Light weight rover for Mars

RobertDyck · 2016-03-01 10:57:49

kbd512 wrote:

Assuming the new cobalt electrode technology for lithium ion batteries delivers the expected energy density increase to 2.5kWh/kg, then I think 2 20kWh batteries would be sufficient with 4 .5kW to 2.5kW motors that are 85% to 90% efficient. The cobalt electrode batteries are reported to charge significantly faster than current technology, too, and resolve electrode corrosion issues.

Batteries from Lithium Technology Corporation, the American division of the Germany company GAIA Akkumulatorenwerke GmbH. These are the batteries I had recommended for the PLSS backpack of the EMU spacesuit.
Cells - 7.5 Ah, 27 Ah, 45 Ah, 55 Ah
PDF file of the 27 Ah cell, the EMU needs 6 of these cells connected in series: HP 601300 NCA

Positive anode made of Lithium nickel cobalt oxide, negative anode is graphite. Specific energy is 99 Wh/kg.

So this already is a lithium ion battery with cobalt electrode. Two of their older cells are further down that same page, they use Lithium iron phosphate for the positive anode, specific energy is 84 Wh/kg.

The new ones have operating temperature -30°C...+60°C, and charge temperature 0°C...+40°C. Older cells had operating temperature that only went down to -20°C, and required 0°C to charge. Mars Exploration Rovers (Spirit and Opportunity) kept its warm electronic box in that temperature range for that reason. New battery cells can handle colder temperature (and hotter).

kbd512 · 2016-03-01 13:55:12

Rob,

The company working on the battery technology I referred to earlier is based in Japan and they're working on battery technology specifically for EV's.

new-rechargeable-cell-has-7x-higher

SpaceNut · 2016-03-01 18:02:26

Well this is a truck as proposed for the moon but it looks adaptable for Mars.

cIclops wrote:

Chariot - lunar truck prototype
In preparation for the US led effort to build a lunar outpost, NASA has completed the first lunar truck prototype, named Chariot. Realizing the importance of crew and payload mobility on the lunar surface, the Exploration Technology Development Program's Human-Robotics Systems Project set out, in Apollo-like style, to build a lunar truck and the team that could shepherd future lunar truck efforts. With only one year to design, manufacture, and assemble Chariot, NASA, teamed with companies from all across America, conquered the challenge.
Key Design Specifications:
Chariot Spec .... Earth Prototype (1g) ... Lunar System (1/6g)

Payload .............. 1000 kg ..................... 3000-6000 kg
Vehicle Mass ....... 2000 kg ..................... 1000 kg
Top Speed .......... 20 KPH ...................... 20 KPH
Slope Climbing .... 15 Deg ...................... 25 deg
Range ................. 25 Km ....................... 100 Km
Animation showing Chariot excavating a site for a nuclear power unit (video 5MB)

SpaceNut · 2016-03-01 20:07:43

kbd512 what you have proposed is what Nasa is terming the small pressurized rover simular to the one with this exploratory document for the moon from the constellation efforts. In this document there is the comparison of what the lunar rover could do for exploration and what we could do for exploration with a small pressurized rover.

http://images.spaceref.com/news/2007/AI … E.2007.pdf

RobertDyck · 2016-03-01 23:10:48

I've seen work on NASA's small pressurized rover. The design has a number of features that bug me. For one, wheel suspension is overly elaborate. Just look at the image above, post #28. Now compare to the Apollo Lunar rover. Why so much complication and mass? More moving parts, more things to break. And more things to get clogged with fines. Remember, Apollo found their suits got coated with Lunar fines. The zipper that closed the pressure seal in the back of an Apollo A7L suit got clogged. How long before that suspension gets clogged? Sojourner, Spirit, Opportunity, and Curiosity used 6-wheel boggy suspension, and it worked. This looks a lot more complicated.

For another, it has suitports. That only works with air-bag hard suits. A suit compatible with suitport requires a hard thorax, and PLSS designed to open into the suitport. So forget MCP suits.

And life support for their small pressurized rover is spacesuit PLSS. When did they start saying that? That's my idea. I made a presentation at the 2005 Mars Society convention about space inflatables. One slide was a space "Pup tent". I described a cylinder with hemisphere ends, 2 metres long and 1 metre diameter. Or a dome tent 2 metres diameter, 1 meter head room. With 85cm diameter ring door seal, which could twist to half diameter for storage, like a child's pop-up tent. O2 and CO2 control by suit PLSS with sublimator turned off. If the suit is MCP, the PLSS wouldn't have a sublimator. 4-mil air mattress, pressurized and tufted. 1-mil interior layers suspended (spaced) by threads. "Muffin fan” to circulate air from air mattress bottom to top, controlled by thermostat to dissipate heat into ground, powered by PLSS battery.

If you want a small, light rover with life support provided by spacesuit PLSS, then just use an open rover and carry a dome tent.

Another point is the cab for this small pressurized rover is designed to be common with zero-G vehicle for an asteroid mission. And designed as the cab for a Mars lander. In every case, the cab is unnecessarily heavy, yet too small for effective living space. This attempt to design one module that is used for everything results in non-optimal design for everything.

kbd512 · 2016-03-02 04:45:20

RobertDyck wrote:

I've seen work on NASA's small pressurized rover. The design has a number of features that bug me. For one, wheel suspension is overly elaborate. Just look at the image above, post #28. Now compare to the Apollo Lunar rover. Why so much complication and mass? More moving parts, more things to break. And more things to get clogged with fines. Remember, Apollo found their suits got coated with Lunar fines. The zipper that closed the pressure seal in the back of an Apollo A7L suit got clogged. How long before that suspension gets clogged? Sojourner, Spirit, Opportunity, and Curiosity used 6-wheel boggy suspension, and it worked. This looks a lot more complicated.

It's overly-complicated because JSC's engineers wanted to demonstrate how sophisticated their rover design was, rather than how practical their rover design was. According to NASA's website, those engineers threw out some traditional assumptions about what a vehicle needs. It looks like simplicity of design was also thrown out. The Chariot rotates the astronaut and all wheels so the astronauts can see where they're going because the Apollo astronauts couldn't see where they were going when driving in reverse. Apparently nobody thought a mirror would ever be useful for a car driven on the moon. Today and we have backup cameras, too. Nope, that's too easy. The solution must be to turn all the wheels of the vehicle around and the people riding in the vehicle. Maybe they hand out prizes at JSC for the most complicated and expensive solutions to simple problems.

