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#8051 Re: Human missions » Artificial gravity station? » 2015-04-20 18:32:05
There are three basic configurations that use existing technology:
1. Connect a module to a counterweight using a tether and spin the module using thrusters (a baton would work the same way, but the tether would be replaced with more modules); if the baton is attached to something, you can use an electric motors for rotation.
2. Rotate a torus using motors if it's attached to something at the center or thrusters if it's not attached to anything at the center
3. Rotate a rotor using the same methods used to rotate a torus
Just like the Schwartz, each method has its upsides and downsides.
#8052 Re: Interplanetary transportation » USS Discovery: Could we build it? » 2015-04-20 18:20:37
Let's concern ourselves with the key technologies we need to put humans on Mars first. After we've thoroughly explored Mars, then we can consider building something like this for an Europa mission. Even if SLS was a 200t HLLV, that's a minimum of 30 flights for something with that mass. We'd probably have to use something along the lines of Rockwell's Star Raker concept or big dumb rockets with 500t+ throws.
Some of the key technologies for Mars exploration:
* Interplanetary transfer vehicle
* Planetary landing vehicle
* Closed loop ECLSS
* Active radiation shielding
* SEP
* ISPP
* ISRU
Quick thoughts:
Eventually, gas core reactors or fusion based power sources are required for exploration of the entire solar system.
Human hibernation may become feasible at some point in the future, but it's still highly experimental.
Even if we had flight rated gas core or fusion reactors today, current plasma thruster tech is not as advanced as current hall thruster tech.
USS Discovery is the size and weight of a small guided missile destroyer and even if F9H cores are reusable up to ten times, access to LEO is still prohibitively expensive.
Lastly, although Elon's a pragmatic business man, he's not too keen on AI, so he may choose not to provide launch services to someone with an AI equipped vehicle that could cause rather significant problems if the navigational computer went haywire and it reentered.
#8053 Re: Planetary transportation » Combining the Rover and Hab - Go RV'ing! » 2015-04-20 00:43:41
I'm not familiar with all the acronyms for the inflatable and flexible heat shield concepts. But I do know that these are all still quite experimental right now.
Very experimental, but also very promising based on previous tests.
One at least I hope "proves out" well enough to be a technology ready-to-apply in time to make the mission/vehicle design decision. That happens early in the process of selecting architecture and launchers, so something needs to mature in the very next few years, if we expect to really use it.
HIAD is further along than ADEPT, but there's no reason to believe that both of these technologies won't "prove out".
I'm not sure why you seem to want to avoid landing rockets at all costs. It has been a proven staple with most of the landers on Mars so far, and has been used "in the field" by the Russians for delivering battle tanks to the battlefield by parachute. That technology is closer to be ready to apply than any of the flexible heat shield concepts, because of that pedigree.
Retro-propulsion increases the weight and complexity of the solution. The use of rockets for de-orbiting the micro capsules is mandatory, but if there's a way to avoid using rockets for landing, then I think we should make every effort to avoid it. Apart from pure development costs, it's also a question of how many times we can test the solution and in how many different ways. Micro capsules are so small and light that we can test a dozen or so at Mars before we ever put humans in them.
What does one or perhaps two landings of a multi-person vehicle tell you about that vehicle's performance in the wildly varying atmospheric conditions on Mars? Two tests is hardly a rigorous testing program. Let's face facts. If NASA or its favorite contractors design a multi-person EDL solution for Mars, it will be anything but inexpensive or simplistic.
Myself, I'd use for entry a flexible heat shield to lower ballistic coefficient if it can be made ready in time; if not, maneuvering on a conventional heat shield plus supersonic retropropulsion should fill that bill.
A hard heat shield necessarily increases the mass and size of the reentry vehicle. If it's not apparent yet, those are the two things I want to hold to avoid.
Once doew to near Mach 2-2.5-ish, a supersonic ringsail chute might have time to slow you just barely subsonic. That technology has been demonstrated on Mars with the probes, butt will need scaleup for manned vehicles.
My thinking was that HIAD would slow the vehicle to subsonic speeds, the mass of the service module and HIAD would be dumped, and a large subsonic ringsail with an inflatable ring for rapid deployment would permit the capsule to soft land without further complication.
Once subsonic, we either use some sort of subsonic landing chute (if that can be made ready in time), or if not, retropropulsive landing (something we already know how to do).
My take on this is that we design the solution we intend to use that we can actually afford to use. Timeline is a make-believe issue for space exploration. Decades after it was first proposed, there is still no real timeline for manned Mars exploration. It's always two or three decades into the future.
The combination of micro capsules, M113/MTVL for surface habitation and exploration, and a MTV that doesn't weigh more than ~85t is about making the mission affordable from a launch costs and development perspective by keeping mass requirements to F9H sized pieces and using single purpose solutions rather than trying to design multi-purpose mission components.
Instead of spending the time and money to design a combination multi-person descent/ascent vehicle that can land with pinpoint precision, a technology set to land a habitat module that weighs as much as a fully loaded 737, or a MTV so massive that it virtually requires SLS, we could build something along the lines of what I suggested for just a fraction of the time and cost of the conventional wisdom solutions.
There is a lot of merit to a potentially-survivable chute landing approach (assuming one can be developed in time) backed up with landing rockets. Use one or both, as you need, since conditions vary so widely on Mars. If one fails, you have the other. That sort of suspenders-and-belt thinking is what one has to do to ensure crew survival.
GW
The only real merit to my human EDL solution is affordability. Powered multi-person descent vehicles that include contingency provisions for the crew and a fully fueled ascent vehicle are definitely the way to go if funding is available. It isn't and won't be for quite some time to come. I'd rather we focused effort on what we can afford to design and test with today's funding realities rather than pout about what we think we should have. There are still things we can do to ensure that progress is made towards our exploration goal, however slowly. I think economically feasible human and cargo EDL solutions and a real mobile surface exploration capability are a good start.
