New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: As a reader of NewMars forum, we have opportunities for you to assist with technical discussions in several initiatives underway. NewMars needs volunteers with appropriate education, skills, talent, motivation and generosity of spirit as a highly valued member. Write to newmarsmember * gmail.com to tell us about your ability's to help contribute to NewMars and become a registered member.

#51 2018-03-24 10:06:15

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,423
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Re "compressing Mars air":

I'm not saying this cannot be done.  I'm saying it will be difficult,  and will require processes we have far less experience with. 

On Earth:  shop air pressures are 6 to 10 bar.  The source air is at 1 bar (sea level) or 0.7 bar (10,000 feet elevation).  The required pressure ratio of no more than about 10 is within the capability of an easily-built machine using either centrifugal or positive-displacement compression devices.  This machine will have a fairly-high energy efficiency exceeding 50%,  and the energy required to compress a unit mass of final product will be fairly reasonable. 

For higher pressure ratios,  only positive-displacement compression devices are feasible,  and only in multistage devices.  The higher the ratio,  the lower the efficiency,  and the higher the energy required per unit mass of final product.  In the limit,  this is the vacuum pump (which compresses from "nothing" to 1 bar),  which has vanishingly-small efficiency and a really,  really high energy to produce a tiny mass of product. 

On Mars:  useful "shop air" pressures still fall in the 6-10 bar range.  The source is 0.006 bar range.  So the compression ratio is at or higher than 1000.  This looks more like a vacuum pump.  Expect the same abysmal performance as a vacuum pump. 

What that means is you must do something very different.  The leading proposal is to cool the CO2 at night enough to freeze,  mechanically harvest the dry ice frost,  stuff it in a pressure-tight bucket,  and warm the bucket to sublime the ice inside.  If you do this "right",  you might end up with a bucket of CO2 gas in the vicinity of 1 bar.  That as a source could be conventionally compressed to 6-10 bar fairly readily,  with efficiency and a favorable energy per unit mass of product. 

What might the efficiency and energy/unit product be for the sublimation bucket?  I dunno.  But it is unlikely to be anything anywhere near what we experience with conventional compression here on Earth.  This will be the limiting step of the process.  And it will be inherently batch production,  and restricted to small batch sizes,  too.  Batch production,  especially in small batch sizes,  is inherently less efficient and more energy-consumptive than steady-state stuff.

Yes,  it can be done.  But you-all need to stay realistic about the energy requirement and equipment masses that will be required.  They will be multiple orders of magnitude larger than any "normal" compression process you are familiar with here on Earth. 

Those same 1000+ compression ratios are why I personally tend to dismiss the notions of airbreathing turbine or IC engines on Mars,  even if somebody dreams up a non-slagging fuel that will burn with CO2.  6 mbar "air" has more in common with the vacuum of space than any sort of Earthly air,  even that atop Mount Everest. 6 mbar is the atmospheric pressure at 110,000 feet here on Earth.

GW

Last edited by GW Johnson (2018-03-24 10:13:51)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#52 2018-03-24 10:32:22

Oldfart1939
Member
Registered: 2016-11-26
Posts: 2,366

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

As GW points out, one of the real features overlooked in many of these proposals is the energy requirement to accomplish such. Yes, the proposed "process" may work, but the energy requirements are outlandish. Just look at things through the lens of the Laws of Thermodynamics before getting overly excited. The key to that is being able to properly define the entire "system."

Offline

#53 2018-03-24 14:38:25

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,782
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Well, I made a presentation at a Mars Society convention about harvesting nitrogen and argon from Mars atmosphere. The purpose is not propulsion, the purpose is diluent gas for constructed Mars habitats (gas to dilute oxygen), nitrogen fertilizer for greenhouses, and argon to fill the gap between window panes for thermal insulation. Yes, you have to compress from 0.007 bar Mars ambient to 10 bar in the production canister. If this is run at Gale Crater where Curiosity is located, or the Elysium Planetia, then Mars ambient will be 0.008 bar. That isn't much better. Yes, compression will require a positive-displacement pump. Yes, compression of more than 1,000 times will require a multi-stage pump. Yes, it will have to be based on a laboratory vacuum pump. Yes, it will be inefficient and require a lot of electric power. I've said that all along. But you just have to do it. Without diluent gas, you can't produce safe breathing air on Mars. Without nitrogen fertilizer, crops won't grow. You just have to do it. So to quote the Nike slogan: "Just Do It!"

