Selenian Boondocks

Jason Rian at the blog Americaspace just ran a series on Newspace trolls and the damage they do to the industry. There were four posts total with Newspace hatred starting and newspace troll tactics for the next three. His theme seems to be that Newspacers hate NASA and Oldspace so much they can’t see straight and constantly indulge in troll tactics. Apparently if you comment on technical or financial matters, you were changing the subject, and if you answered his troll points you were being rude. I only tried a couple of comments before realizing that whatever I said would be wrong. Apparently I have severe trouble with reading comprehension.

There are plenty in Newspace that are rude, wrong or arrogant. I have seen just as many in Oldspace that are as bad with an additional level of arrogance based on accomplishment. Much of that accomplishment seems to be a generation or so back with a circular reasoning on the effectiveness of NASA and company. One difference seems to be that Newspace activists get it that if something is unaffordable, it will end, usually badly.

Jason seemed to think that the message itself must always be polite by his personal definition. His personal definition seems to be that no criticism is allowed unless he does it himself. He talked down to several of us in the course of a few hundred comments accusing several of lying, selective quoting, changing the subject etc…Comment behavior that is accepted in other blogs will not be tolerated here and so on. Selenian Boondocks is a fairly focused and polite place in my opinion. I think that that is because we are interested in accomplishing something like shredding bad ideas and developing good ones. We don’t accuse each other of trolling and hating when we have a difference of opinion. If you look for something to agree or disagree with, you will find it. By Jason’s definition, we would all seem to be rude, trolling, haters. So be it.

The theme that we are killing the industry with our behavior was constant. “I can’t wait to see Newspace screw up and get somebody killed and then pay for its’ behaviour.” is not an exact quote but captures the flavor of fifty or more variations. I think he is incapable of understanding that rude behavior is partially in the eyes of the beholder, or that the behavior of the fan base has little impact on the working industry. I have been POed at Rand, Pat, Ed, and others from time to time, and still consider them friends and read what they write for the information content. Jason, welcome to the group, but get your butt off your shoulders.

Compromise is a totally different concept than work the issues and find the answers. One complaint is that Oldspace gave a bit on SpaceX and therefore Newspace should give a bit on SLS. I don’t mix chili peppers and chocolate ice cream. Each has their place and compromise is not ever it. If the mission is a Mexican dinner, chili peppers, if desert the ice cream. Mix them together on my plate and you will wear them both. Either the chilis or the ice cream can be replaced if cost, quality, or taste dictates. SLS is jalapeno on an ulcer.

Newspace hasn’t demonstrated capability yet? How long since NASA has developed a space launch vehicle? No respect until the rocket has a track record? Yes I am disappointed in Newspace slow progress. I am even more disappointed in Oldspace posturing as if they had the answers when it is their grandfathers that developed the systems they use for the most part.

SLS at the heart of the discussion needs to be addressed constantly and with intensity. No Newspacer I am aware of believes that SLS is affordable. Billions per year for development for a decade or so until flying a couple of missions a year at a billion each is not a realistic plan in the current economic climate. Anyone that cares to address this in a manner that makes sense is welcome to try. Don’t do the stupid percentage of our GNP or national budget though. A hamburger at 1/100 of 1% of my personal budget will rot if the price doubles.

The technical issues with SLS must be addressed if anyone wants a serious discussion. Friends of mine have kept up even if I haven’t on issues of overweight and escape among others. A serious discussion of these issues does not include any variation of take my word for it regardless of the source.

SLS must make a business case for itself if it is to move forward. Government systems not making an honest business case are a strong part of the financial mess the country is in today. Soundbites of commercial to LEO and SLS beyond divide by a negative number and get nonsense. Make the case that SLS is worth the money or leave it alone. It is arrogant in the extreme to claim that SLS is the only way to get manned missions beyond LEO not to mention wrong.

The mission of SLS, if it actually had one of course, could be duplicated by any number of variations of current hardware. A propellant depot in LEO and another at L1 filled by whoever shows up can refuel the upper stage of an Atlas, Delta, Falcon, or other manned vehicle to increase the BEO throw weight by an order of magnitude. Less mission risk as mentioned here hundreds of times as the only mission critical flight is the last one by the most experienced and dependable rocket available at that time.

