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SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Large Ship Chemical Propulsion

After much reading I have come to a conclusion that we need to not only build up the means to get the logistics of the large ships build but as well optimizing the delivery of all materials including fuel to the build location of the large ship.

Earth has a very high penalty due to its gravity well and while mars has less of one we have the other aspect of creating a supply system to not only refuel and resupply but to make that same logistics possible at mars.

A starship get to orbit and while its got the plausible payloads of 100 to 200 mT its empty so how will it get to the elliptical orbit that we are trying to make use of . That means we need a more powerful starship to be able to build here at earth.

On the opposite end we need to be able to build a mars refueling gas station not only built on mars but know the numbers of what we can deliver to a similar orbit around mars. Being able to catch the large ship in mars orbit is a bit more possible as we have a large fuel tank that gives leverage for bringing up the resupply and refueling.

Of course the task of lifting more than 100 people on either end means studying how long we need to use the ship while we move cargo and fuel to the large ship for use.

https://en.wikipedia.org/wiki/Highly_elliptical_orbit

https://slideplayer.com/slide/8865753/

https://www.frontiersin.org/articles/10 … 00034/full

Calliban

Member

From: Northern England, UK

Registered: 2019-08-18

Posts: 3,789

Re: Large Ship Chemical Propulsion

One option would be to fill the propellant tanks with hydrogen lifted from Mars and oxygen manufactured from oxides on Phobos.  If we intend to use space manufacturing to build the large ship in the first place, we could fill the oxygen tank with lunar LOX in high Earth orbit.

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"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."

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Large Ship Chemical Propulsion

If you need the hydrogen from the surface why not just send up water but then again you are using methane so where is the carbon to make the fuel?

Calliban

Member

From: Northern England, UK

Registered: 2019-08-18

Posts: 3,789

Re: Large Ship Chemical Propulsion

If you need the hydrogen from the surface why not just send up water but then again you are using methane so where is the carbon to make the fuel?

Space Nut, we may or may not use methane as a propellant for the large ship.  H2/O2 has better ISP performance.  But is more difficult to store for long periods in space.  H2 is one ninth the total bipropellant mass.  So it makes some sense to produce oxygen in Mars orbit from a source already out of the gravity well, rather than lift it from the surface of Mars.  Whether this is worth the additional complication of mining and reducing oxides from Phobos is uncertain.  But it is an option that is worth mentioning for consideration.

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"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."

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Large Ship Chemical Propulsion

The shear quantity for starship was figured for hydrogen boil-off and its rate of filling if greater than 30 days between filling at the 100 ton rate meant we needed extra flights to get that last top off. That is even greater with the size of the large ship propulsion. Hydrogen is just not practical.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Large Ship Chemical Propulsion

bump topic contains space tug of which several already have the large ship containing the methods and use as described which as well contains the departure and arrival.