Foot hold for manned missions

GW Johnson · 2019-11-28 09:53:54

It is possible to find a paper to cite that says anything you want it to say. All you have to do is look long enough. Being published is not, and has never been, a guarantee of being correct.

I put an article up on "exrocketman" with real pictures taken by Opportunity before it died. This is published NASA data, and indicates that Opportunity's engineers said 11% of normal insolation was required to keep the rover alive. It got down less than that, or else the rover would not have died.

Actual data outweighs cited papers, anytime, anywhere.

If you actually want to look at the real photos and see what the actual NASA article said, go to http://exrocketman.blogspot.com. It's this year (2019), click on "October", then click on the title "A Note on Solar vs ust Storms on Mars".

GW

Oldfart1939 · 2019-11-28 10:12:18

GW Johnson wrote:

It is possible to find a paper to cite that says anything you want it to say. All you have to do is look long enough. Being published is not, and has never been, a guarantee of being correct.
GW

GW- Truer words have never been spoken (or written!). In my 45 year career as a professional chemist, I've been plagued by published experiments that I could not reproduce in my laboratory in my own hands. In many cases, cost me dearly. Even "peer reviewed journals," have fallen prey to flat-out lies.

I'm sure if others look long enough, they will find a review in print discussing which variety of cheese from which the moon is made; no doubt with other references "in print."

Back to the issue at hand; I'm certain that ANY NASA mission to Mars WILL HAVE NUCLEAR POWER. Period. End of story. The current NASA aversion to risk tends to follow the British "belts and braces" approach to holding up one's trousers. Yes. There is a place for solar power; most notably for recharging batteries of construction equipment. But under severe dust storm conditions, all will be plugged into the nuke power in order to protect the batteries.

Calliban · 2019-11-28 10:29:23

GW Johnson wrote:

It is possible to find a paper to cite that says anything you want it to say. All you have to do is look long enough. Being published is not, and has never been, a guarantee of being correct.
I put an article up on "exrocketman" with real pictures taken by Opportunity before it died. This is published NASA data, and indicates that Opportunity's engineers said 11% of normal insolation was required to keep the rover alive. It got down less than that, or else the rover would not have died.
Actual data outweighs cited papers, anytime, anywhere.
If you actually want to look at the real photos and see what the actual NASA article said, go to http://exrocketman.blogspot.com. It's this year (2019), click on "October", then click on the title "A Note on Solar vs ust Storms on Mars".
GW

GW Johnson wrote:

Extracts from GW's Exrocketman, re Martian dust storms:
'Quoting NASA: “99% reduction of direct beam radiation, leaving only diffuse radiation”. Diffuse is usually at most 10% of total.'
'It looks like recoverable power levels went down to something in the 5-10% range (all diffuse) for too long, which is what drained the batteries and “killed” the rover in the cold.'
'The Mariner 9 event in 1969 was worse still: no one since has reported the volcanoes on Tharsis Mons to be obscured in the dust layer. But in 1969, Mariner 9 observed that they were completely obscured, for some 6 months. From adjacent surface to peak, these volcanoes are about 15 km tall. The Martian atmosphere didn’t fully clear for 9 months.'

I think this realistically kills the idea of a solar only solution for any realistic Mars mission. Storing six months' worth of power, or expecting a crew to live on emergency power rations for that long, just isn't an affordable or tolerable situation. Keep in mind that the round trip efficiency of storing electrical energy in methane-oxygen synthetic propellant, is about 5%. How much extra weight does a mission need to drag along just to cope with this contingency?

Longer term, into the colonisation phase, why would a Martian society rely upon an energy source that might get cut off for six months? can you imagine a situation on Earth, in which 90% of grid generating capacity disappeared for six months? The absolute chaos and breakdown of civilisation that would cause.

Last edited by Calliban (2019-11-28 10:37:10)

GW Johnson · 2019-11-28 10:54:46

BTW, Happy Thanksgiving, all!

Oldfart1939: thanks for the vote of approval. I don't disparage the Brits for using the notion of "belts and braces". Working in an explosives plant for 2 decades, I had to be a "professional coward". Nobody ever got hurt or killed on my watch. My version of the Brit sentiment is "suspenders, belt, and armored codpiece".

(You'd be amazed how few people today even know what a codpiece is. Which just goes to show how improperly history is being taught to the young.)

