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I read this article today on the opinion of retired NASA Astronaut, Chris Hadfield, regarding what kind of propulsion technology is required to send humans to Mars. I agree 100%. Chemical rockets aren't suitable for making the transit to Mars. Even with reusability, the solution proposed by SpaceX is only suitable for a more affordable flags and footprints series of high risk exploration missions.
We need purpose-built interplanetary transport vehicles that are not severely mass constrained in the same way that the upper stage of rockets are constrained.
These interplanetary transport vehicles must have the following characteristics:
* artificial gravity habitation modules to prevent the rapid muscle and bone de-conditioning associated with microgravity
* reliable and redundant life support and electrical power systems
* appropriate radiation shielding in the form of water and H / B / N rich plastics and fabrics to shield from SPE's and GCR's
* multi-megawatt class solar or nuclear power systems for electrical power propulsion
* advanced electric propulsion systems that drastically reduce the tonnage of propellant required to go to Mars
* separate human and cargo interplanetary and orbital lander transport of human and cargo to the surface of Mars
There is no sustainable Mars exploration and colonization campaign without those technologies. The mission costs associated with using reusable super heavy lift chemical rockets is just within the realm of economic feasibility for well funded government space exploration agencies like NASA. The lack of artificial gravity, appropriate radiation shielding, and high acceleration loading from interplanetary reentry velocities at both Mars and Earth makes this an extraordinarily dangerous transportation method more suitable for low-value and high-tonnage cargo, like food / water / rocket propellant, than humans. Launch and reentry to/from stable orbits are extreme events as is.
When we have reliable super heavy lift rockets like BFR or SLS, the most appropriate first technology demonstrator we could possibly build would be a real interplanetary transport vehicle that can transport people or cargo to and from Earth and lunar or Mars orbit in relative comfort and without any extreme and potentially lethal events like aerobraking or high velocity reentry. Using those technologies at either end of the trip is an act of desperation because our propulsion systems lack the gas mileage required to establish stable orbits using reasonable quantities of propellants. 90%+ propellant is not a reasonable quantity. It means we're spending more money on gas than we are doing anything useful. That's why we haven't left Earth since Apollo.
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The very small thrust electrical rockets, whilst attaining superior ISps don't have the brute thrust to put a large mass into a useful orbit around another body, or around Earth on return. If you want to raise the ISP substantially above what is possible with chemical rockets and still have the capability of large mass orbit insertion you have only one known and tested option that I am aware of and that is Nuclear thermal. An updated PeeWee might give an ISp of the order of 1000. About 2 1/2 times what a chemical rocket can do.
Had the NERVA program not been knocked on the head it would have taken us to Mars and elsewhere. Congress killed it for that very reason. It wouldn't (and didn't need to) pay for the stream of manned missions that the nuclear vehicle would have enabled.
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I think judgements like that are opinion only. From a technical standpoint, it has been possible since the 1960's to go to Mars with chemical propulsion. Getting home alive turns out to be unlikely, given what we know now. But the chemical propulsion, while a bit better than 1960's, is still capable of doing the job.
By analogy, it took 3-5 months to cross the Atlantic in a 15th-century sailing ship, powered by the wind. Unless you were unaware of the prevailing winds and currents, which might stretch that journey to a year. But it was possible, and some made the journey, although many died. Nuances like citrus to stave off scurvy came later.
Continuing the analogy, a modern steamship can make the same transatlantic crossing in 5-10 days, depending upon the speed of the actual vessel. There's no doubt that is the far better technology for traveling transatlantic. But, the explorers of the 15th, 16th, and 17th centuries did not wait for the late 19th century introduction of steamship technology. They set sail when they did, because they could, and just did what they desired to do.
The crew-killers for 1960's chemical propulsion to Mars were mostly not yet understood. They knew it would take massive amounts of shipped oxygen, water, and food. They did not know how to make astronaut food that would last long enough. They did not then understand the dangers posed by radiation and by weightlessness. That's like not knowing how to stave off scurvy, which did kill a lot of crewmen until the British citrus discovery of the 17th century (which is why British sailors became known as "limeys").
Our modern chemical propulsion is only slightly better than 1960's chemical propulsion. A 6 month journey to Mars is possible, compared to only an 8 month journey back then. Big deal. We understand a lot more about the radiation and what can practically be done about it. We also understand a lot more about microgravity diseases (plural!!!), and that we don't yet know all the nuances of that. So, we know that spin gravity is simply required for many-month voyages, even if many do not want to face that fact yet.
So yes, today, we could expect to go to Mars on chemical propulsion, and expect the crew to come home alive. A bit tricky and dangerous, but it really can be made to work. It will be a long time yet for something better than chemical propulsion to be available, actually ready-to-use. So it gets down to how much you really want to go. Now? Or wait for a better ride later? Simple as that.
