A brake for a space ship?

[wayne_m]

Praise without end for the go-ahead zeal
Of whoever it was who invented the wheel!
But never a word for the poor soul's sake
Who thought ahead, and invented the brake.

I've seen a lot of ink spilled (electrons manipulated?) about massless propulsion, and I realize that it could potentially be used to accelerate a ship "in reverse" to act as a brake, but how would its energy consumption stack up against the following idea, assuming the idea could even work?

Given: Some form of drive has been developed that can get a ship up to a significant fraction of c
Given: A power source sufficient for the job and materials that could withstand the rigors of use
Given: Relativity tells us that an object increases in mass geometrically as it approaches c

Hypothesis:
Accelerating matter (solid, liquid, gas, plasma, whatever,) forward in the ship will cause the mass to increase, and provide reaction mass which we can use to slow the ship.
Now, after the matter has reached its peak mass, and we have used it to slow the ship, we vector it back around so that it is now moving toward the rear of the ship. Now we circle it back around and prepare to recycle it.
Situation:
The ship is moving at a leisurely .5c, and we start accelerating the matter to about .49c before it reaches the end of its tube.
We have accelerated it to .99c or thereabouts (objective reference) and it is becoming very massive, and providing a good "space anchor." Or parachute. Pick your metaphor.

The fuzzy bit - The part I haven't had enough time to ponder and figure out:
As it is vectored (vector as in thrust, not as in math,) around 90 or 180 degrees, it will start losing mass, since it is slowing in the objective frame of reference, until it is traveling toward the rear of the ship - slower than the ship, in the objective frame, so it has (slightly) less mass than when it started.
We can assume that the matter is flowing down a tube and then migrating radially (inward or outward, doesn't much matter,) to the return tube, and thus the lateral thrust is evenly balanced. We could even begin slowing it in the lateral section, so that any "thrust" from slowing the matter cancels out and is turned into tension on the materials of the braking device.

The question, then, is how much of the energy contained in the mass will be returned to forward motion of the ship as its path is bent through the 90 or 180 degrees of the brake.
Where would the energy stored in our highly massive matter go as we slow it back to near-rest (objectively?) Could it be captured and used to continue accelerating our reaction matter?

Sadly, this brake could most likely not be reversed to produce positive "massless" thrust.

anybody have any thoughts on this idea?

The reason I wonder how it would compare in efficiency is the old conundrum of space travel: Okay, how do we stop, now that we're here? Sure, we could turn the engine around, but what if there were a more efficient way? We don't throw our cars in reverse to stop, once we reach grandma's house. We discard the energy through the brakes. It's more efficient that way.

Edited September 23, 2016 by wayne_m

[mathematic]

 

 

Given: Relativity tells us that an object increases in mass geometrically as it approaches c

This increase is only in the frame of an outside observer. In the frame of the object itself, there is no mass increase.

[geordief]

This increase is only in the frame of an outside observer. In the frame of the object itself, there is no mass increase.

Does that increase in mass depend on relative velocity (between 2 frames I suppose) or does acceleration have any bearing on the question? Thanks.

[swansont]

This increase is only in the frame of an outside observer. In the frame of the object itself, there is no mass increase.

 

 

The mass used in the standard equations is the rest mass, so not even then. You have to redefine mass to be the relativistic mass.

 

I've seen a lot of ink spilled (electrons manipulated?) about massless propulsion, and I realize that it could potentially be used to accelerate a ship "in reverse" to act as a brake, but how would its energy consumption stack up against the following idea, assuming the idea could even work?

 

If you mean photons, then yes, it would work in reverse. It would be incredibly weak and inefficient. If you mean reactionless propulsion, then you need to establish that it works before it can work in reverse.

[wayne_m]

If you mean reactionless propulsion, then you need to establish that it works before it can work in reverse.

 

That's why I posted here: To see if anyone who has studied this sort of thing in greater depth than I have would know whether it could even be possible, and then if it is, whether it would be efficient enough, energy-wise, to be worth considering.

It wouldn't be "reactionless," because we are pushing on the mass within our system for reaction. We are just using the change of mass in a lump of matter as we speed it up to relativistic speeds and then slow it back down again. The questions are whether we can direct the energy of the system where we want it to go, and whether the energy difference between frames (our moving ship and the universe at rest) would make it work to bring those frames closer together.

 

This increase is only in the frame of an outside observer. In the frame of the object itself, there is no mass increase.

 

Well, we are slowing a ship to rest with respect to the outside frame - the frame of the star system where we've just arrived at a very high rate of speed.

And now that we're here, we need to stop, unless we're just taking pictures as we pass through on our way to the next system.

The ship and the universe are the outside observers of our mass that we're using as a brake. From either frame, the mass is moving near c, so its mass has increased from our perspective, and we need to "push on it" ever harder to accelerate it, due to its increased mass from our perspective.

 

So my understanding of relativity is that we now need to accelerate some matter to near c (from the frame of the ship - but it will actually get closer to c in both frames) and it will gain mass. The closer we get it to c, the more massive it is, and thus, accelerating it with more force will make the brake more effective, since we're pushing it against the motion of the ship. That opens the question, now, whether the energy required will still be the same as accelerating it near c from absolute rest (i suspect it would) or slightly less, since it is already moving objectively at .5c

Either way, any energy used will be directed to slowing the ship.