That being said, that approach does NOT preclude doing new and daring things, unlike what has been happening at NASA. I worked in cutting-edge new product development, and built and tested a lot of prototypes for things that hadn't ever been done before. With those very explosives.

Taking the precautions is not equivalent to never attempting the experiment out of fear.

Calliban: thanks for the 5% 2-way efficiency figure on methane-LOX as a power source. I had no idea it was that low. Century-plus old lead acid battery technology has a 2-way efficiency of 50%.

There's nothing wrong with renewables like wind and solar, as long as you recognize that they are inherently very variable, and very intermittent. Mars is unique with its giant dust storms. We have no experience here at home with storms lasting months. But we have seen it happen on Mars. Erratically, occasionally, and in that sense, repeatedly.

I favor nuclear power to serve as base load power on Mars. The heating, water production, and oxygen-generation processes are required steady-state. Mars is cold, next-to-a-vacuum, and poisonous to breathe even compressed. This part of life support there CANNOT be subject to variability and intermittency in its power source. You just have to have something steady.

More optional stuff might be building and infrastructure construction activities. No one will be outside doing that in the dark of a raging dust storm, where you cannot see your gloved hand resting on your helmet faceplate. You just need two sets of vehicles and equipment. Two, so one can charge during daylight on solar while the other can be put to work.

As for propellant production, I am no chemical engineer, so Oldfart1939 might be a better expert to consult. But to my knowledge, in that industry, there are almost no batch production plant designs and equipment available. As best I understand, nearly all that stuff works best as steady-state operation, day/night, 24/7-365. There is no credible reason to even suspect that propellant production equipment operating on Mars would be any different. So, that's just more base load for the base load nuclear power.

Sorry, that's just what it's gonna take to build anything but the very smallest outposts on Mars. And without it, even some of those tiny outposts might die in the dark and cold.

Nuke and solar are the only two power sources we know how to use on Mars. There might be a wind-power solution, but it certainly is far from being ready to use (0.7% of Earthly air density is a real problem). The trick is not choosing between wind solar and nuke, but knowing THAT you need both, and also knowing HOW MUCH of each to employ, and for what purposes.

GW

Last edited by GW Johnson (2019-11-28 11:04:44)

Oldfart1939 · 2019-11-28 12:39:22

GW-
I agree that no single source of power should be relied upon, and both solar and nuclear have important roles. Bottom line is, nuclear must be utilized for the basic living power consumption role; the rovers and outside experiments can use solar.

To give a basic overview of chemical processing methods: (1) batch operation, and (2) continuous flow processing. I'll give some very basic descriptions of what these entail for those here who have some interest, as well as facilitating future discussions.

(1) Batch processing. That is pretty simple, since that's what we do when we cook a meal, bake a cake or cookies. We start with a vessel in which to conduct the processing; at home, this is a pot or mixing bowl. In a chemical plant, it would be a Pfaudler or DeDeitrich reactor, which is nothing more than a giant, stirrable pressure cooker. These normally have a jacket around the reaction zones, and either heating or cooling is possible--mainly used to maintain an exact reaction temperature. So--a batch reactor is pretty basic component of any process facility.

(2) Flow processing. There are several analogues that come to mind as flow processes. The easiest to understand is a forced air gas furnace, where cold air is sucked through a heated plenum and warmed to the desired temperature before being blown through a filter for dust removal.

The key here is that batch reactors are capable of handling solids with facility, but flow reactors normally function better with fluids ( fluids include both liquids and gasses). There are several processes needed for the Mars colony and manufacture of return fuel, and I'll address those below.

First and foremost is manufacture of Oxygen. Two possibilities come to mind; first being the Moxie system wherein Carbon Dioxide is catalytically split into Oxygen and Carbon Monoxide. This is a prime candidate for a flow process, wherein the compressed Mars atmosphere is run through a long tube filled with the appropriate catalyst, and the effluent from the tube contains products as well as some unreacted starting materials. Not sure about the remaining apparatus for separation of the toxic components from Oxygen (desired product). Second process is electrolysis of water to produce Hydrogen and Oxygen. This too, can be a continuous flow process, as the products are both fluids and starting material is also fluid.

Preparation of Methane from Martian atmospheric Carbon Dioxide is definitely a flow process, and products are also fluids which can readily be separated by simply cooling the system wherein water condenses from the vapor phase. Clean, gaseous Methane is passed along to a cryogenic plant for storage.