The safety of SLS is questionable to say the least. Minimal full up testing before putting humans on it sounds like a game of Russian roulette.  A virtually untested rocket that probably hasn’t outgrown infant mortality doesn’t seem like a good transportation system six decades into the space age.

Prove me wrong and I back off. Until then, it’s just Oldspace trolling.

Newspace, Oldspace, or just Space fan behavior has virtually no effect on operations, investigations, or even future contracts in this industry. My opinion of SLS has no more effect on the program than my opinion of SpaceX or XCOR has on their operation. This lack of direct effect extends to many of those with far better connections than mine. I posted this one because I was annoyed, which is a terrible reason. Also because many of us need a bit of humility to understand that any effect we have is mostly second or third order in that someone that does do real work might grow a seed from these discussions into a viable plant. We need enough tolerance in our communications to work together, and enough care to dispute points that should not be left standing without argument.

There are a lot of people in NASA that are exceptional. There are a lot of people in the Oldspace companies that are exceptional. Newspace has lower numbers of exceptional people mainly due to the fact that they have far far less people total. Let us honestly evaluate the people, equipment, and systems we consider important without honoring any of them for fictitious performance.

The recent impactor discussions brought up about  the comet that may hit Mars brought to mind some vaguely remembered ideas about terraforming Mars. Volatile rich bodies are directed at Mars to give it an atmosphere of the resulting gasses. If my BOTE numbers are right, the estimated 30km diameter comet would roughly double the atmospheric pressure if it hit and converted all of its’ material to gas that didn’t escape.  If that were the case, then 40-50 comets would give Mars an atmospheric pressure of roughly half Earth sea level. With the quantity of volatiles that either escaped Martian gravity, condensed to liquid, or just weren’t there in the first place, it would take 100-200 comets at least to get the job done.

That would give enough atmosphere for radiation protection, exploration with tanked air instead of spacesuits, and sealed but unpressurized living, working, and farming buildings. Compared to the advances of the last fifty years in space travel, this might seem a very long way off. Compared to the advances of the last century though, it might be much closer than any of us currently would think.

I know this concept has been kicked around for decades. My question is, “What is the recent credible work on it?”

Robert Steinke of Speed Up suggested using a self pressurizing propellant to drive a pump for a less pressurized propellant. In this case nitrous at about 800 psi is vaporized to pump a fuel up to some pressure in between the two. Say a pressure drop of two for the nitrous through the turbine drops it to 400 psi while pumping the fuel from 200 or less up to 400 psi. There was a some discussion of it on A Rocket.  One of the comments suggested that since nitrous is already the bulk of the propellant, just pressurize the fuel and be done with it.

Being the kind of person that steals and modifies ideas as a matter of habit, I decided to see what I could do with the basic concept.Taking a self pressurizing propellant to drive a pump that reduces over all system mass, and hopefully operating cost.

Helium is the pressurant gas of choice for any that require performance. Unfortunately it seems that it is becoming somewhat more expensive and harder to order as the decades roll on. Also, it must be stored as a gas which means a relatively large pressure container. Self pressurizing propellants can get by without helium at the expense of considerably more mass of pressurant gas at the end of the burn. With a self pressurizing propellant driving the turbine after a run through the cooling jacket, It may be possible to do without helium altogether without the mass penalty of heavier gasses for pressurant.

Hopefully my cartoons will be better when I get another computer in a week or so. My desktop computer doesn’t save sketches in a manner that the blog will accept, and my laptop does these tiny things that even I can’t read.

Anyway, a small pressure sphere of LH2 contains less than 1% of the total propellant on board. The liquid hydrogen at 6,000 psi is sent through the cooling jacket to cool the engine and gain energy to drive the turbine. The hot hydrogen gas drives the turbine with a pressure drop of about ten from 5,400 psi after a 10% loss in the cooling phase to 540 or so psi which exhausts into the combustion chamber. The LOX and Kerosene is pumped up to nearly 600 psi to allow for pressure drop through the injectors. With a chamber pressure at 500 psi in a sorta expander cycle Isp will be a bit higher than most pressure fed engines. Mixture of propellants is less than 1LH burns with less than 6LOX+28Kero+65LOX if I have it guestimated correctly.