My rover is a composite storage container, nothing more than a glorified tupperware box with wheels attached to it, and an air bag lashed to the top of it. It has four wheels attached to an articulating suspension for packaging, to provide a wider wheel base to inhibit rollover, and simplicity - similar to a Baja race truck but without the excessive weight, power, and noise. It's intended to travel at moderate speed, rather than walking speed, on Mars. No special features not actually required for Mars surface exploration will be included. No MMOD or SPE protection is required, no matter what your NASA engineer acquaintance thinks. It's made from composites and fabrics primarily to reduce weight, but has the added benefit of not enhancing GCR effects in the way that a thin aluminum can would.

The phrase "light weight" really ought to be given more consideration. Their light rover concept weighs almost as much as my rover does fully loaded. If a rover weighs as much as a small bus, is it still "light weight"?

RobertDyck wrote:

For another, it has suitports. That only works with air-bag hard suits. A suit compatible with suitport requires a hard thorax, and PLSS designed to open into the suitport. So forget MCP suits.

You're preaching to the choir.

RobertDyck wrote:

And life support for their small pressurized rover is spacesuit PLSS. When did they start saying that? That's my idea. I made a presentation at the 2005 Mars Society convention about space inflatables. One slide was a space "Pup tent". I described a cylinder with hemisphere ends, 2 metres long and 1 metre diameter. Or a dome tent 2 metres diameter, 1 meter head room. With 85cm diameter ring door seal, which could twist to half diameter for storage, like a child's pop-up tent. O2 and CO2 control by suit PLSS with sublimator turned off. If the suit is MCP, the PLSS wouldn't have a sublimator. 4-mil air mattress, pressurized and tufted. 1-mil interior layers suspended (spaced) by threads. "Muffin fan” to circulate air from air mattress bottom to top, controlled by thermostat to dissipate heat into ground, powered by PLSS battery.
If you want a small, light rover with life support provided by spacesuit PLSS, then just use an open rover and carry a dome tent.

They included the pressurized tent, too. It was in the presentation that SpaceNut provided.

RobertDyck wrote:

Another point is the cab for this small pressurized rover is designed to be common with zero-G vehicle for an asteroid mission. And designed as the cab for a Mars lander. In every case, the cab is unnecessarily heavy, yet too small for effective living space. This attempt to design one module that is used for everything results in non-optimal design for everything.

Yep.

Last edited by kbd512 (2016-03-02 09:13:33)

SpaceNut · 2016-03-02 20:08:31

RobertDyck wrote:

I've seen work on NASA's small pressurized rover. The design has a number of features that bug me. For one, wheel suspension is overly elaborate. Just look at the image above, post #28.

kbd512 wrote:

It's overly-complicated because JSC's engineers wanted to demonstrate how sophisticated their rover design was, rather than how practical their rover design was. According to NASA's website, those engineers threw out some traditional assumptions about what a vehicle needs.

Well the other mover is Athlete.... which is just as complicated.

You are right that maybe the "phrase "light weight" really" is the wrong term to class a rover by but then again mass without some other length and height as well does not say much. Sure we know these if we call it a bus but then again a rover for mars or the moon would be nothing like a bus once modified for the end use.

GW Johnson · 2016-03-03 10:14:26

Y'all are correct to refer to the depicted designs as busses. Like tanks, when a thing gets too big, you cannot successfully run it off-road. There are as yet no paved highways on Mars.

Why not build an open 4-wheeler like the lunar rover, but with 4-6 seats (that depends on intended surface crew size), so a little bit larger than the lunar rover, but only a little bit larger. Simple battery electric propulsion, just like the lunar rover. At worst, 6 wheels like the robot rovers that have been successful. I'd use knobby rubber off-road tires and apply electric heat to the rims to keep the tires from getting too cold.

Bring a powered jack and some spares, too. You'll need them: those rocks are very sharp. Drag metal through rocks, and eventually the rocks always win. You need resilience and "give" to your wheels to cope with that. (Better think about changing tires in your spacesuit design, too!) This is months on the surface, not a day or three like on the moon. You will have a flat to fix.

Here's an idea: add a string of trailers to fit the task at hand. One trailer might have a pressurized inflatable "tent" and life support supplies exceeding the rover range by a wide margin. Another might have fuel cell supplies and solar panels, a mixed-source power trailer for extended-range operation. The third might be a portable drill rig for deep-drilling. And so forth. Pull one or all of them when you need them, don't hitch 'em up when you don't.

You'll need the power in the rover to pull trailers off-road through the rocks and dirt. It will be slow going, very much like a farm tractor, with low and really-low gears. Designing mission objectives and plans for 30+ km/hr speeds is utter nonsense. Much of Mars is way too rough for that.

Smaller, simpler, lighter, and way-to-hell-and-gone more versatile that modular way with a tractor and a selection of trailers. That last (versatility) is really the most important advantage, after all, because history teaches we will encounter the unexpected / unanticipated.

Going modular, splitting off different functions into various add-on trailers, sure beats trying to design everything imaginable into one single item.

GW

RobertDyck · 2016-03-03 13:34:23

Here is a video of a NASA proposed exploration architecture: Mars Exploration Zones
Technical note: Position the tip of your mouse pointer over coloured text, then click the left button of your mouse. That will take you to the linked page. In this case the page is a YouTube video. There's a bar along the bottom showing video progress, a red ball showing current position, and the bar to the left of the red ball is also red. Beneath the bar is numbers, for example 0:00 / 6:51. That means the current position in the video is "0:00" and video length is "6:51". Use your mouse to drag the red ball until the first number says "2:00".

The lander is shown 2:00 (2 minutes and zero seconds) into the video. The rover is also shown, similar to the small pressurized rover, but extended rear so you can't call it "small". The lander has 3 small pressure modules on a platform, with a crane to drop them to the ground. Instead of one large pressurized habitat with landing legs to land itself. Again, overly complicated, and small living space.