Furthermore, producing diluent gas has another problem. Start with the assumption that you just take Mars atmosphere, filter out dust and compress, freeze out CO2. The result has a major problem: carbon monoxide (CO) at lethal concentration. So you have to do something. After 9/11, NASA developed a catalyst that can be installed in a breathing mask to allow people to evacuate a burning building. The catalyst combines CO with O2 to form CO2. You still breathe CO2, but humans can withstand a lot more of that. And you can exhale CO2 out of your body; if you breathe CO, that binds to hemoglobin in blood instead of oxygen, and never lets go. That hemoglobin becomes unable to transport oxygen, and there's no way to fix it. Red corpuscles in your blood only last 100 to 120 days before they are broken down, recycled. Bone marrow makes new ones. The only way to get CO out of your body is to wait for the red blood cells (corpuscles) to be replaced. My idea for Mars is to use the same catalyst in the diluent gas production canister. Mars atmosphere has more O2 than CO, and one molecule of O2 can bind with 2 molecules of CO, so Mars has more than twice as much oxygen as required to break down all CO. The catalyst must be heated to +24°C, but the canister uses freezer coils at -100°C to remove CO2. Doing this in the same canister means CO2 produced will be removed along with CO2 from Mars atmosphere, but it means the top of the canister has a small catalyst actively heated to +24°C while the bottom has freezer coils at -100°C. That will take a lot of power!

Again, this will take a lot of power. No getting away from it, just do it.

Offline

#54 2018-03-25 12:20:50

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,423
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

What RobertDyck says is correct,  whether you do the vacuum pump-as-compressor or the freeze bucket combined with conventional compression.  You're looking at a piece (or pieces) of equipment that mass the best part of a ton,  that consumes the best part of a kilowatt or more,  and produces only grams per minute of output.  There is no way around that.

As far as breathable atmospheres go,  it is already known that pure oxygen will not suffice,  except as an exposure measured only in hours while in a spacesuit.  It'll suck the moisture right out of your lungs.  There's serious medical consequences for that,  as well as a nasty fire hazard. 

Not to mention what really long-term exposures to only enhanced-oxygen concentrations might do to pregnant women and developing children.  We don’t yet know.  Maybe nothing,  maybe something as catastrophic as the thalidomide disaster.  My point is:  that risk is now unknown.  Until it is known and understood,  the only ethical thing to do is avoid it. 

That being said,  I looked at balancing the competing needs of an enhanced-oxygen two-gas mix as a hab atmosphere,  the wish to avoid pre-breathe time decompressing to a low-pressure pure oxygen suit (of any type),  and mitigating the fire hazards of enhanced oxygen content.  I posted that quite recently over at "exrocketman" as "suit and hab atmospheres 2018",  or something like that.

At the end of that article,  I suggested dividing the habitation spaces into two zones with different atmospheres,  both two-gas.  Where the pregnant women and children are,  I suggested real synthetic air (oxy-nitrogen mix at 20.946% oxygen) at 10.1 psia (equivalent to 10,000 feet).  We have millennia of evolutionary experience at those conditions.  We KNOW it works.

For the rest,  I suggested a lower-pressure two-gas mix:  45.45% oxygen with nitrogen,  at 6.2 psia pressure.  Even the pregnant women and developing children can take temporary exposure to this,  as well as the 2.8 psia pure oxygen suits.  The key is for those at risk not to live in this stuff full time while they are vulnerable,  live in the real synthetic air instead.  Everybody else should be able to take the low-pressure enhanced-oxygen mix just fine on a permanent basis.  We have decades of space station and spacecraft experience that confirms this.

Point is,  it's the same two gases we evolved with:  oxygen and nitrogen.  If you cannot effectively make nitrogen on Mars,  then just plan on shipping it in.  It's really that simple. 