GW
Last edited by GW Johnson (2018-06-18 08:12:40)
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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Elderflower,
You're missing the point. It does not matter one little bit if it takes a month to spiral out from Earth, several months to make the transit to Mars, and a month to spiral into Mars orbit when your ship has the delta-V capability to do that, the radiation protection that makes radiation a negligible concern, and the artificial gravity that prevents microgravity diseases.
If you want to knock a month off the transit time, then the ITV can start in lunar orbit. Nobody has to be aboard the ITV while it transits to lunar orbit. Dragon or Orion can send the crew to lunar orbit. From there, you board the ITV. It doesn't take that long to spiral out because the moon's gravity well is so much weaker than Earth's gravity well.
At the very least, the first "test" you'd do with the ITV would prove it can transit to another planetary body on autopilot and establish a stable orbit there. Who cares if that takes a month or even two months when no consumables, except a little propellant and a little bit of time are used in the process?
No chemical or nuclear rocket engines are required to do that. You can depart from wherever pleases you, take a couple extra months to do that if you want to, establish stable orbit around the target planet, and then deploy the lander at orbital velocity, which is significantly lower than interplanetary velocity, resulting in less wear and tear on the lander's heat shield.
GW,
You and I both know that there's no such thing as "going now" because there's no ride available to take us to Mars. We've spent a lot of money on giant rockets, an admirable first step, but the earliest launch of SLS is still two years out and Mrs. Shotwell says the first BFR flight is 8 to 10 years out. Start designing and building the ITV now so that when we do have a properly tested SLS or BFR ready to go, there's a worthy payload available.
The X3 nested hall thruster completes ground testing this year. It's already been run at 100kWe and will complete 200kWe maximum output firing before the year is out. I've said that several times now. It can run on Argon, Krypton, or Xenon. It's only a matter of available input power. The Ascent Solar thin film arrays have completed long duration space flight testing in the LEO and GEO shooting galleries. Those arrays are going to Jupiter within 2 years aboard JAXA's probe. High power MPD thrusters of the variety I want to use have been run up to 1.5MWe in ground testing. Mo power means mo output and mo Isp with MPD. Does any of that even register with you?
ITV is not a pipe dream. It's the exact type of vehicle that's most suitable for the type of transits that we say we want to make. The thin film arrays are good to go for the moon, Venus, Mars, and even Jupiter. Any further out than that and we'll need fission reactors for propulsion power, but I think our exploration and colonization efforts between Venus and Mars should take precedence over flights to Jupiter, Saturn, Neptune, or Uranus.
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Actually Kbd512, we agree more than we disagree. I posted an"ITV"-type Mars mission concept at "exrocketman" 2 years ago, and pointed that out here on these forums.
That article was titled "Mars Mission Outline" dated May 28, 2016. The site is http://exrocketman.blogspot.com. The plan revolves around a dedicated orbit-to-orbit transport that never lands and is never thrown away. It goes to Mars via chemical propulsion to reduce trip time down to Hohmann transfer 8.5 months, and captures into low Mars orbit, where it rendezvouses with supplies and equipment previously sent there unmanned using the solar electric propulsion that you advocate. Those supplies include the return propellant for the trip home.
My transport is a baton of docked inflatable modules that would be a variant of the Bigelow B330 design. This baton spins head-over-heels for near-1-gee gravity at its tips, and 0-gee at the center. You do your work shift near the tips at 1 gee, recreate at a lower radius where it's fun in partial gee, and sleep near the center, where the 0-gee makes no difference to health effects. The volume allowance is multiple 100's of cubic meters per person at a crew size of 6.
I use the Mars arrival propellant, as tanks clustered around the habitation, for solar flare shielding. I similarly use the Earth arrival propellant for shielding on the way home. This is long-term easy-storable MMH-NTO propellant.
Landers and their propellant supply are the other part of the unmanned stuff sent ahead by solar electric propulsion. These are one-stage reusable landing boats capable of refilling on-orbit (in Mars orbit), and making multiple trips. They use the same MMH-NTO storable propellant.
Your lander is your habitat on the surface during your stay at any given site. They're plenty big to serve this way, about 12-15 m heat shield diameter, and around 60-100 tons ignition weight. The idea was to alternate crews of 3 on the surface for 2-week to 1-month-long stays, with the other 3 watching over them and doing science from orbit, at 1 gee spin gravity in the transport. Mission rules require a rescue lander capability, so I send 3. That way, if one craps out, I do not have to abort.
This mission has to have more delta-vee capability than a single direct landing, but it offers self-rescue capability impossible with the direct landing approach, and (MOST IMPORTANT) it offers the chance to explore more than one site, after going to all the fuss and bother of making the long trip. It does not rely at all on making return propellant on Mars.
If your electric propulsion gets man-rated sooner, then the manned transport could be propelled that way, too, at the cost of about a 12-13 month one way trip spiralling in and out.
Can't do that through the van Allen belts, though. Must fly fast and board or leave the ship outside those belts via rocket and capsule.
