NASA space ship

Thucydides wrote:

The E wrote:Ahh, yes, the "we can get away from all the oppressive governments" dream. Have you never stopped to consider how draconian and intrusive a government has to be in order to ensure the safe, continued existance of the space station it governs?

Governments don't have to be necessarily oppressive for people to still think they would be better off somewhere else. You could look at the English dissenters who settled (and largely created) America, or the Mormons setting out to Utah. American companies are using various means to "leave" the United States due to what they and their shareholders have decided are onerous taxation policies. And the experimentation that the Ancient Greek colonists practiced does not seem to have been driven by oppression, since the entire rational for colonizing in the ancient Greek world was to find more land for citizens of overcrowded city-states.

As well, we are now entering an era where the space infrastructure might not be the domain of governments at all. SpaceX is pretty much finding R&D for their various projects based more on what their founder, Elon Musk. believes rather than what NASA wants to buy. My example includes "company towns", and I suspect that many company towns will see a distinct change in structure as people aboard realize what the company management wants isn't possible, or at least not possible using the systems and procedures management has been given to use.

The other thing to consider is that truly oppressive governments will not be giving their citizens any means to leave Earth at all. The time delay in information transmission (particularly beyond cis Lunar space) starts to degrade the ability of the central organs to dictate and manage what is happening in the hinterlands, and of course any punitive expeditions will take a long time to arrive at the rebellious colony. Far better to have the oppressed directly under your thumb, lest they get ideas, or worse yet, time and resources to act on these ideas......

I'm sorry, but space colonies are not the place to live the libertarian dream. Sure, you won't have a government back on earth oppressing you. No, you'll have your station administration people oppressing you, because there is no way in hell that you can allow the level of personal freedom you're accustomed to on Earth in an environment where the slightest mistake can have catastrophic consequences.

Thucydides wrote:Just to show how "easy" getting around could actually be, the neofuel site http://neofuel.com has detailed papers demonstrating how you could use a NTR with water as the remass/ coolant and deliver a 10.000 ton payload to Jupiter in roughly 3 years. The start mass is an astonishing 358,000 tons of water, but the calculations seem pretty straight forward.
http://neofuel.com/index_neofuel.html

I hope you realise that clean freshwater is one of the top 10 most precious resources on earth, and in less than a century will probably be one of the top 3, quite likely THE most precious resource.

Dumping large amounts of water into space is NOT an option unless you can take it from elsewhere.

fallsfromtrees wrote:

Lord Skimper wrote:A big ship spinning along its axis allows one to accelerate the full way, if you are tumbling end over end you have gravity, sort of, but you lack acceleration unless the engine is perpendicular to the rotation and the engine is in the middle of the ship. Of course your little ship is pretty big and instead of having a hundred little ships in train you end up with one big ship.

Lets just do a little arithmetic as to how fast and far apart you have to be to get a reasonable gravity simulation.

From basic physics: a = v^2/r. v = 2*pi*r*(rev) where rev is the rotation rate in rev/second.

So a = (2*pi*rev)^2*r. Assuming you want 1/2g as your gravity at the end of your tether, that's 4.9 m/sec^2. Substituting the numbers you get r*(rev)^2 = .12411. If you want 1 g, the later constant is .24822.

Assuming a radius of 50 meters (cable length of 100 meter) we get

rev = sqrt(.00248) or .05 revolutions per second or about 3 revs/min.

You have to decide if that's too fast a spin rate. Because revs is a square component in the formula, to half the rotation speed, you have to either quadruple the radius, or cut the required acceleration by a factor of 4 or a combination of both (double the radius and half the acceleration).

How big would the ship diameter need be to have a rotation of 1 per day at 1 G?

What would be the spin rate of the 100 Metre ship diameter at 1 G be? Would it be 35Kph? How many G would you gain if you ran at 15 Kph in the same rotation direction? 1.5G? would you "weigh" 0.5G if you went opposite the rotation direction?