Actually,  that's true of all supplies.  “What you cannot make,  you take (with you)”.  That's why the 1950's Mars mission proposals had such large vehicles:  they were planning on taking everything,  100%.  If all else fails,  you can always do that.  You just get to accomplish your mission with fewer flights of smaller vehicles (at lower budget),  if you can make more of your supplies in situ while you are there. 

Simple as that,  and there IS NOT (and never was !!!) an inherent magic go/no-go number for how much you had to make versus take,  to make the mission “feasible”.  THAT was just the entirely-artificial application of a constraint based on this-versus-that vehicle,  or this-versus-that budget.  This is the same zero-sum game BS that turned a two-stage reusable spaceplane into the vulnerable flying cluster-f*** we called “Space Shuttle”,  that killed 2 crews with its vulnerabilities. 

Note that Russians copied this design,  corrected some of the mistakes in it,  flew it once,  and never again,  as too costly and risky.  That was before they went broke,  too.  Its name was “Buran”. 

Oxygen,  you must make up what is lost due to metabolism,  plus what is lost by leakage.  Nitrogen,  only what is lost by leakage.  If argon gets in there,  fine,  but it doesn't have to.  You'll need to ship enough of these gases to Mars to set up your first habitations,  and further keep them supplied afterwards,  for losses and for habitation volume growth.  If you can do all that in situ,  so much the better.  But it need not preclude going even if we have to ship 100% of these supplies "in perpetuity"!  THAT is just silly.

Just a little perspective here.  Do the best you can with what is working at the time.  Ship the rest from Earth.  What could be simpler?  Just get on with it!  None of these issues should EVER stop us!  This mission is either priceless to us,  or it is not. 

Note also that with launch costs dropping fast,  it now doesn’t break the bank to fly more and larger vehicles,  if we need to. 

As long as we don’t assume that only this-or-that vehicle (SLS) may be used.  Don’t assume such things!  The reason we spell assume the way we do,  is that an ASS is what it makes out of U and ME.

GW

Last edited by GW Johnson (2018-03-25 12:22:35)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#55 2018-03-25 15:01:35

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 28,747

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Some day maybe we will be doing this on Mars.
sochi-snow-3-ht-jt-180325_hpMain_12x5_992.jpg

sochi-snow-1-ht-jt-180325_hpEmbed_4x3_992.jpg

Offline

#56 2018-03-25 17:22:25

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,782
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Well. The Mars Society has argued strenuously for Mars Direct since it's founding in 1998. That's what Robert Zubrin wanted, and why he founded the society. Mars Direct was a way to go to Mars in 1990. On July 20, 1989, President Bush Sr. gave NASA a directive to go to Mars. Mars Direct was devised as a way to fulfill the president's order. It would have worked, we could have had an unmanned test on Mars by 1997, and humans on Mars in 1999. But contractors and certain NASA administrators got greedy; that killed it. SLS is Ares. Period. Ares was designed as part of Mars Direct, intended to be a launch vehicle as powerful as Saturn V, intended to use the same facilities as Saturn V (VAB, launch pad, etc), and made from Space Shuttle parts because those were current in production. The only difference between SLS block 2 as originally announced vs Ares is that the main engines were moved axial under the tank. That required modification to the Mobile Launch Platform, but Shuttle isn't flying any more so now it's possible. SLS isn't absolutely necessary, it's just what we've grown to expect. We know it could do the job. But this is 2018, there are other options now.

As for breathing air: we could just use what Apollo and Skylab used. Robert Zubrin argued for that in his Mars Direct mission plan. That was 5.0 psi total, with 60% oxygen / 40% nitrogen. We know it works, because it did work. That's 3.0 psi partial pressure O2, and 2.0 psi partial pressure N2. Earth air at sea level has 3.0 psi partial pressure O2, so that's actually the same as the launch site at KSC. For human breathing, partial pressure is critical. However, flames are more complicated.

Some people have argued for greater pressure for plants. However, work done at Guelph University showed plants grow just as well in low pressure. Actually, they can handle lower pressure than humans can. Spinach grew at the same rate regardless of pressure, down to and including 10 kPa = 100 mbar = 1.45 psia. The trick was to ensure it had plenty of water. The lower the pressure, the more water transpired through plant leaves. However, in a sealed greenhouse, that water doesn't go anywhere. It just condenses on cold walls, runs down into a collection trough that runs back into soil. So in a sealed greenhouse, it doesn't consume more water. That's true of spinach and other leafy plants; however, wheat requires as much oxygen as humans.