#8054 Re: Human missions » Laundry » 2015-04-17 18:11:57
I think NASA's fears of artificial gravity date back to the Gemini-Agena docking experiments. They're afraid of killing the crew because of a thruster or motor gone haywire. Back then we had no empirical knowledge of what we were doing because we were doing it for the first time. Times have changed and technology has improved.
I provided a lightweight proposal, relative to the mass of a rotating inflatable, for artificial gravity to permit the crew to spend their rest periods at 1G while simultaneously permitting the use of electric propulsion without the need for constant course corrections or thruster alignment with the direction of travel. Rotating the entire vehicle may be fine for cooking, cleaning, laundry, and other chores, but it means impulsive burns with chemical rockets because we never developed nuclear rockets or continuous thruster alignment with the direction of travel if we're using electric propulsion. From a propulsion standpoint, neither of those solutions are optimal.
One would think that a zero-G washer/dryer would be a higher priority item than an espresso machine, but good coffee's pretty important, too. Personally, I find nasty clothes to be far worse than plain black coffee.
As it pertains to making the unit light enough for space, I would think a titanium drum is the way to go. The number of ounces shaved off an already lightweight unit is unimportant compared to how durable the unit is. If this unit malfunctions during the trip because we decided to be overly clever in how many ounces we saved, it may cause actual problems for the mission.
#8055 Re: Human missions » Laundry » 2015-04-17 12:38:58
What y'all are discussing is developing new technologies and equipment for this deep space trip. Most of this new equipment development could be entirely avoided if you did the deep space mission planning on spin "gravity" from the outset. Then all you need are lightweight versions of the very same equipment and processes we use down here, plus what we already do for short time stints in zero-gee.
There's no way to guarantee artificial gravity.
If you keep the zero-gee intervals fairly short, you can just wait to do your laundry, you can queue up at a few zero-gee toilets, and you can eat camp food. Otherwise, conventional laundry, ordinary sanitary facilities, and conventional free-surface water cooking are the norm while spinning.
Why do things the hard way if you don't have to?
If artificial gravity generation fails, then what? What's the contingency plan?
And there is the "new technology development" effect: if your flight vehicle prove-out program incorporates brand new technology developments as critical items, it is very likely you will never fly. That's been the history of government-funded work for decade upon decade now.
An interplanetary transfer vehicle is new technology, something that's never been built before. The requirements for travel to another planet with a trip duration of months is something that's never been done before. New technology is simply required or we're not going. NASA has stated that repeatedly and it's a valid point. The only question is whether or not what they're doing about it will lead to cost effective solutions delivered in a timely manner.
The history of cost plus contracts let by the government are expensive and poor solutions or lots of money spent with nothing to show for it. You can't put any government contractor on a cost plus contract and expect them not to run up the cost of the contract. If there's no financial incentive for the company to come up with a cost effective solution in a timely manner, expect poor performance.
This is NASA we're talking about, fer cryin out loud. If they can't build a washer/dryer combo that works in zero-G or hire someone who can, they need to be de-funded post-haste.
I'm of the opinion that NASA needs to be responsible for development of CL-ECLSS, clothing, cleaning supplies, and human habitation requirements for space. There's no existing commercial or military application for these technologies. This is simply something that the NASA will have to hire people to develop (something it has already done).
What newcomers to the industry like Spacex and some others are doing is the exception that gives hope, but only as long as they are not fully dependent upon government-funded work. There's something enslaving about that, that kills all major accomplishment potential. We've all seen it.
GW
Dependency on government work for contracts is not enslavement and doesn't guarantee failure. The contractors involved and their government overseers need to have personal integrity and an overriding drive to produce cost effective solutions that actually work. A company making American cheese because Americans want American cheese is not enslavement.
#8056 Re: Planetary transportation » Combining the Rover and Hab - Go RV'ing! » 2015-04-17 01:54:39
KDB512:
I had not thought about inflatable stiffeners for a chute to force it open for low canopy loadings. Intriguing idea. If I understand your idea correctly, you are proposing not a ballute, but something somewhere in-between a ballute and a parachute.
I rather think that if opening can be forced in some way, then a large-enough canopy are might be fitted to a small-enough weight to achieve a survivable landing speed on Mars. That's been a real problem up to now.
I'd caution that you need to be well-subsonic before even attempting such a thing, though. Inflatable structures don't generally do well under supersonic air loads. The exception is real ballutes, but only sometimes.
GW
GW,
I want to use HIAD to bleed as much speed as we reasonably can (I can't think of any reason why HIAD could not reasonably be expected to slow the micro capsule to subsonic speeds), dump HIAD and the service module it's attached to (getting rid of most of the mass of the reentry system), leaving only the capsule and its parachute system. An inflatable ring attached by line to the edges of the canopy would deploy the parachute. The ring would serve two purposes. The first, obviously, is deployment of a parachute that would not otherwise open. The second would be control. By varying the area of the opening between specific sections of the ring and the edges of the canopy by tugging on risers connected midway between the lines that connect the ring to the canopy, it should be possible to steer the capsule towards the landing beacon by increasing the volume of air permitted to flow between a specific portion of the canopy and the ring.
There has to be some way to avoid using rockets for anything other than reentry and attitude control.
#8057 Re: Interplanetary transportation » Super-heavy Space Rocket Project in Russia(Successor to Buran/Energia) » 2015-04-17 01:18:22
This is old news. The Russians have been talking about going to the moon and Mars for decades. So far, apart from the one political aberration that lead America to put men on the moon, all it's been is talk. They've run into the same problems we have. Talking about it is a lot easier than actually doing it. I wish them good luck and hope they're successful.
#8058 Re: Planetary transportation » Combining the Rover and Hab - Go RV'ing! » 2015-04-14 18:27:19
GW,
Is there no possible way to increase the size of the chute and have it deployed successfully?
What about an inflatable stiffeners?