GW Johnson · 2016-03-03 14:17:22

Well, as the titles up front on the NASA animation explicitly say, that's a big base decades after the first mission, after dozens of earlier missions. Nothing like what's on that movie will go on that first small exploration party.

Myself, I have great difficulty believing NASA (or any other agency anywhere on the planet) will send more than one small exploration party to Mars, if that. Essentially 0% of politicians want to spend the money to do it.

The surface rover for that first landing will be only a bit bigger than the old lunar rover. If they're smart at NASA (I see no evidence of that yet) it'll pull trailers as needed. The ascent vehicle will likely also be the surface habitat. They'll have to solve the problem of pinpoint reliable landings, or else send everything down in one huge landing boat that is also (at least in part) the ascent vehicle.

The manned transit vehicle will have to stay in orbit and serve both ways. It had better spin for gravity, or they will end up killing their crew. They'd also better do something about a solar flare shelter, or it is very likely they will kill their crew. It really is that simple, and yet it really is that hard to do right.

I just posted some bounding-analysis calculations for spin gravity over at http://exrocketman.blogspot.com. You do not need any of that giant spinning wheel, truss-connected, or cable-connected nonsense, for a well-trained crew tolerating 8 rpm. The numbers are quite clear. It's the latest post, "Effects of Microgravity Demand Artificial Gravity", dated 3-3-16. It only deals with the gravity issue.

GW

kbd512 · 2016-03-03 14:26:19

SpaceNut wrote:

Well the other mover is Athlete.... which is just as complicated.
http://www-robotics.jpl.nasa.gov/images … er-590.jpg

Unlike NASA, I'm not interested in trying to move a building around another planet. To start with, the objects NASA wants to move using ATHLETE weighs more than what any reasonably cost effective rocket can deliver. If that wasn't enough to kill the idea, I would think the problem of supplying enough power to make ATHLETE practical would. If the first two problems are dealt with, there are mechanical issues inherent to soft landing a two story building sitting on a two piece detachable wheeled robot that is in turn sitting on a gas can as high as a one or two story building.

Surely a four wheeler with a loaded weight equivalent to a light truck is simpler and easier to construct and test than Chariot or ATHLETE. There are a couple types of movement that these robots can use that my four wheeler can't, but how practical and useful are those features?

Why are no vehicles like Chariot or Athlete in use here on Earth? Could it be that such vehicles are simply impractical?

Chariot's chassis and drive train are a perfect example of needless complexity driven by an attempt to use enough wheels to overcome ground pressure limitations that tracked vehicles easily overcome. If a vehicle carrying any significant payload must operate in rough terrain, tracks are better than wheels. This has been proven so thoroughly that there's no mathematical argument for using wheels for an off-road vehicle carrying a payload of any substantial mass. A tracked vehicle will have equal or better practical mobility, generally substantially better, when compared with a wheeled vehicle of equal weight in a rocky mountainous desert.

SpaceNut wrote:

You are right that maybe the "phrase "light weight" really" is the wrong term to class a rover by but then again mass without some other length and height as well does not say much. Sure we know these if we call it a bus but then again a rover for mars or the moon would be nothing like a bus once modified for the end use.

To the best of my knowledge, a light pressurized rover with any significant range will have a mass equivalent to a light truck here on Earth. Even if power generation, locomotive, and life support systems essentially weigh nothing, which will not be the case in our lifetimes, the food and water that have to be carried by the vehicle to provide sustenance for its crew will ensure that this is the minimum practical weight for such a vehicle.

I have to admit that I'd not given my light rover concept nearly as much thought as my heavy rover concept, mostly because tracked vehicles like the MTVL can carry more of everything required to sustain life and are better vehicles for general off-road mobility and long term durability.

Now that I've thought about this quite a bit more, I think light wheeled rovers are all that NASA can realistically afford to send to Mars with all the other competing technology development programs required to complete the mission. Mars bases built with heavy habitat modules emplaced by sophisticated robots like ATHLETE will have to wait for funding availability.

More importantly, there's only so much exploration that will be done if the astronauts are tethered to a base. If each astronaut has their own rover to drive around in, a lot more exploration will be done because the base that the astronauts are tethered to is a vehicle with substantial mobility. Even with a light solar powered vehicle that can only travel at 25kph for 8 hours a day, with three days of every week designated as travel days during a nominal 71 week surface stay, that's 42,600km worth of travel. So you can ring the planet twice with these light rovers, even with solar power. Even if travel is at half that speed, it's still possible to ring the planet.

GW Johnson · 2016-03-03 15:47:17

There are ground pressure load limits even for track-laying vehicles. These have been known reasonably well since the end of WW2, and repeatedly confirmed by unsuccessful attempts to exceed them ever since. Please excuse the US customary units, but the last time I did any soil mechanics, those were the units I used.

Upper-limit practical tank: about 60 tons of weight (not mass). Typical tread dimensions for a 60 ton tank: about 2 feet wide and 25 feet long in ground contact; two (L & R) for 100 sq.ft of contact area. Ground pressure: about 120,000 lb/100 ft^2 = 1200 lb/ft^2. And that's for hardpan clay or stronger. Cut that to 600 psf for soft moist topsoil, or to about 300 psf for mud or for soft shifting sand.

I like track-laying vehicles for off-road use. But be aware that there is a lot of soft, shifting sand on Mars. Stay under 300 psf contact pressure (based on weight/area) with your proposed designs. That's equivalent to about 1/7th of an atmosphere (2116 psf), or about 14 KPa. Square-cube scaling says such vehicles "can only be so big".

It's easier to fix a flat tire in a spacesuit than it is to change-out a damaged tread link in a spacesuit. The closest suit design to anything practical for this would be MCP. Just something else to think about besides ground pressure limits.

GW

kbd512 · 2016-03-04 01:18:46

GW Johnson wrote:

Y'all are correct to refer to the depicted designs as busses. Like tanks, when a thing gets too big, you cannot successfully run it off-road. There are as yet no paved highways on Mars.

Agreed.

GW Johnson wrote:

Why not build an open 4-wheeler like the lunar rover, but with 4-6 seats (that depends on intended surface crew size), so a little bit larger than the lunar rover, but only a little bit larger. Simple battery electric propulsion, just like the lunar rover. At worst, 6 wheels like the robot rovers that have been successful. I'd use knobby rubber off-road tires and apply electric heat to the rims to keep the tires from getting too cold.

