Alpha Centauri Explorer

[vidar]

I would like to see pictures of Alpha Centauri. A spaceship can, in theory, be sent there very soon. Close pictures from the star system will give humanity a new perspective of itself and the surroundings. It is merely a question of time before it is done. <br />An Alpha Centauri Explorer (ACE), that can weight some hundred kilos, can be lifted to Earth's orbit by a space shuttle. From there, it can start its long journey towards the star system Alpha Centauri. A stable laser beam should point at the star, as a leading thread on the way. The beam can also carry data. <br /><br />If ACE is accelerated with 10 G, it will reach the speed of light in a month. The whole journey will last 5 years according to classic physic (v=at). If Einstein's use of the Lorentz transformation is correct, and the theoretical speed limit is real, the ship can be accelerated to f.ex. 1/2 c, and the journey will last twice as long. Anyhow the speed, ACE will be a of the RT too. <br /><br />ACE can not be controlled from Earth. Its speed and distance requires pre-programmed navigation, procedures and responses to unforeseen challenges. A good share of luck will also help, for success for the first ship. <br /><br />ACE should primarily bring a relay station for laser transmission and steering for future ships, - but important as well, a satellite for scanning the star system. The transmission of pictures will take 4 years. That is a long time to wait. But then there can be a constant flow of pictures as long as the satellite lives. <br /><br />The following ships can very well be sent yearly. With the path and the target mapped, the journeys will be safer and easier. Unforeseen events with preceding satellites can be compensated and improved. In 10-20 years, the star system will be mapped like our own. <br /><br />The propulsion, that shall accelerate a month and reduce the speed just as long, should be nuclear. Such a solution is criticised. However, that seems political and irrational because space

 

[henryhallam]

<font color="yellow"><br />If ACE is accelerated with 10 G<br /></font><br />How do you propose to achieve this for a whole month???<br />Nuclear rockets aren't -that- good.

 

[tap_sa]

Bussard ramjet of course! Just floor it and watch that speedometer inching towards tau zero. Driving while universum collapse/rebirth voids warranty.

 

[vidar]

You are right, present nuclear space engines do not seem to be good enough for ACE.<br /><br />I am quite disappointed, when looking into it, that most research for nuclear propulsion was stopped by Nixon in the 60-70. (Thanks for not interfere with the Apollo program, though.) Consequently, space exploration was set back a generation.<br /><br />I am quite certain it is possible to make engines strong enough for such proposed flights. Without the research termination, we would possibly have such engines by now. However, there are two other possibilities. 1. The development was not terminated, but continued under another administration and in secret from other nations. 2. Other space agencies like the Russian, European, Chinese, Indian, Japanese, in addition to commercial actors like Virgin, might provide a solution faster than NASA.<br /><br />Anyway, comparing existing nuclear engines to ACE needs, there should be enough energy, shouldn’t it?<br />

 

[thinice]

<i>If ACE is accelerated with 10 G, it will reach the speed of light in a month.</i><br /><br />...and turn into the light flash itself.

 

[nacnud]

<font color="yellow">Bussard ramjet of course!<br /><br /><font color="white">Bussard ramjets creat more drag than thrust <img src="/images/icons/frown.gif" /></font></font>

 

[tap_sa]

Do you have other proof than Zubrin/Andrews analysis in 1985? They made some assumptions that can be considered faulty or not applicaple to different kinds of Bussard ramjet designs.

 

[nacnud]

IIRC the density of the interstella medium was too low to overcome the magnetic drag of the scoop, I don't have the reference from where I heard this though...

 

[vidar]

Accelerating any ship 10G for a month or two would be the ultimate test of the speed limit stated in the Relative Theory. This would be the ultimate test of the theory.<br /><br />However, on second thought, such a test should not be done by ACE. The project might be halted by scientific superstition. Let’s go for c/2 and avoid such hindrances.<br />

 

[nacnud]

Physicists accelerate things to near the speed of light every day, in fact its odds on that you're staring at a particle accelerator right now!

 

[tap_sa]

Quick googling confirms what you, so magnetic scoop is probably out of the question. But it's not the only possible design, just an proposal for saving mass. Maybe electrostatic scoop or just plain huge physical unobtainium-cone <img src="/images/icons/smile.gif" />

 

[nacnud]

Umm an unobtainium cone, tasty, can I have a flake in mine <img src="/images/icons/laugh.gif" /><br /><br /><br /><br />

 

[vidar]

Could that Bussard ramjet ship take a few rounds around the sun to collect fuel and gain speed before being cast towards the next sun. <br />(The idea is from the novel Rama, I think.)