Here's one of the imponderables: where do we get water? If we find a conveniently placed subsurface glacier, then the steam injection process suggested by GW is THE answer. Alternatively, we find regolith containing a significant amount of water but then we are faced with a multiple batch processing situation; mining and cooking regolith in a series of batch reaction systems. Probably would need 3 big reactors and a couple big chemical centrifuges. Why do we need this type setup? Easy; one reactor is being loaded with frozen regolith or heavily regolith-contaminated ice chunks are loaded into a huge reactor, the top sealed and the water cooked into a mud slurry; the second is "in process" while one is being loaded; reactor 3 is in process of discharging the regolith "mud" into a centrifuge. This has a possibility of sufficiently "cleaning" the regolith from perchlorates and generation of agricultural "soil." This is often referred to as a continuous batch operation.

All of these fanciful ideas about how easy everything will be may originate with those never facing the real world of chemical operations. Chemical industry will be the FIRST industry on Mars, if we want to keep breathing, return to Earth, eat food, and drink water.

SpaceNut · 2019-11-28 14:12:35

Bottom line is we are at a crawl with man pressence on mars with rovers and probes ect with the BF starship combination at a full bore run... We will need something in between that will allow for man to get there prove we can do it safely and survive to come back home. Once we do that we will get way more funds and chances to get going to stay.

Currently we have capability to land around the 2 mT of payload to the surface and need to get it higher so as to allow for a design of equipment to make sense. Theoretically we should be able to get to 20 mt payloads with with larger heatshield, adapt, hiad and hypercone but when are the missions to go to mars going to take one of these along for proof of use?

GW Johnson · 2019-11-29 10:57:10

There is a technology-ready-to-apply issue often lost in our discussions. For example, the EDL technology Spacenut just mentioned. Ordinary heat shields, supersonic parachutes, and last-second retropropulsion work for landing up to around a ton or so. That's what we have been using since Viking.

The science/physics limiting this to 1 or 2 tons on Mars is well-established, and fundamentally just a ballistic-coefficient type thing. Higher tonnages are higher ballistic coefficients, even if everything else is unchanged, simply because of square-cube scaling. You come out of hypersonics at too low an altitude to get a chute deployed, much less have the time to decelerate significantly below high supersonic.

You either lower your ballistic coefficient, or you do "something else" to land. There are no other choices.

The extendible heat shields (HIAD, ADEPT, etc) are a means to lower ballistic coefficient by adding lots of area and only a little mass. This technology has seen a couple of experimental tests that were feasibility demonstrations, but nothing more. They will not be ready-to-apply technologies anytime soon. You will have seen many payloads returned from Earth orbit, experimentally, and then routinely, before it is even conceivably worth the risk to try them at another planet. Nobody has yet stepped up to the bar to do that development work.

That's not to say they won't work, because they will. Eventually. How long do you want to wait for it?

One of the "something else's" is to delete the chute entirely, and just go to retropropulsive landings as soon as the hypersonics are over. It's more propellant to carry, but it offers an "out" when chutes don't, for those same fundamental science/physics reasons. This technology is exactly what Spacex (and to some extent Blue Origin) have been doing, so it really is becoming ready-to-apply, but not by "everybody" yet.

Knowing that not "everybody" can do it means you have fewer vendors to go to, if this is required for what you want to do. Alternatively, for Spacex, this is how you acquire high market share, in the transient interval before "everybody" can do it. So, guess why Spacex is NOT a favored contractor for NASA yet!

Now, doing retropropulsive landings on Mars is NOT the same as doing retropropulsive landings on Earth, precisely because the surface air densities are so wildly different. Landing on the plains of Mars would be very much like landing on an Earthly plateau about 110,000 feet above sea level, where the air pressure is first cousin to space vacuum. There is little wind pressure (dynamic pressure) with which to make lift, unless you are still high supersonic. It is THAT different, and so almost-impossibly hard to test here on Earth, because such a high plateau does not exist here.

So, this technology may be just-about-ready for Earth, but is NOT YET ready to apply at Mars! Not by a long shot. Not yet. Many more tests here have to be run before Mars can be attempted. I harbor severe doubts about the pull-up Spacex depicts in that thin air to set up the tail-first flip and retropropusion ignition. I think they will need thrust to pull up at all, which means they start it at end of hypersonics, not in a transonic pull-up a km or two from impact. More propellant than they are planning.