The unpressurized rover provides no operational advantages over a light pressurized rover. Are you going to travel inside a deployed tent atop an unpressurized rover or trailer or wear your space suit 12 hours a day? I could be wrong, but that doesn't seem very practical to me. With respect to heating the rubber wheels, that was my first thought. What are the power requirements to do that?

GW Johnson wrote:

Bring a powered jack and some spares, too. You'll need them: those rocks are very sharp. Drag metal through rocks, and eventually the rocks always win. You need resilience and "give" to your wheels to cope with that. (Better think about changing tires in your spacesuit design, too!) This is months on the surface, not a day or three like on the moon. You will have a flat to fix.

The only power tool on my light rover design is a drill used for scientific purposes. Each rover will carry a bottle jack and a spare wheel or two, but only hand tools will be used. The bolts connecting the wheel to the suspension arm will be turned by hand.

GW Johnson wrote:

Here's an idea: add a string of trailers to fit the task at hand. One trailer might have a pressurized inflatable "tent" and life support supplies exceeding the rover range by a wide margin. Another might have fuel cell supplies and solar panels, a mixed-source power trailer for extended-range operation. The third might be a portable drill rig for deep-drilling. And so forth. Pull one or all of them when you need them, don't hitch 'em up when you don't.

Every vehicle needs power and habitation capability. Structural mass for cargo storage must be minimized using advanced materials and reasonably intelligent vehicle design. Dragging trailers behind a prime mover doesn't make the math involved with delivering the required tonnage any easier and needlessly complicates travel.

I want to deliver four light trucks to Mars because that's all that's really required for initial surface exploration. Any habitation more extravagant than a light pressurized rover comes from the investment of more funding for improved habitation and purchases of additional launches to deliver a habitation module.

If there's available funding for additional hardware to increase exploration returns, perhaps a base unit equipped with LOX/LCH4 tanks and ISPP plant and a base unit equipped with a methalox powered drill can be sent for extraction of core samples.

GW Johnson wrote:

You'll need the power in the rover to pull trailers off-road through the rocks and dirt. It will be slow going, very much like a farm tractor, with low and really-low gears. Designing mission objectives and plans for 30+ km/hr speeds is utter nonsense. Much of Mars is way too rough for that.

My light truck has electric hub motors that permit speeds of 50+ km/hr over level and smooth ground because 10kW of power is sufficient for that purpose in a vehicle that only weighs .95t fully loaded. Gearing implies the addition of a heavy mechanical device (transmission) that adds mass and another potential mechanical failure that will be more difficult to repair or replace than a hub motor. I don't believe a transmission is required, nor even desirable, and adding a transmission increases the mass of the vehicle and thus the mass of the suspension.

The fact that the rover is capable of 50+ km/h doesn't mean that that's a recommended travel speed. There's no desire on my part to travel at speeds that the terrain won't permit. The burst speed capability is useful for quickly arriving in the landing area after the astronauts land in their capsule and quickly arriving at the scene of a vehicular accident. More importantly, the slight excess of torque and power over what's minimally required provides the gradient climbing capability that off-road vehicles require and also permits retrieval or towing of stuck or disabled vehicles.

GW Johnson wrote:

Smaller, simpler, lighter, and way-to-hell-and-gone more versatile that modular way with a tractor and a selection of trailers. That last (versatility) is really the most important advantage, after all, because history teaches we will encounter the unexpected / unanticipated.
Going modular, splitting off different functions into various add-on trailers, sure beats trying to design everything imaginable into one single item.
GW

Chariot and ATHLETE integrate too many tools and technologies for surface exploration into a single vehicle that must also provide habitation. The high structural mass and mechanical complexity of Chariot and ATHLETE are exactly what I want to avoid by using simple light electric trucks. Each vehicle is sized to carry one quarter of the consumables required to support a 500 day nominal surface stay with 4 crew members, assuming ISRU for oxygen and water. Each vehicle has ECLSS intended to support one or two crew members, so loss of a vehicle through mechanical failure is not equivalent to loss of crew or mission.

The solution you're proposing adds back structural mass in the form of towed vehicles. With a loaded mass of 2.5t and loaded weight of .95t on Mars, the vehicles I propose are so light that trailers aren't required. The proposal to not tow trailers if they're not required for a particular expedition is functionally equivalent to tethering the astronauts to a base or supply dump. I don't want the astronauts tethered to a base or supply dump. I want real mobility. I think the best way to achieve that is through the use of multiple identical and appropriately sized trucks.

Why must a vehicle like ATHLETE pick up objects when a human can just as easily pick them up?

Why must a vehicle like ATHLETE dig when a human can just as easily use a shovel?

Why must a vehicle like ATHLETE drill when a human can just as easily operate a drill?

Why must a vehicle like Chariot rotate all its wheels and occupants 180 degrees to back up when mirrors or backup cameras work just as well for visualizing where you're going in reverse and have negligible associated cost and complexity?

Why must a vehicle like Chariot use so many wheels, motors, and suspension components when it's readily apparent that tracks can provide even lower ground pressure, better traction, better payload carrying capacity, and equivalent or better mobility for equivalent or lesser weight?

RobertDyck · 2016-03-04 08:03:02

kbd512 wrote:

The unpressurized rover provides no operational advantages over a light pressurized rover. Are you going to travel inside a deployed tent atop an unpressurized rover or trailer or wear your space suit 12 hours a day?

Spacesuit 12 hours per day. The tent is deployed on ground, when the vehicle stops for the night. It's depressurized and folded to repack in it's bag to resume driving.

During normal operations, the open rover will only be used during daylight. Astronauts will return to base for night. After all, over rough terrain you want to see where you're going. Visited my sister yesterday. Purpose of the trip doesn't matter, what does matter is she and her husband live in a small bedroom community just outside the city. As we drove along the Perimeter highway (some American cities call that a Beltway), street lights were out. We drove in the dark with only headlights. My sister commented it felt like we were driving into an abyss. Several streetlights within the city were out as well. And I don't mean one here and one there, I mean entire blocks. But we had assurance that the highway has actual pavement. We couldn't see the black of asphalt, just painted lines, and only as far as low-beam headlights shine. Now imagine driving like that on Mars with craters and ravines. You might be able to safely drive on an established path close to the habitat with packed wheel tracks, but not open ground. When sun sets, stop for the night.

