# Spacecraft and pulsar

## Homework Statement

In the year 2212, humans send an unmanned spacecraft towards a faraway pulsar.
The pulsar sends the signals in a plane (say plane A) which passes through the Earth.
The spacecraft is designed in such a way that it has a continuous and a constant
magnitude of acceleration of 10 SI units on its way to the pulsar (as seen from an
inertial frame). What is the best way for the spacecraft to proceed on its journey,
through the plane A or above (or below) the plane A? Give reasons.
Note: Assume that there are no hindrances in its path and that it does not need to
stop for fuel or anything else on its journey.

## The Attempt at a Solution

what does it mean by a plane passes through th Earth?? got stucked up here :(

## Answers and Replies

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As far as I understand the question, A plane passing through the Earth would be like visualising a flat sheet expanding off in all directions.

So for something for you to visualise, Imagine the Earths Equator strached out to infinity. This would create a plane through the Earth.

gneill
Mentor
Without knowing the purpose and design of the spacecraft, how can one possibly answer?

We are given no hint as to the materials or technology comprising the craft, so we cannot know if the pulsar emissions will adversely affect the on-board systems as it approaches the pulsar (for all we know they could have nanofluid hydraulic computers in 2212!). Perhaps the purpose of the craft is to directly sample the pulsar emissions all along the path. Perhaps there's a time constraint on the mission, so a direct path is mandatory. We just don't know.

It's a badly written question.

It is indeed. Though simply what it appears to be asking is whether the em radiation from the pulsar would affect the travelling on the spacecraft. Which It wouldnt. Though when you get close I imagine some particles would be in the plane of A and thus may impeede the process of flying somewhat.

It's a badly written question.
Even I feel the same but I have to answer it and cant one decide the direction, ignoring the spacecraft design properties etc?

How about ignoring the design and other aspects and going in a simple plain way !!

I think......from this, what they meant by the best way may be such that pulsar and spacecraft meet in a short while, instead of the craft reachng the pulsar or the signal reaching the aliens .

Am I right or going wrong somewhere?

gneill
Mentor
I think you'll have to answer it in the context of the course material that it is associated with. For example, if it's a question in a book section entitled "Space Radiation Hazards", then you know which way to go with it...

Though when you get close I imagine some particles would be in the plane of A and thus may impeede the process of flying somewhat.
Um....is it about affecting the craft? Do you mean that the signals would be harmful to the craft ? Or is it the aliens would be trying to receive signals from the pulsar?

Um....sorry if am asking silly questions but try to answer them as I am really a Beginner

supratim1
Gold Member
The spacecraft should travel above (or below) and parallel to the plane containing the pulsar and earth. This question seems to assume a very small radiation pressure on the spacecraft due to the EM waves of the pulsar, which would hinder the motion of spacecraft, though by a minuscule amount.

This question is just to apply the concept of radiation pressure.

I think you'll have to answer it in the context of the course material that it is associated with. For example, if it's a question in a book section entitled "Space Radiation Hazards", then you know which way to go with it...
Um....yeah !! but it is given along with some random questions and the answers are quite fine if it is in the context of Space radiation hazards kind of thing but what if it is about Extra terrestrial Intelligence hunt kind of thing?

Um....sorry if am asking silly questions but try to answer them as I am really a Beginner

The spacecraft should travel above (or below) and parallel to the plane containing the pulsar and earth. This question seems to assume a very small radiation pressure on the spacecraft due to the EM waves of the pulsar, which would hinder the motion of spacecraft, though by a minuscule amount.

This question is just to apply the concept of radiation pressure.
Then how can you say that it should travel above or below, parallel to the plane?

Um....sorry if am asking silly questions but try to answer them as I am really a Beginner

supratim1
Gold Member
Then how can you say that it should travel above or below, parallel to the plane?
Because my dear, the EM waves and thus the photons will travel in the plane containing earth and pulsar, and if the spacecraft is also on the same plane, it will be hit by the photons. So the best way is to travel on another plane parallel to it, above or below, to remain out of hit of photons.

Because my dear, the EM waves and thus the photons will travel in the plane containing earth and pulsar, and if the spacecraft is also on the same plane, it will be hit by the photons. So the best way is to travel on another plane parallel to it, above or below, to remain out of hit of photons.
Yeah ... kk....but no one is answering me to my other question of what if the craft and signals were to meet? Ignore the hazards and please answer me in the context of civilizations trying to record the signls from pulsar :(

supratim1
Gold Member
Ignore the hazards and please answer me in the context of civilizations trying to record the signls from pulsar :(
oh...to receive and record the signals, one doesn't need to send a spacecraft to the pulsar. pulsar signals are very strong, and as the earth and pulsar are in same plane, so the signals can be recorded from the earth itself using radio telescopes.

gneill
Mentor
Because my dear, the EM waves and thus the photons will travel in the plane containing earth and pulsar, and if the spacecraft is also on the same plane, it will be hit by the photons. So the best way is to travel on another plane parallel to it, above or below, to remain out of hit of photons.
There is no way to answer this question because the problem did not specify what the meaning of "best" is. It could mean shortest time, least radiation, most radiation, greatest signal to noise ratio for telemetry versus time of flight, arrival date should not be when pulsar is behind the Sun as viewed from Earth, arrival date should coincide with the mission director's birthday, avoiding space dragons that hunt in the plane of the pulsar's signal,.... the list is endless, mostly baseless, largely frivolous, and therefor pointless.

The craft is stated to have a continuous and constant acceleration and no refueling requirements, so radiation pressure on the craft is not a consideration; it could add up to millions of Newtons and it wouldn't matter because the engines would compensate.

There is no way to answer this question because the problem did not specify what the meaning of "best" is.

what would it be if the best way means "shortest distance?"

Um.....sorry if am asking silly questions but am really a beginner .... so please try to answer them.

supratim1
Gold Member
There is no way to answer this question because the problem did not specify what the meaning of "best" is.

what would it be if the best way means "shortest distance?"
if shortest distance is best, and radiation pressure is neglected, then of course the best way will be to travel on the plane.

And if shortest distance is best and radiation pressure is not to be neglected (Im here assuming the question is really badly worded and the acceleration it means is that of the rockets propulsion, NOT its total accelration) then above the plane is the way to go, since that will not have radiation pressure hindering it.

supratim1
Gold Member
yes, i agree.