You'd need to add some of the lander propellant to it for radiation shielding during the interplanetary trip. It's a very flexible approach, adaptable to changes in available technology.
See there? I actually do agree with you. I like that kind of orbit-to-orbit transport design even better than Musk's BFR/BFS approach, although I do believe he can do what he dreams. You take fewer risks doing it orbit-to-orbit.
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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Hadfield's comments are just NASA-inspired pessimistic tosh. Yes, if you're frightened of your own shadow you won't go out of the house, but if you're not you will, assuming you have the use of two good legs (which we do).
Radiation can be guarded against. The only significant risk to human health is the zero/low G environment. However, my view is that there is a degree of hysteria about that. The mission architecture can of course be trialled on the moon, so it is not as though we have to risk everything on a single throw. I think a lunar trial will show the risks to human health are grossly overstated.
Last edited by louis (2018-06-18 14:16:07)
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis,
A pessimist wouldn't strap himself to the largest conventional bomb ever made, especially after watching what happened to Challenger, and he certainly wouldn't do that multiple times. Astronauts that can't walk on their own after 6 months or less aboard ISS is not hysteria. That's just hard scientific reality. All of humanity is utterly clueless as to what .38g does to humans, but according to you NASA is just holding everyone back. Throw caution to the wind and everything will turn out just fine. It makes me wonder a little bit.
Maybe you're willing to try anything yourself just to see what happens, but imagine for a moment that there's someone you really care about in this world and you're about to give the order for them to try what you're merely assuming will work. How cavalier an attitude are you willing to take with their life?
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There are plenty of people happy to go into space for over one year.
Space medicine is improving all the time.
As indicated, there is no reason why this can't all be trialled with an analogue mission to the Moon. No one's life need be put at risk.
Louis,
A pessimist wouldn't strap himself to the largest conventional bomb ever made, especially after watching what happened to Challenger, and he certainly wouldn't do that multiple times. Astronauts that can't walk on their own after 6 months or less aboard ISS is not hysteria. That's just hard scientific reality. All of humanity is utterly clueless as to what .38g does to humans, but according to you NASA is just holding everyone back. Throw caution to the wind and everything will turn out just fine. It makes me wonder a little bit.
Maybe you're willing to try anything yourself just to see what happens, but imagine for a moment that there's someone you really care about in this world and you're about to give the order for them to try what you're merely assuming will work. How cavalier an attitude are you willing to take with their life?
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis,
It was a simple question, but you already answered it with your redirect. You don't even believe the things you claim.
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Louis,
A pessimist wouldn't strap himself to the largest conventional bomb ever made, especially after watching what happened to Challenger, and he certainly wouldn't do that multiple times. Astronauts that can't walk on their own after 6 months or less aboard ISS is not hysteria. That's just hard scientific reality.
But we perfectly know how to make artificial gravity by spinning, so what's the problem?
It's only just a bit more expensive, but certainly less expensive than a dead crew.
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Quaoar,
There's no problem. There's no rush, either. We won't even have the BFR for another 8 to 10 years. If spending two to five years testing a real ITV now is too costly, then as you and GW always ask, how expensive will a dead crew from ignorance-based assumptions be?
All of this stuff can be built and tested using Falcon Heavy. When it's ready, then it's ready, but not a moment before.
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Quaoar,
There's no problem. There's no rush, either. We won't even have the BFR for another 8 to 10 years. If spending two to five years testing a real ITV now is too costly, then as you and GW always ask, how expensive will a dead crew from ignorance-based assumptions be?
All of this stuff can be built and tested using Falcon Heavy. When it's ready, then it's ready, but not a moment before.
The issue is not only about artificial gravity: I also have some doubts that in the next 10 years they will be able to build a reliable megawatt-range ISRU device able to produce 1100 tons of LOX-CH4 from martian atmosphere. Does somebody know if they have just started to project and test it?
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I would say that all exploration through human history has involved some element of risk and danger. On the basis of your approach no new aircraft would ever be tried out by a test pilot because we would not wish our loved ones to be subjected to such a risky enterprise. But in fact there are also plenty of parents and children who have together entered upon such risky enterprises or separately supported each other in such enterprises.
The risk has to be a reasonable one. We aren't talking about sending soldiers into the firing line. I doubt we are even at the "climbing Mt Everest" or the "riding a motor bike at speed on urban streets" risk level. Remember, not a single Apollo astronaut was ever killed in flight or on the lunar surface.
Subject to there being a proper analogue mission to the Moon, I don't think the risk for crew on a Mars mission would be no greater than 1 in a 1000. There would have to be some serious, critical systems failure (similar to the Challenger disaster) or some v. unlucky event (eg a major meteorite hit on the base) or major human error or suchlike.
Louis,
It was a simple question, but you already answered it with your redirect. You don't even believe the things you claim.
