### Author Topic: Lake Matthew - 2036  (Read 54800 times)

#### MikeAtkinson

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##### Re: Lake Matthew - 2036
« Reply #20 on: 04/11/2016 02:39 PM »
It would be easier to redirect a near Mars asteroid of the equivalent size.

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #21 on: 04/11/2016 03:08 PM »
Need some help.  If anyone is curious to follow the idea of launching a boulder of the surface of Phobos in order to impact Mars and release 10^18 joules.   Phobos is at an altitude of 6000 km.   At that orbital height, it is moving at around 2141 m/s.   How do you calculate the velocity of a body that will be d-orbited from that height to surface impact?

How this calculates out will be recursive in determining the size of boulder needed to release 10^18 Joules.   I made my guestimate using 5000 m/s as the minimum velocity, ( martian escape velocity)  since any rock deorbited from a higher energy orbit will gain velocity on the path down the gravity well, it will have a higher velocity than martian escape velocity.  This means the rock/boulder can be much smaller & lighter than a 340m diameter rock.

#### R7

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##### Re: Lake Matthew - 2036
« Reply #22 on: 04/11/2016 05:19 PM »
Need some help.  If anyone is curious to follow the idea of launching a boulder of the surface of Phobos in order to impact Mars and release 10^18 joules.   Phobos is at an altitude of 6000 km.   At that orbital height, it is moving at around 2141 m/s.   How do you calculate the velocity of a body that will be d-orbited from that height to surface impact?

Calculating a Hohmann transfer orbit from Phobos to Mars surface is one starting point. If I did the math right the required dv is about 0.6km/s.

#### LMT

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##### Re: Lake Matthew - 2036
« Reply #23 on: 04/11/2016 05:24 PM »
Heat & Water

How to heat the proposed hab and greenhouse domes to room temperature?  Trying a rough calc:

Assumptions:

Domes are circular, 300 m diameter.

Dome external surface temperature is 5 C (water).

Heat exchanger transfers treated water at 50 C from Lake Matthew bed, with heating required 18 hr / sol.

There is negligible heat loss through bedrock in the micro-environment.

Dome U value is 1 W / m2K.

Rough result:

Water flux is ~23 liter / second.  [corrected]

Pump power requirement is ~14 kW, or ~19 hp.  [corrected]

And would anyone want to estimate the heating power requirement, without terraformation?
« Last Edit: 12/14/2016 07:29 PM by LMT »

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #24 on: 04/11/2016 05:44 PM »
It would be easier to redirect a near Mars asteroid of the equivalent size.

I was thinking about that, however Phobos escape velocity requires only 11.4m/s, and it's right on the front porch of Mars.  I didn't think moving anything from the asteroid belt or even near Mars intercept would be cheaper in DV.   The problem is actually getting something massive off the surface of Phobos.   It still requires enormous thrust, and  that makes SEP unworkable from the Phobos surface.

I'm also thinking that if you could get a rock off the surface of Phobos, you don't necessarily need to lower the orbit, you just need to add eccentricity and lower the perigee so it impacts the surface.   So I really need to figure the DV for a perigee lowering maneuver from a 600km high martian orbit.

I'm gonna have to read my old textbooks.

edit:  I just saw R7 did that math with a Hohman transfer orbit.  Thanks!  So from the surface of Phobos it requires around 612 m/s to get an object to impact.
Any other asteroid candidates with less DV requirements than that?
« Last Edit: 04/11/2016 05:50 PM by Stan-1967 »

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #25 on: 04/11/2016 06:04 PM »
Need some help.  If anyone is curious to follow the idea of launching a boulder of the surface of Phobos in order to impact Mars and release 10^18 joules.   Phobos is at an altitude of 6000 km.   At that orbital height, it is moving at around 2141 m/s.   How do you calculate the velocity of a body that will be d-orbited from that height to surface impact?

Calculating a Hohmann transfer orbit from Phobos to Mars surface is one starting point. If I did the math right the required dv is about 0.6km/s.

Any idea on the velocity at perigee?

#### Robotbeat

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##### Re: Lake Matthew - 2036
« Reply #26 on: 04/11/2016 07:07 PM »
Don't need nuclear explosives. A 1GWe nuclear reactor produces about 3GW of thermal energy. There are pi*10^7 seconds in a year, so after 10 Earth years, you'll have produced 10^18 Joules of heat. Don't know what's patentable about that.