Low pressure tanks for the Kero/LOX at a bit less than a cubic meter per metric ton would be partnered with about about 100 liters or so of LH2 in high pressure spheres. System dry mass should be less than that with the helium spheres and medium pressure tanks of most current set ups. A quality trade study will probably find the sweet spot to be less pressure than I am suggesting on this first pass. More LH2 at a 1,500 psi would feel like a better solution as long as it didn’t go overboard and become a pressure fed hydrogen rocket.

Kerosene impeller tip speed will be on the order of 350 ft/sec with LOX impeller at about 290 ft/sec. For perspective, a 2″ disk on a 35,000 rpm Dremel tool has a tip speed of 300 ft/sec. My 14″ demolition saw at 6,000 rpm has a tip speed of 350 ft/sec. Most people worry about the turbine. This one is driven by hydrogen that is fairly warm though well below turbine temperatures on almost any application you can think of. It will require a multistage turbine to extract the energy both from the low turbine speeds and the very high pressure drop.

A variation that would get more turbine drive with less hydrogen mass would be to discharge the hydrogen gas into the expansion nozzle as extension skirt cooling. Prior art suggests that the Isp hit is not that severe, and pressure drop down to 50 psi or so is possible. With a turbine exhaust in the 50 psi range, the hydrogen spheres might optimize toward the 1,000 psi range.

There’s been a lot of discussion over the past year or two on a few blogs (this one, Transterrestrial Musings, and also Wayne Hale’s blog, among several others) about the proper level of emphasis on crew safety for commercial crew vehicles. The basic thesis that I and several of these other bloggers have made was that crew safety was only one of several important metrics, and shouldn’t be overemphasized at the expense of all others. The fear being that if “safety is our first priority”, then actually accomplishing the mission, or doing things affordably enough to enable new commercial markets often take the backseat (if not being neglected entirely). The problem is that it’s easy to brush off this argument. After all, we’re talking about human lives here. So what if it takes an extra billion or two, and adds 2-3 years to the development time, and ultimately costs so much that the resulting vehicles are only affordable for NASA, so long as we reduce the risk to our brave astronauts who’ll be flying on these risky commercial vehicles?

I had an interesting thought experiment that I think puts this line of thinking in a different perspective.

One of the most promising applications I’ve seen for microgravity research on the station is the development of vaccines. Apparently some infectious diseases (I think mostly bacterial ones) behave very different in microgravity–they grow much faster. This increase in virulence combined with turning off some of the confounding factors supposedly enables researchers to more quickly isolate the cell receptors, genes and such that govern the spread of the disease, allowing researchers to craft vaccines that have fewer negative side effects, are more effective, and in theory can make it through clinical testing and to market faster than terrestrial-developed counterparts. At least that’s the theory as I understand it, in semi-layman’s terms. Two specific diseases are currently being worked on by NASA and commercial firms like Astrogenetix are Salmonella and MRSA (Methicillin-Resistant Staphylococcus Aureus). The theory is that a MRSA vaccine developed on the station will be more effective than a terrestrial version, and will have fewer negative side effects.

So here’s the thought experiment. Right now, according to a little googling, MRSA kills about 19,000 Americans per year. As I understand it, there are a few terrestrially developed antibiotics and vaccines in the works, but say that a microgravity developed MRSA vaccine was effective 10% more often (ie that if say the terrestrial versions could save someone’s life 50% of the time, the microgravity-developed vaccine could save someone’s life 60% of the time). That would equate to ~1900 lives saved per year, 158 lives saved per month, or approximately 5 lives saved per day. And mind you, those numbers are only for American lives saved.

Right now the development of vaccines like this are highly dependent on the frequency of up and downmass opportunities on the space station as well as on the crew time available for doing research. From conversations I’ve had with CASIS, the ISS National Lab, and some others at NASA over the past few weeks, those two challenges (delivery/return frequency and crew research availability) are by far the two biggest challenges to effective use of the ISS. While there are several potential solutions to these problems–and in fact, I’m working on some really intriguing ones on the crew research availability side at Altius at the moment–one of the simplest ways to help improve the situation for both of these problems would be for Commercial Crew to enter operational services quicker.