Last edited by louis (2018-06-19 11:23:36)
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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All new aircraft are extensively tested before we put anyone in the cockpit. During flight testing, non-essential personnel aren't permitted aboard the aircraft, either. Boeing doesn't put a single passenger aboard their new jetliners until they've been tested six ways to Sunday and FAA gets a warm fuzzy that the new bird flies right. All subsequent aircraft of the same design are also tested first, then handed off to paying customers. The manufacturer doesn't merely assume that since they made a dozen just like it that that particular aircraft won't have any problems.
So many aspects of this mission have never even been attempted in a more benign environment that the idea of betting lives on all of it working according to plan seems naive at best and downright criminal if the people making the decisions know the technology isn't ready.
If one of the Apollo missions had its schedule shifted by a week, the astronauts in the capsule would've been irradiated to death from a massive solar flare. That's what I'm talking about. These people aren't ants on your ant farm. There's a duty and responsibility to protect their lives from people who think we should pedal faster. Pedaling faster into a brick wall only increases the severity of the injury. We're going to new worlds, not taping another episode of Jackass.
All the "I think", "I believe", and "I feel" that I've read from you means nothing to me. I want to see the test results. If it's never been tested before and I'm the FAA administrator or NASA launch coordinator, I'm not signing off on that mission. If TPTB wants to override my decision, so be it. I guarantee you that the people actually in those positions think the exact same way I do when it comes to this matter.
A piece of rubber that cost less than the training for any member of the crew killed 7 astronauts. A block of foam that nobody thought would ever hurt the orbiter killed 7 more. BFR has 10 times as many engines as the Space Shuttle in the first stage alone. There's plenty that can go wrong. There's no reason for any of this brain dead "gotta-get-there-itis" to claim a half dozen more. We've killed enough people with our hubris. Making sure that everything we think will work actually does when it matters is not wasted time and effort.
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You really make the point for me - we know a lot more about rocket/capsule safety now. Are there really any more major health issues to be identified? Most astronauts seem to live into old age, which in some cases is surprising as many of the earlier ones came from a very hard-drinking fighter pilot tradition.
You can't make a Mars Mission risk-free and there are plenty of brave explorers ready to take on the challenge at a reasonable risk level.
All new aircraft are extensively tested before we put anyone in the cockpit. During flight testing, non-essential personnel aren't permitted aboard the aircraft, either. Boeing doesn't put a single passenger aboard their new jetliners until they've been tested six ways to Sunday and FAA gets a warm fuzzy that the new bird flies right. All subsequent aircraft of the same design are also tested first, then handed off to paying customers. The manufacturer doesn't merely assume that since they made a dozen just like it that that particular aircraft won't have any problems.
So many aspects of this mission have never even been attempted in a more benign environment that the idea of betting lives on all of it working according to plan seems naive at best and downright criminal if the people making the decisions know the technology isn't ready.
If one of the Apollo missions had its schedule shifted by a week, the astronauts in the capsule would've been irradiated to death from a massive solar flare. That's what I'm talking about. These people aren't ants on your ant farm. There's a duty and responsibility to protect their lives from people who think we should pedal faster. Pedaling faster into a brick wall only increases the severity of the injury. We're going to new worlds, not taping another episode of Jackass.
All the "I think", "I believe", and "I feel" that I've read from you means nothing to me. I want to see the test results. If it's never been tested before and I'm the FAA administrator or NASA launch coordinator, I'm not signing off on that mission. If TPTB wants to override my decision, so be it. I guarantee you that the people actually in those positions think the exact same way I do when it comes to this matter.
A piece of rubber that cost less than the training for any member of the crew killed 7 astronauts. A block of foam that nobody thought would ever hurt the orbiter killed 7 more. BFR has 10 times as many engines as the Space Shuttle in the first stage alone. There's plenty that can go wrong. There's no reason for any of this brain dead "gotta-get-there-itis" to claim a half dozen more. We've killed enough people with our hubris. Making sure that everything we think will work actually does when it matters is not wasted time and effort.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis,
Sounds great. It's good to know it's all that simple to you.
Since SpaceX knows so much more now, we shouldn't see any more B-reel of exploding rockets. Come to think of it, they should've landed the Falcon Heavy's center core since they knew so much more than everyone else about that process. Then there was the small matter of injecting Star Man into the wrong orbit, despite their extensive launch experience.
One Falcon 9 exploded in flight from the Helium COPV. Then a second Falcon 9 exploded on the pad, stricken by another Helium COPV. We're still using COPV's to pressurize the propellant tanks, but we know a lot more now, or so I've been told. Apparently just not enough to know that Helium COPV's cause expensive rockets and payloads to rapidly deconstruct in an unscheduled manner. A minor detail.
I'd settle for people who simply know what the risks are at this point. I'm sure we can get people who don't know anything about what they're doing to march off to their deaths. The military does that all the time.