#8059 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-14 18:05:50
UHMWPE becomes brittle at temperatures below -150°C. That's a concern for Earth orbit or interplanetary space, but Mars at night does not get that cold. In fact, the lowest temperature I saw recorded by Mars Global Surveyor for the southern pole was -140°C. And I doubt you would send humans to a Martian pole.
Yeah, interplanetary space is effing cold, so heating elements are required. From my very limited understanding, you don't want the running gear or track anywhere near Tg, especially if the parts are under load. So, heating elements are a requirement.
I was thinking that the tracks should be made from some kind of silicone compound with low Tg, maybe PVMQ.
I nearly forgot about radiation. I have no idea what the effects of radiation on UHMWPE or PVMQ are. I'm guessing it's not good.
So we need running gear and tracks with the following properties:
* Very low glass transition temperature
* Molding in heating elements into the parts
* Resistance to high UV exposure
* Resistance to moderate radiation exposure
All in all, a lot to consider.
It's not advisable to expose UHMWPE to temperatures above 80 to 100°C for long periods of time. But the highest temperature I saw from MGS was +24°C. Some people claim they saw a few degrees above that, but don't expect Mars surface to get above +30°C. Ever. So high temperatures are not a concern. UHMWPE can withstand temperatures on Mars. However, UV is another concern.
High UV exposure and moderate radiation exposure are the biggest questions I would like answered. The physical and chemical properties of the materials are fairly well understood and are suitable for the application I want to use them for here on Earth.
UHMWPE is a marvellous material. Sold under brand names Spectra or Dyneema, these are the core for mountain climbing ropes. I have hoped that it could be used as a tether for spin to produce artificial gravity. Temperatures swings in LEO exceed this materials limits, both high and low. Is it possible to design a sleeve to protect a rope core of UHMWPE? The goal of the sleeve would be to moderate temperature between the extreme heat of direct sunlight, and extreme cold of shade in space. That's two sides of the same rope, and the rope would be rotating so alternately exposed to sunlight or shade. It should be possible. But that's for LEO or interplanetary space. UHMWPE would not have a temperature problem on Mars; UV perhaps, but not temperature.
Maybe something like this would work for your tether and not require thermal conditioning or require less thermal conditioning:
#8060 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-14 03:54:23
As always, too much work to do and not enough time. I will reply in detail in due course. Just a few thoughts to throw into the discussion...
Mars gets colder than anywhere on Earth, litterally cryogenically cold, and it is that cold everywhere at night. This presents some materials problems for a rover, as flexing parts like the chassis cannot be made from ordinary steel. On Earth, we can get around the problem by adding more manganese to steels thereby reducing their brittle transition temperatures, but Mars is far too cold for that.
This is the primary concern I had for the running gear and tracks, the entire vehicle, actually. The extreme cold is the biggest problem. Heating is the obvious solution, but that requires a lot of power.
Austenitic stainless steels would retain their strength, as would aluminium alloys, I'm not sure about marageing steels. Aluminium alloys are undesirable, as they have a finite fatigue life and a chassis will be flexing a lot. An aluminium chassis would need to be designed to minimise bending strain and a rover would need some sort of flight history to ensure a margin of safety. Aluminium alloys could be used in wheels that are not subject to heavy strain. Again, getting around these problems ruins a lot of the weight advantages of aluminium. For obvious reasons, you would not want to use aluminium in vehicle tracks. Stainless steel would do better, but it does not have the strength-weight of some of the stronger non-austenitic steels.
Aluminum alloys were selected for the M113 over the steels available in the 1950'S because the aluminum alloys increased chassis rigidity to the point that reinforcement was no longer required.
Tyres present a design problem, as most polymers would be brittle at Mars night time temperatures. This supports your decision to opt for a tracked vehicle, but it comes at the cost of additional weight. An imperial walker would be good from the point of view of dust contamination, but suffers stability issues, not to mention a lot of complex control issues and moving parts.
The UHMWPE running gear and rubber tracks would require embedded heating elements to survive Martian nights and using compounds with low Tg would be required. I'm also concerned about the increased UV exposure. I'm less concerned about the corrosive salts, but it's something that requires more data to characterize.
Not an easy design project, especially when you consider that breaking down in the middle of nowhere could easily be fatal.
None of this was an issue for the original lunar rovers because their design lives were short and they were only used during the lunar day.
Nothing is easy about Mars. Rovers are no exception.
#8061 Re: Planetary transportation » Combining the Rover and Hab - Go RV'ing! » 2015-04-14 03:26:22
What if you had as part of your descent vehicle something resembling a lunar rover, but with an inflatable operator's cabin? Say a range around 10-50 km? If you land within that distance, you can just motor your way to destination. If that takes a sleep period, you have the inflatable operator's cabin. Sort of a pup-tent-on-wheels. Any merit to that idea?
Well, you could include a mini rover but then you'd increase the weight of the EDL solution you're landing in to something that would definitely require retrorockets. Everyone seems to want to increase the weight of the human EDL solution. Of course that provides more options after EDL, but it also causes as many problems as it solves- problems that are more expensive to design solutions for and far more difficult to properly test.
As to multiple vehicles landed at 1 site, I'd think the min distance would be around 100 m, with a max around 1 km. With too close, you risk damage from rocket blast, and rocket blast-thrown rocks. Too far, and it compromises your everyday operations. The real trouble is using in-situ-produced propellant: you gotta be close enough to drag the hoses. Unless, the propellant is made and stored in the vehicle that is going to use it.
GW
If you don't land with retrorockets, then blast from retrorockets is not a consideration. HIAD + parachute + airbags may ultimately be required for a soft landing in a micro capsule, but that's as complicated as I would want to get for a human EDL solution. As far as landing accuracy is concerned, if you can land within 30km or so of the landing area, then a real rover like a M113/MTVL can reach you in one to three hours. I think it's reasonable to expect a capsule to land within 30km of its target, even a capsule using parachutes. Our landing accuracy is already far better than that.