Right now other than very tiny payloads on Soyuz, Dragon is the only way of getting payloads back from the station, and even when Elon’s team gets up to full speed, that’s only three opportunities per year. Any of the commercial crew vehicles being developed would add substantially not just to total downmass “tonnage” but more importantly to the frequency of downmass opportunities, increasing that number to potentially 5-6 times per year.

Additionally once commercial crew vehicles are flying, their lifeboat capability (and I agree with Rand’s take on how necessary that really is) will enable adding an extra crew-person to the ISS, bringing it to a total of seven crewmembers, with four of them on the US side. Right now between the three crewmembers on the ISS, we’re only getting about 1800-1900 man-hours of research work done per year on the station, with an average of about 35hrs per week total between the three of them. Just adding an additional crew member on the USOS side would likely double that number, potentially doubling the ROI for the station.

Between these two changes enabled by getting Commercial Crew into operations, experiments like the MRSA vaccine development process can proceed much quicker. As Tom Pickens of Astrogenetix explained at a Space Angels Network event I was presenting at in Houston a bit over a year ago, their development process depends on the ability to do 5-6 launch/process/return iteration cycles during the development of a given vaccine. Adding additional flight opportunities, and making sure that the experiment gets processed while the delivery vehicle is on station so it can make it back on the same vehicle (“Sortie Science” as the National Lab folks are calling it), can both greatly shorten the amount of time it takes to get the vaccine developed and into clinical testing.

While shortening the development cycle has serious positive commercial profitability benefits (a vaccine or design that isn’t completed is like a non-interest bearing checking account with a very high monthly fee that you only get profit from once the product actually hits the market), it has a dramatic value in saved lives in this particular case. Put simply, every day a vaccine like this gets to market sooner means a certain number of people who aren’t going to die painfully and prematurely. In the particular case of a 10% better MRSA vaccine, we’re talking about saving an extra 5 American citizens per day sooner that you get the MRSA vaccine to market.

So what does this have to do with space safety? Pretty simple. If NASA isn’t blowing smoke about the benefits of microgravity research for developing vaccines (and I for one believe them in this case), the delays in Commercial Crew availability due to added safety requirements come with an impressive cost in human lives. Adding an extra year to bump the theoretical reliability of commercial crew from 99% to 99.5% for instance just potentially cost you almost 2000 American lives, just from this one vaccine alone. These are lives that could’ve been saved by allowing a faster, more streamlined commercial crew development process. And by not starving it for funds to pay for heavy-lift rockets without destinations.

Think about that. Just shaving 36 hours off of the availability date of commercial crew could potentially save more lives than would be lost in the worst case Commercial Crew crash. Even if expediting the process, dropping many of the NASA Human Rating requirements, dropping some of the abort tests, and sticking with Space Act Agreements instead of FAR Contracts really meant a massive decrease in actual safety (I don’t think it would) to say a 5% chance of losing a crew on a given flight, over the course of the ISS’s life you would have saved hundreds of times more US lives by taking that course than you would potentially risk in astronaut lives.

Gives you some perspective, doesn’t it?

If a dinokoller asteroid was spotted on collision course for Earth with impact in the next ten years, it would be a race to divert it. I happen to disagree with many of my friends here that everyone would pull together to solve the problem. I happen to believe that all too many of the would be working their own agenda at the expense of us all. I also believe that many would oppose any effort to avert disaster with the belief that we would only make things worse, or possibly even that we planned on taking a near miss and turning it into a bulls eye strike on an enemy. Enemy can be anyone in the world if you go deep enough into the paranoia that tends to exist in many places.

In my opinion, what we need is a series of methods of mitigating the potential disaster of a real strike. This post is a thought experiment for using almost entirely ISRU resources with equipment that could be in space within the next decade without bankrupting the organization that funds it. By using assetts that are already in space, and under the control of people with real expertese in operating those resources, the possible political and hysteria roadblocks can be mitigated to a considerable degree.

The first set of assetts that absolutely must be developed is a survey of every reasonable threat to this world. Earth and space based telescopes and databases have to be developed in such a way that a comprehensive knowledge of every Earth crossing body of above a thousand tons or so is known and mapped for the foreseeable future. Second is to find and map orbits on the smaller bodies and bodies that intersect the potential dangerous Earth crossers. It would be cold comfort knowing that Humanitykiller One  was caused by two ‘safe’ rocks that collided in such a way as to send either or both of them our way. Only after a thorough catalogue is available can we say with reasonable certainty that no danger exists within some given time frame.