So the emergency case of the crew lander/habitat landing more than walking distance from the ERV or MAV. You have to stop for the night anyway. May as well ride in spacesuits, with a dome tent for the night. Remember, my mission plan includes a pressurized rover with built-in recycling life support. That pressurized rover would pre-landed with the laboratory. The crew lander would carry an open rover in order to keep mass to minimum. So driving more than a day in the open rover is emergency only. Only to get you to the ERV (Mars Direct) or MAV (my mission plan).

kbd512 · 2016-03-04 10:14:36

RobertDyck wrote:

Spacesuit 12 hours per day. The tent is deployed on ground, when the vehicle stops for the night. It's depressurized and folded to repack in it's bag to resume driving.

For sanitary reasons I want to avoid forcing the astronauts to urinate and defecate on themselves. I would also like to recycle the water from the waste. The fecal matter can be discarded in plastic bags after we get the water out of it. No matter how comfortable MCP suits are, I can't imagine anyone wanting to spend one out of every two hours of a day inside a pressure suit.

Do you really want to send 500 diapers per person to Mars? It's guaranteed that somewhere in a 12 hour span that an active person will have to urinate. If that's not what you're proposing, then tell me what advantage an inflatable tent provides over an inflatable habitat attached to the top of the rover body.

My inflatable habitat module has sufficient volume for two seats, bedding, a toilet, a galley to rehydrate meals, and storage compartments for rations / suits / electronics / scientific instruments. It's directly connected to the rover base unit that contains the life support equipment, water storage tanks, batteries, and storage compartment for rations. An inflatable tent still requires all of that equipment and must still be carried by the rover.

RobertDyck wrote:

During normal operations, the open rover will only be used during daylight. Astronauts will return to base for night. After all, over rough terrain you want to see where you're going. Visited my sister yesterday. Purpose of the trip doesn't matter, what does matter is she and her husband live in a small bedroom community just outside the city. As we drove along the Perimeter highway (some American cities call that a Beltway), street lights were out. We drove in the dark with only headlights. My sister commented it felt like we were driving into an abyss. Several streetlights within the city were out as well. And I don't mean one here and one there, I mean entire blocks. But we had assurance that the highway has actual pavement. We couldn't see the black of asphalt, just painted lines, and only as far as low-beam headlights shine. Now imagine driving like that on Mars with craters and ravines. You might be able to safely drive on an established path close to the habitat with packed wheel tracks, but not open ground. When sun sets, stop for the night.

With an accurate map and accurate position fixing, you can drive in the dark. Moreover, since you made it to where you were going, I'm going to assume it's not as much of a problem as you're making it out to be. We already have very detailed maps of the surface of Mars, so all we need for human exploration are position fixing mini satellites.

RobertDyck wrote:

So the emergency case of the crew lander/habitat landing more than walking distance from the ERV or MAV. You have to stop for the night anyway. May as well ride in spacesuits, with a dome tent for the night. Remember, my mission plan includes a pressurized rover with built-in recycling life support. That pressurized rover would pre-landed with the laboratory. The crew lander would carry an open rover in order to keep mass to minimum. So driving more than a day in the open rover is emergency only. Only to get you to the ERV (Mars Direct) or MAV (my mission plan).

In the case of providing four pressurized rovers that carry or generate all of the consumables required for an entire surface stay, it really doesn't matter where the nearest stationary habitat module is located because the rovers provide everything required for the surface stay, the rovers retrieve the astronauts from their capsule(s), and our landing accuracy is not so wildly inaccurate that said rovers can't converge on the capsule landing site(s) in a reasonable amount of time.

There is some risk involved with not landing in a pressurized habitat module capable of supporting the entire crew for the entire surface stay. My contention is that the risk is acceptable. Apart from landing the MAV with the habitat module, there's no way to avoid some travel risk.

If there's funding to purchase another Falcon Heavy, send four more rovers, two being complete pressurized habitat modules and the other two being a methalox powered drill and ISPP demonstrator. If the methalox plant and ICE drill function as intended, it confirms the feasibility of ISPP and ICE powered equipment and vehicles. If not, the surface mission still receives the benefits of additional like-kind spares.

GW Johnson · 2016-03-04 17:01:25

Don’t discount the trailer idea so fast. My old farm truck F-150 weighs about 4000 lb and legally carries max 1000 lb payload, for a total of 5000 lb loaded. It’s comfy and fairly fast. Really tough, too.

I was able to move the same 1000 lb of payload with a 3000 lb VW camper bus, which was my farm truck before the F-150. The only differences were (1) slower, (2) not airconditioned, (3) about 2/3 the fuel usage, and (4) 1000 lb less loaded weight.

I never did this out on the farm, but I could have: decades ago I used a 1960-vintage VW beetle of a mere 36 HP to pull a 4x6 enclosed-box U-Haul trailer loaded with everything we owned, when I left school and we first moved to Waco.

Progress was very slow: the poor little thing would pull well at 42 mph in 3rd gear at 67% manifold pressure (and would not sustain in 4th gear, even “firewalled”). But it did the job without any damage whatsoever (that the 67% manifold pressure limitation for adequate long-duration cooling). That’s about 3000 lb of loaded trailer plus a 1600 lb car plus about another 500 lb (me, her, some luggage filling the back seat, and a very small boat tied on the roof).

That’s 5100 lb moving at half the fuel usage of the F-150. My only problem was remembering to start braking very early and very gently: nobody at VW ever envisioned pulling trailers with beetles. I had to custom-make the hitch. The brakes were intended for 2100 lb max.

My point is this: why carry all the load-hauling mass around when you don’t need it? Your basic rover can be small, light, and very economical of energy. When you need to haul extra stuff, don’t look at a bigger rover, just add a trailer to your small one. Trailers can be specifically designed to carry whatever you desire, so that the rover does not have to be.

GW

PS – I still have the beetle and the bus in deep storage out here on the farm, plus another later beetle I converted to burn ethanol instead of gasoline (and it ran better; my 1944-vintage farm tractor also runs on ethanol, and I did that conversion, too). I kept my best cars against future need. Meanwhile the F-150 and a small Nissan that my wife used to drive serve me quite well. If the Nissan had a hitch, I really wouldn’t need the F-150. But I like it, so I keep it.