Rather than exerting yourself and wasting precious oxygen, you're better off relaxing in your capsule or perhaps taking your first steps on Mars and waiting for the retrieval vehicle to come to you. The micro capsule solution includes one or two contingency oxygen bottles and a water bottle, but that's it. Take a nap and wait for the cavalry to arrive. There will be at least two of four MTVL's making their way to you, guided by your team mates from orbit. Robotic MTVL operation using radio beacon homing is available as a backup.
If we're really that concerned about this, the answer is a solid oxide electrolysis unit to make oxygen from Martian CO2. Your micro capsule would then carry solar panels to power the oxygen generation unit and provide heat, rather than carrying extra oxygen bottles.
#8062 Re: Planetary transportation » Combining the Rover and Hab - Go RV'ing! » 2015-04-13 04:07:43
I think it's reasonable for the astronauts to walk up to 1km on the surface of Mars to the habitat, but for any distances over 1km the habitat should really come to you.
The 15t-17t payloads representative of realistic mobile surface exploration mission elements are an intermediate step for initial exploratory missions before we begin continuous surface operations using static habitation modules ranging in mass between 40t and 80t. Think of it as an ADEPT and mobile surface habitat technology demonstrator mission to land something that's useful for surface exploration and provides contingency astronaut retrieval.
In any event, the main selling point for development of mobile habitation elements is not contingency operations, but field science. The exploratory missions need to locate sites with lots of water in the ground that's relatively easy to extract. Once those sites have been found and experimentation conducted to confirm the feasibility of obtaining the water, then we can decide where to land the static habitation modules and how many personnel can be continuously supported using local resources.
Baby steps…
#8063 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-13 00:33:38
Regarding the OT subject matter, all counter arguments up to this point have been that micro capsules are "unsafe" because you can become stranded if you land substantially off-course or that you can't land without retrorockets.
Reality would seem to indicate the following:
1. Absent a fully fueled ascent vehicle any substantially off-course landing has only one possible outcome and it really doesn't matter if you land the crew individually or together. With micro capsules, if something goes wrong, you kill crew members individually rather than collectively. Killing any crew member is really, really bad. Would killing the entire crew be any better? If so, how so?
2. It may or may not be possible to land without retrorockets, but no payload with the mass and parachute diameter I was thinking of has been landed. All landed payloads have been substantially heavier than what I proposed and therefore required retrorockets. Is there any hard data or mathematical model to indicate that landing a 150kg payload without retrorockets is impossible? I would immediately stop arguing the point if there is.
3. A fully fueled ascent vehicle atop the descent vehicle may present an abort option that micro capsules don't provide, but it will definitely not be comparatively inexpensive. Is there any concept or study that indicates that this proposed descent/ascent vehicle will be comparable in terms of cost, and therefore feasibility, to what I proposed?
I think we're all in agreement that Orion and SLS are a colossal waste of time and money that divert much needed funding and engineering effort away from development of hardware that's actually required for space exploration, but these programs have survived two administrations. Is there any reason to think these programs will go away after President Obama leaves office?
I would love to have multi-person descent/ascent vehicles and a Mars base. Even if we could afford multi-person descent/ascent vehicles and the other programs we're currently funding, would there be any funding left for MTV's and CL-ECLSS? We have to have all of the hardware components to execute the mission. Right now, because everyone seems to be stuck in the mud regarding what they really want to have, if only there was funding, we don't have a single piece of the required hardware.
#8064 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-12 23:49:05
SpaceNut,
BAE's proposed hybrid-electric Bradley replacement is an entirely different vehicle from the M113 and MTVL (both of which are real, not proposed, vehicles in service with various North and South American, European, Middle Eastern, and Asian countries). I spoke to a former Army tank platoon commander (served in M1's, M2's, and M113's) about this on my flight from Houston to Atlanta.
The diversion from the OT had to do with the critique about landing a micro capsule off-course and not being able to reach the habitat. If the habitats are mobile and comes to you, then you wait in your capsule after you land for the mobile habitat to arrive or you cache supplies in and around the landing area.
The mobile mission architecture has everything to do with stated surface exploration objectives and keeping payload masses within the launch capability of one F9H. A beneficial side effect of mobile mission architecture is the ability to retrieve astronauts who have landed slightly off-course. Apart from astronaut comfort, one 40t or 80t stationary habitat module is not better than four 15t-17t mobile habitat modules. No matter the architecture, this mission costs too much to abandon because one of anything failed. It's also impossible to quickly (meaning with two or three missions) characterize Martian geology and resources if you're tied to a static or base site. I'm designing this mission as if we're only going to get two or three opportunities.
I see no real benefit to blowing our bankroll on a multi-person EDL vehicle that sees a few minutes of use with each mission, even though those seven minutes are critical to mission success. There's no such thing as simpler or easier when it comes to building it bigger, especially on Mars.
Getting back to the OT, Red Dragon only lands ~2t worth of people and supplies. Its landing capability in the highly variable Martian atmosphere is marginal. From a mathematics standpoint it's actually doable, but you're on thin margins with your propellant. My solution may require a sizable parachute and inflatable decelerator, but the mass of the landed payload (a human) is a more favorable portion of the total mass required for EDL. The only way giving up more mass for EDL makes sense to me is if the descent and ascent vehicle are one and the same.
As previously stated, for various reasons here on Earth any vehicle that goes through reentry is not reusable without substantial refurbishment at highly specialized facilities with sizable work forces that simply don't exist on Mars and won't exist in the immediate future. Obviously HIAD and ADEPT prevent the worst effects of reentry from adversely affecting the vehicle, but actual reuse has never been done.
If you land substantially off-course with any reasonably affordable EDL solution and don't have a mobile habitat or rover, the mission is still over, it just takes a little longer for the astronauts to run out of supplies and die. The alternative scenarios where you don't die if you land substantially off course involve using far more substantial and therefore expensive fully fueled ascent vehicles or landing the astronauts in the habitat module. I think we've come full circle and now we're right back to where we started.