The second set of assetts is an affordable and robust transportation industry to at least LEO and hopefully cislunar space as well. Developing asteroids is dependant on the first and would benefit hugely by the second. A fledgling asteroid development industry would vastly improve the Dinokiller diversion effort I am going to suggest, and a mature one would make protection trivial.

My suggestion this time is that a fully mapped NEO inventory could use one asteroid to bump another off course. If a gigaton rock were going to hit Earth in a few years, then a diversion of a single meter per second would make it miss by a substantial amount. A meter per second is 3.6 km/hr, which is 86 km/day, which is over 30,000 km/year. While theoretically a few months might be enough to save the Earth, I would prefer a lot more margin.

Say this gigaton rock named Eight Ball is scheduled to land in the Earth pocket in October 2025. A second asteroid named Cue Ball orbits inside of Earths orbit and has a near miss with Eight Ball in January 2024. A mining operation is diverted to Cue Ball in 2022 to fully characterize its’ orbit, mass and composition. In the meantime a comprehensive survey expedition is sent to Eight Ball. Both teams follow transponder units that have been sent ahead to tag both bodies in order to nail their orbits down to within a few meters at any given time for the next decade. By the time both missions arrive, it has been firmly established that Eight Ball will strike Earth on October 11, 2025 at 9:35 PM Grenwich time with the center somewhere in Iowa. The daylight strike will obliterate the US instantly with the rest of the world to follow in short order.

Cue Ball is determined to mass a megaton itself and has a rubble pile composition. A large boulder or bag of pebbles is lifted off the surface of Cue Ball and suspended a short distance above the surface, The mining ship reels out enough tether to be well clear of both the bag of material and the asteroid itself. Using solar sails or ion engines or both, the mining ship uses the ISRU material as a gravity tractor to change the orbit of Cue Ball. With a constant track of orbits of Cue Ball and Eight Ball, the adjusted orbit is changed enough that Cue Ball will strike Eight Ball dead center on January 15 2024.

The mining ship stays to Shepperd Cue Ball all the way to impact. With a megaton of rubble impacting a gigaton of asteroid at 10 km/sec, the orbit of gigaton Eight Ball, or its’ resulting rubble, should change by an average of 10 m/sec. If everything went according to plan, Eight Ball, or its’ debris field, should miss Earth outside the orbit of the moon. 

The mining ship for Cue Ball is now in the wrong orbit to follow the results, but the  survey expedition to Eight Ball can stay on site for a while after the impact to assess the result. If Eight Ball has been determined to now be in a safe orbit, the survey expedition does a comprehensive after strike analysis of the results. Any useful and readily available materials are collected for return to whichever facility seems appropriate for research or exploitation.

If Eight Ball has not been safed, then the survey expedition must go to diversion plan two. Diversion plan two is the one you suggest.

In the gravity tractor post, there seemed to be some misconception that there is One True Way to accomplish a given goal. I think this is a mistake. We need as many different options as we can get if this comes to pass. Not to build all of them in the hopes that one of them will work, but to understand as many possibilities as we reasonably can. Under real threat, it is amazing what an individual or nation can get done.

Nukes are the favored response by many, and properly so in my opinion. Unfortunately there are people that would rather the planet die (Or at least humanity) than allow such nasty things to be used. Some would go so far as to say that a dinokiller on the way would be the will of God and that we should accept his will. We cannot ignore either of those viewpoints entirely or many others that don’t share our desire to live and prosper from now on. We also don’t have to let them dictate our options, and possibly demise. The first set of tools in the toolbox must include as many useful methods as possible for dealing with people, politicians, and organizations that would prevent even the attempt to save our civilization, however flawed.

Another type that must be dealt with are the ones that will hold the whole planet hostage to their agenda. Think of how many times some apparently worthy bill in congress has had so much pork and so many riders on it as to reverse the original intent. Now multiply that by every special interest world wide that has any capability of  hurting an effort at planetary rescue. It shouldn’t be hard to imagine a terrorist/freedom fighter with ASAT capabilities demanding religious freedom for the cannibal society of Northern Muckistan or the orbiting depot gets hit. Unfortunately, any critical mission to save the planet will have to have layers of defenses against people that would take us all hostage to their agenda, or even want to stop even the attempt.