Time to fire up Ecxel.

Lord Skimper wrote:How big would the ship diameter need be to have a rotation of 1 per day at 1 G?

About 4e9m and with a circumferential velocity of 145 km/s. I somewhat doubt the practical possibility.

Lord Skimper wrote:What would be the spin rate of the 100 Metre ship diameter at 1 G be? Would it be 35Kph?

No about 80 km/h, 35 km/h for a diameter of 20 m.

Lord Skimper wrote:How many G would you gain if you ran at 15 Kph in the same rotation direction? 1.5G? would you "weigh" 0.5G if you went opposite the rotation direction?

20 m diameter
20 km/h - 0.3 g
35 km/h - 1 g
50 km/h - 1.9 g

100 m diameter
65 km/h - 0.7 g
80 km/h - 1 g
95 km/h - 1.4 g

Tenshinai wrote:

Thucydides wrote:Just to show how "easy" getting around could actually be, the neofuel site http://neofuel.com has detailed papers demonstrating how you could use a NTR with water as the remass/ coolant and deliver a 10.000 ton payload to Jupiter in roughly 3 years. The start mass is an astonishing 358,000 tons of water, but the calculations seem pretty straight forward.
http://neofuel.com/index_neofuel.html

I hope you realise that clean freshwater is one of the top 10 most precious resources on earth, and in less than a century will probably be one of the top 3, quite likely THE most precious resource.

Dumping large amounts of water into space is NOT an option unless you can take it from elsewhere.

You don't need clean freshwater to power an NTR. You need to filter and purify the water somewhat to get rid of contaminants that will degrade the NTR.

And clean freshwater isn't really a problem if you do things right and are prepared to pay for it. The REAL problem is the lifestyle we have, that's why clean water is fast becoming a scarce resource.

I don't know what you mean by "large quantities", but any possible usage of water by an NTR barely registers compared to the total amount of water on earth (332,500,000 cubic miles/1,386,000,000 cubic kilometers).

Reading the entire article on the Neofuel site will put some of the concerns to rest. No one that I know of is proposing to boost 300,000 tons of water into orbit, rather the author is showing how it is conceptually possible to create a relatively inexpensive and rugged spaceship using mostly resources recovered in situ (Lunar ice, water in NEO's, ice from Callisto etc.) The overhead is already calculated into the equations, one of the thing the author wants to stress is limiting the amount of overhead (the LH2 powered ship is conceptually smaller and faster, until you add the various equipment needed to process water, split it into H2 and O2, liquify the H2 and the cryogenic tankage to store it).

And of course, the flight time to Callisto from Earth is relatively quick (about 3 years), which is one of the big objections to many other drive systems; they take too long.

For myself, I would be more interested in very high performance solar sails, which can flit about the Solar System without 300,000 tons of remass. Magsails or electrostatic sails might also make a good choice, but the understanding of these systems is far more theoretical.

As for space warfare, Sneaky's litterbox is intended as a humorous example, but a cloud of cat litter unexpected released into the path of a spaceship at high relative velocity will do some pretty dramatic things to exposed optics, antenna, radiators and other systems exposed outside of the radiation/micrometeor shielding. The point is anything moving at orbital and interplanetary velocities will create a danger to your spacecraft, space installation or even moon or asteroid (any planet that does not have a pretty thick atmosphere, really).

For the "Space Navy", there is some good news. If they find a piece of space debris or uncontrolled spacecraft that is on a collision course with something important, it could be "nudged" aside with a very small change in deltaV, as long as it can be identified far enough away. The closer you get, the larger amount of deltaV needed to change the object's course and avoid a collision.