Does everyone here want to wait another decade or so until NASA has funding for a necessarily large and expensive descent/ascent vehicle or an equally large and expensive stationary habitat module or consider comparatively inexpensive mobile habitats, small descent vehicles, and small ascent vehicles so we can afford to develop, test, and launch these mission hardware components? ISS, Orion, and SLS are funding nightmare scenarios that have become reality and aren't likely to go away in the immediate future.
#8065 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-11 16:43:31
If, for whatever reason I can't think of at the moment, it's necessary to severely constrain propellant mass requirements for return to Earth and to reuse the SEP tugs that transfer the rovers and the MTV to Mars, we'd develop an updated PROFAC (PROpulsive Fluid ACcumulator) to separate Ar from CO2 and O2 from CO2 (for use in chemical kick stages with methane imported from Earth).
PROFAC is a space-based nuclear reactor that collects and liquefies the atmosphere from a low orbit, uses a portion for propulsion to counteract gravity and drag losses and stores the rest for transfer to other vehicles.
Mars atmosphere is about ~1.9% Argon. Argon is not as good as Xenon for electric propulsion, but Xenon is insanely expensive and the cost of launching it to Mars is added to that. Once the hardware has been developed and the PROFAC units are in operation in LMO, return propellant for use with SEP is essentially unlimited and the MTV's need not carry the added mass of propellant for return to Earth.
The LOX for chemical kick stages would come from PROFAC, too. Using a VUV laser (presumably a 10MW nuclear reactor can provide power for the laser), you can separate carbon from carbon dioxide.
The chemical kick stages are only necessary if someone is insistent on "getting there fast."
Anyway, just an afterthought for lowering the mission masses and reusing the SEP tugs required to ship all this hardware to Mars.
Some trade studies would have to be conducted to determine how many missions we'd have to execute for the hardware to pay for itself in terms of operational costs.
#8066 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-11 15:40:34
Regarding the internal design and parts replacement schedule for the rovers, each MTVL will have user replaceable subsystems.
After the initial effort to land the fully functional and loaded rovers, subsequent mission will send only parts and crew consumables, rather than entirely new rovers.
Every two years, the band tracks (we want to use these if at all possible because they weigh approximately 45% of what steel M113 tracks weigh and have a much better operational life; the M113 band tracks weigh approximately ~730kg figure around ~810kg for the longer MTVL tracks - provided by Soucy International from Canada), batteries (I presume Tesla lithium ion), running gear (UHMWPE with an ultra-low glass transition temperature - also provided by Soucy International), navigational computer (Apple), radios (Harris or Thales), CL-ECLSS units (NASA), solar panels (ATK), shower (NASA), and toilet (NASA) are replaced.
The band tracks have a design life of ~8000km (a newer design than the design tested by DoD), a ~67% lower rolling resistance compared to steel tracks, and 50% to 70% lower vibration (this is extremely important because prolonged high levels of WBV can cause nausea) compared to steel tracks. Actual DoD testing has shown that the band tracks have a life of ~4700km here on Earth before separation (20% paved roads, 40% gravel, 40% off road; we need to test on 100% crushed granite and/or lava to determine performance on Mars), but we'll assume the tracks only have a 2000km life on Mars. Although not a good analog for Mars, the Soucy band tracks have been used on combat vehicles in Afghanistan.
Every four years, the water tanks, food storage units, and food preparation unit are replaced.
Here on Earth, M113's are in service for decades prior to replacement, but we'll assume an ultimate design life limitation of ten years due to numerous pressurization cycles and exposure to severe temperature changes. Changing a single track takes two people approximately 90 minutes here on earth, which is much longer than for steel tracks, but we'll assume approximately 3 hours on Mars. The first day or two of each subsequent mission is spent refitting and restocking consumables in the rovers and the second or third day is for retest of all critical subsystems using the new components.
Assuming no complete rover failures that strand a particular rover or rovers, each subsequent mission could expect to deliver a single replacement parts kit for four rovers and replacement consumables via two F9H flights. This means that any additional flights budgeted would be devoted to stationary habitat modules, if appropriate for mission objectives, or multi-person ascent/descent vehicles as funding for those technologies becomes available.
#8067 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-11 09:44:58
Interesting thread. I've only read about half of the posts so far and I am not so up to speed on the Mars thing anymore, so forgive me if I say something ignorant. A number of thoughts come to mind based on what I have read:
The pertinent points are:
* Absolute minimum mass EDL solution using single person unpressurized capsules with HIAD + parachutes for EDL
* Four single person ascent vehicles pre-positioned and fueled on Mars using ISRU in a designated launch area (ten kilometers or more away from the landing area)
* Three or four all-electric rovers based on the thoroughly proven MTVL (larger M113 variant) design pre-positioned on Mars
* Two crewed rovers, seating two astronauts apiece, are tele-robotically operated by the remaining crew in the MTV to collect the first two astronauts who land; radio homing beacons and robotic operation are a backup
* One or two robotically controlled rovers as mobile spares (identically equipped to the crewed rovers except for spare parts, a mini-lab for samples analysis, and units to obtain oxygen and water from Mars)
* The unmanned rover or rovers follow the manned rovers in convoy for exploration ops; if a rover fails, for whatever reason, there's a backup traveling with you wherever you happen to be
* ~15t to ~17t landed cargo mass cap, so each MTVL requires a single F9H launch and lands using ADEPT + retrorockets for EDL; the MTVL can actually carry far heavier payloads at lower speeds, if required
* All cargo landed on Mars uses a single F9H (MTVL's, crew supplies and spare parts, experiments)
* Only the Mars Transfer Vehicle requires multiple launches (a manned mission to Mars is a flagship mission, so the insanely expensive SLS may validly be utilized to launch the core module or modules to reduce assembly steps)
1. kbd512 raises some valuable points w.r.t the large redundant masses that might be avoided in repeat lander vehicles by scaling down hotel requirements. However, the use of minimalist lander vehicles with reduced long term life support imposes specific limitations on the use of those vehicles (i.e. landing in vicinity of a well-stocked, manned base). It also imposes additional risks, as the crew are in grave peril if they fail to do so. I would point out that there are risk analysis tools that allow engineers to balance risks against cost. This can in turn be used to determine a required minimal survival time for the vehicle in order to reach tolerable risk. If you are delivering to a manned base, then people can presumably reach you within a week, even if you land 1000km from the base. On the other hand, reduced hotel capabilities may prevent using the vehicle being used to reach another part of the planet to carry survey missions or a rescue. All of these things would have to be brought into a cost-benefit analysis.
