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Old 03-18-2015, 11:34 AM   #16
TMac3000
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Thanks, dgatsoulis. But I can't see them on my work computer...so I'll check them out this evening and get back to you

---------- Post added 03-18-15 at 05:38 AM ---------- Previous post was 03-17-15 at 01:37 PM ----------

Hey, that's really interesting! It makes me think the tankage could be inside the ship, so I would not have to worry about meshing and designing it...

---------- Post added at 07:34 AM ---------- Previous post was at 05:38 AM ----------

Just a thought--if I used a Venus-Earth-Jupiter-Saturn trajectory, it would save dV, but doesn't the time added to the mission mean the extra consumable mass would out-weigh the fuel-mass savings?
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Old 03-18-2015, 12:34 PM   #17
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Just a thought--if I used a Venus-Earth-Jupiter-Saturn trajectory, it would save dV, but doesn't the time added to the mission mean the extra consumable mass would out-weigh the fuel-mass savings?
Is a optimization problem. But 6000 days are already a dwarf below 20 years - that's a lot of dedication for an astronaut, so a few years more will very likely be no problem for the already convinced.

But then... 20 years also mean a lot of time for illnesses, accidents, warfare, zombie attacks....
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Old 03-18-2015, 01:22 PM   #18
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 tampons
Either send an all-male crew, or have women undergo hysterectomy. You're not going to send anyone below 30 (training!), and with a 16-year trip it means they will be at least 46 at return -- that's generally past the child-bearing age, plus the radiation damage to ovaries is going to be considerable.

---------- Post added at 02:22 PM ---------- Previous post was at 02:17 PM ----------

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 NASA recommends 0.8 kg of oxygen per astronaut per day.
This is with breaking down CO2, or without?

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 to figure the nitrogen in too. I want a 70/30 atmo at three-quarters of a bar, so I need a...about 5-foot LN2 tank to supply that.
N2 is not consumed by humans You may however want to have enough of both O2 and N2 to repressurize the entire ship, possibly several times (in case of decompression).

Also, you want to keep that in several tanks, placed in different parts of the ship.
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Old 03-18-2015, 01:46 PM   #19
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Why did you choose just Iapetus... Assuming one could travel to the Saturn system, they would probably also have the ability to visit multiple moons in the system.
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Old 03-18-2015, 01:51 PM   #20
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 N2 is not consumed by humans You may however want to have enough of both O2 and N2 to repressurize the entire ship, possibly several times (in case of decompression).

Also, you want to keep that in several tanks, placed in different parts of the ship.
In reality, you also have to include leakage, since there is no perfect seal in the world.

But that's some unknown variable, because we have no real idea how the leakage will develop from launch to EOM.
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Old 03-18-2015, 02:01 PM   #21
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 Why did you choose just Iapetus... Assuming one could travel to the Saturn system, they would probably also have the ability to visit multiple moons in the system.
That's a lot of delta-v though... http://www.projectrho.com/public_htm...ingraiders.php (the table is halfway through the page)
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Old 03-18-2015, 02:38 PM   #22
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 Is a optimization problem. But 6000 days are already a dwarf below 20 years - that's a lot of dedication for an astronaut, so a few years more will very likely be no problem for the already convinced.
Morale isn't necessarily the problem...although it is A problem...
The problem is, though you might save fuel with a series of slings, those slings would add some years to your travel time. More time means more food, more food needs more mass. So what efficiency you gain in fuel, you lose in consumables. Am I right?

---------- Post added at 10:34 AM ---------- Previous post was at 10:29 AM ----------

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 Either send an all-male crew, or have women undergo hysterectomy. You're not going to send anyone below 30 (training!), and with a 16-year trip it means they will be at least 46 at return -- that's generally past the child-bearing age, plus the radiation damage to ovaries is going to be considerable.
Good point. I just wanted to be inclusive--can't have anybody thinking I'm closed-minded

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This is with breaking down CO2, or without?
Without, I think...