Some people at NASA have assumed experiments on Shuttle and ISS require 1 full atmosphere pressure. There's that word again: Assume. Apollo era engineers and scientists didn't assume, they did the research. It wasn't always pretty; Apollo 1 resulted in 3 deaths. But they learned. One thing they learned is that 5.0 psi works.

Offline

#57 2018-03-25 17:42:41

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,782
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

SpaceNut wrote:

Some day maybe we will be doing this on Mars.

You know, right now that doesn't look attractive. This is March, end of winter. Here in Winnipeg we've had snow since November. Here March is always a month of melting snow. Beginning of the month is full winter, with cold and deep snow. Later in the month it melts during the day, freezes at night. Puddles form on streets; when that freezes at night it forms polished ice. With clear ice over black asphalt, we call that "black ice". It's much more slippery than packed snow, very dangerous to drive on. Driving conditions this month are the worst of the entire year. As I type this, there's a puddle in the back lane behind my house. At least snow and ice obstructing storm drains on the street have cleared, allowing melt water to drain away. Weather report says it's +0.8°C right now. Most of the snow is gone by April 1st, but there's often one last snow storm the first weekend of April, but the last snow melts completely away within a week.

This time of year people can be seen outside without a parka. You can stay outside for several minutes without any jacket at all. Winnipeggers often go out in this weather with snow boots, light jacket, and shorts. Or jeans and a shirt, no jacket at all. I can take the garbage out wearing snow boots, jeans and a T-shirt, but can't stay out there long without a light jacket.

It's muddy, dirty. Grass hasn't started to grow yet, but ground is exposed in places were snow was shallow. Ground is thawing, and with melt water everywhere it's mud. Garbage hidden in snow over the winter is exposed as snow melts away. Dead leaves from last fall, wet and rotting. Sand spread on roads by city trucks to provide traction on packed snow in winter. Much of that sand was scraped off when snow was plowed onto boulevards beside the street. So snow banks beside the street are black with sand, dirt, rotting leaves exposed by melting snow. That black stuff warms more during the day so melts into the snow bank. March is an ugly mess. April: grass grows, trees bud new leaves, flowers start to sprout. April is beautiful spring. But right now it's ugly. When my father retired, he decided to spend every March in Phoenix Arizona. Why live through March when you don't have to?

So pardon me that I find your scene of skiing not attractive.

Offline

#58 2018-03-25 18:03:43

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,782
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Out my bedroom window right now.

::Edit:: I posted that image to another web forum. They replaced the image with logos for their website. Hmm...

I was going to add an image of my front lawn, showing it's still covered in snow. I could post to the Mars Society local chapter website, but why? You get the point.

Last edited by RobertDyck (2018-03-26 13:11:30)

Offline

#59 2018-03-25 18:29:30

Oldfart1939
Member
Registered: 2016-11-26
Posts: 2,366

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Robert-

At least your sense of humor remains intact, eh?

Offline

#60 2018-03-25 18:35:34

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Laughable. Musk is way ahead of the game. He may be optimisitic on a 2024 landing but I'll be surprised if he doesn't get humans there by 2026 at the latest.

Your comments suggest you know nothing about the latest PV and energy storage technologies, and also that you haven't yet absorbed that Space X will be landing 300 tonnes of cargo as their precursor mission to Mars. In case you don't realise: that's rather a lot of mass.

clark wrote:

GW, NASA has had a long term target of 2030's for human to Mars for a while now. Various administrations from Bush 1 on have had various iterations of what that meant, but the target window has been pretty consistent.

Musk can get some meat bags orbiting Mars, but boots on the ground and back requires technology and expertise outside of his current vertical. NASA isn't even ready with solutions for the biological challenges inherent in a chemical trip. And if power is solely solar, then there is almost zero margin for error and limited to no science value since duration would be exceedingly short.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

Offline

#61 2018-03-25 19:16:25

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,782
Website

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Oldfart1939 wrote:

Robert-

At least your sense of humor remains intact, eh?