PPS – If instead of trying to compensate for failed precision landings, you go instead for a big landing boat from orbit, you avoid the whole long forced travel rover problem. Everything comes down in one vehicle, one time, end of issue. The rover design then devolves to exactly the mission it served on the moon. We have more experience with that design than anything we’ve been talking about here. A drill rig and tent would be the only trailers you need.

kbd512 · 2016-03-04 18:08:12

ISS maximum food storage volume and mass allowances per person per day:

6570 cubic centimeters -> 3.285 cubic meters per person for 500 days

2.38 kg -> 1190 kg per person for 500 days (I think we can get this down to 1000kg with improved packaging and high energy breakfast bars)

Edit: According to this NASA Sustaining Life article, 915kg of food is required for 500 days, so our food and water are roughly 1290kg of our 1500kg payload. That leaves 210kg for other stuff (most likely spare rover parts, tools, and electronics).

Rover Habitation Unit Dimensions:

Habitation Module: 2m D x 5m L (could be reduced to 2m D x 4m L, but it'd be pretty cramped)
Airlock: 1m D x 2m L

Rover Base Unit Dimensions / Volumes / Masses (dimensions do not include the attached rocker bogie assemblies):

Core Unit: 4m L x 2.5m W x .5m H

Core Unit Cargo Volume: 5 cubic meters

Cargo Volume Use Breakdown:

3.285 m3 - Astronaut Rations

.375m3 - 3m L x 2.5m W x .05m H - 375L (for fresh and grey water tanks and SPE protection - astronauts hide in a ditch under their rover and attach power/air/water umbilicals to the rover)

.0738 m3 - GAIA HE 602030 NCA cells split into two 10kW battery packs containing 50 cells each (won't be used because energy density is only 132Wh/kg, yielding 151kg for 20kWh capacity, but gives an idea of the upper limit to battery weight and volume; Panasonic NCR18650B cells provide 243Wh/kg, so 82kg for 20kWh capacity although in all reality we'd just add capacity up to about 100kg or so)

.06627 m3 - 4 MOXIE oxygen generators (I really need the mass for MOXIE, anyone have it?)
# m3 - 2 CL-ECLSS (anybody know what type of ECLSS is required for a 2m x 5m inflatable cylinder with a 1m x 2m airlock attached to it?)

I don't know what volumes and masses are required for tools or life support, but it's probably a safe bet that the base unit can be shorter or narrower than my stated dimensions because we're only up to 3.74 m3 and have 1.26m3 worth of volume remaining. If we have substantial volume remaining after the ECLSS and water generator hardware have been accounted for, then we can shrink the base unit height to reduce volume and weight.

If anyone can help spec this vehicle out, feel free to contribute.

Last edited by kbd512 (2016-03-04 20:19:11)

kbd512 · 2016-03-04 18:48:50

GW Johnson wrote:

Don’t discount the trailer idea so fast. My old farm truck F-150 weighs about 4000 lb and legally carries max 1000 lb payload, for a total of 5000 lb loaded. It’s comfy and fairly fast. Really tough, too.

GW, what do you want to haul that the astronauts really need that can't just as easily be hauled in the rover? I'm sure the rover could pull a trailer to decrease its size, but then the size and mass of the trailer has to be accounted for.

I've thought about putting the rations in the inflatable unit, but how high does that place the vehicle's CG? Obviously the base/core unit could be shrunk considerably, but is that feasible from a vehicle mechanics standpoint?

The base or core unit is already .5m above the ground and the 1000kg worth of rations sit on top of the water tank.

Loaded mass for my rover is only 2.5t. Loaded weight is only .95t on Mars. The rover has four 2.5kW (13.41hp) electric hub motors and I can understand four 4kW (21.45hp) electric motors if the energy density of the lithium batteries improves to about 300Wh/kg, with a 100kg mass budget for the batteries and 20kg/motor mass budget for the 4kW electric motors (15kg mass budgeted for the 2.5kW electric motors).

We need to work out the mass and size of the radiators. How much heat rejection is required for the inflatable and is there any reason why we integrate the radiators into the base unit?

RobertDyck · 2016-03-04 19:14:36

When I was a teenager, I think 15, we visited my grandparent's farm in Saskatchewan. Some uncles and their families came too, so we couldn't stay in the house. My parents brought a tent trailer. At one point I walked from the farm house to the camper trailer, after night fell. When they turned out house lights, there were no lights on at all. Our only flashlight was in the camper trailer, so I had to get there without it. With lights out, I couldn't see my hand in front of my face. Sky was clear, no moon. You could clearly see the Milky Way. The sky was beautiful! But there was no way I could make it just a couple hundred feet to the trailer. A couple uncles went into the house to get their flashlight, I asked one to keep the house light on long enough for me to get to the trailer.

Anyone who has never left the lights of a city can't appreciate how dark night can be.

kbd512 · 2016-03-04 19:43:17

RobertDyck wrote:

When I was a teenager, I think 15, we visited my grandparent's farm in Saskatchewan. Some uncles and their families came too, so we couldn't stay in the house. My parents brought a tent trailer. At one point I walked from the farm house to the camper trailer, after night fell. When they turned out house lights, there were no lights on at all. Our only flashlight was in the camper trailer, so I had to get there without it. With lights out, I couldn't see my hand in front of my face. Sky was clear, no moon. You could clearly see the Milky Way. The sky was beautiful! But there was no way I could make it just a couple hundred feet to the trailer. A couple uncles went into the house to get their flashlight, I asked one to keep the house light on long enough for me to get to the trailer.
Anyone who has never left the lights of a city can't appreciate how dark night can be.

Rob,

I can't think of any 1t vehicles that can't brake from 50km/h to 0km/h in 500m, even in sand.

Darkness is just not that much of a problem: SureFire ARC3

Mount four of those things on the front of the rover. Problem solved.

Can we focus on ECLSS now?

RobertDyck · 2016-03-04 20:42:48

Well, I've said before that it really isn't that hard. Well, sort of. Base life support on the system currently on ISS.