If you are completely mobile on Mars, you don't have to worry about how far you landed from a stationary habitat module. If a habitat module becomes uninhabitable or you can't reach it to begin with, you have a serious problem. Each MTVL is laden with approximately half of the supplies required to sustain the explorers for a 500 day surface stay (the number I used when I calculated how much food, water, and oxygen was required).
This architecture is not about better survivability, that's just a welcome benefit that comes from layers of redundancy, it's about better mobility and having a real capability to explore. The MTVL is your home, not a large stationary habitat module that virtually guarantees you'll never explore very far from home.
2. The use of regional resupply dumps for rovers is a good idea in my opinion. It allows the range of surface exploration to be extended without the mass requirements of an entirely new Mars Direct mission. The supply station merely needs to contain additional fuel, food, water and maybe some spare parts for a rover. Landing mass might not be much more than a tonne, with a small solar powered Sabatier reactor making fuel and water.
Then you have to travel to the supply dump for resupply, rather than carrying supplies and spares with you in additional rovers. What's better in the Sahara, having a supply dump 100 kilometers away or another fully functional vehicle in your convoy? The rovers don't use fuel, so no fuel is required. The all-electric rovers would need spare batteries, solar panels, and running gear. No Sabatier reactor or nuclear reactor is required, either, except at the ascent vehicle launch sites.
3. If such architecture is workable from a risk point of view, then the Mars Direct architecture should be abandoned. It would appear more economical to focus all manned landings at a specific point on the planet starting with the first mission and use long range rovers to explore the entire planet from that point. That way, you don’t need to deliver a new hab to the planet for every new mission and you can use that additional payload to ship out valuable equipment, which could extend the capabilities of the base. Establishing a single base from day 1 has a lot of advantages in terms of concentrating resources. In that case, you would want to choose a site for which it is easy to achieve a landing, relatively close to the equator and low altitude. Isidis and Chryse Planitia appear to provide a good balance for these requirements.
With a completely mobile architecture, we're not tied to a specific point on the surface. That means we could just as easily land our ascent vehicles and rovers on the other side of the planet for subsequent missions. The entire problem with using stationary habitats is what it costs to land it on Mars. It's a launch vehicle economics problem. You would need a minimum of two F9H launches to land one 40t habitat module. You land 6t more of supplies/habitat with two F9H launches, but your cost doubles and you don't get double your initial capability with that second launch, as most of the mass of the second launch is for EDL equipment.
4. If reusable landing vehicles are developed, then it also makes sense to develop a reusable Earth-Mars solar electric transfer vehicle. Only humans strictly need to return to Earth, so my suspicion is that the transfer vehicle would be dedicated to human transport, plus a few rock samples on the return trips. Cargo delivery will probably be carried out using direct throw heavy lift vehicles for some time to come, which only need to travel in one direction.
My MTV proposal uses SEP. The MTV is assembled and loaded with supplies in LEO at ISS, robotically transferred to L1, the crew use Dragon and F9 or F9H to transfer to the MTV, and the crew departs for Mars from L1.
There's no such thing as a reusable lander. Once reentry is performed, refurbishment is required. This requires facilities and transportation infrastructure to accomplish that is not present on Mars.
Cargo delivery from direct throw severely limits payload. Therefore, I am using the same SEP tug being developed for ARM in my mission architecture.
#8068 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-11 01:30:34
Imperial ton of 2,240 lbs. or 1,000 kilograms is equivalent to approximately 2,204.6 pounds, 1.10 tons US long
Problem one for mars temperature which even if it could have the oxygen to allow the diesel to work would gel and clog in the tank.... 12.3 tons or 12.1 long ton... as compared to the MOLAB 8200 pounds or 3.72 tons and needs no extra oxygen to run.....Sure it has some things to change but its not massive beyond the small envolope profile which is what we wanted.
Also the tracks would be torn up in no time with mars jagged rocks and temperatures....much like the tires would and even the rims that we have on mars at current will not be good enough either for any rover for a crew In my mind...
The capacity for crew passenger while nice as you would want it filled with supplies but we are already to heavy to even land...
I agree that a thick shell is of importance but we can go overboard.
I understand tried and true for dependability but its still got to make the grade for use and on mars it does not....nor does the molab....
SpaceNut,
Please read what I proposed. I did not propose using diesel powered M113's on Mars. In fact, there is no internal combustion engine anywhere in my proposal. I proposed using all-electric MTVL's (the MTVL is a longer M113 produced by BAE with six versus five road wheels and 20% more internal volume). When you take all the heavy stuff out of the MTVL that has no use on Mars (equipment removal includes the diesel engine and transmission, top hatches, heavy weapons ring and turret, glacis plate, and steel tracks), you have a much lighter and more capacious vehicle.
My MTVL proposal is solar-powered. The vehicle would have two 30kW electric motors and a top speed not to exceed 32kph (20mph for us Americans) on Mars.
MTVL has multiple track options, ranging from rubber band tracks (requires a synthetic compound with a low glass transition temperature, as explained in previous posts), aluminum, and steel. Steel will not be "cut up" by the rocks on Mars. However, I think a particular compound with a very low glass transition temperature (developed by Dow IIRC) will permit use of lighter weight rubber band tracks.