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Risk adversion will mean man will not go, Risk acceptance will allow man to go even if death occurs or happens, Risk ignorance will be just public out cry if death did happen.
All of which are governed by ethics no matter whom provides the ride, no matter what it might cost to do so.
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SpaceNut,
That's exactly what I'm saying. Ethics should dictate an incremental approach to testing. I'm in no way stating that we shouldn't go. When we go, we should go only after due diligence has been performed on every aspect of the mission. If there's something we didn't account for happens, then we'll just have to fly by the seat of our pants. Every reasonable effort should be made to prevent that sort of flying. Some people here are acting like we already have everything we need to go to Mars and expect to live there. We don't. It's blatantly obvious that we don't. That's our current reality. Our government obviously doesn't care about cost and neither do the people, up to a point.
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Case in point how many own a sabetier reactor, a kilowatt reactor, ....
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Just a case in point statement regarding the Sabatier reaction. This is late 1800's technology which can be improved upon to only a minor degree. Paul Sabatier won the Nobel for this discovery. Not complicated at all. It's exothermic once started, uses cheap catalyst. This is H.S. Science Fair type technology.
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SpaceNut,
Every aspect of this mission is an extreme act. To the extent that it's even possible to do so, I want the risks we know mitigated in meaningful ways. We know what happens to humans when we expose them to microgravity and radiation. Needlessly and purposefully exposing them to such environments when it's not required to complete the mission is pointless and stupid. When sustaining life demands reliable electrical power for life support, failing to recognize that fact is equally pointless and stupid.
From a simple human perspective, you're as alone as anyone has ever been and there is no means by which outside assistance can be provided. Even so, with proper planning, rigorous training, the right attitude, and sufficiently advanced technology can overcome such obstacles. Someone needs to put a dozen people in a hostile environment and truly cut them off from outside support. If they survive, then that's a good indication that human ingenuity and perseverance will overcome the challenges Mars presents when there is no help and no escape. In so doing, those who live and follow in their footsteps will learn that fate is what you make it.
This mission is not suicide, but anyone with a little introspection should have their affairs are in order prior to departure. Any mistake you make, no matter how seemingly inconsequential at the time, may very well be your last.
I understand the apprehension people have towards nuclear power, but nuclear power technology also provides life sustaining power when it's most needed. I've seen no actual technical arguments advanced as to why it's unusable, just vague ignorance-based fear of something most people don't understand. That said, I also think a little fear is a healthy thing. Most people can't wrap their heads around how a block of metal smaller than a 1 gallon bucket can produce enough power to run several houses for decades. It's completely foreign to what they know and understand.
The reactor is perfectly safe with the control rod inserted. If the rod comes out, then you'd better not be anywhere near it because the neutron and gamma radiation will deliver a lethal dose in seconds. I'm sure the anti-nuclear crowd will just love this analogy, but it truly is like a grenade. The grenade is an exceptionally simple device and no more intrinsically dangerous than any other explosive device. However, after you pull the pin you've set an irreversible sequence of events into motion. It doesn't matter what you meant to do, only what you did do, because the grenade will do what it was designed to do after the pin is pulled.
Contrary to popular belief, nuclear engineers test what will happen to reactors when the coolant loop fails. In this case, complete removal of the coolant loop would have no effect on the reactor's operation, apart from no longer generating electrical power. The block of Uranium has insufficient mass, relative to its surface area, to melt down. Even if it did melt down, insufficient material is present to sustain nuclear fission without the moderator. That means that even if the core melts through the stainless steel containment can, fission ceases almost immediately. That was one of the design principles of this reactor. The design of this type of simplistic nuclear reactor design is science, rather than art.
Most people probably don't understand just how energetic the chemicals are within the 85kWh battery in a Tesla Model S. The battery pack stores about as much chemical energy as 41kg of TNT. If you short circuit or puncture a cell in a pack like that, you may very well get an up-close and personal look at what the explosive filler in seven 155mm artillery rounds looks like. Even so, it does not mean the battery pack is intrinsically dangerous or that people should fear using them. If anything, the battery packs are far less dangerous than driving around with a tank of gasoline. In the end, if you short circuit a battery or rupture a gas tank, the end result can be the same.
I look at this from the perspective of how fast things can go wrong. For electrical equipment or matter/anti-matter reactions, it's nearly instantaneous. For chemical propellants and other conventional explosives, it's milliseconds. For batteries and fuel cells, it's seconds. For nuclear fission reactors, it's hours. That doesn't make the end results equal in any way. A lot is dependent upon circumstances of the event. If you're inside a rocket that suffered a structural failure that punctured a fuel tank or fuel line, there's a vanishingly small window of time in which to escape the massive explosion that's all but certain to follow. If you're inside a car that catches fire, you can generally pull over and exit the vehicle. If a nuclear reactor melts down, that process doesn't occur in an instant, so there's time to react. The mass of materials and distance between you and the reactor are what matters most.
