Undergrad Questions about the Voyager spacecraft

[abdossamad2003]

Is there a possibility of a celestial body colliding with the Voyager spacecraft ?
Is there an alternative to the Voyager that runs faster and faster?
For example, at a speed of 100 kilometers per second

 

[PeroK]

Is there a possibility of a celestial body colliding with the Voyager spacecraft ?

Yes, but not for a while.

Is there an alternative to the Voyager that runs faster and faster?
For example, at a speed of 100 kilometers per second

Being able to accelerate significantly in empty space is an unsolved engineering problem. Extraterrestrial spacecraft generally cruise through empty space at the speed they leave the Earth's atmosphere - give or take the effects of gravitation.

 

[abdossamad2003]

Is it due to the lack of oxygen outside the Earth's atmosphere?

 

[PeroK]

Is it due to the lack of oxygen outside the Earth's atmosphere?

It's the lack of anything to get a grip on in a near vacuum.

 

[PeroK]

PS see, for example:

https://en.wikipedia.org/wiki/Spacecraft_propulsion

 

[abdossamad2003]

Missile systems work with a mass reduction mechanism (due to the exit of mass from inside it) that causes acceleration. Can not this mechanism be implemented in spacecraft ?

 

[phyzguy]

Missile systems work with a mass reduction mechanism (due to the exit of mass from inside it) that causes acceleration. Can not this mechanism be implemented in spacecraft ?

Of course. That's how it got to the outer solar system in the first place. But eventually you run out of fuel.

 

[PeroK]

Missile systems work with a mass reduction mechanism (due to the exit of mass from inside it) that causes acceleration. Can not this mechanism be implemented in spacecraft ?

Yes. The most efficient would be the photon rocket. The problem is the mass of the fuel/expellant, which needs to be launched from the ground.

https://en.wikipedia.org/wiki/Photon_rocket

 

[abdossamad2003]

Does NASA plan to produce faster, more fuel-powered spacecraft ? Replacement for Voyager 1
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[Janus]

Is it due to the lack of oxygen outside the Earth's atmosphere?

No, it's due to fuel limitations. There are no refueling stations in space, so the craft has to carry all the fuel its going to ever need. When accelerating a craft, you not only are accelerating it, but also the fuel it will will be burning later. This results in the amount of fuel needed going up much faster than the gain in speed.
To increase the final speed by a factor of 2 means you need to up the initial fuel supply by over 7 times, and to increase it by a factor of 3, you need 20 times more fuel.
And more fuel mean larger fuel tanks, superstructure to support them, larger rocket engines in order to be able to lift it all into space... All of which adds even more mass to the craft that has to be accelerated.
It soon becomes too much to be practical.

 

[PeroK]

Does NASA plan to produce faster, more fuel-powered spacecraft ? Replacement for Voyager 1
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We're happy to answer such questions, but you can also research them yourself:

https://www.nasa.gov/mission_pages/tdm/sep/index.html

 

[phyzguy]

Does NASA plan to produce faster, more fuel-powered spacecraft ? Replacement for Voyager 1

What does "more fuel-powered" mean? All spacecraft are already "fuel powered".

 

[Janus]

Does NASA plan to produce faster, more fuel-powered spacecraft ? Replacement for Voyager 1
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They are working on all kinds of new propulsion systems. Ion drives, for example. They are much more efficient in terms of fuel usage vs. final velocity than chemical rockets. The problem is that they are very low thrust, very low acceleration and thus take a great deal of time to get up to speed. Plus their low thrust makes them useless for getting craft off the surface of the Earth.
Ion thrusters are more efficient because they have higher exhaust velocities. If you double the exhaust velocity you double the the final craft velocity using the same amount of fuel.
However, the downside is that it takes 4 times the energy to double the exhaust velocity.
So the trick is balancing between increased fuel efficiency and your available power source.

 

[abdossamad2003]

That is, with more energy storage that can communicate with the Earth for up to 100 years, also with a better design that has a faster speed in space.

 

[phyzguy]

That is, with more energy storage that can communicate with the Earth for up to 100 years, also with a better design that has a faster speed in space.

I suggest you study how spacecraft work and how they achieve the speeds they do. Then perhaps you could come up with specific proposals for, "a better design that has a faster speed in space". It is not an easy problem.

