I need a quick answer to a stupid theoretical question.
Imagine a Spaceship travelling in outer space, i.e. almost perfect vacuum. Could the propulsion system theoretically be placed far off center of mass and still move the ship in the right direction without eventually causing the ship to enter a spin?
My theory is that since there is no air resistance, it should be possible. Or am I missing something?
angular momentum
You could, but it would be inefficient.
This.
Give it a go in KSP and let us know how it works out for you.
It'll spin.
You could use reaction wheels to counter the spin, or thrust in pulses as you rotate. Overly complex and inefficient though.
Ok, so I did miss something. Ty, at least you saved me from having to reinstall KSP again
Yeah, but the Atlus isn't designed to go straight with those boosters. They want the angular momentum to assist getting into orbit.
The drive can be far from the center-of-mass.
Rockets have their engines at the very tail.
But the line of thrust has to point THROUGH the center of mass or the ship will simply twirl like a pinwheel instead of going places.
Real rockets can gimbal the motors a few degrees to ensure the thrust stays through the mass-center. Early rockets like the V2 pushed deflector vanes (rudders) into the exhaust stream rather than trying to swivel the single motor. This works, but the wear and tear on the vanes is terrific. They'd say, "If you see glowing fireballs coming out the exhaust, she's lost her vanes -- so RUN!"
>Spaceship with propulsion system at the center
It'll work just as well as this one did
What type of a moran uses the same thrust?
Reaction wheels won't work. Reaction wheels just take the spin out of the ship and store it in the rotor. Off-center thrust continually adds angular momentum. Eventually you reach the limit of the wheels and they disintegrate. You could do it for a BRIEF period, while the motors were on. But then you'd either have to throw the rotors away or brake them and put the spin back on the ship.
Sure, if they can gimbal enough. It would be really dumb though, because you would be taking cosine losses for no reason other than aesthetics.
If we're talking propulsion then check this shit out!
If the center of trust doesn't go through the center of mass, the trust will create a spin.
Being not so retarded you just pull yourself against some mass that is resting compared to you in outer space all the time.
No cosine loss. So long as the thrust passes through the mass-center, the drive can be anywhere and it doesn't hurt the efficiency.
Let me correct that. If you have several motors pointing in different directions but the net thrust is through the mass-center, you don't spin but you DO lose efficiency. The escape towers atop space capsules work that way -- a necessary loss if you don't want to cook your astronauts in the blast.
>Could the propulsion system theoretically be placed far off center of mass
why?
Not exactly. Unless you place the engine directly in the barycenter of the ship, it will ALWAYS be off center. I think what you're meaning to ask is, if the thrust were not vectored directly away from the center of mass, would the ship fly without spin? and the answer is no - a torque would result: a component of thrust tangential to the center of mass.
>step 1: stop spin using reaction wheels
>step 2: stop the wheels
>step 2: stop the wheels
Then you would just start spinning again.
How about monopropellant then?
Or, if multiple engines on the ship, varying the throttle on some of them to change the center of thrust?
fucking why. Then you're wasting monopropellant. Just put the center of thrust at the center of mass. Why would you do anything else?
The bigger question should be why an asymmetrical design is needed in the first place?
Asymmetrical designs are normal and reasonable. What's stupid is pointing the engine(s) out of line with the centre of mass.
Why is a asymmetrical design normal and reasonable?
Most on-screen spacecraft (Serenity, Stars Wars, Star Trek, Galactica) are WW2 capital ships or aircraft with jets tacked on. Decks are oriented such that internal gravity is "down" while the direction of flight is "forward".
The FEW exceptions include some of the Earth Alliance warships of Babylon 5 and the Camden Lock (pictured) from a British comedy series.
You may not like it, but this is what peak spacecraft performance looks like.
It depends where the centre of mass of the rocket is. If it's directly in front of your engine, the component of your thrust that would create a moment would be 0 so it wouldn't turn. If the centre of mass is off-centre, there will be a moment and the ship will begin to spin.
>[distant eurobeat].jpg
kek
And this.
Expanse?
I started reading the books and a ship receives a distress call. They are the closest ship and, by law, they have to go to the rescue. Which is a stupid law. They might be nearby but doing 800 KPS relative in the wrong direction. A ship further away, but which was already on more favorable vector could get there first.
I concluded the authors either didn't understand ballistics or didn't give a s*** so I stopped reading.
"More realistic than most sci-fi shows" is damning with faint praise.
Now, THIS is more like what a fusion-engine spacecraft should look like!
The authors of the expanse admit they’re not scientists, but they consult with a lot of experts on stuff and try to make their narrative at least plausible. They’re like the GRRM of sci-fi, in the sense that GRRM one time read that EyeWitness children’s picture book about Castles and then he wrote ASOIAF. Also one of the Expanse authors is literally GRRM’s assistant
All ships have magic unlimited Delta-V drives
That alone should cause you to put down the book
We have no example of working energy positive fusion yet, so talking about what that drive would look like is nonsense
Obviously you wouldn't use a "nozzle" for any super high Isp engine, it would be electro magnets controlling the stream.
The illustration in is modeled after Project Daedalus, a serious study of an interstellar probe with an "Orion" style drive.
Except that the "bombs" aren't kiloton nuclear weapons but pellets of tritium-helium 3 ignited by converging electron beams (those circles around the engine bell.) Project of the British Interplanetary Society. Inertial confinement fusion has turned out to be more difficult than anyone imagined a few decades ago.
Deuterium-tritium fusion gives a (theoretical)exhaust velocity of 8.65% of lightspeed. "Theoretical" means no losses, not even to neutrinos.
A voyage of 10 AU, turning over at mid-point, at a constant 1 gee requires starting out with 34% of your final (empty tanks) mass in fuel.
Maybe ships in The Expanse always travel at low-accelerations to save fuel. I don't know. Do they ever attack each other by playing their exhausts over the enemy? Hard to think of a more effective weapon. ("The Kzinti Lesson")
is this just the BT tower with rockets on the end?
Yep! BBC In-joke.
en.wikipedia.org
Episodes on YouTube.
youtube.com