Orbiter-Forum  

Go Back   Orbiter-Forum > Far Side of the Moon > Math & Physics
Register Blogs Orbinauts List Social Groups FAQ Projects Mark Forums Read

Math & Physics Mathematical and physical problems of space flight and astronomy.

Reply
 
Thread Tools
Old 12-22-2017, 09:16 PM   #1
LakeMatthewTeam
Orbinaut
Default Free Launch, or Mars Clathrate Mining

Exploring an Idea

From “Methane Hydrate on Mars: A Resource-Rich Stepping Stone to the Outer Planets?
The detection of methane establishes the subsurface of Mars as a hydrocarbon province... Methane gas and hydrate deposits may occur in the subsurface at shallow depths on the order of ~15-30 m. Shallow methane gas deposits could constitute the most important near-term in-situ resource. Utilizing the natural resources of Mars could significantly reduce the cost of human exploration when compared with what would be required if these same resources were transported from Earth. In fact, the availability of these natural resources may prove to be the critical factor that will enable the continued human exploration of the solar system.

A new paradigm of a resource-rich Mars should now be considered the basis of the planning of future human exploration, whether on Mars or beyond -- turning Mars from a remote, dead-end destination to a self-sustaining outpost that can serve as a stepping stone to the outer Solar System.
Application

Theoretically methane from underground can be trapped in martian ice as clathrate, especially atop fault lines, which may channel methane toward the surface. Thereby ice-rich regions such as ice caps could conceivably accumulate clathrate. A regional clathrate deposit could contain enough methane to justify mining for spacecraft use.

SpaceX estimates propellant production could use more than half of a facility’s electrical power. Hypothetically a clathrate mine would free that power for use elsewhere. If methane manufacture is not required, oxygen production can use less power also. One might replace power-hungry water electrolysis with oxygen-byproduct harvesting in, say, dense algae oxygen farms, or in some existing oxide-reduction factory. Result: a very significant reduction in facility power requirement.

Challenges

What would be some basic challenges of such a venture? They include:
  • Prospecting: locate a rich clathrate deposit
  • Mining: get methane out of the ice
  • Storage: store methane at fleet scale
All would have to be done efficiently of course.

Clathrate Prospecting

Clathrate prospecting on Mars is certainly speculative. But perhaps some terrestrial prospecting tech could be adapted for this purpose. Might reflection seismology be applicable? Clathrate prospecting on Earth has been performed using seismic methods. Examples: 1, 2.

If a seismic method were workable on martian ice caps, a spacecraft might implement. For example it could deploy small self-guided impactors across the cap, to produce a gridded set of seismic impacts. The spacecraft would also deploy small sensors across the ice cap, perhaps as lightweight autorotation landers, to record the dataset of impact seismic waves. Prospecting software would convert the dataset into a model of the ice cap, marking possible clathrate deposits.

What other prospecting methods might be feasible?

Clathrate Mining and Methane Storage

How might clathrate mining and methane storage be accomplished, efficiently and at fleet scale? Conceivably, and rather simply, one might use heat as a mining tool, and use the ice cap as a storage vessel. Illustrating one such scenario, just as an “ice-breaker”:



Here an ice cap is dark blue, with a landed spacecraft at top right. Clathrate is mined with a Kilopower-class reactor (red). The reactor produces electrical power and heat for mining. Reactor melt hollows out chambers.

The reactor would be cooled by vapor convection inside the chamber. Radiated heat vaporizes ice, and convecting vapor circulates, removing heat from the chamber when released.

In deployment, the reactor is lowered quickly from the surface, forming a narrow ice pipe. At clathrate depth the speed is reduced, to allow the reactor to melt out the greatest possible chamber diameter and maximize methane release.

In this merely conceivable scenario, multiple chambers are melted out and used for several purposes. Purposes are noted in the following production and storage steps:
  1. An active clathrate methane mining chamber has a cap which opens to release the warm vapor into insulated surface piping.

  2. The pipe connects to an evacuated vessel chamber, mined out previously, now serving as a vapor separator. In this cold chamber the high-fraction water vapor freezes out (light blue), leaving methane, nitrogen, CO2 and other clathrate components in vapor phase or gaseous phase.