For CO2 sorbent your primary choices are LiOH for non-reusable, disposable sorbent. Obviously not something you want to use on Mars. Or silver oxide, which has compact volume but significant mass. I said granules are lower mass per unit of CO2 adsorbed, and compatible with microwave regeneration. Or amine. Nuclear submarines use liquid amine, but that would float into cabin air in zero-G, so NASA developed a solid amine. It's a paste, painted on styrofoam peas. Lower total mass, but significant volume. They currently use silver oxide sheet metal for the PLSS backpack on EMU spacesuits, and the extended duration orbiter pallet for Shuttle used amine paste on styrofoam peas. Not sure what they use on the American side of ISS. But the idea is the same: either absorb or adsorb CO2, when it gets full bake it out. Cabin dehumidifier collects cabin moisture. Effluent from the dehumidifier goes directly to the water processor assembly. Urine collection tube goes to the urine processor assembly, then effluent from that goes to the water processor assembly. Resulting water used both as drinking water, and fed to the water electrolysis device. It uses membrane electrolysis to separate gasses from water in zero-G. All the hydrogen from water electrolysis, and half the CO2 from the sorbent system are fed to a Sabatier reactor. That reactor must be heated to a fairly high temperature to work, but it's exothermic; once it starts to operate it generates more heat than it consumes. Result is methane and water. The water is fed back to the water storage tank, available for drinking or electrolysis. All the methane and the other half of CO2 is vented to space.

Additions I want for Mars:
- direct CO2 electrolysis. This uses a thin membrane catalyst tube. The CO2 must be heated to +900°C. This breaks 80% of the CO2 to CO and O2. The O2 passes through the membrane, CO2 and CO don't. While water electrolysis and Sabatier recover 100% of oxygen from water and CO2, this system recovers 50% of oxygen from 80% of the CO2. In other words, only 40% of O2 possible. However, this operates on the CO2 that would otherwise be dumped in space. So this produces oxygen to replenish recycling losses from the primary system.
- recover moisture from feces. Either the Russian system, vacuum desiccation. Or bake it out, an electro-resistive oven, aka electric oven.
- sink and shower to recover wash water. On ISS a sink is a glove box with neoprene rubber dam for each hand. On Mars the sink is just a sink. On ISS the shower would be based on the Skylab shower. On Mars it would be just a shower with low-flow shower head.
- laundry machine. With laundry soap compatible with the water processor assembly. That's probably laundry soap instead of detergent. On Mars the laundry machine would be an RV washer/dryer combo, made of light-weight yet durable materials, and power compatible with vehicle systems.

All this would go on the habitat. On a large pressurized rover, you would put the primary life support system, but not laundry, sink/shower, toilet, or direct CO2 electrolysis. Instead collect feces in a plastic baggie (with a really good zip-lock!), and collect excess CO2 gas. That could be fed into habitat systems when you get back.

Notice I said "large pressurized rover". I don't see how you could fit all that on a small rover. You could try to redesign current equipment to shrink it a little, but how much can you shrink it?

Water Processor Assembly, and Urine Processor. Installed on US side of ISS, sized for 3 astronauts.

Oxygen Generation System, with space reserved for Sabatier

Carbon Dioxide Removal Assembly

Last edited by RobertDyck (2016-03-05 08:34:50)

SpaceNut · 2016-03-04 21:50:07

Nice images RobertDyck....

The rover that kbd512 is envisioning is probably a decade down the road once we are able to land man on mars so the need to explore long range from a base will need to wait as we will be trying to dig in a good solid foothold within that first decade.

SpaceNut · 2016-03-05 21:51:45

So looking back at the page 1 initial posted lunar rover image...
We would want more battery capacity, an additional 2 seats for a total crew of 4 other wise just send 2 of them, removal of the antenna as we would use a different method of communications, longer lasting tires as well as spares and stronger motors to be used on all 4 tires. Other options are a pull behind trailer for pitching a tent for getting out of the space suit within, to place cargo to transport on, and of course food for a longer useage within the tent, and of course a means to stay wrm if we do use it that way.

kbd512 · 2016-03-05 22:09:50

RobertDyck wrote:

Well, I've said before that it really isn't that hard. Well, sort of. Base life support on the system currently on ISS.

I think the photos you provided indicate pretty well why ISS type ECLSS won't work for a light rover.

RobertDyck wrote:

For CO2 sorbent your primary choices are LiOH for non-reusable, disposable sorbent. Obviously not something you want to use on Mars. Or silver oxide, which has compact volume but significant mass. I said granules are lower mass per unit of CO2 adsorbed, and compatible with microwave regeneration. Or amine. Nuclear submarines use liquid amine, but that would float into cabin air in zero-G, so NASA developed a solid amine. It's a paste, painted on styrofoam peas. Lower total mass, but significant volume. They currently use silver oxide sheet metal for the PLSS backpack on EMU spacesuits, and the extended duration orbiter pallet for Shuttle used amine paste on styrofoam peas. Not sure what they use on the American side of ISS. But the idea is the same: either absorb or adsorb CO2, when it gets full bake it out. Cabin dehumidifier collects cabin moisture. Effluent from the dehumidifier goes directly to the water processor assembly. Urine collection tube goes to the urine processor assembly, then effluent from that goes to the water processor assembly. Resulting water used both as drinking water, and fed to the water electrolysis device. It uses membrane electrolysis to separate gasses from water in zero-G. All the hydrogen from water electrolysis, and half the CO2 from the sorbent system are fed to a Sabatier reactor. That reactor must be heated to a fairly high temperature to work, but it's exothermic; once it starts to operate it generates more heat than it consumes. Result is methane and water. The water is fed back to the water storage tank, available for drinking or electrolysis. All the methane and the other half of CO2 is vented to space.

I think NASA is already hard at work here, but what's the primary advantage of silver oxide sorbents over other technologies? Is it simplicity, cost, developmental status, or a combination of all of some or all of those?

How much power does the microwave oven require to bake the silver oxide spheres to revitalize the sorbent and how long does the process take?

