VASIMR plasma rocket fires

[docm]

Reuters link....<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><b>Scientists in Costa Rica set plasma engine record</b><br /><br />SAN JOSE, Costa Rica (Reuters) - Scientists in Costa Rica have run a plasma rocket engine continuously for a record of more than four hours, the latest achievement in a mission to cut costs and travel time for spacecraft.<br /><br />The Ad Astra Rocket Company, led by Costa Rican-born former NASA astronaut Franklin Chang-Diaz, said on Wednesday it hopes to use its rocket engines to stabilize space stations in a few years, and then to power a trip to Mars within two decades.<br /><br />"The first objective is to move small spacecraft in low orbit by 2010," Ad Astra executive director Ronald Chang-Diaz, the astronaut's brother, told Reuters.<br /><br />In December, the scientists ran the engine for two minutes but had to turn it off because it was overheating. They have spent much of the past six months designing cooling systems.<br /><br />Scientists believe propulsion engines that run on plasma, a material composed of atoms stripped of electrons and found in high-pressure and -temperature environments like stars and lightning bolts, will be faster and cheaper than rockets currently used in space travel.<br /><br />Considered the fourth state of matter because it is neither a solid, liquid or gas, plasma can reach millions of degrees, making it a potentially light but powerful fuel.<br /><br />It is hoped that the engine, which uses Variable Specific-Impulse Magnetoplasma Rocket technology conceived in the 1970s, could eventually cut travel time to Mars by about a third, to around three months.<br /><br />Scientists at Ad Astra's Houston laboratory are conducting tests aimed at boosting the engine's overall power, while in Costa Rica they focus on endurance, Ronald Chang-Diaz said.<p><hr /></p></p></blockquote> <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Excellent news.<br /><br />This is a thrust source for future long term missions we will need. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[owenander]

Thanks for the update, I've always wondered, is it possible to scale up with this and put four on the same spacecraft in order to launch it from sea level into orbit?

 

[docm]

No. It's thrust is lower than a chemical rocket so no surface launches, but in theory its thrust (much higher than ion drives) can be maintained for months at a time...as long as you have fuel & electric power. This results in a high SI, specific impulse, and is perfect for interplanetary missions. <br /><br />Big need for manned missions: a compact nuclear reactor....maybe a pebble bed. Simple, gas cooled & pretty much runaway-proof. <br /><br />Basically if orbit insertion were the plan you'd accelerate half the way there then turn the ship around and decelerate the other half. In both cases a small G "force" would be generated, helping a bit with biological effects due to microgravity. <div class="Discussion_UserSignature"> </div>

 

[docm]

Superconductive. Not sure what they found as the cause. <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Like almost all propulsion systems involving wrestling gravity to orbit <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[Boris_Badenov]

<font color="yellow"> ... and then a boom sound. </font><br /><br /> In space there is no sound.<img src="/images/icons/shocked.gif" /> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[gunsandrockets]

VASIMR mostly hype?<br /><br />I've been doing a little research on electric rocket propulsion, so naturally I had to look into the VASIMR because of all the good things said about it, how it would be a breakthrough propulsion technology. I discovered that the VASIMR while interesting is not the great interplanetary hope that the hype makes it out to be.<br /><br />The only real difference between VASIMR and the other kinds of electric rockets is the ability to exchange thrust for ISP over a huge range of numbers. But even the ability to run at higher or lower ISP is not unique to the VASIMR, as NASA is experimenting with Hall effect plasma thrusters which also can run at variable rates.<br /><br />The problem with the VASIMR, or any other electric rocket, is the crappy thrust to weight ratio. A ratio which the VASIMR does not seem to have any advantage over any other electric rocket.<br /><br />Okay let me go into greater detail. There are all kinds of electric rockets most of which only operate at a single thrust and ISP rating. The USAF experimented with an electrothermal arc-jet with ammonia propellant with an ISP of 800 s. Deep Space One ran an ion engine with xenon propellant with an ISP of 3,000 s. SMART-1 ran a Hall effect plasma thruster with an ISP of 1,350 s.<br /><br />The electric rockets with lower ISP (generally) have higher thrust in an exactly equal ratio. An engine with double the thrust will have half the ISP. There is no free lunch, sadly. And as far as I have found the VASIMR doesn't improve on this fundamental electric rocket ratio. The VASIMR doesn't generate thrust any more efficiently than any of the other electric rockets, it just can vary it's ISP and thrust more than any other electric rocket. Even perform at an ISP up into the range of tens of thousands of seconds!<br /><br />The problem is thrust is so tiny at the upper end of ISP that trip time increases because of slow acceleration, which isn't what we want for a manned spacecraft. B

 

[qso1]

As I recall, VASIMR was reportedly promising three month travel times to mars. That number had to come from something fundamental like thrust, ISP, etc. How would such a thing be so badly missreported if not true or close to true? <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[gunsandrockets]

<As I recall, VASIMR was reportedly promising three month travel times to mars. That number had to come from something fundamental like thrust, ISP, etc. How would such a thing be so badly missreported if not true or close to true?><br /><br />It could be true if VASIMR was combined with an unobtainium power source. But then almost any electric rocket would have short travel times if provided enough power.<br /><br />Rough rule of thumb for electric rockets is 9 lbf of thrust for every megawatt of electric power when operating at an ISP of 3000 s.

 

[qso1]

I'll have to go back and review what data I have. I lost touch with the factual aspects of the VASIMR program some time ago. I utilized it as the basis for a propulsion system in my graphic novels because it sounded like the most revolutionary yet feasible propulsion concept to come along since NERVA. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[vishniac2]

Here is a great article on VASIMR:<br />http://www.adastrarocket.com/SciAm2000.pdf<br /><br />You seem right that it needs a spiral path to leave or enter orbit.