The bottom line is that if you're dependent upon electrical power simply to draw your next breath, then no amount of blind faith in any particular electrical power production technology will save you from your folly. You've seen your last day. This should not be the fate of the ambassadors of a civilization advanced enough to send people to other worlds.
"It's always easier to believe something, than to understand it." - Christopher Hadfield
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SpaceNut,
Every aspect of this mission is an extreme act. To the extent that it's even possible to do so, I want the risks we know mitigated in meaningful ways. We know what happens to humans when we expose them to microgravity and radiation. Needlessly and purposefully exposing them to such environments when it's not required to complete the mission is pointless and stupid. When sustaining life demands reliable electrical power for life support, failing to recognize that fact is equally pointless and stupid.
I don't think anyone, certainly not Musk, is planning to needlessly expose anyone to radiation. The radiation threat is one well covered I believe by shelters within the BFS and by specially designed habs plus regolith cover on Mars. Zero gravity exposure will be limited. 1 gravity can be mimicked on Mars with use of weighted suits. There are effects on the immune system from long exposure to microgravity but no one has died or suffered serious illness as a result. Besides, I would not expect anyone to be sent to Mars before the Mission design is tested with an analogue mission to Mars.
I think there has been exaggeration about the physical recovery period following zero G. It's not advisable to immediately try to walk, drive etc immediately after landing. But people make a very good recovery. It might be that your crew would stay in the landed BFS for a few days, getting used to Mars gravity, wearing weight suits and G suits to maintain good blood pressure around the body. Some crew members may do better than others, and they will take the lead in making preparations for exiting the BFS and setting up the hab.
Clearly no one will be chosen for the Mission who is going to cope badly with zero G and its effects. You'd probably choose people around age 29 who would train for 5 years and be in their mid 30s while on Mars.
From a simple human perspective, you're as alone as anyone has ever been and there is no means by which outside assistance can be provided. Even so, with proper planning, rigorous training, the right attitude, and sufficiently advanced technology can overcome such obstacles. Someone needs to put a dozen people in a hostile environment and truly cut them off from outside support. If they survive, then that's a good indication that human ingenuity and perseverance will overcome the challenges Mars presents when there is no help and no escape. In so doing, those who live and follow in their footsteps will learn that fate is what you make it.
I don't think there really will be that many challenges for the crew to overcome, as opposed to the engineers and designers. So much of the Mission will be automated, including landing the craft. The crew will of course need good genes, physical fitness, ability to follow procedures, determination, focus, relevant skills base and mental endurance. But it's not as if they will be jungle explorers who might have to improvise a solution to ensure their survival.
Assistance in the formal of verbal guidance and support will be available to them at nearly all times. They certainly aren't going to be lonely or lacking stimulating activity on the journey there or during their stay on Mars. They will be buoyed up to hear of the avid interest from the media and people at large in their Mission.
This mission is not suicide, but anyone with a little introspection should have their affairs are in order prior to departure. Any mistake you make, no matter how seemingly inconsequential at the time, may very well be your last.
Of course. There is risk with any rocket based mission.
I understand the apprehension people have towards nuclear power, but nuclear power technology also provides life sustaining power when it's most needed. I've seen no actual technical arguments advanced as to why it's unusable, just vague ignorance-based fear of something most people don't understand. That said, I also think a little fear is a healthy thing. Most people can't wrap their heads around how a block of metal smaller than a 1 gallon bucket can produce enough power to run several houses for decades. It's completely foreign to what they know and understand.
The reactor is perfectly safe with the control rod inserted. If the rod comes out, then you'd better not be anywhere near it because the neutron and gamma radiation will deliver a lethal dose in seconds. I'm sure the anti-nuclear crowd will just love this analogy, but it truly is like a grenade. The grenade is an exceptionally simple device and no more intrinsically dangerous than any other explosive device. However, after you pull the pin you've set an irreversible sequence of events into motion. It doesn't matter what you meant to do, only what you did do, because the grenade will do what it was designed to do after the pin is pulled.
Contrary to popular belief, nuclear engineers test what will happen to reactors when the coolant loop fails. In this case, complete removal of the coolant loop would have no effect on the reactor's operation, apart from no longer generating electrical power. The block of Uranium has insufficient mass, relative to its surface area, to melt down. Even if it did melt down, insufficient material is present to sustain nuclear fission without the moderator. That means that even if the core melts through the stainless steel containment can, fission ceases almost immediately. That was one of the design principles of this reactor. The design of this type of simplistic nuclear reactor design is science, rather than art.
Most people probably don't understand just how energetic the chemicals are within the 85kWh battery in a Tesla Model S. The battery pack stores about as much chemical energy as 41kg of TNT. If you short circuit or puncture a cell in a pack like that, you may very well get an up-close and personal look at what the explosive filler in seven 155mm artillery rounds looks like. Even so, it does not mean the battery pack is intrinsically dangerous or that people should fear using them. If anything, the battery packs are far less dangerous than driving around with a tank of gasoline. In the end, if you short circuit a battery or rupture a gas tank, the end result can be the same.
