- #36
Drakkith
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Yes, the light in front of you is heavily blueshifted while behind you it is redshifted.
DHF said:Ok good to know.
so because its being blueshifted the frequency increses. how would I calculate how much of an increase in radiation my intrepid crew would be facing? would the blueshifting in radiation make the impact such that the acceleration would be pointless? it seems your speed would be limited not only by the energy needed for propulsion but you would need to devote just as much energy to some form of electromagnetic shield to divert the radiation.
DHF said:Ok good to know.
so because its being blueshifted the frequency increses. how would I calculate how much of an increase in radiation my intrepid crew would be facing? would the blueshifting in radiation make the impact such that the acceleration would be pointless? it seems your speed would be limited not only by the energy needed for propulsion but you would need to devote just as much energy to some form of electro-magnetic shield to divert the radiation.
Varun Bhardwaj said:to cross the barrier means traveling a distance in zero time. if you do it than your 1 dimension will loss (you are three dimensional) . And you will not stop anywhere.
DHF said:I like the aspect of the crew waking up to find that their civilization had passed them by.
DHF said:Yes OCR that had come to mind :) I actually quite like the idea of exploring what cizilization comes after our own but that won't be in the cards for this tale :)
I know giving them a 1G acceleration would be out of the question, the mass ration would be be almost 900:1 and that just won't fly. I was thinking about giving them an acceleration of 0.10%G or even 0.05% G.
DHF said:I got around the whole keeping the crew alive thing by ditching a living crew. The current crew will be androids with AIs based on human astronauts back on Earth. In this way the life support can be ditched and the mass of the ship can be further reduced because they won't have to worry about a return flight. Once the ship arrives, the crew will be stationed in the Alpha Centuri Star system permanently, intending to explore and run experiments while transmitting the results back home. The drama will arrive when certain members of the crew start to realize that their programming has changed during the flight, they come to the conclusion that they are self aware and tensions arise when members of the crew question the idea of being abandoned light years from home.
DHF said:would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?
DHF said:OK that works for me. so the only cap on speed is the amount of fuel you can carry. So if they wanted to go .12c its simply a matter of: can you carry enough fuel to accelerate to that speed and still have enough fuel to decelerate?
DHF said:would the ship be able to communicate with Earth while they are in transit or would communications be distorted from them moving away at relativistic speeds?
DHF said:Thanks for the help :)
Ryan_m_b said:then to get to .12c would require ~8*1037 kg of fuel (much more than the mass of the solar system). And that's just to reach the speed! Not even to slow down again..
DHF said:augh! damn you reality with all your numbers!
DHF said:the heck with it, I am just going to put them in a trash can and give them a good shove. they should get there in a few million years, they are androids, they won't care.
Very true... Too bad :( if it was real, hypothetically speaking, would time stop?Ryan_m_b said:It's impossible for objects with mass to attain the speed of light. You're question is therefore unanswerable because it essentially asks "if we ignore the laws of physics what do the laws of physical say?"
Travis_King said:This is why many SF writers who want to lean toward the hard side of SF tend to:
d) Use space-time warping as their mode of travel rather than actual ship velocity. I've seen several instances of this type where you don't even have to explain how; the main characters don't know how it works, they just know that someone in their world knows and created the drive.
then-DHF said:I got around the whole keeping the crew alive thing by ditching a living crew. The current crew will be androids with AIs based on human astronauts back on Earth. In this way the life support can be ditched and the mass of the ship can be further reduced because they won't have to worry about a return flight. Once the ship arrives, the crew will be stationed in the Alpha Centuri Star system permanently, intending to explore and run experiments while transmitting the results back home. The drama will arrive when certain members of the crew start to realize that their programming has changed during the flight, they come to the conclusion that they are self aware and tensions arise when members of the crew question the idea of being abandoned light years from home.
http://en.wikipedia.org/wiki/Project_LongshotUnlike Daedalus' (see the next quote) closed-cycle fusion engine, Longshot would use a long-lived nuclear fission reactor for power. Initially generating 300 kilowatts, the reactor would power a number of lasers in the engine that would be used to ignite inertial confinement fusion similar to that in Daedalus. The main design difference is that Daedalus would rely on the fusion reaction being able to power the ship as well, whereas in Longshot the internal reactor would provide this power.