The tires/rims on the Mars rovers are the dinkiest things imaginable that can still support the weight of the vehicle. Military vehicles routinely see abuse that NASA wouldn't dream of putting a rover through. Trust me, the tracks will be fine.
This is a cutaway of a hybrid electric MTVL interior (hybrid electric MTVL's with much more powerful electric motors and lead acid batteries have been built and tested):
http://www.combatreform.org/mtvlHEDtroopsinside.jpg
Using ADEPT + retrorockets and a SEP tug for orbital transfer (the SEP tug is a current development item for ARM), which is exactly what I prosed, we're not too heavy to land. I calculated the weight of the MTVL to be around ~15t fully loaded, but that weight could grow to ~17t and not present an issue with respect to mailing it to Mars with a single F9H flight. The SEP tug is around ~8t. That leaves ~25t for ADEPT and retro-propulsion mass with a ~3t margin.
Internally, the two crewed MTVL's would carry two astronauts, two navigational computers, two radios, two water storage units, two CL-ECLSS units, two food storage units, two mechanical counter-pressure suits, two hookah hoses for use while repairing the vehicle's running gear, two hammocks and blankets for nap time, one mini sit-down shower enclosure, one mini washer/dryer unit, one tool kit for field repairs, one medical kit, and one user's manual.
It might make sense to have a hatch separate the driver's compartment from the main compartment so that the driver does not have to don a suit while his or her partner performs an EVA.
Externally, the two crewed MTVL's would have two solar panels for recharging the batteries, two omni-directional antenna for the radios, a complete set of running lights (the vehicles are traveling in a convoy), and one spotlight for signaling and exploration of dark places (like lava tubes).
Internally, the two robotic MTVL's would carry two navigational computers, two radios, two water storage units, two CL-ECLSS units, two food storage units, two additional mechanical counter-pressure suits - one for each astronaut, two hookah hoses, one mini sit-down shower enclosure, one mini washer/dryer unit, spare rover batteries and electrical parts, one LOX generation unit for replenishment of the manned rovers, one mini-lab for samples analysis, one medical kit, and one user's manual.
Externally, the two robotic MTVL's would have two solar panels for recharging the batteries, two omni-directional antenna for the radios, and one unit for obtaining water from the Martian soil for water replenishment of the manned rovers.
My MTVL design puts the user replaceable batteries in the main compartment on the floor of the vehicle. The water bladders and food storage units are side-by-side over the tracks. The mini washer/dryer unit, mini shower, and kitchen are against the driver's compartment bulkhead. The suits and clothing are stowed near the exit hatch at the rear of the vehicle. One ECLSS unit is in the driver's compartment and the other is in the main compartment. The latrine is near the exit opposite where the suits are stowed. This arrangement leaves an open area in the main compartment so that the astronauts can move about without bumping into each other and hang their hammocks.
In short, my proposal ensures that our four Martians remain mobile in vehicles that are substantial enough to survive and small enough to transport using a single F9H flight. I'm not sure how much more detailed I can get before we start going through design processes.
#8069 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-10 12:16:07
Your exploration mission is a demand for on-going copious quantities of cash. As long as you demand that, you get nothing. To use your words: "ain't gonna happen."
Rob,
NASA has been supplied with ongoing copious quantities of cash for many, many years now. In fact, we've been at Apollo program levels of funding for many years now. It's been more than four decades since we've left low earth orbit. Sooner or later, someone's going to want something to show for all that money spent. Wouldn't it be better if NASA could say, "Mr. President, we have interplanetary transfer vehicles, landers, rovers to explore the surface of other planets with, and we use affordable rockets to launch it all." This would be in direct opposition to "Mr. President, we don't have manned space flight capability because our spacecraft costs too much to develop and we have a rocket we can't afford to launch it on."
Why do you think that development of things that we don't have money to develop, much less operate, is better than development of things we could actually afford?
If a single person lander is too expensive to develop, why would a multi-person lander cost any less?
If using armored personnel carriers that have been manufactured continuously for more than fifty years for surface exploration is too expensive, would development of a rover from scratch cost any less?
If using ISS modules or SLS tanks for a MTV is too expensive, are there other proposals that would actually cost less?
Everything I've proposed, apart from the landers, is reusable. Here on Earth, there's no such thing as reusability after reentry. There are spacecraft that are reused after months of refurbishment work in facilities employing hundreds of workers, but nothing amounting to actual reusability.
I don't understand your logic. Please elaborate.
#8070 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-10 11:39:28
If you don't build anything, then as soon as some politician wants to spend money on something else, probably on Earth, they'll cancel the Mars stuff. What you are describing is the next flags-and-footprints that will be cancelled as fast as Apollo.
Rob,
In all probability, there's a 1% or less chance of colonizing Mars within our lifetime and that's being overly optimistic. That'd be math speak for "ain't gonna happen."
However, we could, if we decided to, affordably put humans on Mars using the architecture I've outlined. All the science and technology development directed towards that effort doesn't have to completely disappear if NASA decides to maintain it rather than abandoning it as has been the case with the lunar program technology. There's a golden opportunity here to set sail for a new world. All that's required for that to come to fruition is for a decision to be made.
I don't think going to the moon was a mistake.
I don't think going back to the moon would be a mistake.
I don't think going to Mars would be a mistake.
I think trying to develop an unaffordable mission architecture would guarantee that we don't go anywhere within our lifetime and therefore would be a mistake.
The general public perception and the perception of politicians is that NASA is a special interest group and/or jobs program for intellectuals. They're not intelligent enough to make the connection between what NASA does and how it improves everyday life here on Earth and they never will make that connection. The spending is tolerated because it's tolerable.
Do we want to continue to dream about what could be if only the government rained down funding on NASA or develop a mission architecture that's affordable, in terms of both development and operations, with the existing budget?