 

[sophiecentaur]

Being able to accelerate significantly in empty space is an unsolved engineering problem.

Acceleration is not the problem; it's the amount of Energy needed to achieve changes in gravitational potential.

It's the lack of anything to get a grip on in a near vacuum.

Rockets don't need "a grip" on anything. They work by the reaction force from the ejected material that are expelled at high velocity. Anything that could be 'gripped' will also cause drag.

 

[sophiecentaur]

Ion drives, for example. They are much more efficient in terms of fuel usage vs. final velocity than chemical rockets. The problem is that they are very low thrust, very low acceleration and thus take a great deal of time to get up to speed.

The great advantage with ion drives is that, for a given quantity of Mechanical energy ( work done), the drive uses a fraction of the ejecta mass that's needed for a chemical rocket. That's because of the extremely high speeds of the ejected ions; momentum from a small mass of very fast ions provides added momentum to the craft, which can have a lower mass on its whole journey. The fact that the ion drive needs to run for days or even years, rather than for minutes, is not a particular disadvantage for deep space travel. (Nothing like enough thrust for getting into Earth orbit, of course but, at around $2k per kg to insert a payload into orbit - these days - I think that conventional launching could be with us for a long time.

 

[abdossamad2003]

What is the speeds of the ejected ions? Does it need an atmosphere or does it work outside the atmosphere?

 

[sophiecentaur]

What is the speeds of the ejected ions? Does it need an atmosphere or does it work outside the atmosphere?

Look at this Wiki article. It tells you all you'd want to know, first time around. Ions are ejected at speeds of between 20 and 50 km/s. Mostly the ion thrusters are low power these days (only a few kW input power) but, of course, they are switched on 24/7. Such low thrust would only be useful a long way from a planet's gravitational potential well.
I would imagine that any atmosphere could be a bad thing because it could contaminate the system with unwanted elements. Not sure about that, though.

 

[phinds]

Extraterrestrial spacecraft generally cruise through empty space at the speed they leave the Earth's atmosphere - give or take the effects of gravitation.

Yes, if by "effects of gravitation" you include significant speed increases due to slingshot maneuvers.

 

[sophiecentaur]

Extraterrestrial spacecraft generally cruise through empty space at the speed they leave the Earth's atmosphere - give or take the effects of gravitation.

That is a very strange remark. The whole point about orbital mechanics is the relationship that always exists between Kinetic and Gravitational Potential Energy. An "extraterrestrial spacecraft " (that sounds like tautology in fact) will always lose speed as it leaves the surface of a planet if it's drifting, unpowered. That applies to all but perfectly circular orbits, in fact.

Chemical rockets are always (afaik) operated in bursts so the majority of a journey in space will be trading off KE to the loss of GPE as you go further away from the 'local' large mass. A gravity assist (slingshot) path takes a craft near another planet and results in the craft re-gaining speed as it goes past the second planet. Its speed of separation from the second planet will be the same as its approach speed, taking you from an inferior orbit (path) to a superior orbit.
Using Jupiter is a favourite manoeuvre, giving you the same speed that you had half way to Jupiter, at a position half way to Saturn FOR FFREE! That's what the Voyager craft did, all those years ago. The navigation is tricky but it works reliably.

There's nothing to prevent using gravity assist even if you are using a continuous drive (e.g. Ion thrust) at the same time; you still get the enormous benefit. I can't imagine ever not using it as there will always be huge energy considerations in space travel.

 

[PeroK]

Being able to accelerate significantly in empty space is an unsolved engineering problem. Extraterrestrial spacecraft generally cruise through empty space at the speed they leave the Earth's atmosphere - give or take the effects of gravitation.

That is a very strange remark. The whole point about orbital mechanics is the relationship that always exists between Kinetic and Gravitational Potential Energy.

https://mars.nasa.gov/mars2020/timeline/cruise/

"The cruise phase begins after the spacecraft separates from the rocket, soon after launch. The spacecraft departs Earth at a speed of about 24,600 mph (about 39,600 kph). The trip to Mars will take about seven months and about 300 million miles (480 million kilometers). During that journey, engineers have several opportunities to adjust the spacecraft ’s flight path, to make sure its speed and direction are best for arrival at Jezero Crater on Mars. The first tweak to the spacecraft ’s flight path happens about 15 days after launch."