I look at this from the perspective of how fast things can go wrong. For electrical equipment or matter/anti-matter reactions, it's nearly instantaneous. For chemical propellants and other conventional explosives, it's milliseconds. For batteries and fuel cells, it's seconds. For nuclear fission reactors, it's hours. That doesn't make the end results equal in any way. A lot is dependent upon circumstances of the event. If you're inside a rocket that suffered a structural failure that punctured a fuel tank or fuel line, there's a vanishingly small window of time in which to escape the massive explosion that's all but certain to follow. If you're inside a car that catches fire, you can generally pull over and exit the vehicle. If a nuclear reactor melts down, that process doesn't occur in an instant, so there's time to react. The mass of materials and distance between you and the reactor are what matters most.
The bottom line is that if you're dependent upon electrical power simply to draw your next breath, then no amount of blind faith in any particular electrical power production technology will save you from your folly. You've seen your last day. This should not be the fate of the ambassadors of a civilization advanced enough to send people to other worlds.
"It's always easier to believe something, than to understand it." - Christopher Hadfield
I don't think I have "apprehension" about nuclear power. It's very unlikely to cause anyone serious harm if used on Mission One. What I am concerned about is Mission Complexity. You've made reference to the reactors being sited 5 kms away from the hab...so you've got to unload 102 x 1.5 tonne* 10Kw reactors (I've added two to the baseline 10 in order to give you some redundancy) and then get them to a location 5 kms away from the hab? That's a huge, huge task.
If that isn't necessary and you can leave them on the BFS that would be better but I don't know if that is practical...It might present its own problems in an emergency.
By contrast PV rolls could be unloaded by chute in a matter of minutes and then deployed in and around the base.
How much monitoring will these nuclear power reactors require?
Then there's the waste heat issue - not clear how suited they are to operating on a planetary surface that might be like permafrost.
Finally these proposed reactors have not yet been built and proven to last well in Mars conditions! They involve stirling engines which can certainly go wrong. Why take on this added complexity and risk when you have a known solution ready and available?
* this was Kbd's figure...presumably incorporating heavy duty shielding. Wikipedia gives an expected figure of 250 Kgs for something that can be used on robot space missions.
To my mind, it's the opposite of irrational fear of nuclear, it denotes an irrational enthusiasm for nuclear.
Last edited by louis (2018-06-20 07:51:00)
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis,
I already planned on taking 13 of the KiloPower units to Mars in order to run the reactors at 75% of full rated output to make the fuel last as long as possible and limit the thermal stress associated with continuous full output. If run in that manner, the reactors could last for at least a couple of decades. That's enough power to keep LOX/LH2 cold at night.
The 10kWe KiloPower reactors weigh 1,544kg on Earth, but only 587kg on Mars. There's no way a minimally useful rover would have a lower mass than that, either. If you can't take 1t of equipment out of the BFS without toppling it, then BFS won't work on Mars, period. There are manual cranes, operated by hand, that can hoist that amount of weight and they see regular use in most auto repair shops here on Earth. For the floor of the cargo hold to even support 150t of cargo in a 3g acceleration, it has to be built to take the weight and then some. It's an unavoidable aspect of BFS design. KiloPower presents no challenge to the design in that regard.
Please don't tell me that the batteries would weigh less or would be stored inside your ride home. In real life here on Earth, the batteries are sited near the solar arrays for efficient transfer of power to the batteries. There'd be no issue whatsoever with keeping them warm at night if you really were drawing 1MWh/hr. You'd have the opposite problem, just like a fission reactor. The Li-Ion cells aboard ISS have to have superb thermal management, not because of the current draw, but because of the staggering +250/-250 temperature swings. The Mars surface thermal environment is downright peachy in that regard, but still cold enough to kill batteries at night without thermal stabilization.
Each solar array would have its own bank of batteries. Power cables then distribute that power through the grid. The miniature Mars grid would be much smaller than an Earth grid, but the same basic prudent engineering principles apply.
SpaceX puts large batteries outside of the Dragon pressure vessel, as does everyone else, because the engineers know what will happen if a large Li-Ion battery catches fire from a short circuit or physical damage. The batteries don't even need to be mishandled, over-charged, or under-charged for that to happen. A simple manufacturing defect or wear from repeated use can cause that issue to occur. All mass manufactured items like batteries are manufactured to within tolerance ranges because it's not possible to manufacture hundreds of megawatt-hours of storage batteries like they're Rolex watches, even if they are marvels of engineering in their own right. That's just engineering reality. Boeing failed to take that into account, as did Tesla, and we've seen the results. All flight hardware is industrial grade stuff as a function of the environment it's subjected to.