 

Since we have no way to cancel inertia, and we don't want to splatter our crew against the bulkheads, we would have to slow the ship gradually, so the mass in the system would be cycled through the system many times. (unless the ship is really long ) This means that there would necessarily need to be some way to slow the mass without re-accelerating the ship. Thus the question about how much of the energy would be transferred back to forward motion as we vector (again, in terms of thrust, not math,) the mass away from the axis of the ship. If the mass is still moving at or very near the speed it was moving before we started vectoring it, would it carry that energy "sideways" and not "redeposit" it axially?

And upon this consideration, I have to wonder: if this sort of setup didn't transfer all of the energy back to forward motion, would it be useful for propulsion, if used in reverse? For some reason, I think that I've considered this before, and proved (to myself, at least,) that it wasn't possible.

My impression is that the system would have no acceleration from the frame of the ship, and therefore, as the ship's frame approaches the frame of the rest of the universe, it would have less effect until the frames matched (not really possible, in this scenario, but for the sake of argument...) at which time, it would not have any effect at all.

My understanding is also that mass increase is not terribly great until you get pretty close to c. So at .5c, your ship (and your reaction mass) would only mass about 15% more than it did when it was stopped. But once you get up to .99c, it masses about 7 times as much, and at .9999c, ~5000 times as much.

At the moment, I'm not worried about the machinery that would accelerate the mass to these speeds. A genie came out of his bottle and gave it to us. It works. (See: "Given" section in OP.) But "it works" is not the same thing as "the machine does what we want it to do."

As a final note, I know that I made a few mistakes in the original post. It was way past my bedtime, and I'm working from a vague memory of something I thought about years ago but finally decided to ask. Feel free to point out any errors, but try not to be too hard on me

Edited September 24, 2016 by wayne_m

[swansont]

 

That's why I posted here: To see if anyone who has studied this sort of thing in greater depth than I have would know whether it could even be possible, and then if it is, whether it would be efficient enough, energy-wise, to be worth considering.

It wouldn't be "reactionless," because we are pushing on the mass within our system for reaction. We are just using the change of mass in a lump of matter as we speed it up to relativistic speeds and then slow it back down again. The questions are whether we can direct the energy of the system where we want it to go, and whether the energy difference between frames (our moving ship and the universe at rest) would make it work to bring those frames closer together.

 

 

There's nothing ejected from the system. That's a reactionless drive. Momentum is not conserved.

 

It won't work. It doesn't matter what goes on inside the spaceship.

[wayne_m]

Out of curiosity, where did you get the tagline?
It's a bit confusing; the cases don't seem to match. Minimus is nominative singular, but cantorum is genetive plural. Balorum isn't even really a word. "Carborata" might be a play on carborundum, so sand? It's not Latin. "Panto" means "everything." I'm guessing, by context, that whoever wrote it meant "trousers." Unless it means that a little carborata makes everything fall down.

Maybe it should be:

"Candantus minimus, Ballandus minimus, Bracca mea arenam minimam labendo" (A little singing, a little dancing, a little sand [going] down my trousers)

Edited September 25, 2016 by wayne_m

[swansont]

Out of curiosity, where did you get the tagline?

 

 

The internet. It's never wrong (the internet told me so)

[imatfaal]

Out of curiosity, where did you get the tagline?

It's a bit confusing; the cases don't seem to match. Minimus is nominative singular, but cantorum is genetive plural. Balorum isn't even really a word. "Carborata" might be a play on carborundum, so sand? It's not Latin. "Panto" means "everything." I'm guessing, by context, that whoever wrote it meant "trousers." Unless it means that a little carborata makes everything fall down.

Maybe it should be:

"Candantus minimus, Ballandus minimus, Bracca mea arenam minimam labendo" (A little singing, a little dancing, a little sand [going] down my trousers)

.

It is dog latin - beloved of schoolboys everywhere (really?) - looks like latin sounds like Latin but isn't

 

A little singing, a little dancing, and a little fizz down the trousers

[swansont]

.

It is dog latin - beloved of schoolboys everywhere (really?) - looks like latin sounds like Latin but isn't

 

A little singing, a little dancing, and a little fizz down the trousers

 

 

The alleged translation is (or it is allegedly a translation of) "A little song, a little dance, a little seltzer down your pants". So, pretty close.

 

It's an example of the adage Quidquidne latine dictum sit, altum viditur. (Whatever is said in Latin sounds profound.)

 

Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.

“I have a catapult. Give me all the money, or I will fling an enormous rock at your head.”

[wayne_m]

Ow, ow, ow...

I'm not even good at Latin, but it still hurts.

Dictare - to speak, videre - to see

"Altum sonueram," maybe?

Or "...scriptus sit...?"

 

[edit again]

 

Okay, now that I've had time to google around a bit...

...How have I never seen these lists of useful Latin phrases?

Edited September 26, 2016 by wayne_m

[wayne_m]

"A little song, a little dance, a little seltzer down your pants"

 

It took a while, but my memory was finally jogged!

 

Chuckles the clown.

 

One of the funniest episodes from the Mary Tyler Moore show was when he died.

 

How did I not remember this?