Register to reply

Protons to accelerate a space probe

by josephcollins
Tags: accelerate, probe, protons, space
Share this thread:
josephcollins
#1
Oct13-04, 01:51 PM
P: 60
Okay ppl, I have a question, I'd just like you to check that my working here is correct.

Q: A space probe of mass m=490kg is driven by an ion propulsion motor that involves the use of positive ions, each of mass m=2.18*10^-25 kg and having a charge of magnitude e=1.6*10^-19 C. These ions, having a negligible initial velocity, are accelerated by a potential difference of magnitude 1.2*10^3 V that exists between two electrodes which are a distance of 5cm apart. The ejection of these accelerated ions from the space probe generates a forward thrust that drives the probe.


I got the velocity with which the ions leave the probe, using the argument that kinetic energy and velocity are equal. So mv^2=QV and v turns out to be 419169.8 m/s

Then I had to calculate the Force exerted on the ions when the number of ions between the electrodes is 2*10^13. This I did by saying that F=EQ, and since E=V/separation, F=VQ/separation. I got an answer of 0.0768N.

Lastly I had to calculate the time taken to accelerate the probe from 0 to 100km/h. I did this by first getting the acceleration of the probe. It is equal to F/m where F=0.0768N and m=490kg. so a=1.567*10^-4 m/s^2. Then I used (v-u)/a gives the time and set v= 100000/3600 and used the accn just calculated to get a time of 49.23 hrs. Could someone just verify that I did this correctly in terms of the logic involved?

Thanks, Joe
Phys.Org News Partner Science news on Phys.org
Bees able to spot which flowers offer best rewards before landing
Classic Lewis Carroll character inspires new ecological model
When cooperation counts: Researchers find sperm benefit from grouping together in mice
Soveraign
#2
Oct13-04, 05:02 PM
P: 54
I get the same final answers you do, 49.23 hours to get to 100km/h but [itex] \frac 1 2 m v^2 = QV [/itex] gives 4.197 x 10^4 m/s.


[tex] v = \sqrt{\frac{(1.6 \star 10^{-19})(1.2 \star 10^3)}{(.5)(2.18 \star 10^{-25})}} [/tex]


Register to reply

Related Discussions
Measuring pH probe potential and interfacing probe with uC Electrical Engineering 1
What makes car to accelerate? Introductory Physics Homework 4
Can photons accelerate? Special & General Relativity 3
Space probe b Special & General Relativity 2
Space probe, planet, and sun.... Introductory Physics Homework 9