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Various reaction drives in M-Space and their fuel


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1 hour ago, seneschal said:


Our NASA link says, among other things, rhat a spacecraft traveling as fast as the International Space Station would take about 18 years to go from Earth to Neptune.  That's a long trip but perhaps doable in a human lifetime.  It would be a 40-ish year round trip.  Problem is, our articles on solar sailors seem to indicate that they would be slower than the International Space Station..  What does that mean for our doughty spacehands?  A voyage to the outer planets would be at least a career-length commitment if not a lifetime commitment.

That's a generation ship already, if only one extra generation.

Unsupported solar sailors starting from a neutral orbital vector will take that much to get up to speed. That's where mirrors or solar-pumped lasers come into play, creating a significantly higher light pressure.


1 hour ago, seneschal said:

Jim Hawkins signs on as cabin boy of the Space Hispaniola at age 8 or 10 (the Treasure Island character was about 12).  He is 50-ish when he returns to Earth. 

What's your assumed life expectancy for Jim Hawkins? Stevensons protagonists were approaching ancient around fifty. Our intrepid space-farers might well expect to be in good working order well into their seventies (provided space doesn't offer wildly deleterious circumstances to life expectancy). Aided with implants, their internal repair service might well make a sixty year term of service just the prequel to your civilian career. (Another development completely missing from Traveller...)


1 hour ago, seneschal said:

What happened to all the adult crewmen he shipped with?  They are in their 90s or older.  Do we assume advanced medical care will keep them spry?

How spry do you need to be in a lowered G environment? The effects of low G on the human body aren't known yet (unlike the efects of prolonged zero G). Solar sailors would need to rely on rotational simulation of gravity, probably some bola solution for their habitats, or possibly an aquatic environment in zero G (hasn't been tried yet, but might stimulate body musculature better than simulated G).

They'd still want some "down" time, e.g. when catching a cold. Poor Chris Hadfield proved that our coping mechanism with the sniffles results in extreme unhappiness in zero G.


1 hour ago, seneschal said:

 Or perhaps we staff our spaceships with virile 20-year-olds.  

Nubile 20-year-olds, rather. You don't need that many men on a generation ship.

1 hour ago, seneschal said:

They are in their early 60s upon return while Jim is in his early 50s.  Sounds more practical and explains all those grizzled Classic Traveller veterans.  Still you've got to account for training and education time so they can operate the ship.  So mid-60s upon return.  

Information can be transported on flight, so what you would want is a small crew of experienced teachers/trainers, a bunch of POs with a solid foundation, and a batch of cadets (and wonder boys/girls) to train on the way.

Or you might bring a nursery.

1 hour ago, seneschal said:

Would you sign up for a space voyage straight out of high school or college, knowing that you might never see you parents or favorite aunt alive again?  

That's not that different from deciding to emigrate at that age in an time prior to widely available inter-continental flights (e.g. back in the sixties of last century). The time lag between video messages may be half a day at your furthest, so you aren't entirely out of the world.

1 hour ago, seneschal said:

That your high school or college sweetheart wouldn't wait 40 years for you (and why should she)?  

Hands up who has reached 40 years of happy or at least tolerable cohabitation with their high school sweetheart...

The biological problem is that you spend all your fertile time in that tin-can, so you had better frozen a bunch of embryos or at least viable gametes before lift-off.

1 hour ago, seneschal said:

That your friends and siblings will marry, raise families, and be spoiling their grandkids while you are toddling around in the void?

They (or the commune that brought you up) might raise some of your kids in your stead.

1 hour ago, seneschal said:

 That's a heck of a commitment to make, especially at an age when most people are still trying to figure out who they are and what they want to do with their lives.  Once they seal the hatch behind you, you are stuck.  No turning back.

It's like making the trek across the great plains - you assume that to be a one-way trek. If you get to see the kin you left behind again, that's only because they may follow on your trail.

You might (have to) create a sub-culture preparing such spacers, or have them develop organically from their ancestors' choices (like in C.J. Cherryh's space trader families).

Telling how it is excessive verbis


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Joerg, Thot, it is quickly becoming apparent that much as I love Traveller, that game's starship rules can't handle the realities our research is turning up.  😭

I think that the lifespan and healthcare that our young Jim Hawkins can expect are key here.  If people now normally live to 120 or 130 in relatively good health and activity, then returning at 65 isn't as big a deal.  Age 65 is the new 40; and we all know life doesn't begin until 40.  Hawkins can expect to launch a second career, assuming space doesn't kill him first.  Since a lot of folks today aren't getting married and starting families until their 30s or even early 40s, Hawkins could even enjoy domesticity after his voyage.  Although freezing crew members' sperm or eggs beforehand might still be a wise precaution.  We don't know what the various energies surging through space might do to human reproductive capability.

If we go with the virile/nubile scenario we open up a bunch of other possibilities (cans of worms?).  Suddenly Star Trek becomes a CW show, with horny youthfully spacehands dealing with all sorts of distractions from the mission.  Or at least Robotsch Macross.

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Moderator Spacesuit Helmet On. 

As we're again wandering away from the OP and into the territory of gender mixes on generational spaceships, I'm fairly certain now that this thread has run its course and needs to go into hypersleep. 

By all means continue the discussion in Alastor, where generational starship demographics and other such matters can be pondered into infinity and beyond. 

Thanks everyone. 

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