, and it is most definitely not pie-in-the-sky technology, the weight of the heat shield required for aerobraking would exceed the weight of propellant required to propulsively capture.
To explain what AC did to Mars DRM 5.0 using solid fuel NTR's, the weight of the cargo lander heat shields increased from 10t to 40t. The weight of the cargo lander and propulsion module would be beyond the capability of the evolved SLS platform at that point. If the payload and propulsion modules were each at or below 110t, then we're talking about something an evolved SLS could reasonably lift, with margin.
GCNR's also eliminate the need for the wacky truss structure, LH2 drop tank, and contingency supplies canister. We're down to 6 SLS launches spread across 4 years along with 2 Falcon 9 launches to deliver the crew and two Red Dragon spacecraft to the Mars transit vehicle. That's conceivably within NASA's budget, whereas 7 or more SLS launches is probably not.
The massive amount of money required for development of Orion is killing everything else, including this near term asteroid mission, and I'll be a monkey's uncle if it flies with humans aboard before Dragon does. As I've indicated in my various posts about ET repurposing, STS had more utility than Orion ever will and somehow each flight costs less. I'll never figure that out, but whatever. SLS was and is expensive but it's necessary for sizable payloads. The GCNR development maximizes payload and eliminates the necessity for aerocapturing.
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Aerobraking requires a light heat shield. You call it heavy, but as you just pointed out, only GCNR has sufficient thrust and Isp to make propulsive capture lower propellant weight. And GCNR will take a lot of development. NASA is currently working on a carbon fibre parasol for aerocapture and aerobraking. So that technology is already in the works. Yes, I would like GCNR, but it doesn't look like it's happening.
In "updating Mars Direct", I came up with a list of equipment necessary to use Dragon as Earth Return Vehicle. Red Dragon is supposed to use its Draco thrusters to land on Mars. But the life support upgrades I list will also be necessary.
GCNR's also eliminate the need for the wacky truss structure, LH2 drop tank, and contingency supplies canister. We're down to 6 SLS launches spread across 4 years along with 2 Falcon 9 launches to deliver the crew and two Red Dragon spacecraft to the Mars transit vehicle. That's conceivably within NASA's budget, whereas 7 or more SLS launches is probably not.
Mars Direct requires 2 SLS Block 2 launches. Actually, 3 for the first mission, plus 2 per mission thereafter. That's because a second ERV sent behind the hab. And Mars Direct uses direct entry for the ERV, aerobraking for the hab. And includes artificial gravity for the transit to Mars, using a tether. But zero gravity for the return to Earth, in a capsule as small as Dragon. My discussion "updating Mars Direct" proposes actually using Dragon for that.
Then there's my alternate mission architecture. I call it "Mars orbit rendezvous". One person on this forum asked Robert Zubrin about it, and he reports that Robert Zubrin used the name "Hybrid Direct". That's because it takes elements from Mars Direct and NASA's DRM. It's flattering that Dr. Zubrin himself gave a name to my mission architecture. Mine uses a reusable craft to travel from ISS to Mars orbit and back. That reusable craft can be a lot more spacious, and dedicated for in-space operation. One option is artificial gravity, using the same system as Mars Direct. Updated launch requirements are here and here. I'll copy the list of launches for the first mission for one option:
- 1 SLS Block 2 for MAV (direct launch from KSC to Mars surface)
- 1 SLS Block 2 for lab & pressurized rover (direct launch)
- 1 Falcon Heavy for ITV
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 for lander & unpressurized rover
- 1 Falcon 9 for Dragon
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