  3. The vapor separator’s cap opens and the remaining gases are pumped into surface piping. Notionally the cap employs low-pressure membrane filters to separate nitrogen, CO2 and other unwanted impurities out of the gas stream, venting them into the ambient atmosphere. This leaves methane product in the pipe. The separator chamber is now evacuated for reuse.

  4. The pumped methane is compressed into the liquid methane storage chamber vessel. The methane is compressed above 10 atm pressure to hold it in liquid phase at ambient ice cap temperature. No refrigeration is required. This chamber vessel would need to be created at a depth having ice strength adequate for the pressure vessel. (Open question: How quickly would methane escape into the surrounding ice?)

  5. The liquid methane vessel’s cap opens to pump liquid methane into the awaiting spacecraft. The spacecraft’s methane tank is filled completely, but only a fraction is used in the hop to a Mars facility. The balance is used for the return flight, and to fuel another craft at a Mars facility. That excess methane is essentially “in-tank cargo”.
LOX Storage

Assuming as before that oxygen is now a facility byproduct, LOX bulk storage remains a problem. The infrastructure to store LOX for a fleet of spacecraft could require immense ISRU manufacturing at a Mars facility (assuming Omaha Crater reservoir inflatables are not available). To get around that problem, spacecraft might tank extra LOX in the ice cap alongside methane. This LOX would be carried essentially as in-tank cargo, on the hop from a Mars facility to the clathrate mine. After the spacecraft lands, its excess LOX is pumped into a storage chamber vessel that’s similar to the liquid methane vessel.

One difference: LOX would need refrigeration. Refrigeration requires power, but less in an ice cap than at a Mars facility. And of course the power saving derived from the hypothetical clathrate mine would be immense. Altogether this might not be a completely “free launch,” but if feasible it would be at least a “cheap launch.”

Open topic.

Refs

Gas-hydrate concentration estimated from P- and S-wave velocities at the Mallik 2L-38 research well, Mackenzie Delta, Canada
Geophysical methods to quantify gas hydrates and free gas in the shallow subsurface: Review and Outlook
Methane Clathrates in the Solar System
Methane Hydrate on Mars: A Resource-Rich Stepping Stone to the Outer Planets?
Methane Seepage on Mars - Where to Look and Why
Nuclear Systems Kilopower Overview

Last edited by LakeMatthewTeam; 12-27-2017 at 05:44 PM.
LakeMatthewTeam is offline   Reply With Quote
Old 10-04-2019, 07:26 AM   #2
marathonboats
Orbinaut
Default

can anyone tell me What would be some basic challenges of such a venture? They include:
Prospecting: locate a rich clathrate deposit
Mining: get methane out of the ice
Storage: store methane at fleet scale
All would have to be done efficiently of course.
maybe this the answer?


_______________
kontraktorkonstruksikapal
marathonboats is offline   Reply With Quote
Old 10-06-2019, 08:17 PM   #3
Thunder Chicken
Fine Threads since 2008
 
Thunder Chicken's Avatar
Default

This is all wildly speculative. Methane detections on Mars have ranged from 60 ppb to below detection limit. The density of CO2 in the atmosphere with the exisitence of water ice in the presence of radiation makes Fischer-Tropsch synthesis theoretically possible.


Methane clathrate deposits on earth are also commonly found with sulfur compounds - there is no evidence of any SOx or other releases of sulfur on Mars. There just isn't any significant evidence of any large quantity of stable methane on Mars.



It would be interesting to explore the use of clathrates here on Earth because there is quite a lot of it, and harnessing it is a challenge.
Thunder Chicken is offline   Reply With Quote
Reply

  Orbiter-Forum > Far Side of the Moon > Math & Physics

Tags
clathrate, mars, methane, propellant, spacex


Thread Tools

Posting Rules
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
Forum Jump


All times are GMT. The time now is 12:43 AM.

Quick Links Need Help?


About Us | Rules & Guidelines | TOS Policy | Privacy Policy

Orbiter-Forum is hosted at Orbithangar.com
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Copyright 2007 - 2017, Orbiter-Forum.com. All rights reserved.