The reactor would also be used to power a laser for communications back to Earth, with a maximum power of 250 kilowatts. For most of the journey this would be used at a much lower power for sending data about the interstellar medium, but during the flyby the main engine section would be discarded and the entire power capacity dedicated to communications at about 1 kilobit per second.
Longshot would have a mass of 396 metric tons (873,000 lb) at the start of the mission, including 264 tonnes of Helium-3/Deuterium pellet fuel/propellant. The active mission payload, which includes the fission reactor but not the discarded main propulsion section, would have a mass of around 30 tonnes.
A difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star while the higher speed Daedalus would do a one shot fly-by lasting a comparatively short time.
The journey to Alpha Centauri B orbit would take about 100 years, at an average velocity of approximately 13411 km/s, about 4.5% the speed of light, and another 4.39 years would be necessary for the data to reach Earth
http://en.wikipedia.org/wiki/Project_DaedalusAlan Bond led a team of scientists and engineers who proposed using a fusion rocket to reach Barnard's Star, only 5.9 light years away. The trip was estimated to take 50 years, but the design was required to be flexible enough that it could be sent to any of a number of other target stars.
[..]
Daedalus would be propelled by a fusion rocket using pellets of deuterium/helium-3 mix that would be ignited in the reaction chamber by inertial confinement using electron beams. The electron beam system would be powered by a set of induction coils tapping energy from the plasma exhaust stream. 250 pellets would be detonated per second, and the resulting plasma would be directed by a magnetic nozzle. The computed burn-up fraction for the fusion fuels was 0.175 and 0.133 for the First & Second stages, producing exhaust velocities of 10,600 km/s and 9,210 km/s, respectively. Due to the scarcity of helium-3 it was to be mined from the atmosphere of Jupiter via large hot-air balloon supported robotic factories over a 20 year period.
The second stage would have two 5-meter optical telescopes and two 20-meter radio telescopes. About 25 years after launch these telescopes would begin examining the area around Barnard's Star to learn more about any accompanying planets. This information would be sent back to Earth, using the 40-meter diameter second stage engine bell as a communications dish, and targets of interest would be selected. Since the spacecraft would not decelerate upon reaching Barnard's Star, Daedalus would carry 18 autonomous sub-probes that would be launched between 7.2 and 1.8 years before the main craft entered the target system. These sub-probes would be propelled by nuclear-powered ion drives and carry cameras, spectrometers, and other sensory equipment. They would fly past their targets, still traveling at 12% of the speed of light, and transmit their findings back to the Daedalus second stage mothership for relay back to Earth.
The ship's payload bay containing its sub-probes, telescopes, and other equipment would be protected from the interstellar medium during transit by a beryllium disk up to 7 mm thick and weighing up to 50 tonnes. This erosion shield would be made from beryllium due to its lightness and high latent heat of vaporisation. Larger obstacles that might be encountered while passing through the target system would be dispersed by an artificially generated cloud of particles, ejected by support vehicles called dust bugs, some 200 km ahead of the vehicle. The spacecraft would carry a number of robot "wardens" capable of autonomously repairing damage or malfunctions.
Overall length: 190 metres
Propellant mass first stage: 46,000 tonnes
Propellant mass second stage: 4,000 tonnes
First stage empty mass at staging: 1,690 tonnes
Second stage mass at cruise speed: 980 tonnes
Engine burn time first stage: 2.05 years
Engine burn time second stage: 1.76 years
Thrust first stage: 7,540,000 Newtons
Thrust second stage: 663,000 Newtons
Engine exhaust velocity: 10,600,000 m/s & 9,210,000 m/s
Payload mass: 450 tonnes
DHF said:Everything I have read advocates putting the engine in front of the ship and pulling the bulk of the ship rather then pushing it in order to reduce the amount of mass the engines have to move.
DHF said:My first Idea was to build the engines and fuel tanks as a self contained unit, The Cargo and crew quarters will be a separate ship that is pushed in front of the Engines by electro magnets. Does this design have any feasibility? will pushing the bulk by magnets relieve any of the burden of mass on the engines or will the mass be the same even though there is no physical connection between the engines and the cargo and crew vessel?
DHF said:The other idea was to build it Tie Fighter style, with the Bulk of the ship being built flush with the Engines so that there is nothing being pushed in front of the engines or being pulled behind them. would this be more fuel efficient then pushing the bulk of the ship in front of the engines?