Others will believe it is a manufactured crisis to take resources from their pet projects. With the layers of disinformation in the world as it is now, fully answering those groups is nearly impossible. Look at the financial mess of most of the nations in the world today for an understanding of the reluctance of leaders to tackle the core issues that are a cancer to their own people.

The tools to handle the people are the most critical to the eventual success of any planetary defense. They are also the ones I have no grasp on except to know that they must be available for the possible emergency. I do know that they cannot be safely ignored.

The technical side is sooo much easier and fun. We can consider all kinds of ways to deal with dinokillers and city busters without mental heartburn. We can discuss nukes and gravity tractors. Argue ion engines and solar sails. Debate nuclear thermal engines for getting there vs depots for chemical rockets vs microwave powered ion drives until we can’t stay awake any longer without losing any sleep over the winners or losers. How to attach or even if we should have a physical attachment. The comment in the last post about there possibly only being time for one probe when I think we would find the time and launchers for instance can be debated now when we are not under threat.

Let us add to the toolbox as much as we can so that if the mechanic needs to go to Dinokiller Humanitykiller One, it is just a matter of grabbing the right wrench. The right time to buy a repair kit is not when you are stranded a days walk from civilization, but rather when you are packing for the trip.

Due to the lasting nature of communicating on these various internet sites, I am on record in several places as saying that gravity tractors for moving asteroids are stupid. I could see no way that gravitational attraction between an asteroid of a few hundred thousand tons and a spacecraft of a few thousand pounds could make sense as a means of linking them for thrust, however gentle. So after my last snark over at transterrestrialmusings.com, Doug Jones destroyed my  little conceit with numbers. John Schilling weighed in with a bit more conceit destruction.

Doug brought in something that I hadn’t realized with his numbers. He worked them with a spacecraft mass a couple of hundred tons. I had made the assumption that the craft would be yet another of the fragile constructs similar to most probes flying out there now. With a couple of hundred tons of spacecraft though, it becomes possible to have enough coupling to actually move the asteroid, albeit very slowly. The other two things Doug and John Shilling brought in were the difficulty of finding good attachment and the fragile nature of rubble pile asteroids. The lasso and drag that I had assumed could be more difficult than I had thought and might just tear the rubble pile apart.

Without the numbers from a known rocket scientist, plumber, I might have quibbled a bit more even on the losing end. I am not, after all a graceful looser, nor do I like being shown up as a fool. So as revenge, I modify the concept to fool people into thinking that maybe it was my idea all along. If two hundred tons is good, two thousand tons would be better, especially with ISRU.

Sending a two hundred ton vehicle to a dangerous asteroid would be a bit difficult today. IMLEO would probably be on the order of a thousand tons or so. Even under the dinokiller or city buster threat, the empire builders might just delay things by scarfing funding for heavy lift, nuclear thermal, or other program that could easily extend beyond the launch window for the threat.

I suggest it might be possible to get similar results with less spacecraft with a bit of low tech ISRU. The spacecraft uses the previous flyby surveys to locate a boulder that masses enough to generate the gravity attraction desired. It lassos the boulder from the rubble pile and pulls it free of the rest of the asteroid. The spacecraft then pulls the boulder into the appropriate location to attract the rest of the asteroid along the desired thrust vector. The craft lets out enough tether to hold the boulder in the right place while being well clear of the asteroid itself.

The advantages would be less cosine losses from the thrusters as the spacecraft itself would be well clear of the asteroid at the end of the lasso/tether. Acceleration could be higher with more mass of ISRU boulder than deliverable spacecraft. And less spacecraft to get the job done, which could be the difference between on time success and too little too late with the original concept if too much time is wasted on ‘perfection’.