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N2 is not consumed by humans You may however want to have enough of both O2 and N2 to repressurize the entire ship, possibly several times (in case of decompression).
Correct...N2 is rejected by the body, right? It's there in the ship's atmosphere so we don't have one spark that incinerates us. So you recommend maybe doubling the size of the O2 and N2 tanks?

---------- Post added at 10:38 AM ---------- Previous post was at 10:34 AM ----------

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 Why did you choose just Iapetus... Assuming one could travel to the Saturn system, they would probably also have the ability to visit multiple moons in the system.
Iapetus would be the primary target, but there is no reason we can't have Arroway do a Saturn sling and examine a few other moons before settling into a polar Saturn orbit.
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Old 03-18-2015, 04:44 PM   #23
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Im pretty sure sending a crew into the system just as a flyby will be far easier(but just as symbolic) than landing and colonizing a strange moon. You could carry along several thousand nano sats to observe the Saturn system and use robotics to remotely explore moons from orbit.

And the 16year trip...That sounds more like a prison than a mission. You should consider shortening it.

I developed a Saturn Tour mission. I could give you the details on my mission and you could base some things off that.
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Old 03-18-2015, 04:52 PM   #24
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 So you recommend maybe doubling the size of the O2 and N2 tanks?
Take a look at this study of a Mars mission, page 207.

Last edited by kamaz; 03-18-2015 at 04:59 PM.
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Old 03-18-2015, 05:28 PM   #25
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That is very interesting! I will give it a much closer look tonight.

---------- Post added at 01:28 PM ---------- Previous post was at 01:25 PM ----------

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 And the 16year trip...That sounds more like a prison than a mission. You should consider shortening it.
Sixteen years is for both ways, via Hohmann orbit, and assumes 4 years on site. It can be shortened to 13, depending on the date of the next Earth window after landing.

I don't know of any way to make it shorter than that without straining dv requirements
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Old 03-18-2015, 05:31 PM   #26
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 I don't know of any way to make it shorter than that without straining dv requirements
You could for example look for a jupiter assist, which does only slightly strain the dv budget - or use Saturn or Titan aerobraking.
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Old 03-18-2015, 06:00 PM   #27
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The Jupiter flyby sounds good--I think I'll avoid a Venus sling.

Next question: propellant tank size.

There is a Saturn launch window on Feb 21, 2017 with arrival March 10, 2023. This is when Arroway/Sharapova will launch.

If MINOTAUR launches at the next Hohmann window after that--March 6, 2018, with arrival March 23, 2024--we will need 15,732 m/s dv for the trip there. For the trip back, we can depart March 1, 2025 and return to Earth as triumphant heros on March 18, 2031. This would take another 15.7 km/s. Add a 20% fudge-factor, and we're going to need a dv budget of about 38 km/s.

I guess I need to know the ship's final mass before determining what sort of propellant is needed

Last edited by TMac3000; 03-18-2015 at 06:02 PM.
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Old 03-18-2015, 06:12 PM   #28
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Try that study:

https://info.aiaa.org/Regions/Wester...09-5309%29.pdf
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Old 03-18-2015, 06:28 PM   #29
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That's awesome! I have only one objection--maybe I just haven't read in enough detail yet, but LH2? I know that most NTRs call for this, but it's volatile stuff--that would need to be one heavily armored core tank, otherwise one pea-sized micrometeorite could blow you right to hell.
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Old 03-18-2015, 06:36 PM   #30
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Originally Posted by TMac3000 View Post
 That's awesome! I have only one objection--maybe I just haven't read in enough detail yet, but LH2? I know that most NTRs call for this, but it's volatile stuff--that would need to be one heavily armored core tank, otherwise one pea-sized micrometeorite could blow you right to hell.
Sorry - no. One pea-sized micrometeorite could punch a large hole into the tank and make it vent high-pressure H2.

But if you have no oxygen-hydrogen mixture you can also have no explosion. Pure hydrogen does not explode.
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