This kind of goes to Tony's point as well; most weapons or systems that can be adapted to become weaponry in Space will most likely be robotic in nature. Cargo drones, or even ISO containers shot out of a mass driver to drift in a low energy orbit to the market will be unmanned to save on mass and cost, while lasers or microwave systems designed to beam power to cooperative targets to power spacecraft will also be robotic in order to maintain a high degree of pointing accuracy across long distances (or track rapidly moving spacecraft at short range; imagine a boost laser launching a spacecraft from Earth). Since they will be dual purpose, and "unpredictable" (i.e. they could be secretly programmed or reprogrammed to be used as weapons without others being aware of it), and since response time can be measured in years even in the best case scenario, the proper counter would be to have "sleeper" cells in place wherever your potential enemies are. An attack using space weaponry will be met with terrorism or assassination, cyber attacks and sabotage in the attacker's home station/asteroid/moon.

Lastly, I think it is possible to have degrees of personal freedom even in a space colony or spaceship. The trick is to incalculate all personnel with the proper set of training and values. Think of light aircraft pilots, who are essentially flying small missiles around your neighbourhood, or the Swiss, who are conscripted to military service and where virtually every male citizen has an automatic rifle in his house, yet also has one of the lowest gun crime rates in the world. Safety will also be built up by using robust and redundant systems, so if you accidentally open the airlock while taking out the trash, the effects will be limited to a small area.

aairfccha wrote:Time to fire up Ecxel.

Lord Skimper wrote:How big would the ship diameter need be to have a rotation of 1 per day at 1 G?

About 4e9m and with a circumferential velocity of 145 km/s. I somewhat doubt the practical possibility.

Lord Skimper wrote:What would be the spin rate of the 100 Metre ship diameter at 1 G be? Would it be 35Kph?

No about 80 km/h, 35 km/h for a diameter of 20 m.

Lord Skimper wrote:How many G would you gain if you ran at 15 Kph in the same rotation direction? 1.5G? would you "weigh" 0.5G if you went opposite the rotation direction?

20 m diameter
20 km/h - 0.3 g
35 km/h - 1 g
50 km/h - 1.9 g

100 m diameter
65 km/h - 0.7 g
80 km/h - 1 g
95 km/h - 1.4 g

Thank you

What is "About 4e9m and with a circumferential velocity of 145 km/s. I somewhat doubt the practical possibility." 4e9m?

How many revolutions or Speed of revolution would a ship with a diameter of about 5KM for 1G or 1/3G? (Thinking Earth Gravity or Mars Gravity)

The reason I wonder about this is for how an airplane (sort of airplane) would take off and land in such a ship. Once matching rotation speed it effectively lifts off with 0G vertical take off and landing. Flying around would be odd as the 0 G would make the wings useless for lift but good for manoeuvring.

A 5 KM diameter ship would allow for approximately 16km/ 10 Mile circumference. with however long it is offering a large enough space to have "community" sections living in.

using an Ion Drive which is good that it is slow to keep life in the ship relatively stable without having too much of a thrust disruption upon the residence of the ship. Flying the ship "Sideways" would add the minuscule thrust as a mild gravity plus minus and side thrust without it being an end on effect.

I'm not sure what kind of wind a Ship like this would have nor the effect on water currents? Any Thoughts?

aairfccha wrote:Time to fire up Ecxel.

Lord Skimper wrote:How big would the ship diameter need be to have a rotation of 1 per day at 1 G?

About 4e9m and with a circumferential velocity of 145 km/s. I somewhat doubt the practical possibility.

Lord Skimper wrote:What would be the spin rate of the 100 Metre ship diameter at 1 G be? Would it be 35Kph?

No about 80 km/h, 35 km/h for a diameter of 20 m.

Lord Skimper wrote:How many G would you gain if you ran at 15 Kph in the same rotation direction? 1.5G? would you "weigh" 0.5G if you went opposite the rotation direction?

20 m diameter
20 km/h - 0.3 g
35 km/h - 1 g
50 km/h - 1.9 g

100 m diameter
65 km/h - 0.7 g
80 km/h - 1 g
95 km/h - 1.4 g

Lord Skimper wrote:Thank you

What is "About 4e9m and with a circumferential velocity of 145 km/s. I somewhat doubt the practical possibility." 4e9m?