Still unemployed. When I worked in Miami, I was solely responsible for the computer system for one county tax. I was paid $50/hour with 8 billable hours per day, 8:00am to 5:00pm. No pay for lunch or coffee breaks. No vacation pay, not paid for statutory holidays. No sick time. No benefits. I had to pay income tax to both the IRS and Canada Revenue Agency; at least what I paid to IRS was a "foreign tax deduction". Under the Canada/US income tax treaty, they're supposed to deduct whatever I paid to the other country, charge me the remainder. They had a complicated formula resulting in me paying a little more; you always pay more. And I had to pay American Social Security, despite the fact I wasn't eligible to collect. If I earned enough working hours in the US, I would be, but I haven't. I also had to pay Canada Pension Plan premiums. When I worked in Calgary in 1995/1996 and Virginia in 1996, I had to pay Employment Insurance Premiums, even though a contractor is not eligible to collect; but by 1999 they changed the rules so contractors neither pay nor collect. CPP and EI together are Canadian equivalent to SS. Florida doesn't have state income tax, but Manitoba does. They charged me Manitoba tax since that was the last province I lived in before moving to Florida. And I had to pay my own moving expenses to get to Miami, and return. But despite all that, with an hourly rate that high, I was living very well! It was the highest paid job I had in my life.

Now I'm stuck back here, unemployed and on welfare. EI benefits ran out years ago. I got some work last fall, so welfare kicked me off, closed the case. But with only 8 days work in September, no work in October, 11 days in November? That was just enough to pay my annual house insurance, annual burglar alarm monitoring, utility bills and groceries. My vehicle is still parked, not insured. In December I got 1 day teaching introduction to computers, 1 more day in February, and 1 day last week. That's it. I had hoped the employer from September/November would hire provide more work, but that hasn't worked out. He told me his client is having software problems, they won't be ready until May earliest. Beginning of February I applied to get back on welfare. They have been bureaucratic, keep stalling. Friday I filed an appeal with with Social Service Appeals Board. This is getting to be a habit: they kick me off welfare about once a year, and I have to file an appeal to get back on. Yes, I should be working. I keep sending out job applications. One of the many ironies is that in 1998 I worked for the city welfare department, as a contractor because the department was about to close, the province decided to absorb the city department. All computer system analysts did leave for other jobs within the city, and even the computer manager left. I managed the mainframe computer for the city department for the last two months. When I had to apply for welfare myself the first time, one former co-worker was one of my in-take workers. That was awkward. So why doesn't the province hire me? I have tried to apply. If welfare really wants me to get off assistance, then talk to their own computer department. But they won't do that. I also applied to be an "information specialist" for provincial welfare; that's the guy who determines how much recipients get each month. I could do a better job than most I've worked with. Many don't know how to read an electric bill. And when I first got on welfare, I told them I have a home business doing computer repairs. I wrote the income declaration as a formal accounting statement of income and expenses. None of them knew how to read that; I've had to "dummy it down", rewrite in plain English so they can understand. They still often make mistakes. I did get a formal acknowledgement of my job application, but nothing more.

Well, good news is I got a credit card. When my problems happened in 2007/2008, someone caused major problems with my bank. The bank branch manager was on my side, but someone powerful was out to get me. I had won the nomination for the federal election. The party disallowed my nomination over these problems, appointed someone else to run in my place. Two days after the public announcement that he was the candidate, the same bank went after him. He was 69 years old in 2008, had the volume of his cell phone cranked up so loud that I could clearly hear both sides of the conversation. They did to him exactly the same thing they did to me. That other guy was forced to sell his business. Since he was 70 by the time the court proceedings were through, he chose to treat it as retirement. The fact the same bank pulled the same stunt on two individuals for the same party in the same electoral district in the same year for the same election? No one will convince me that's a coincidence. The bank tried to foreclose on my house despite the fact I don't have a mortgage. They played some nasty legal tricks. I sort-of won. I kept my house, and only had to pay what I owed the bank, I didn't pay the extra money the lawyer tried to defraud out of me. But now I owe family members that money. My credit is shot. I couldn't get even a basic bank account until the court proceedings were done. Now I have a chequing account with bank card and online banking, but credit rating is damaged. At first they put a 2 week hold on any cheque deposited, they put a hold on any deposit through an ATM. After 6 months they allowed me to deposit up to $300 without a hold, then a couple years later increased it to $1,000. Just Friday I got a basic credit card, with the lowest credit limit. At least I got something. I'm slowly rebuilding credit.