Sorry to throw a wet blanket on how ready we are to go, but building cities is way premature. NONE of the supporting technologies for that are ready-to-apply on Mars. Not electric power, not making oxygen, not obtaining water, not making propellant, not construction equipment and procedures, not even rovers. We are ready to visit briefly. We ARE NOT ready to stay permanently.

Spacex is trying to build the rocket to get there from here. Nobody has seriously bellied-up-yo-the-bar to create and make ready those other things. NASA has tinkered with nuclear reactors, but has downsized to 10 KW electric, from an earlier 400 KW electric. When they should be looking at MW scale. The rest is just academic lab-type benchtop feasibility experiments, not usable technologies. Not yet.

Spacex needs a backup plan: I would suggest 6 or 7 Starship tankers sent to Mars to refuel the one Starship with a crew, so they can come home. The crewed ship can carry some experimental prototypes for this other stuff, and leave them there running, to see if they really work at all. Small crew, lots of tonnage.

But they need a lot of practice refueling from those tankers, while sitting in a gravity well and vacuum, before they bet lives on it for Mars.

Sorry, that's just my realistic estimate for how to do this without killing crew after crew. Something not even Musk can afford.

GW

Last edited by GW Johnson (2019-11-29 11:39:32)

louis · 2019-11-29 12:00:16

There seems general agreement that the requirement for propellant production will be more like an average of 1MwE. You adjust PV array size to account for worst case dust storm scenarios. If you were losing 60% of norm over 9 months out of maybe 18 months of propellant production, then you might need an array that is 30% larger than would otherwise be the case. You probably need to build in some loss in efficiency also for battery charging and for potentially building up methane-oxygen as an emergency energy store. So you might be looking at a system that can generate 1.4 MwE average in normal conditions. I'm guessing that might mean you need something like 7 MwE capacity. That might translate into an array of something like 200 metres x 200 metres with a mass of around 40 tons.

SpaceNut wrote:

In this era of flight to mars we are stuck with payloads of 20 mt and at best no more than 50mt preloaded for the next decade when man could go.
So lets go with the 40% typical over just how many months, with some getting even deeper for a couple months for the dust storms.
Lets say we have 2 x 100 kw solar array systems and batteries to match as thats all we could preload for a single manned landing.
Now lets say we need 100 kw just to sustain ISPP fuel production and 50 kw to sustain mans life support of that 200kw.
A storm that last months at 40% means we are at 120kw available for the support of man to stay and be able to leave.
So what gets sacrificed will be the ISPP fuel production during that time span.
Also man's life support may be able to trim to 40kw but its probably not going to get all that much lower.
I hope that the compound losses on a fixed level of energy can not cause a lose of mission or that the worse we could expect for out come is missing a return home cycle. With that man could only hope that the next cargo cycle delivers more arrays and supplies and not a new crew to allow for a prolonged stay to survive.

SpaceNut · 2019-11-29 21:35:28

Well a 20% gets you an array of solid thin film of a panel that is with frame at least an inch in depth and you need to have 40,000 panels stacked inside a tiny volume that can only handle 2mt... which for the mass is 20 capsules to mars and by volume you need even more as a stack of the panels would be 3,333 ft tall.

The flexible thin film have efficiency sub 15 % not sure of mass or of the roll down size which they can be fitted into the capsule.

https://www.spacex.com/dragon https://en.wikipedia.org/wiki/SpaceX_Dragon
SpaceX’s Dragon capsule back on Earth with 3,400 pounds of cargo but thats with a parachute and splash down to which for mars means a trade of parachute mass and boosting the fuel to do a retro landing.

while its 4 m diameter its got an internal volume of just under 9 and about 6 m tall or roughly 200 inches.

shape is anything but not adaptible for the panels to fit in. of which a single from the door upward stack and maybe 2 or 3 in a layer until we are at the door hatch entrance at maybe 1.5 to 2 from the bottom. Sure a man could load from the top hatch but if we can not get them out of the normal hatch then we will have a problem with that one as well.

So 200 panels single stacked per capsule out of the 40,000 you think we need is 200 capsules and if the number is 250 or 300 then the count will drop to 160 to 135 by volume required and thats just the panels....