All batteries, solar panels, fission reactors, and anything else that will become infrastructure on Mars needs to be at least 5km away from the launch site. You're not going to put that equipment right next to a rocket you intend to use. A MW class solar array or battery bank is not easily transportable after construction, although the solar array would be easier to move than the batteries.
SpaceX shows a crane or hoist on their rocket's cargo hold because in real life people use cranes to lower delicate cargo. Thin film solar arrays that produce 1kW/kg are not amenable to rough handling. It's thinner than paper. If you add plastic to make it tougher, then the mass goes up and the output goes down. There's no way around that. This is not the same stuff you'd take camping to recharge your cell phone.
KiloPower:
The only remotely operated control on the reactor that I'm aware of is the control rod. There are a handful of sensors on the reactor for remote monitoring, but the only things that really matter are the pressure and temperature in the coolant loop and the temperature of the core. The coolant loops are separate from each other and feed one of the 8 turbogenerators. It's a very small block of metal, so conduction carries heat across the entire core, such that the other coolant loops can continue to cool the core if one loop ruptures. The control rod design was intended to permit load following to extend the life of the core, but output could be fixed by dumping excess electrical power to ground.
The thermal and mechanical behavior to reactivity transients was tested by repeatedly executing what amounts to a throttle slam in a jet engine where you rapidly go from idle to full power. The core was subjected to repeated fast cycling to see what would happen. The neutronics are so terrible that the slight swelling of the fuel block self limited the reactivity rate. In a core that small, fission stops in seconds when the control rod is inserted. After a couple of days, an astronaut can work on the core for a limited period of time. After a month, nearly all of the highly radioactive fission products have decayed to a point where there's no real issue with moving the reactor by hand.
How long would water stay liquid when exposed to a piece of stainless steel that's hot enough to melt brass? Why does a Dakota fire hole work here on Earth in frozen tundra if that's a real problem? Why doesn't the water in the soil or the snow on top of the soil extinguish the fire? This sounds like a made-up problem or the fire holes I've dug in frozen ground would never work. The ground didn't turn to mud, pool, and kill my fire, so I call BS on this. I've no idea where Elderflower got this nonsense from, or why you blindly accepted that it was a problem, but she's either never been camping up north or never dug a fire hole. It's not a real problem here on Earth with even more water in the ground, so how is this a problem with less water?
A 10% scale KiloPower demonstrator has been built, ground testing is nearly complete, and the test article utilized all of the components intended for the flight model. KiloPower was based upon TOPAZ. Although shut down now, TOPAZ is still flying in space and the thermal environment in GEO is more severe than the thermal environment on Mars. It didn't explode, leak, or have any other problems. A Stirling engine can fail, but so can batteries. KiloPower has 4 to 8 Stirling engines, dependent upon the model. Electric motors and rocket engines can fail, too, yet any power and propulsion solution will be replete with those. A heat engine is simpler in operation than a solar panel and battery solution. This seems like another straw man argument. Anything capable of providing a tens of kilowatts to megawatts of continuous power will be complicated.
Actually, I think you have an irrational blind faith in solar panels and batteries, while Mars is actively providing an object lesson in how those technologies fail. Nearly any problem can be overcome by "blowing harder" and rockets prove that. A bus will fly if you put a rocket engine on it, but that doesn't mean a bus is a particularly well designed aerospace vehicle. We've made aircraft that are mostly steel. Their fuel consumption sucks and fatigue limits the airframe longevity, but a jet engine with enough power can make nearly anything fly. I think that point is lost on you.
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I wish people would stop assuming that weighted suits on Mars will compensate for the gravitational differential, which is a scientific fallacy. The extreme exercise routines done on the ISS have done little to alleviate the effects of microgravity disease. All that wearing a weighted suit on Mars will do is make the wearer tired and reduce productive output. To make this assumption is simply dismissive of reality and morally irresponsible.
Robert Zubrin didn't dismiss this problem; for Musk to do so is overlooking one of the major stumbling blocks in his plan to colonize Mars.
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Oldfart1939,
Chris said that they managed to limit the bone loss to just the pelvic girdle and femurs with their latest fancy exercise equipment, but that still leaves you unable to walk and he said the vertigo and nausea upon return to Earth was severe. His body replaced the 8% lost bone mass over the course of a year. He was only aboard ISS for 166 days, so getting to Mars quickly is advisable if you don't have artificial gravity. He further stated that some heart muscle atrophy appears unavoidable. That's not good news for anyone pulling a 7g reentry. Apparently Soyuz can pull 20g if you screw up the reentry angle and they've done that a few times. He said it's survivable in a reclined position and healthy astronauts and cosmonauts have survived that and even remained conscious, but being in a seated position would kill you. The average Soyuz reentry was 4g to 5g. The period of severe acceleration appears to last about 30 seconds. A 20g reentry would destroy BFS. There's no way it has that kind of structural integrity at just 85t. Soyuz is built like a Russian tank.
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