This is the reality of a space flight to Mars. The craft has no ability to accelerate significantly through empty space. If the spacecraft could accelerate and decelerate at $1m/s$ even for one day, it could increase its cruising speed to $350,000 kph$. And it would reach Mars in less than a month.

 

[sophiecentaur]

The craft has no ability to accelerate significantly through empty space.

The craft has rocket engines which will allow acceleration. The fact is, the mission is designed so as to carry minimal fuel so, apart from very occasional course and speed adjustments, its path is ballistic (unpowered). The term "cruise" is, imo, a bad one because it suggests the engines are running all the time (as with cars, planes and boats). Cars 'freewheel' and planes 'glide' when unpowered. The Nasa document was not aimed at thinking Physicists, I think.

it could increase its cruising speed to $350,000 kph$. And it would each Mars in less than a month.

Again, this is misleading. To take a path that allows approach to Mars at a speed that will allow an orbit involves a journey time of around 8 months. That route involves the least amount of fuel because it doesn't need to decelerate as it approaches Mars. Its speed drops naturally because it is gaining GPE between Earth's orbit and Mars' orbit.

The Voyager craft passed though the orbit distance of Mars much sooner because the were aiming for a Slingshot past Jupiter etc. etc. (look it up)

The Juno mission took much longer to get to stop by Jupiter at the right speed for orbit. That flight involved a second orbit round the Sun, for a slingshot by Earth. (also look it up)

Every space mission involves the minimal use of fuel and usually takes a lot longer than just to 'get' somewhere.

 

[abdossamad2003]

A spacecraft with as much fuel as possible can reach any speed. For example, if the spacecraft 's fuel is 10^9 kg, it results in the simplest case, that is, the conservaton of the momentum for the variable mass.(extremely high speeds of the ejected ions=50 km/s)

vi=0, Mi=10^9 kg, Mf=10^3 kg, vrel=50000 m/s
vf=vi+vrel*ln(Mf/Mi)=690.7 km/s !
with more fuel the final speed is more

 

[sophiecentaur]

with more fuel the final speed is more

Well, yes but. If we are in the world of Engineering and not Magic, we will always have a requirement for payload. If that payload includes humans it will be enormous and, even if the ejected mass can be small, there is still a need for Energy. Solutions will be there, eventually (we have to believe) butt no one will hang around until fusion is off the shelf in the way that Kerosine and Oxygen are, today.
And you need to remember that final speed is not the only consideration. In the real world of space travel, where you are is as important as how fast you are going. I can't believe that the basics of space navigation will be any less relevant of the foreseeable future. Getting close to the Sun involves both speeding up and slowing down and a vast amount of energy, despite you're going down into a potential well.
Then there's always the problem of getting back . . . . . .

 

[phyzguy]

A spacecraft with as much fuel as possible can reach any speed. For example, if the spacecraft 's fuel is 10^9 kg, it results in the simplest case, that is, the conservaton of the momentum for the variable mass.(extremely high speeds of the ejected ions=50 km/s)

How would you propose to launch a spacecraft weighing 10^9 kg into space?

 

[abdossamad2003]

Well, yes but. If we are in the world of Engineering and not Magic, we will always have a requirement for payload. If that payload includes humans it will be enormous and, even if the ejected mass can be small, there is still a need for Energy. Solutions will be there, eventually (we have to believe) button one will hang around until fusion is off the shelf in the way that Kerosine and Oxygen are, today.
And you need to remember that final speed is not the only consideration. In the real world of space travel, where you are is as important as how fast you are going. I can't believe that the basics of space navigation will be any less relevant of the foreseeable future. Getting close to the Sun involves both speeding up and slowing down and a vast amount of energy, despite you're going down into a potential well.
Then there's always the problem of getting back . . . . . .

To travel to interstellar space requires the final speed and highest speed without return and slow down.

 

[phinds]

To travel to interstellar space requires the final speed and highest speed without return and slow down.

This is ridiculous. If you are not going to slow down, then if humans are on board, they all just eventually die.

 

[DaveC426913]

This is ridiculous. If you are not going to slow down, then if humans are on board, they all just eventually die.

Well you don't tell them that!

 

[DaveC426913]

How would you propose to launch a spacecraft weighing 10^9 kg into space?

You don't. You build it in space.