09-17-2020, 10:54 AM | #11 | |
Join Date: Aug 2007
|
Re: [Spaceships] Martian “Gas” Station
Quote:
Hard science ships can't just "stop". They have to spend Delta-V. So the efficient thing is usually to accelerate once and then decelerate once while you coast at maximum speed in between.
__________________
Fred Brackin |
|
09-17-2020, 12:54 PM | #12 |
Join Date: Jan 2014
|
Re: [Spaceships] Martian “Gas” Station
Well, it depends on how you set up the case. For example, say we have rocket with a dry mass of 1 ton and ISP of 1 km/s. It can travel from A to B for a ΔV of 4 km/s, or from A to M for 3 km/s then M to B for another 3 km/s. While the A to B via M route appears less efficient (taking 2 more km/s), if you can refill propellant tanks at M, it would save 15 tons of propellant compared to the A-B route.
|
09-17-2020, 01:28 PM | #13 |
Join Date: Feb 2016
|
Re: [Spaceships] Martian “Gas” Station
An exhausted velocity of 1 km/s is a weak drive. Assuming that the drive tosses out 3 kg/s/metric ton of mass, that would only allow an object with a dry mass of 1 metric ton and a wet mass of 2 metric tons an acceleration of 0.1 g for 1000 seconds (a delta-v of only 980 m/s).
|
09-17-2020, 01:50 PM | #14 | |
Join Date: Aug 2007
|
Re: [Spaceships] Martian “Gas” Station
Quote:
If M is exactly between A and B you're doing 5 million kilometers on each leg at an average velocity of 1.5 million km/s and it will take you 3,333,333 seconds on each leg or about 77 days ignoring any time you spend finding and refining. Note that these are the maximally favorable assuptions for the relative positions of A,B and M. Zig-zagging will take even longer. Spending almost 3 weeks longer and putting 50% more wear on your engines will be less efficient by most standards.
__________________
Fred Brackin |
|
09-17-2020, 02:16 PM | #15 |
Join Date: Jan 2014
|
Re: [Spaceships] Martian “Gas” Station
I'll admit I'm a bit biased towards "Time is Cheap, Mass is Expensive", though looking at near-future space travel that seems plausible enough (traveling outward would take months if not years). I'm also a little biased towards one-way flights.
|
09-17-2020, 02:29 PM | #16 | |
Join Date: Aug 2004
Location: Hamilton, Ont. CANADA
|
Re: [Spaceships] Martian “Gas” Station
Okay, we are getting a little off focus here. If there was a reliable source of reaction mass, oxygen, food and water in Mars orbit incoming ships from Earth could re-provision themselves there for the return trip and reserve more room for cargo and passengers. Note that without a CO2 atmosphere there would be no methane production so that capacity on the moons would be dedicated to processing ice. A big import from Earth would probably be certain organic compounds to promote food production.
Quote:
Dalton “another political comment avoided” Spence
Last edited by DaltonS; 09-17-2020 at 02:33 PM. |
|
09-17-2020, 05:24 PM | #17 |
Join Date: Feb 2005
Location: Berkeley, CA
|
Re: [Spaceships] Martian “Gas” Station
I would note that you may want to rethink ratios of production to storage.
A basic refinery complex is 3 mining modules feeding one refinery, plus power plants capable of providing 4 energy points. At SM+10, that costs $40M for the mining modules, and $120M for fission reactors (solar power is vastly more expensive -- it starts at $200M, but because of martian sunlight and the fact that it only operates during the daytime, you actually need more than 5x as much. Note that both reactors and solar panels have options that are cheaper but heavier). It produces 150 tons per hour. 15,000 tons of fuel tanks costs $100M, so if your normal business cycle is 100 hours of business and then 10,000 hours of inactivity, you can drop down to SM+8 mining modules (total cost is $116M) and still refill your tanks in six weeks. |
09-17-2020, 08:20 PM | #18 |
Join Date: Aug 2004
Location: Hamilton, Ont. CANADA
|
Re: [Spaceships] Martian “Gas” Station
Looks like I may have to redesign the whole thing. My problem is the first step: breaking down water into hydrogen and oxygen. The result is eight tons of oxygen for every ton of hydrogen. I see this as two standard and two small tanks for oxygen, one small tank for hydrogen, a standard mining system, two small refineries (LOH, CH4), a small fission reactor (powers one refinery at a time), a regular methane tank and a regular fission reactor (powers the mine). The H2 and O2 tanks take 30 hours to fill while the methane tank takes ten.
That takes care of the bottom section. I think I'll leave the top level much the same and work on the middle one tomorrow. Dalton “Martian “Gas” Station 2.0?” Spence
|
09-17-2020, 09:03 PM | #19 | |
Join Date: May 2005
Location: Oz
|
Re: [Spaceships] Martian “Gas” Station
Quote:
__________________
Decay is inherent in all composite things. Nod head. Get treat. |
|
09-18-2020, 06:33 AM | #20 | |
Join Date: Aug 2004
Location: Hamilton, Ont. CANADA
|
Re: [Spaceships] Martian “Gas” Station
Quote:
Dalton “So let's pop this balloon and get back to my station.” Spence
|
|
Tags |
mars, spaceships |
Thread Tools | |
Display Modes | |
|
|