 

[henryhallam]

Even though I am not qualified to do so I will try to work out some numbers.<br /><br />To avoid issues with relativity equations let's work out what it would take to get to 0.5c using a nuclear rocket of some kind.<br /><br />I will be generous and allow launch by a SDHLV rather than just the STS. So we start off with an initial mass of about 100 tonnes. The payload can be 100kgs as you say but we must also carry a nuclear reactor and/or engine. Being very generous we will let the total "dry mass" be a mere 1 tonne.<br /><br />dV = (exhaust velocity) * ln(initial mass / final mass)<br />0.5c = Ve * ln(100)<br />so Ve = about 32500 km/s.<br /><br />Using hydrogen as the reaction mass, we can assume that it will be split into individual protons due to the extreme temperatures involved. In order to give a proton this velocity it will have a kinetic energy of 0.5 * Mp * Ve^2 = 9e-13 joules or about 5 MeV.<br /><br />Using a nuclear thermal rocket the temperature would have to be pretty high. We can calculate it using the equation Ek=3/2 k T, giving a temperature of about 4e10 Kelvin. That is 40 <b>trillion</b> degrees celsius! Building a thermal engine that can withstand that temperature is not feasible.<br /><br />The only way to realistically produce these velocities would be with a particle accelerator. An accelerator capable of producing 5MeV protons is fairly routine on Earth but would weigh rather a lot more than the 1 tonne we allocated to reactor and engine. Furthermore it would produce very little thrust. I think I recall that most accelerators produce beam currents on the order of a few milliamps. Let's be generous again and say that we can do a whole amp. This corresponds to 6e8 protons per second. Multiplying by the momentum of the proton gives a thrust of a magnificent 0.4 Newtons.<br /><br />Again completely throwing out any sort of realism let's imagine we have a magical accelerator that can pump out the protons at literally several million times the rate o

 

[ehs40]

alpha centauri explorer it will happen just not really soon

 

[vidar]

Henryhallam<br /><br />I agree with ehs40 saying, ACE will happen just not really soon.<br />What is your best solutions then?<br />

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>What is your best solutions then? <p><hr /></p></p></blockquote><br /><br />Go to the moon, en masse, build up a working space based industry and economy in cislunar space. Through radically increased launch volumes and rates achieve the dream of CATS, explore the possibilities of tapping further into solar system, first NEO's and asteroids, then inner solar system planets. <br />By the time when lots of people work and live on surface of Europa and Mercury for example, someone will come up with a workable plan to visit the nearby stars.<br /><br />Sound like a good solution to you ?

 

[astrophoto]

We'll have sent probes to other stars long before we live on Europa and Mercury, I can guarantee you that.

 

[spacefire]

assuming we send the probe just zipping through the system-and maybe go somewhere else if its onboard computer can figure out how to do a gravity assist from the three suns and point it somewhere else, we could have a probe that would yield a lot of valuable information over the next few hundred years, until we figure out a way to go FTL.<br />Something like the Orion should be used for propulsion, but since this would be an unmanned probe maybe we can increase the acceleration to 100Gs dumping some big bombs in the wake.<br />Speed of light=3*10^8m/s;1/10th of that is 3^10^7m/s<br />100Gs=1000m/s^2<br />to achieve 1/10th c at 100Gs acceleration would take 30000seconds =8.33 hours of acceleration.<br />This way the probe would get to Alpha Centauri in 43 years. <br />Let's freaking do it!<br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[astrophoto]

We have the technology to shoot something there, why wait for better technology? We'll always be caught in that loop that 'tomorrow will be better' and we'll never get going!

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>We'll have sent probes to other stars long before we live on Europa and Mercury<p><hr /></p></p></blockquote><br />I dont see what for. Living and working on other accessible planets can actually improve our lives everywhere, simply by providing access to new resources and even just new living room.<br />What tangible benefit do you get from a stellar probe that shows you places you cannot visit for several lifetimes at least ?<br />Its sort of rhetorical question though, i assume i know the "answers" already.

 

[astrophoto]

You missed the point. The technology to send a probe to another star system is already available. The technology to live on Mercury or Europa is beyond my comprehension at this point, and is certainly far in the future.

 

[tap_sa]

<font color="yellow">"Could that Bussard ramjet ship take a few rounds around the sun to collect fuel and gain speed before being cast towards the next sun."</font><br /><br />Do you mean that the ship would accelerate to it's max speed, for example 0.1c, around the sun and then slingshot away once it's reached? No can do, solar system's espace velocity is much lower, the ship would have to keep thrusting towards the sun in order to stay orbiting it. One swoop through the solar system is doable.

 

[le3119]

Generally, a vehicle approaching 300,000 km per second (lightspeed) would ram into interstellar particles and dust granules. At that velocity, those particles are likely to turn the ACE into swiss cheese, unless ACE projects a deflector shield. But a velocity at 10% lightspeed would pose similiar hazards. And besides, how would you propose achieving 10G for that length of time while keeping the ship structure and instruments intact? We don't have the materials, or the variety of propulsion, to do this yet. We lack the alloy strong enough to allow an aircraft to achieve Mach 10 or higher, in Earth's atmosphere. How much more hazardous is the interstellar medium, we can only imagine. <br /><br />Until we achieve a breakthrough in physics (some exotic "warp" drive) I don't see how we can visit other star systems. We will be able to map them from here, with advanced interferometer telescopes, but going there, IMO, is more of a fantasy for the forseeable future. Accelerating a few particles in an atom smasher is one thing, sending a vehicle through space at such velocities is a whole other affair.

 

[spacefire]

I think we can do it with the Orion! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>