Quite a fall from my Miami job.

Offline

#62 2018-03-25 20:44:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 28,747

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

I do hope brighter days are a head for you and that winter ends soon so that you can go back to work. I have been in the same shoes and feel lucky to be working for the past 9 years at a good job but before that not so much. Yes that was quite a income fall as well too. On the note of Social security I did recieve my report notice of earnings per year of working with an estimate of what I might recieve when I retire someday. So I know what its like to be earning less that $6,000 a year for multiple years in a row before getting a break and this has happen a couple of times in the last 3 decades.  Those years of low income have taken there toll on my credit abilities as well but I did keep my large family clothed, housed, fed, and getting there education as well as healthy all those years. Property taxes on my home are still in arears but I am catching up too. It will get better...

Offline

#63 2021-10-19 11:03:08

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 8,892

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Trump now has his own blog, he is mostly banned across social media Snapchat, Facebook, Twitter, Youtube, Instagram they all banned Trump.

The China factor?
http://nasawatch.com/archives/2021/10/b … ths-1.html
Building Earth's Other Space Station

Opinion: The Biden administration lacks a coherent China policy
https://www.marketwatch.com/story/the-b … 1634087566

The ‘Biden Build Back Better Budget Bomb’ promises the moon without paying for it.
https://www.kentucky.com/opinion/op-ed/ … 08762.html

While I do agree the Trump Admin could have been better at times
Trump did help in continued efforts in commercialization and on the Private Sector

Newly-minted public space company Rocket Lab acquires software firm
https://washingtontechnology.com/articl … ition.aspx

However not all of them are the same, Blue and SpaceX are sometimes seen very differently

NASA blasts Blue Origin and claims Jeff Bezos' space firm 'seeks to prioritise its own fortunes over that of NASA, the United States, and every person alive today'
https://www.dailymail.co.uk/sciencetech … tunes.html

Last edited by Mars_B4_Moon (2021-10-19 11:04:06)

Offline

#64 2021-10-19 12:11:48

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,352

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

GW Johnson wrote:

Re "compressing Mars air":

I'm not saying this cannot be done.  I'm saying it will be difficult,  and will require processes we have far less experience with. 

On Earth:  shop air pressures are 6 to 10 bar.  The source air is at 1 bar (sea level) or 0.7 bar (10,000 feet elevation).  The required pressure ratio of no more than about 10 is within the capability of an easily-built machine using either centrifugal or positive-displacement compression devices.  This machine will have a fairly-high energy efficiency exceeding 50%,  and the energy required to compress a unit mass of final product will be fairly reasonable. 

For higher pressure ratios,  only positive-displacement compression devices are feasible,  and only in multistage devices.  The higher the ratio,  the lower the efficiency,  and the higher the energy required per unit mass of final product.  In the limit,  this is the vacuum pump (which compresses from "nothing" to 1 bar),  which has vanishingly-small efficiency and a really,  really high energy to produce a tiny mass of product. 

On Mars:  useful "shop air" pressures still fall in the 6-10 bar range.  The source is 0.006 bar range.  So the compression ratio is at or higher than 1000.  This looks more like a vacuum pump.  Expect the same abysmal performance as a vacuum pump. 

What that means is you must do something very different.  The leading proposal is to cool the CO2 at night enough to freeze,  mechanically harvest the dry ice frost,  stuff it in a pressure-tight bucket,  and warm the bucket to sublime the ice inside.  If you do this "right",  you might end up with a bucket of CO2 gas in the vicinity of 1 bar.  That as a source could be conventionally compressed to 6-10 bar fairly readily,  with efficiency and a favorable energy per unit mass of product. 