From my perspective, not going because we can't have everything we really want seems more like a tantrum rather than the behavior of reasonable adults who work with what they're given to work with and make the best of what they have.
A handful of real manned missions with an affordable architecture is about as good as it's going to get.
#8071 Re: Human missions » Historical: 1965 Mars Flyby CSM » 2015-04-10 11:16:10
What was their plan for dealing with solar flares? Looping out to the asteroid belt? That's slightly insane, but that was probably normal in 1965.
#8072 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-10 10:55:54
We're going to Mars to establish the first off-world human settlement. That means building a home. Construction requires industry to mine and refine materials, to machine and manufacture parts. That starts as a workshop, and grows. And feeding settlers requires some sort of farm, most likely a greenhouse.
NASA's charter is to explore. I have no problem with them investigating technologies for colonization but NASA is a space exploration agency, not a space colonization agency.
SpaceX and others can concern themselves with the colonization of Mars. NASA desperately needs to develop a coherent development program to get there. Everything that Dr. Zubrin said about how you plan a mission is spot on. You first decide where you want to go and what you want to do. Then, you build the technology to achieve those goals. Giving people something to do is not a plan for space exploration, it's a plan to keep people busy. We could easily keep people busy developing the technologies that take us where we want to go so that we can do what we say we want to do.
Development of low cost descent/ascent vehicles and mobile surface exploration architecture is all about economic feasibility and getting the greatest science returns. We can't do the missions we say we want to do if we can't afford the vehicles to go where we want to go or if we intentionally make the explorers dependent upon a fixed site for operations.
If you take into account what's most affordable and therefore doable with reality based budgets to develop hardware in support of mission objectives, you'll see a running theme throughout everything I've proposed.
* F9H for launch services, whenever possible- Using the most affordable existing rocket to send hardware to Mars
* SLS tank and/or ISS module to construct the MTV- A proposal to use existing hardware for transit to/from Mars
* Single person landers- A proposal for using existing and demonstrated EDL technology to land humans on Mars
* M113 variants as rovers- Using existing, durable, and thoroughly demonstrated vehicles for mobility on Mars
I've intentionally set the technology development bar very low so that money can be directed to the handful of technologies that make all future long duration space exploration missions possible, namely closed loop life support, artificial gravity, and active radiation shielding.
If any part of a mission architecture is not affordable with respect to the overall budget, we simply won't do the mission. Each successive program for manned space exploration has been increasingly unaffordable. The giant multi-person descent/ascent vehicles (ERV's), giant space capsules (Orion), and giant rockets (SLS) are all unaffordable within existing budgets.
The maximum payload mass I want to land on Mars is around ~15t. All other plans call for landing payloads between ~40t and ~80t. There may be absolutely no difference in technology required to land ~80t, as opposed to ~15t, but one payload requires a single launch of the most affordable rocket we have, which is still $100M to $150M per flight, whereas the ~80t payload would require at least two flights. How many missions could we realistically afford if simply landing a habitat module cost more than a quarter billion dollars? No advanced mathematics are required to figure this out.
Part of my strategy is to establish a permanent human base on Mars, and park at ISS a reusable interplanetary spacecraft. Politicians will have difficulty not using them. If they do cancel all Mars efforts, then it becomes easy for a commercial like SpaceX to use them.
As far as a commercial enterprise coming in and operating mission hardware built by other companies for NASA, that's unlikely to say the least. SpaceX has its own hardware development plans for Mars colonization. That's a good thing because SpaceX could never afford to operate the way NASA does.
#8073 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-09 20:55:33
The reason for not establishing a base with the first missions is simple. We're going to Mars to explore and to determine where the resources are. You only tend to do that when you're mission architecture is mobile. Any mission architecture that uses immobile habitat modules tends to have operations centered around that fixed site. That's the exact opposite of what we need if we truly intend to explore.
The only fixed site in my architecture is a designated launch area for four single person ascent vehicles, each vehicle separated by a few kilometers or so, for return to the MTV in LMO. My contention is that my MTV concept is suitable for deep space transit whereas small capsule ERV designs are not. My MTV concept has triple redundant power, life support, avionics, active radiation shielding, distribution of consumables amongst the three MTV modules, and artificial gravity. I think the most hazardous part of the mission, apart from ascent/descent from Earth and Mars, is the transit to/from Mars. Skimping on mass for the return to Earth makes no sense whatsoever. If anything goes wrong in transit, there is literally nowhere for the crew to escape to.
#8074 Re: Human missions » Smallest Human Ascent or Descent Lander for Mars Or Earth » 2015-04-09 20:10:37
SpaceNut,
Molab is far higher off the ground than the M113. The prototype shown is not reflective of the actual model NASA intended to use on the moon. Molab, like all NASA specials, uses giant wheels with little contact with the ground and a paper thin pressure vessel. Look at how much contact the M113 has and how thick the hull is. I would also like to point out that the variants you posted have five road wheels and are shorter than the MTVL, which has six road wheels and more internal space for cargo. The M113 weighs substantially more than MOLAB because it's more durable.
I found a photo that better illustrates NASA's MOLAB concept:
NASA recently revived the idea of putting a cylindrical habitat module on wheels. Dr. Zubrin proposed the "The War of the Worlds" thing years ago. What can I say? Some people really like wasting time and money.
#8075 Re: Human missions » Nasa Shuttle, ISS Woes & To-Mars » 2015-04-09 19:29:09
We're always kicking the can down the road to Mars. It's a favorite pastime of the President, Congress, and NASA.
We may eventually put humans on Mars, but it will probably be in spite of the President, Congress, and NASA, not because of them.
Nobody in charge at NASA is interested in actual space exploration. I can't believe I just said that. It's sad.
We live in a strange new world where corporate execs are more interested in spending their own money to explore other worlds than our own government sponsored agency specifically created for that purpose is.