SpaceNut · 2019-11-30 19:28:22

The thin film plastic flexible while its bendible the radius seems to be quite large for a sheet panel and its a 1/4 to to 1/2 due to the wiring attachment of the panels which will need to be wired together to form the voltage output that we desire.

https://www.alibaba.com/showroom/flexib … panel.html

https://www.alibaba.com/showroom/flexib … -roll.html

louis · 2019-11-30 19:45:32

I think Flisom is probably the closest to what I envisage.

https://flisom.com/industries-customize … els-films/

There is no need for heavy supportive frames on Mars - there ain't gonna be no hail, no thunder and lightning, no powerful tornadoes, no earthquakes, no floods, no rainstorms, no snowstorms...

The thin PV film could be attached to v. lightweight steel supports at intervals.

SpaceNut wrote:

The thin film plastic flexible while its bendible the radius seems to be quite large for a sheet panel and its a 1/4 to to 1/2 due to the wiring attachment of the panels which will need to be wired together to form the voltage output that we desire.
https://www.alibaba.com/showroom/flexib … panel.html
https://www.alibaba.com/showroom/flexib … -roll.html

SpaceNut · 2019-12-01 11:51:39

If we can make the first circumference 4 meters for the 4 panel layer for maximum bend and work to the inner diameter from the outer winding them in from the hatch door would be very difficult so its got to be from the top hatch for going in and out. That makes the inner diameter about 1.5 meters with the outer diameter say 3 meters. Panel is 1 cm depth per layer winding them in a circle inside each other.
So 70 layers of 4 panels on average is 280 possibly 300 max coiled up inside the Dragon.
That makes flexible only marginally better but at a 1/3 less power....

SpaceNut · 2019-12-01 14:22:30

This is my question is that if we used the fairing or shroud for mars lander design could we do better as the shell would stay intact until its on the surface using retro rocket landing. All that would be ditched on the way down is the heatshield to all of the landing struts and engines to do there thing for a mars cargo lander.

For the ATK ultraflex panels in a capsule cargo the motor would load in first from the top and would guess that we are looking at 10 to 15 assembly pairs. The sizing of the sets are customized in wattage and size so its going to hard to figure out the exact numbers but from this we do know what can be done. Mars solar for a pair is 10kw upward on diameter sizing.

http://rascal.nianet.org/wp-content/upl … tsheet.pdf

https://www.jpl.nasa.gov/nmp/st8/tech/solar_array3.html

https://esto.nasa.gov/conferences/nstc2 … 7-0048.pdf

tahanson43206 · 2019-12-14 07:32:20

The article at the link below may be old news on the NewMars forum, but if it is a reprise may be in order.

It definitely seems to fit the theme of this topic:

https://www.yahoo.com/news/nasa-pinpoin … 00732.html

(th)

SpaceNut · 2019-12-14 11:06:14

We have seen the water ice reports for a decade now from all of the various probes and landers making all sorts of claims as to the quantity and quality of what can be gotten without any attempts to get a lander rover combination to any of these locations to prove out any and all claimed sensing facts.

Its just one of the keys needed for man to be able to go in any quantity of crew and to be able to return safely from Mars.

It is also the reason that man would go more than 1 time to mars as well in that we are assured the long term safety and growth of science exploration on mars as well can expand to become settlers.

Its just the first step in insitu materials locating and use to make it possible for man to survive without a constant resupply or preloading site cargo trips long before men step foot on mars.

Nasa is also struggling with getting sufficient payload mass to mars currently just under 2 mT, let along getting it for a reasonable cost with its not yet flown SLS orion combination.

Nasa still has yet to make a lunar lander let alone a mars crewed vehicle for mars landing. With the decades being kidded down the path towards mars.

GW Johnson · 2019-12-15 11:51:03

There is definitely ice on Mars. The real questions are what forms and how clean or pure? The answers vary greatly. Each answer demands different equipment and processes for recovery. All are heavy and energy-consumptive.

The Mars polar lander did not dig deep enough to find what we might call permafrost. What it uncovered were ellipsoidal lenses of ice scattered like rocks in the surface regolith, just not real numerous compared to the stones. And this was near the polar cap. Maybe that permafrost is down there somewhere, and maybe it is not. Point is, we still don't know. Not knowing will likely kill.