Quite often some form of bulldozer on the moon or Mars to dig ores or cover habitats is suggested. There seems to be a meme out there that the best way to move sandy gravely material is similar to the way it is done here on Earth. It is sometimes suggested that this moondozer will have to be weighted down to get sufficient traction to dig up the packed lunar regolith for mining or radiation protection.  A better approach might be to design a more limited machine for a specific type of task. Such a design effort might profit by looking at older technology that was in use before the availability of large reliable diesel engines. People that had to do things with a ten horsepower engine that weighed a ton* or more had to find ways of applying that power.            *On display at Florida Flywheelers park in Ft Meade FL.

One reason for looking at other techniques are shipment costs from Earth at  a hundred grand or so a pound, depending on assumptions. My small Caterpillar rubber track loader weighs about seven thousand pounds.  Seven hundred million dollars to deliver a machine that won’t even work properly when it gets there is a show stopper. It would weigh about twelve hundred pounds on the moon which wouldn’t provide enough traction to dig up packed soil.

The second main reason is the problems of a mobile power plant in an airless environment. Even if you put an electric motor with the same power in my loader, it would need a massive extension cord to deliver voltage for a sixty horsepower engine. That or a massive battery pack that would be even heavier and more shipment cost. Heat dissipation from both the electric motor and extension cord would be a problem with no air to get rid of the excess heat.

The traction issue would be as large a problem as the heat dissipation unless a few tons of ballast were added to the loader. The view of most equipment designers I’ve talked to seems to be that ballast is a sign of poor engineering. Whether that is totally true or not, it remains that carrying excess mass costs energy and causes equipment wear.

My excavator weighs about the same as the loader and would have many of the same problems. Anyone that has ever tried to dig hard ground with an excavator or backhoe will understand that the machine needs weight to hold it down. Then the material has to be transported to the ore processing facility  or habitat being covered. Excavators do poorly at material transport.

Robots of smaller dimensions will certainly be used in the early stages. Moving a hundred tons of material with a hundred pound machine is certainly feasible in a lunar day. The problem is that even the smaller robots have the same drawbacks as the larger machines.

An older tech that is still in use is the pan type machine. Still in use today hauling millions of tons of material around mines and construction sites, they started out much smaller behind horses. In the simple description, a pan is a box with four wheels and an open end. The horses, oxen, or tractor drag the box along the ground with the open end first. As the box fills, it adds weight to the pan, which both makes it harder to pull and adds ability to dig deeper. When the pan is filled, the box is raised just a bit to clear the ground and the material is transported to the material dump site. At the dump site the bottom of the box is opened so that the material falls out in the right location. Different techniques like shovels or bulldozers are used to push the material the last few feet when desired.

A different old tech is a stationary traction engine pair. A steam engine, windmill, or early internal combustion engine at a fixed location pulled a cable across a field. The plow or other farm implement attached to the cable was pulled across without the need for wheels or tracks that could supply the traction. The best current mind picture would be a couple of fast winches on opposite sides of the field to drag the implement back and forth. As clumsy as this method is to us, it was an advance on feeding and tending livestock year around in some parts of the world when they could only work a few months a year at best.

For a Lunar regolith mover, I suggest a single traction engine at the mine or habitat site that pulls a simple pan to gather regolith and pulls it right up to the stationary location. The traction engine can be powered by solar or nuclear power that also serves the base. A tiny electric motor on the pan just sufficient to move the empty pan reverses to the back of the digging area before the next regolith pull. The traction engine can serve two or more pans by pulling in one while the other reverses for its’ next load.

The first landing with telerobotic pans and traction engines could well total under a ton. A few pans that weigh ten pounds or so each with a similar mass of cable could be used to test gather material to the stationary lander. A ten pound pan could gather fifty pounds or so of material on each pass. At ten miles an hour and a 300 foot radius, each pan could make seven trips an hour. Two pans could gather seven hundred pounds of material an hour for a total of about a hundred tons during one Lunar day.

The stationary power source could be shielded by the first lunar night with regolith which, sun heated, could keep the machinery warm until sunrise. If nuclear powered instead of solar, it could run an active base on a constant basis. A pre-landed human base could be radiation protected by a very small system in a fairly short time. Given a few cycles of small development, a large mining operation could be assured of reliable large scale gathering on the first try.

After development and test on the moon, it should be considerably easier to engineer soil movers on Mars and other low gravity, no oxygen bodies in the solar system.