What might the efficiency and energy/unit product be for the sublimation bucket?  I dunno.  But it is unlikely to be anything anywhere near what we experience with conventional compression here on Earth.  This will be the limiting step of the process.  And it will be inherently batch production,  and restricted to small batch sizes,  too.  Batch production,  especially in small batch sizes,  is inherently less efficient and more energy-consumptive than steady-state stuff.

Yes,  it can be done.  But you-all need to stay realistic about the energy requirement and equipment masses that will be required.  They will be multiple orders of magnitude larger than any "normal" compression process you are familiar with here on Earth. 

Those same 1000+ compression ratios are why I personally tend to dismiss the notions of airbreathing turbine or IC engines on Mars,  even if somebody dreams up a non-slagging fuel that will burn with CO2.  6 mbar "air" has more in common with the vacuum of space than any sort of Earthly air,  even that atop Mount Everest. 6 mbar is the atmospheric pressure at 110,000 feet here on Earth.

GW

GW, one significant difference is that air (on Earth) is practically an ideal gas as it is far above its critical point.  However, CO2 on Mars, especially if harvested during Martian night, is far beneath its critical temperature of 31C and sits close to its triple point.  This means far less compressor work is needed, because the gas won't get appreciably hot under compression.  Compress it to 5.1 bar and it will condense into liquid.  However, frictional pumping losses would be far greater in a device compressing highly diffuse gas.  The situation is very dissimilar to the compression of normal air at temperatures that we are accustomed to.

Last edited by Calliban (2021-10-19 12:29:24)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

Offline

#65 2021-12-30 08:23:24

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 8,892

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

2021: A year of space tourism, flights on Mars, China's rise

https://www.spacedaily.com/reports/2021 … e_999.html

Biden and Kamala hail the launch of NASA's James Webb Space Telescope

https://www.dailymail.co.uk/news/articl … l?EdNo=002

Russia started testing ASAT weapons, shooting down its own satellite and creating a cloud of debris, Iran is launching rockets, North Korea is testing missiles again, the Chinese seem to have tested hypersonic cruise missile thing to get past defenses or counter-weaponry, China, Russia or other nations seem now to be developing technologies such as nuclear power for space surface planetary applications and space vehicle propulsion.

The military industrial complex or 'Space Force' that Biden admin was critical of might now get lots of money.

Last edited by Mars_B4_Moon (2021-12-30 08:29:45)

Offline

#66 2021-12-30 11:29:27

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,352

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

Mars_B4_Moon wrote:

2021: A year of space tourism, flights on Mars, China's rise

https://www.spacedaily.com/reports/2021 … e_999.html

Biden and Kamala hail the launch of NASA's James Webb Space Telescope

https://www.dailymail.co.uk/news/articl … l?EdNo=002

Russia started testing ASAT weapons, shooting down its own satellite and creating a cloud of debris, Iran is launching rockets, North Korea is testing missiles again, the Chinese seem to have tested hypersonic cruise missile thing to get past defenses or counter-weaponry, China, Russia or other nations seem now to be developing technologies such as nuclear power for space surface planetary applications and space vehicle propulsion.

The military industrial complex or 'Space Force' that Biden admin was critical of might now get lots of money.

Yeah.  Trouble is none of that money is really getting used for anything constructive.  Money spent on satellite defence systems is not going to be useful in furthering human presence in space.  The theatre of war in space is low Earth orbit.  That is a spherical shell, about 13,000km inner diameter and 500km thick.  A very narrow gulf of space that everything must pass through to get to other places.  If someone were to launch a single Starship payload full of ball bearings into LEO, they could effectively end human spaceflight for generations.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

Offline

#67 2021-12-30 11:39:38

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 28,747

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

So what existing treaty stops or deters this and even if you did have one its most like a political football in the UN.

Getting Nations to finally agree that war is stupid is still a long ways off for some nations.

Offline

#68 2022-08-26 07:17:35

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 8,892

Re: Trump says NASA is "way ahead of schedule" in getting humans to Mars!!

SLS Contractors Are Everywhere
https://www.planetary.org/space-images/ … ractor-map

VP Kamala Harris to attend Artemis 1 moon launch (exclusive)
https://www.space.com/vice-president-ka … s-1-launch

Offline

Board footer

Powered by FluxBB