# The Moon or Mars:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, May 20, 2015.

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Not in the least, and quite dishonest of you to say so. I most certainly recognise the facts as apply today, and I most certainly recognise that at this time and probably within the near future, it is impossible for us to achieve with present technology.
Where I differ from your "stick in the mud" attitude, is that I recognise that improvements and technologies will improve with possibly new discoveries in time.
And of course without any progress in any warp travel technology, a generation ship is always an option.
And I have often mentioned with these disaster scenarios you seem so focused on, that the stars being our destiny, does certainly depend on how we overcome our Earthly problems also.

So again putting it all in a nut shell, we will return to the Moon, [and so we should] and we will send man to Mars, [as also we should] just as eventually we will also mine Asteroids.
Startreking probably not in the immediate foreseeable future, but as long as we can survive our Earthly follies, in time that also will eventuate.

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5. ### cosmictravelerBe kind to yourself always.Valued Senior Member

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Solutions will be found to address the problems we face today. It will take some time of course but eventually we will overcome those problems and others that may crop up.

7. ### billvonValued Senior Member

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"The popular mind often pictures gigantic flying machines speeding across the Atlantic, carrying innumerable passengers. It seems safe to say that such ideas must be wholly visionary. Even if such a machine could get across with one or two passengers, it would be prohibitive to any but the capitalist who could own his own yacht."

— William Pickering, Harvard astronomer, 1910.

8. ### orcotValued Senior Member

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A couple of years ago I've calculated how long it would take to travel to mars under a 1G acceleration (speed up for the first halve slow down for the second half and account for the orbital speed difference between earth and mars). It was like slightly under 48 hours for the shortest possible distance and 1 week if earth and mars where on opposite places.

In 1912 the titanic left on it's way to America despite the high casualty number people often forget the titanic was only traveling and 50% capacity the reason for that was because the olympic (a other ship) went there at full capacity 10 months before. The trip would have taken roughly 7 days back then.
So depending on how you calculate it, it took you anewhere from 7 days to 10 months to cross the ocean back then. Now you can do it in a couple of hours.

Right now people talk abouth exotic stuff like EM-drive alcubierre drive etc. These things are purely speculation but still the research is on it's way, but if that seems a little to far off there is still the creation and storage of antimatter. I do believe there are plans today that could achieve 1% c for manned flight and 10% for probes.

And that is for today, who can say what people will come up with in a couple of hunderd years. Time= distance/speed. We're currently developing speed and it's effeciencies but it's clear the distance can also be manipulated.

It is still a far way off tough.

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Can Mars One colonise the red planet?
Alexandra Doyle has signed up for a one-way trip to Mars. What makes her, and 99 others, so ready to leave Earth behind? Meet the red planet’s would-be pioneers – and the man who promises he can get them there

Alexandra Doyle: ‘There’s so much about the Earth that I love, but that doesn’t mean there’s not something else out there.’ Photograph: Manuel Vazquez for the Guardian

When Nasa’s first rover set down on the surface of Mars in 1997, its streamed colour images caused an early internet sensation. After centuries of dreaming, here we were, at eye level to our closest potentially habitable neighbour, and the sight was as bleakly majestic as we could have imagined: a rocky, red desertscape on a scale entirely alien to Earth. One mountain, Olympus Mons, was the largest in our solar system (three times the height of Everest, with a footprint the size of Sweden); dune-seas swept its northern hemisphere while 7km-deep canyons veined the south.

Watching on a clunky desktop computer in the Dutch university town of Twente, 20-year-old Bas Lansdorp’s first thought was one of wonder; his second of longing (“I want to go there!”), then the melancholy realisation that, being Dutch, he could never fly with Nasa. So he’d have to do it himself.

What kind of a person thinks such outlandish thoughts, then tries to make them real? Eighteen years later, Lansdorp and I are on a train en route to Heathrow, discussing Mars One, a real company with real investors and a fledgling astronaut training programme, while our fellow passengers fall silent and pretend not to earwig. Lansdorp has a brusque, crystal-eyed positivity; a boyish charm you see in many entrepreneurs that, combined with his Dutch accent, makes him seem sincere and persuasive. All the same, the woman next to me has been staring at the same smartphone screen for the past 10 minutes, and her thought bubble reads: “This man is talking about going to Mars. Soon. Like he means it. Am I dreaming?”

Lansdorp began by thinking about Mars as an intellectual exercise, a hobby: how might a privately funded Mars mission actually work? He knew that when George Bush Sr ordered Nasa to cost the trip in the early 90s, they came back with a figure of $450bn, after which human travel to Mars became the mad uncle in the shed of space. One Nasa engineer I spoke to identified a “giggle factor” attending its very mention at the agency. Gradually, though, Lansdorp came to believe there was a way to slash costs by accepting a simple truth: that the hardest part of a Mars trip was not going, but coming back. Nix the return and your tech troubles fell away, to the extent that no new technology would be required. For a public body like Nasa, such a leap would be politically unthinkable. But for a privately funded one – why not? Suddenly, Lansdorp was talking about an enterprise no one else dared even moot: a Mars settlement mission, for$6bn, small change to governments and a growing cadre of individuals.