The other thing is redirecting an asteroid or comet (or perhaps moonlet parts) into Mars. Also not patentable.
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#### RocketmanUS

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##### Re: Lake Matthew - 2036
« Reply #27 on: 04/11/2016 07:14 PM »
Geothermal energy?
From their web page "sensible heat is liberated".

From their web page, lake deep water not to exceed 50 degrees celsius. The is hotter that water in a hot tub!

Heat & Water

How to heat the proposed hab and greenhouse domes to room temperature?  Trying a rough calc:

Assumptions:

Domes are circular, 300 m diameter.

Dome external surface temperature is 5 C (water).

Heat exchanger transfers treated water at 50 C from Lake Matthew bed, with heating required 18 hr / sol.

There is negligible heat loss through bedrock in the micro-environment.

Dome U value is 1 W / m2K.

Rough result:

Water flux is ~1 liter / second.

Pump power requirement is ~0.6 kW, or ~0.8 hp.

And would anyone want to estimate the heating power requirement, without terraformation?
Then heat transfer to the air inside the dome from water fountain in lake from the deep water . Water that is cooled by the air is now on the surface of the lake?

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #28 on: 04/11/2016 07:30 PM »
Heat & Water

I think the considerations WSTEWART explains regarding the water as the media to moderate ecosystem stability has to do with the influx of water to the center of a crater after the impact event.   There are lots of photos from orbit of hydrothermal looking deposits on Mars, and iirc, the Spirit rover basically ended it's life on the edge of a hydrothermal feature.   There have also been many papers published showing the longevity of residual impact heat in the crater center lasting for thousands of years in big impacts.

The plan for Lake Matthew would likely target a area of Mars with a higher than nominal heat flux, and the right rock permeability to let water flow to the crater center to be heated by the residual impact heat.

See this paper explaining it all. ( especially section 3)
http://www.es.ucsc.edu/~fnimmo/website/Mars_hydrothermal.pdf

I agree with QuantumG that a 1GWe nuke could do all this, but what are the trades?   Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.  Plus you do not get the benefits of moderating an entire potential ecosystem.  I would only see this as a initial method to give colonizers a toe hold on Mars.   After that, building nukes of whatever capacity, MW or GW, will be the enabler.   ( & ECLSS)

If the plan can show how it gets it done in just one or two FH or SLS flights, that would arguably be much fewer flights needed than for a 1GWe nuclear power plant.

#### Elmar Moelzer

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##### Re: Lake Matthew - 2036
« Reply #29 on: 04/11/2016 07:50 PM »
Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.
What makes you think that? Nuclear reactors can be very compact and small. They can even be their own way to get there (NERVA), The bigger issue with nuclear plants in space is the political resistance to them.
« Last Edit: 04/11/2016 07:52 PM by Elmar Moelzer »

#### RocketmanUS

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##### Re: Lake Matthew - 2036
« Reply #30 on: 04/11/2016 07:57 PM »
Asteroid hitting Mars?

How much dust would be put in the atmosphere of Mars from such an impact.?

Building more colonies, how would any preexisting colony handle a new asteroid impact ( quake ) on Mars?

#### LMT

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##### Re: Lake Matthew - 2036
« Reply #31 on: 04/11/2016 09:08 PM »
Then heat transfer to the air inside the dome from water fountain in lake from the deep water . Water that is cooled by the air is now on the surface of the lake?
Cooled water would be transferred first to the exterior of the dome.  Eventually it would flow to the lake, completing the loop.

#### LMT

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##### Re: Lake Matthew - 2036
« Reply #32 on: 04/11/2016 09:18 PM »
...A 1GWe nuclear reactor...
Quote from: LMT
The methods are non-nuclear and shown to be safe.
« Last Edit: 12/14/2016 07:29 PM by LMT »

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #33 on: 04/11/2016 10:36 PM »
Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.
What makes you think that? Nuclear reactors can be very compact and small. They can even be their own way to get there (NERVA), The bigger issue with nuclear plants in space is the political resistance to them.
A 1 gigawatt nuclear reactor core Weighs hundreds of tons and requires huge amounts of cooling.

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #34 on: 04/11/2016 11:02 PM »
Asteroid hitting Mars?

How much dust would be put in the atmosphere of Mars from such an impact.?

Building more colonies, how would any preexisting colony handle a new asteroid impact ( quake ) on Mars?

Mars has very large seasonal dust storms.  Dust will settle out rapidly in the very thin atmosphere.   How much dust depends on the size and velocity of the impactor, and the resulting crater.