How many revolutions or Speed of revolution would a ship with a diameter of about 5KM for 1G or 1/3G? (Thinking Earth Gravity or Mars Gravity)

The reason I wonder about this is for how an airplane (sort of airplane) would take off and land in such a ship. Once matching rotation speed it effectively lifts off with 0G vertical take off and landing. Flying around would be odd as the 0 G would make the wings useless for lift but good for manoeuvring.

A 5 KM diameter ship would allow for approximately 16km/ 10 Mile circumference. with however long it is offering a large enough space to have "community" sections living in.

using an Ion Drive which is good that it is slow to keep life in the ship relatively stable without having too much of a thrust disruption upon the residence of the ship. Flying the ship "Sideways" would add the minuscule thrust as a mild gravity plus minus and side thrust without it being an end on effect.

I'm not sure what kind of wind a Ship like this would have nor the effect on water currents? Any Thoughts?

Why not do the numbers your self? The formulas were given above - for you information here they are again.

From basic physics: a = v^2/r. v = 2*pi*r*(rev) where rev is the rotation rate in rev/second.

So a = (2*pi*rev)^2*r. Assuming you want 1/2g as your gravity at the end of your tether, that's 4.9 m/sec^2. Substituting the numbers you get r*(rev)^2 = .12411. If you want 1 g, the later constant is .24822.

if you you want the formula for rev in terms of a given acceleration and radius (half the diameter) it is:
rev = sqrt(a/r)/(2*pi).

I don't know what you mean by "large quantities", but any possible usage of water by an NTR barely registers compared to the total amount of water on earth (332,500,000 cubic miles/1,386,000,000 cubic kilometers).

If you expect any large scale activity in space, then you are going to needs MANY ships making many trips every year, since almost none of the water goes back to earth, it´s a matter of time before there is trouble with the amounts taken out.

If you refuel such ships 5 times a year the outtake indeed will barely be noticed.
But once you refuel maybe 10000 times in a year, it will quickly begin to be noticeable.

You don't need clean freshwater to power an NTR. You need to filter and purify the water somewhat to get rid of contaminants that will degrade the NTR.

And do you really expect cheapskates holding the purse strings to say "sure go ahead and purify water from the ocean att 100 times the price of filtering tap water"?

And clean freshwater isn't really a problem if you do things right and are prepared to pay for it. The REAL problem is the lifestyle we have, that's why clean water is fast becoming a scarce resource.

Of course. Doesn´t negate the problem though.

Tenshinai wrote:If you expect any large scale activity in space, then you are going to needs MANY ships making many trips every year, since almost none of the water goes back to earth, it´s a matter of time before there is trouble with the amounts taken out.

If you refuel such ships 5 times a year the outtake indeed will barely be noticed.
But once you refuel maybe 10000 times in a year, it will quickly begin to be noticeable.

And why would you need to lift that much water out of a gravity well when you can mine it from other sources in space (Europa, asteroid belt etc) as soon you can establish the infrastructure for it?

Joat42 wrote:You don't need clean freshwater to power an NTR. You need to filter and purify the water somewhat to get rid of contaminants that will degrade the NTR.

Tenshinai wrote:And do you really expect cheapskates holding the purse strings to say "sure go ahead and purify water from the ocean at 100 times the price of filtering tap water"?

Why would it cost 100x than filtering tap water since NTR's doesn't need potable water? And your reasoning that some people are cheapskates isn't relevant at all in this discussion.

Joat42 wrote:And clean freshwater isn't really a problem if you do things right and are prepared to pay for it. The REAL problem is the lifestyle we have, that's why clean water is fast becoming a scarce resource.

Tenshinai wrote:Of course. Doesn't negate the problem though.

No, but the problem isn't relevant to NTR's at all.