Much more on this interesting subject, the man proposing it, and the volunteers at.....
http://www.theguardian.com/science/2015/may/30/can-mars-one-colonise-red-planet

As I have said previously, while I find his dreams at this time, rather grandeur, I give 100% hope in that he achieves what he hopes to achieve in all respects.
He along with others such as "Tau Zero" and the "100 Year Starship Co" and NASA/ESA etc of course, are giving plenty food for thought and research.

Last edited: Jun 8, 2015
10. ### Simeon FlorescuRegistered Member

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That to but if you go to the moon there isn't the same gravitational pull of 1 atmosphere and people are going to be weakened the longer they stay on the moon and after they enter earth again the change in the gravitational pull will just crush the person

11. ### orcotValued Senior Member

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Gravity will favor the moon in the short run.
- It's easier to launch hardware to the moon then to mars
- On average astronauts will experience more gravity for a lunar stay then for a mars stay.

The first one is easy you don't have to escape earths gravity entirly to reach the moon and it's easier to return from the lunar surface then from mars.
The second part has to do with travel limitations:
It takes between 3-4 days to reach the moon and roughly a 100 days to reach mars (one way)
During this time the astronauts will experience 0G

By this logic it's entirly possible that a lunar mission will set off to the moon stay there for 3 months (experiencing lunar G) on the surface and return home before a mars mission even reaches Mars (all the while experiencing 0G).

This isn't really a cheat it's the reality of todays current technological capabilities. Sure better and fasther space ships could be developed and so could artificial gravity. And altough I'm sure that 1 day these options will become avaible, today we're far away from this point.

(there is offcourse going to be a point that depending on how long they stay mars gravity will be the better option but how long would that be considering the 200 days travel timefor Mars. I'm certain it would take more then 1 year. And if permanent settlement isn't a option then this would be getting close to the max time you want them to spend away from home anyway.

(Also the stronger gravitational pull of mars could crush the astronauts for the first few days whilst they walk around in their heavy clothes afther that long in 0 G. They will probably be fine eventually but how long will you wait on impaired astronauts who can barely walk.)

12. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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You might find it interesting and informative to calculate:
(1) the exhaust mass needed with the "rocket equation" and the highest specific impulse chemical fuel for 48 hours of 1 G acceleration. My quick and lazy guess is it a mass comparable to or greater than the mass of the earth.
And if you plan to used mostly ionic relativistic particles* to produce thrust to reduce the mass requirements, say with protons and equal number of electrons separately ejected to keep space craft electrically neutral:
(2) What power level are you postulating? - I. e. how does it compare to the total electric power generated on earth? (And a few words about the necessary generation efficiency so the heat production does not fry you.)
(3) Same two questions as in (2) if you plan on a Photon Drive."

Another thing to note is after 24 hour of 1G acceleration you are travel at significant high fraction of the speed of light. Space is not empty. - The many hydrogen ions and some atoms you hit will be very damaging artificial "cosmic rays." With their numbers greatly increased as "daughters" are produced when they pass thur the skin of your space craft, if its skin is not several inches thick high atomic number (lead or greater) material.

PS: Technology will change but not this basic physics.
* Also it might be interesting to learn what fraction of the electrical energy needed to operate the LHC ends up as energy in the particles it can accelerate.

Last edited: Jun 14, 2015
13. ### billvonValued Senior Member

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True. However it's easier to land on Mars due to the atmosphere there,
The Mars Direct mission uses a cable to connect the upper (departure) stage with the lander, then spins the two. That results in Mars-normal gravity during the few months it takes to reach Mars.

14. ### orcotValued Senior Member

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First let's re-do the calculations.

the formulla= t=sqrt((2*D)/a)
T=time, D=distance, a= acceleration.
Take in account that we only accelerate to the halfway point and the rest of the journey we decelerate.

So mars at it's shortest distance is 227939100000-14959826100 meters away divided by 2 is 39170419500
this gives us 89363.38 seconds (24.823 hours) from this point the ship would need to decelerate a equal amount of time to be back at rest ones it arrivés at mars (not really Earth travels at 29.78 km/s whilst mars travels at 24.077 km/s but close enough for this purpose)so you arrive at 178726.76 seconds at mars or 49.64 hours.