 

 

After following a discussion on ARocket for the last few weeks, I had a thought on building propellant tanks that is mostly a combination of other peoples’ ideas. John Carmack made a good case for spiral welded propellant tanks. Instead of sheets of material welded at all four edges, a roll of material is used to produce a tank out of one continuous piece of metal with a continuous spiral weld. You get the full hoop strength of the base material with the welds only potentially weakening the long direction. Others discussed methods of producing isogrid tanks, which are desirable for the relative stiffness for a given tank weight.

 

The only problem with spiral welded tanks seems to be that it produces a tank with uniform thickness walls. Not too bad for pressure fed at current sizes and pressures, possibly a problem in larger sizes or pump fed vehicles. The apparent problem with isogrid tanks seems to be enormous labor costs of milling in all the little pockets in the full thickness of material that must be removed. Well over half of the original metal is removed by machine tools or chemical milling with some mention of combinations.

 

I am thinking in terms of producing isogrid tank material from a continuous roll to produce a Carmack style spiral welded tank out of isogrid material. By creating the isogrid material in a continuous piece before it is formed into a tank, less labor intensive and wasteful machining operations become possible. I am thinking of hammer forging the isogrid recesses in an assembly line type operation. The aluminum roll is delivered and threaded through a hammer forge with a die to match the isogrid recesses. When the die hammers into the material, the aluminum is squeezed up into the grids similar to the way a cartridge case is formed. With the pocket material forced into the grid sections, no material has to be recycled or trashed as in the milling options.

 

I have seen video of industrial stamping with the hammer seeming to come down every second or less. If it took ten die hits to create a single set of grids of an inch in length, then the material would be moving through the process at six inches per minute or thirty feet an hour. Two hundred forty feet an eight hour shift of four foot wide material would be nine hundred sixty square feet. That would be about thirty feet of ten foot diameter tank. Depending on the height of the grids and the characteristics of the material being forged, it may be necessary to have multiple forging machines with annealing steps between them.

 

Pressing or stamping parts is frequently mentioned as one of the most economical of metal shaping operations. The machines are very old tech. The skill required after initial set up is reported to be minimal. The tooling dies should be considerably cheaper than the milling bits, especially over the life of a long production run. They are said to be low maintenance production machines. An appropriate machine could probably be found in a closed factory considering the economy and the off shoring of so much manufacturing.

 

Roll forming the material for the spiral welding process is also old tech that should probably be done as the stamped material exits the forging area. For tanks four meters diameter and under, it could be set right on the semi trailer as it exits the rolling operation even if it is not welded at that time by having supports built into the trailer to handle the incomplete tank to prevent deformation during transport.

 

 

 

A ten foot diameter tank one hundred feet long would require less than eight hundred linear feet of weld using the Carmack spiral concept. The dome ends would be a separate assembly of course. This would be ideal for an automatic welding process as the material would be fed past the welder at a constant rate dictated by the initial stamping operation. Extra material could be left on the edges to compensate for any loss of strength the welding caused. At the production rate of material I suggested, it would take just over a three shift day to do the ten by one hundred foot tube. Thirty feet of weld an hour is six inches per minute. This should be slow enough to allow continuous inspection with fixed x-ray and other devices as well as allow time for correction while the tank is very near the welding station.

 

This is not an area I have ever studied. I will be interesting to see if there is any merit at all in this thought post.

 

With yesterday’s meteorite impact in Russia, I’ve seen several clever tweets featuring this clever picture:

But to me, meteor impacts today are nature’s way of asking “Have you thought about donating to the B612 Foundation’s Sentinel Mission lately?” Most serious students of NEOs have suggested that a space-based IR telescope like Sentinel is the key to really understanding what’s out there in our planetary backyard, which is the first real step towards actually being able to predict and potentially do something about asteroids like the one that hit Russia yesterday.

And unlike signing a petition on WhiteHouse.gov asking for the government to raise everyone’s taxes (or run up the credit card) to give NASA a bigger budget, or making clever tweets on the internet, donating to the B612 Foundation actually has some probability of making a difference as far as planetary protection goes. Sure it will actually cost you more than a few seconds of your time, but it would definitely be a good way to put a little money where your mouth is if you really care about planetary protection.

I don’t have a lot of cash, but I think I’m going to skip lunches next week so I can at least chip in the minimum donation.