RobertDyck wrote:

Additions I want for Mars:
- direct CO2 electrolysis. This uses a thin membrane catalyst tube. The CO2 must be heated to +900°C. This breaks 80% of the CO2 to CO and O2. The O2 passes through the membrane, CO2 and CO don't. While water electrolysis and Sabatier recover 100% of oxygen from water and CO2, this system recovers 50% of oxygen from 80% of the CO2. In other words, only 40% of O2 possible. However, this operates on the CO2 that would otherwise be dumped in space. So this produces oxygen to replenish recycling losses from the primary system.
- recover moisture from feces. Either the Russian system, vacuum desiccation. Or bake it out, an electro-resistive oven, aka electric oven.
- sink and shower to recover wash water. On ISS a sink is a glove box with neoprene rubber dam for each hand. On Mars the sink is just a sink. On ISS the shower would be based on the Skylab shower. On Mars it would be just a shower with low-flow shower head.
- laundry machine. With laundry soap compatible with the water processor assembly. That's probably laundry soap instead of detergent. On Mars the laundry machine would be an RV washer/dryer combo, made of light-weight yet durable materials, and power compatible with vehicle systems.

How much power and heat rejection are required?

RobertDyck wrote:

All this would go on the habitat. On a large pressurized rover, you would put the primary life support system, but not laundry, sink/shower, toilet, or direct CO2 electrolysis. Instead collect feces in a plastic baggie (with a really good zip-lock!), and collect excess CO2 gas. That could be fed into habitat systems when you get back.

Before we build a base somewhere, wouldn't it be a good idea to figure out where the best quality water, minerals, and ores are located first?

RobertDyck wrote:

Notice I said "large pressurized rover". I don't see how you could fit all that on a small rover. You could try to redesign current equipment to shrink it a little, but how much can you shrink it?

I don't think you could appreciably shrink that system. I think that technology is an initial effort directed towards closing the loop. It's far better than nothing, but not good enough for Mars.

RobertDyck wrote:

Water Processor Assembly, and Urine Processor. Installed on US side of ISS, sized for 3 astronauts.

This is what I had in mind: Paragon IWP

Thoughts?

RobertDyck wrote:

Oxygen Generation System, with space reserved for Sabatier

Compact, Lightweight Adsorber and Sabatier Reactor for CO2 Capture and Reduction for Consumable and Propellant Production

What are the pros and cons of ISS water electrolysis vs solid oxide electrolysis (MOXIE) vs catalytic conversion (Microlith)?

RobertDyck wrote:

Carbon Dioxide Removal Assembly

Microlith-based Structured Sorbent for Carbon Dioxide, Humidity, and Trace Contaminant Control in Manned Space Habitats

kbd512 · 2016-03-05 22:39:29

SpaceNut wrote:

So looking back at the page 1 initial posted lunar rover image...
We would want more battery capacity, an additional 2 seats for a total crew of 4 other wise just send 2 of them, removal of the antenna as we would use a different method of communications, longer lasting tires as well as spares and stronger motors to be used on all 4 tires. Other options are a pull behind trailer for pitching a tent for getting out of the space suit within, to place cargo to transport on, and of course food for a longer useage within the tent, and of course a means to stay wrm if we do use it that way.

SpaceNut,

A rather simplistic light unpressurized rover that's a four seat reprise of the Apollo era lunar rover could easily be built, but it's an incredibly expensive golf cart with limited utility. Its utility during the Apollo Program was the fact that that was all that the LM could carry with it to improve surface mobility for the crew.

As an aside, I really don't understand the desire to build bases in locations that we really know next to nothing about. Unpressurized rovers have maximum utility near bases that provide pressurization and SPE protection. Nearly any means of transportation will be faster than walking, but there are so many other practical reasons not to build a reprise of the lunar rovers for use on Mars.

With the pressurized tent solution, you still need life support and you still have to carry it, but you have to spend time deploying and stowing it. Tents work well on Earth because no pressurization is required since we can breathe the atmosphere here and we can simply walk outside to obtain water. None of that applies to a tent on Mars. All I'm saying is mount the tent on the vehicle.

The trailer solution works well here on Earth because we're in a power rich environment provided by easily obtainable hydrocarbon fuels that we use to pull loads and so the additional structural mass of the trailer is worth the small loss in mechanical efficiency from towing it with a truck. If the trailer has a mechanical failure or can't be towed due to overload, another truck is available to replace the damaged trailer or transfer the load. None of that applies on Mars. All I'm saying is design a vehicle that's large enough and powerful enough to carry whatever you think needs to be carried.

New Mars Forums

Announcement

#26 2016-03-01 10:57:49

Re: Light weight rover for Mars

#27 2016-03-01 13:55:12

Re: Light weight rover for Mars

#28 2016-03-01 18:02:26

Re: Light weight rover for Mars

#29 2016-03-01 20:07:43

Re: Light weight rover for Mars

#30 2016-03-01 23:10:48

Re: Light weight rover for Mars

#31 2016-03-02 04:45:20

Re: Light weight rover for Mars

#32 2016-03-02 20:08:31

Re: Light weight rover for Mars

#33 2016-03-03 10:14:26

Re: Light weight rover for Mars

#34 2016-03-03 13:34:23

Re: Light weight rover for Mars

#35 2016-03-03 14:17:22

Re: Light weight rover for Mars

#36 2016-03-03 14:26:19

Re: Light weight rover for Mars

#37 2016-03-03 15:47:17

Re: Light weight rover for Mars

#38 2016-03-04 01:18:46

Re: Light weight rover for Mars

#39 2016-03-04 08:03:02

Re: Light weight rover for Mars

#40 2016-03-04 10:14:36

Re: Light weight rover for Mars

#41 2016-03-04 17:01:25

Re: Light weight rover for Mars

#42 2016-03-04 18:08:12

Re: Light weight rover for Mars

#43 2016-03-04 18:48:50

Re: Light weight rover for Mars

#44 2016-03-04 19:14:36

Re: Light weight rover for Mars

#45 2016-03-04 19:43:17

Re: Light weight rover for Mars

#46 2016-03-04 20:42:48

Re: Light weight rover for Mars

#47 2016-03-04 21:50:07

Re: Light weight rover for Mars

#48 2016-03-05 21:51:45

Re: Light weight rover for Mars

#49 2016-03-05 22:09:50

Re: Light weight rover for Mars

#50 2016-03-05 22:39:29

Re: Light weight rover for Mars

Board footer