This scenario looks good to give a early colony a toehold on Mars.  I agree it's a significant hazard to existing settlements.

#### Stan-1967

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##### Re: Lake Matthew - 2036
« Reply #35 on: 04/11/2016 11:11 PM »
It would be easier to redirect a near Mars asteroid of the equivalent size.

I'm going to agree with this and abondon my previous thoughts of pulling it off the surface of Phobos.   This will mean the impactor can be much smaller, as its velocity wil be much higher.  All the orbit needs is to be adjusted to intercept Mars.   Any list of asteroids with close passes to Mars in the 2-4 years prior to the 2036 target date?

#### Elmar Moelzer

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##### Re: Lake Matthew - 2036
« Reply #36 on: 04/11/2016 11:43 PM »
Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.
What makes you think that? Nuclear reactors can be very compact and small. They can even be their own way to get there (NERVA), The bigger issue with nuclear plants in space is the political resistance to them.
A 1 gigawatt nuclear reactor core Weighs hundreds of tons and requires huge amounts of cooling.
1. Since we want to heat a lake, we have the cooling right there. We are not going to build a carnot cycle. We are just interested in the thermal output.
2. The reactor core can be in the rage of 10 tons, or so. The rest is shielding, mostly. Timberwind showed that you can build high power reactors with a relatively small weight footprint.

#### virnin

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##### Re: Lake Matthew - 2036
« Reply #37 on: 04/12/2016 12:23 AM »
Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.
What makes you think that? Nuclear reactors can be very compact and small. They can even be their own way to get there (NERVA), The bigger issue with nuclear plants in space is the political resistance to them.
A 1 gigawatt nuclear reactor core Weighs hundreds of tons and requires huge amounts of cooling.
1. Since we want to heat a lake, we have the cooling right there. We are not going to build a carnot cycle. We are just interested in the thermal output.
2. The reactor core can be in the rage of 10 tons, or so. The rest is shielding, mostly. Timberwind showed that you can build high power reactors with a relatively small weight footprint.

I'm pretty sure there won't be a lake until after a significant portion of the heating has been accomplished so you would still need a significant system of some kind to deliver the heat from the reactor core into a fairly large surrounding area.

At the end, you would have a lake with a fission reactor sunk in the middle of it.  Not my first choice for a swimming hole.

#### Robotbeat

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##### Re: Lake Matthew - 2036
« Reply #38 on: 04/12/2016 12:52 AM »
Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.
What makes you think that? Nuclear reactors can be very compact and small. They can even be their own way to get there (NERVA), The bigger issue with nuclear plants in space is the political resistance to them.
A 1 gigawatt nuclear reactor core Weighs hundreds of tons and requires huge amounts of cooling.
NERVA is a nuclear reactor core, output multiple GW and had a mass of just a few tons. Almost a gigawatt per ton for some designs. And we actually tested NERVA, so it's not like this overall idea is ridiculous. You could land a 10-20ton Gigawatt reactor on Mars on a typical human-rated lander design. You would need ~12 tons of fuel if you had perfect burn-up. About 40 tons for a more realistic 40% burn-up. That's not a crazy number, but you'd likely need either an advanced breeder reactor design or highly enriched uranium. 20% burn-up (80 tons) has been demonstrated at this breeder reactor: https://en.wikipedia.org/wiki/Experimental_Breeder_Reactor_II

That's actually the neatest thing about nuclear thermal rockets is how ridiculously power dense. If you can find other uses for it other than wasting a bunch of precious liquid hydrogen with it, you're golden.

You'd cool the reactor with Martian water, recirculating through the bedrock.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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#### gospacex

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##### Re: Lake Matthew - 2036
« Reply #39 on: 04/12/2016 01:00 AM »
Building a 1 GWe nuke plant on Mars is arguably further out of our technical grasp than diverting a very small asteroid.
What makes you think that? Nuclear reactors can be very compact and small. They can even be their own way to get there (NERVA), The bigger issue with nuclear plants in space is the political resistance to them.
A 1 gigawatt nuclear reactor core Weighs hundreds of tons and requires huge amounts of cooling.
NERVA is a nuclear reactor core, output multiple GW and had a mass of just a few tons. Almost a gigawatt per ton for some designs. And we actually tested NERVA, so it's not like this overall idea is ridiculous. You could land a 10-20ton Gigawatt reactor on Mars on a typical human-rated lander design.

NERVA at full power doesn't melt only because it rejects heat in the exhaust. Without exhaust, with its power density of some 500kW/kg it would melt in seconds.

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