That scattered-thinly sort of thing will be like gold mining: you will have to process vast quantities of regolith to get just small quantities of ice, when you need tons of it per day. That is just NOT attractive at all in terms of effort and energy required. Even if done by robots. Effort wears them out, you know!

There is photography that suggests massive buried glaciers in many places on Mars. The trouble with that is no ground truth. ZERO. The history of remote sensing suggests (1) yes, we are better at than we were in 1965, but (2) we still get it wrong enough to screw up projects and maybe kill people.

"Massive buried glaciers" could be anything from huge buried layers of ice to intimate mixtures of ice and rocks/dirt. We just do NOT know. It would be prudent to set a robot lander down on one of these things, equipped with that Canadian drill rig, not the cockamamie thing we just sent on Insight. We might get an answer for that one site we land on. But I would strongly caution AGAINST generalizing to other sites.

I notice that no space agency has even proposed to send such a thing. Not so very prudent after all, are they? Does that qualify as brain dead, in the context of proposing manned Mars missions?

Spacex has its hands full developing the transportation. But, I see nobody working on real equipment to recover the resources Spacex already has said it has to utilize for the trip not to be one way. Lab benchtop experiments are NOT usable equipment. They simply say it is possible.

So EXACTLY WHO is developing said equipment? The silence is deafening. Only crickets chirping. Sometimes.

So if you cannot trust government-run space agencies not to behave totally brain-dead, and there aren't enough visionary companies out there working on the necessary equipment, then just precisely how is that first mission to Mars NOT going to be a one-way suicide mission, even if any of us actually live long enough to see it happen?

I have good reason for such pessimism. Even though I hate being pessimistic.

GW

kbd512 · 2019-12-15 14:23:11

GW,

Quite right. It's readily apparent that nobody with serious funding is working on any of these required supporting technologies and that would be why we need not worry about a Mars mission happening at any time in our immediate future. Until I see a Sabatier reactor design that's capable of producing a couple tons of propellant per day, I won't believe that anyone is serious about going there and coming back. Im sure that there are people who are willing to undertake suicide missions just to say they went somewhere new, but there's not many of those people with the intellect required to contend with all the potential problems and most governments simply won't allow their citizens to undertake suicide missions with no clearly definable reasons mandating that type of sacrifice.

SpaceNut · 2019-12-15 16:17:55

So what is a mT of liquid methane relate to volume and that of gaseous methane as we make it for later use?
https://www.engineeringtoolbox.com/meth … _1090.html
https://www.aqua-calc.com/calculate/vol … ank-liquid
Most are familar with the 1,000 gallon liquid propane tank for size....A standard 1000 gallon tank holds 800 gallons of propane and is generally installed for commercial and industrial applications. Large commercial and industrial installations may require multiple 1000-gallon tanks. Each tank is 16’ 1½” long and 41” in diameter.
https://www.gasteconline.com/tank-chart.php

SpaceNut · 2020-01-05 19:51:59

future of being on mars to stay requires that we get to this level of insitu use....

tahanson43206 · 2020-01-05 20:47:06

For SpaceNut re #44

Impressive find!

SearchTerm:FlowChartMars

http://newmars.com/forums/viewtopic.php … 22#p163922

SpaceNut · 2020-08-20 18:44:13

Energy in must be efficiently used to get the most out of valuable resources.

SpaceNut · 2020-09-20 07:08:30

This will work for a secondary location for the module data work up:

RobertDyck wrote:

Example of hull from Wikipedia: Multi-Purpose Logistics Module (MPLM)
Length – 6.6 m (cylindrical part 4.8 m)
Width – 4.57 m
Mass – 4,082 kg empty; 13,154 kg fully loaded
Habitable volume – 31 m3
Material – stainless steel
cylinder
4.57m diameter x 4.8m long, circumference = Pi x 4.57m = 14.357m
area = circumference x length = 68.913976449145704478916545255619m²
Wikipedia: Common Berthing Mechanism
Length ~16 in (0.4 m)
Diameter ~71 in (1.8 m)
Active CBM (Type I)
Mass 540 lb (240 kg) (specified)
mass without CBM hatch = 4,082kg - 240kg = 3,842kg
total length 6.6m - cylinder / 2 = 0.9m each cone
truncated cone surface area = 16.527204523019666m²
back end disk area: 1.8m diameter. area = Pi * R² = 2.5446900494077325231547411404564m²
total hull area = cylinder + both cones + disk = 68.913976449145704478916545255619m² + 16.527204523019666m² x 2 + 2.5446900494077325231547411404564m² = 104.51307554459276900207128639608m²
mass per square metre of hull: 3,842kg / 104.51307554459276900207128639608m² = 36.760950531598579018448795991648 kg/m²
round to 36.76 kg/m²
Ring radius to surface of floor: 37.6992m
Thickness of floor (guess): 5mm
SPACE STATION MMOD SHIELDING
Typical ISS MMOD shield: 2mm Al outer hull, MLI, Nextel, Kevlar, 4.8mm Al inner hull. Total thickness 11cm.
This is with an aluminum instead of stainless steel, but let's use 11.5cm total for hull thickness from surface of floor.
If someone wants to argue for aluminum alloy pressure hull like Discovery instead of stainless steel like Leonardo, then could you give me mass and dimensions of the hull without equipment or fittings?
So ring side wall is disk area subtract disk that isn't there.
Outside radius 37.6992 + 0.115 = 37.8142m
Inside radius 37.6992 - 2.4 - 0.115 = 35.1842m
(2.4 metres = 7 foot, 10.488 inches. And this accounts for 5mm thick ceiling treatment.)
Pi x R² (outer) - Pi x R² (inner) = 603.14m² (each side)
Floor hull: Pi x D where D is 2 x outside radius = circumference
Ring width is 19m + forward hull + wall panel against forward metal hull + aft hull + stand alone wall panel.
But the aft wall has a water reservoir / water wall. 10.2cm (4.01575") thick water tank. Wall panel will be 1cm thick to hold in water bladder.
Ring width is 19m + 0.11 + 0.005 + 0.102 + 0.11 + 0.010 = 19.337m
area = circumference x width = 4,594.348m²
Roof hull: assume flat cylinder (not arched), and not including greenhouse or observation deck.
Pi x (2 x inside radius)
area = 4,274.808m²
Total ring hull area: 4,594.348m² + 4,274.808m² + 2 x 603.14m² = 10,075.436m²
Ring hull mass = area x 36.76 kg/m² = 370,373 kg
This doesn't include interior pressure hulls or pressure doors. Can anyone help with that before we start with cabin mass?

RobertDyck wrote:

Alright. Cygnus Spacecraft
Cygnus standard PCM dry mass 1,500kg, enhanced 1,800kg
Diameter 3.07m
PCM length: standard 3.66m, enhanced 5.05m
passive CBM: 200kg
CBM length: 0.4m
cylinder:
length without CBM: 5.05 - 0.4 = 4.65m
difference between standard (2 segment) and enhanced (3 segment): 5.05-3.66=1.39m
so cylinder length of enhanced: 1.39 x 3 = 4.17m
end cone length: (4.65 - 4.17)/2 = 0.24m
area: Pi x 3.07m x 4.17m = 40.2m²
end truncated cone:
5.192982441052105m² each
back end disk:
Pi x (1.8/2)² = 2.54469m²
Note: Wikipedia article on CBM says diameter 1.8m, but Spaceflight101 article on Cygnus mentions the hatch "in the 127-centimeter [CBM] ring". I'm assuming 1.8m is outside diameter, 1.27m is inside diameter.
PCM surface area: 40.2m² + 2 x 5.192982441052105m² + 2.54469m² = 53.13m² (rounded)
enhanced dry mass without CBM: 1,800kg - 200kg = 1,600kg
density = 1,600kg / 53.13m² = 30.1148 kg/m²
That's a little lighter than Leonardo's 36.76 kg/m². And I used figures for Leonardo from its MPLM configuration, not PMM.

Mars_B4_Moon · 2021-05-23 07:26:19

Robo Diggers, autonomous versions for Moons and Planets? https://www.cnbc.com/2019/10/23/caterpi … -moon.html

Elon Musk says Mars city is 'next logical step' for humanity
https://www.express.co.uk/news/science/ … witter-evg

CBS News reporter explains SpaceX efforts to colonize Mars
https://www.valleycentral.com/news/loca … nize-mars/

SpaceNut · 2024-03-17 17:13:07

Going to mars are getting closer with the advent of the commercial rocket build but we know that we are not fully without a better plan than what we have currently.

The size of the payload and preloading of a landing site will matter even for a small crew.

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