The mass that you will use to get there depends on the exhaust velocity and element x. The speed of light is 299792458m/s your acceleration should be 10m/s by shear logic it doesn't have to be enormous. (element x is the unknown stuff might be invented that make all of this pointless a EM drive for example would not use any exhaust)

none I assume you simply have the energy to accelerate at 1G does it matter for the example?

see element x

This site gives a nice summary if you like (altough they use different distances for Mars their results are:
http://space.stackexchange.com/questions/840/how-fast-will-1g-get-you-there

the moon: 3h 20m 24s
Mercury: 2d 1h 19m 12s
Venus: 1d 11h 28m 48s
Mars: 1d 21h 13m 1s
Jupiter: 5d 16h 2m 2s
Saturn: 8d 2h 20m 24s
Uranus: 11d 20h 24m 0s
Neptune: 15d 7h 52m 48s

So 24G of acceleration wouldn't bring you that far at it would take closer to a year to get near C

15. ### orcotValued Senior Member

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At great cost this technology could indeed be developed and in the large sheme of things it should be. Luna doesn't need this technology. This again gives some advantage to Luna altough this artificial gravity will still need to be developed for other things (I still hope the ISS will get the nautilus x). Surface time on the moon will probably be shorter then a year meaning muscle/bone degeneration could be handled and the ability to teleoperate safly from Earth makes for a decend gravity field. For missions under 1 year the moon wins in gravity or in the necessary hardware.

16. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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To Orcot; You are correct, my guess was wrong. Accerating at 10m/s^2 for 89363.38 seconds only gets your craft up to 893,634 m/s far below C, so don't need to consider mass increase. At that half way point much of the lift off fuel will have been burnt - no longer needs to be decelerated for a "one way trip."

Here is discussion of how to go to Mars (5 Ton pay load of crew, fuel empty last stage landed there, I think after quick skim of many pages free to read. Lots of data on lift off weight and propulsion types. He is an optimist - think human can do it.):
Google search: "Graph of the rocket equation" then click on the Martin Turner book hit - it will dump you on page125, but page up and down gets what I skimmed.

Last edited: Jun 14, 2015
17. ### billvonValued Senior Member

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There's really nothing new to be developed. Aerobraking for Mars landing has been demonstrated; it's just a question of engineering. And the technology of swinging things around on a cable has been around for hundreds of years.

18. ### orcotValued Senior Member

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Billy T I can't find it

Billvon Yet for all that it has never been succesfully attempted
http://www.science20.com/robert_inv...rtificial_gravity_almost_no_extra_fuel-131278
There's reasonable proposals that are at first sight both cheap and safe. But they never attempted it. Having it would be a nice bonus but it's not mission critical. Also this might cause problems both with sending and recieving information and thrust short chemical burns will probably be OK but the moment you start with long ion burst you might actually get a problem. With the ISS prioritising the VASIMR over nautilus-x I'm afraid we're moving further away from artificial gravity at this moment.

Aerobraking a massive craft for Mars has only recently been demonstrated (on earth).

I do like the Id for artificial gravity on phobos, due to it's low mass and relative fast rotation a space elevator would only have to be 10 493,52 meters long (earths would be 35564026 meters long).
This seems do-able from Phobos people could teleoperate equipment on mars (mind you from earth people could teleoperate equipment on the moon for a fraction of the cost).

19. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Strange. I just tested again. It was the ninth hit down from my Goggle search on: Graph of the rocket equation
and dumped me on page 125, from which page up and down got many dozens more pages.

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21. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Try this: https://books.google.com.br/books?id=abIKvmDXh_kC&pg=PA324&lpg=PA324&dq=expedition to Mars by Martin Turner&source=bl&ots=555DcdTieb&sig=g8z3Gwjl8AF4elIiV8yDPjL66io&hl=en&sa=X&ved=0CCMQ6AEwAmoVChMIsN3h3OyPxgIVxToUCh1MGQVS#v=onepage&q=expedition to Mars by Martin Turner&f=false

I will test is soon after posting. No that did not give most of the by "click on" it but I notice the last part was not "highlighted" so will copy it all and manually enter that.
That failed too.

Google search on: expedition to Mars by Martin Turner
which seems to drop you at back cover of his book, and page up from there is first pages of photographs, then more page up get you to page 161 and many earlier pages. (for me at least) but some of my efforts now get message that I have reached unavailable page or the limit of my free viewing.
If you can't get it this way, I give up.

Last edited: Jun 15, 2015
22. ### billvonValued Senior Member

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It has never needed to be, so it never has been. It's akin to using lunar regolith to provide protection from radiation. Will it work? Probably. Do we need to test it? No, not really. We know it will work.

23. ### orcotValued Senior Member

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the cables could snap, many solar sails have mallperformed whilst extending, coriolis forces have never been tested on this scale firing your engines would be a deadtrap, Gemini 11 's experiment only managed to produce 0.00015G. It was deemed a failure
Could it work? Probably Do we need to test it? Definitly.

Testing the lunar regolith to see how much radiation (the bad ones and the good ones) will pass trough it should also be tested. Both on the moon and Mars