# In order to reach nearby suns, what is the limit to the speed we can accelerate a probe using gravitational assists or other means?

#### haberm

Let's get started now on interstellar probes!

#### rod

Okay, if we travel at 20 km/s, how long does it take to travel one-light year distance? My answer is 15,000 earth years. How long do you want to take to reach *nearby stars*? Remember Newton's 2nd law of motion here too.

#### JasonFrels

If we send an interstellar probe now, we might end up passing it by with a better probe that is created a century or two from now. Kind of hard to determine when to launch.

It seems like now, the telescope technology his being improved at a fast rate and maybe it would be better to wait a century to send a probe.

#### EjmMissouri

How fast can you accelerate a probe using gravitational assists? I do not know how to do the math, but if the elusive planet 9 turns out to be a primordial black hole as some have speculated, then you should be able to get one heck of a gravitational assist from it.

#### Mike_Moody

I would think that it would be possible to obtain a velocity of 200 to 300 km per second just using a space rated nuclear fission drive. We are close to the ability to build such a space power plant now. By the time we are able to harvest sufficient liquid hydrogen from, say, Ceres, we ought to be able to build such a craft. But realistically we would need to achieve a velocity of 30,000 km per second (roughly ten percent of the speed of light if I did the numbers right) before it would be worthwhile to bother with. I do not have any opinion on whether or not that kind of velocity would be achievable with a fusion drive, which is still very far in the future. We would probably being selling liquid hydrogen like we do a tank of gas in the asteroid belt before that happened.

#### rod

I go back to my earlier comment using one-light year distance and 20 km/s velocity model. If we travel at 300 km/s, it will take nearly 1,000 earth years to travel one-light year distance from earth. It looks like from this discussion, much work remains to travel to the stars (and beyond)

#### newtons_laws

Of course another big problem with sending a probe a couple of light years distance to the nearest stars is how would we send back any data that the probe acquires at that distance. Based on existing radio or laser communication technology you'd need a pretty powerful radio or laser transmitter on the probe to send back any data, which it seems to me would rule out the recently proposed concept of laser propelled probes with a mass of about 1 gram! https://www.space.com/29950-lasers-power-tiny-interstellar-spacecraft.html

#### William Pennat

Back in the early '90's the British Interplanetary Society published an interesting design for an unmanned interstellar probe that could reach velocities of 1/10th light speed. Its propulsion system is a matter-antimatter reactor. The only difficulty for such a design is, apparently, simply generating enough antimatter fuel! There is also the fact, that it would use up all its fuel just getting to 0.1 c. But it would be highly useful as an automated probe using very sophisticated AI. It would then transmit data back to Earth as it went along and passed through the Proxima system. Traveling at 0.1c, it could reach Proxima Centauri (closest star to us) in something like 40-odd years. Its course would then be gravity-adjusted in passing near the star so as to take it to its next closest target and on and on....

Truthseeker007

#### Truthseeker007

BANNED
My answer is simple. Ask the aliens how they get their speed so fast.

#### rod

We have a new study out now that directly addresses this issue using current, NASA space probes and travel times. The minimum travel time is 90,000 earth years with some travel times closer to 1 million years and much, much longer. ""A pair of researchers, one with the Max Planck Institute for Astronomy, the other with the Jet Propulsion Laboratory at CIT, has found a way to estimate how long it will take already launched space vehicles to arrive at other star systems.", Calculating the time it will take spacecraft to find their way to other star systems

Truthseeker007

#### Truthseeker007

BANNED
We have a new study out now that directly addresses this issue using current, NASA space probes and travel times. The minimum travel time is 90,000 earth years with some travel times closer to 1 million years and much, much longer. ""A pair of researchers, one with the Max Planck Institute for Astronomy, the other with the Jet Propulsion Laboratory at CIT, has found a way to estimate how long it will take already launched space vehicles to arrive at other star systems.", Calculating the time it will take spacecraft to find their way to other star systems

Has anybody every thought of using some of Nicholas Tesla technologies? Then again a lot of his papers were gobbled up by the government and locked away. Although I don't think they totally locked it away and have used some of it such as with the case in the HAARP technology and earthquake machines. Maybe even the black ops space program if their is one already travels on things we serfs and slaves didn't even think of yet. Just some thoughts. Not saying is this is true are not. As Mental Avanger likes to put it in his 60's style talk my conspiracy theories.

#### Antifuse

Of course another big problem with sending a probe a couple of light years distance to the nearest stars is how would we send back any data that the probe acquires at that distance. Based on existing radio or laser communication technology you'd need a pretty powerful radio or laser transmitter on the probe to send back any data, which it seems to me would rule out the recently proposed concept of laser propelled probes with a mass of about 1 gram! https://www.space.com/29950-lasers-power-tiny-interstellar-spacecraft.html
I have always wondered why we haven't (that I am aware of) developed a retransmission setup for probes sent into deep space? Does anyone know of any projects working towards this goal?

#### Wolfern

Star Trek is the closest we will ever come to traveling to other stars. Enjoy.

#### Mental Avenger

Has anybody every thought of using some of Nicholas Tesla technologies? Then again a lot of his papers were gobbled up by the government and locked away.
Please provide verifiable proof of that claim or rescind it.

Although I don't think they totally locked it away and have used some of it such as with the case in the HAARP technology and earthquake machines.
HAARP deals with near vacuum above 43 miles, while all of Earth’s weather occurs within the first 7 miles. At 43 miles the molecules are spread thin and create a plasma, which is what HAARP energizes to facilitate the propagation of microwaves at that altitude.

#### voidpotentialenergy

Same as the 1960's nuclear powered.
Gets you to a max speed of 1/4 C
A one way trip for a probe 21 Y travel and 4 years of speeding up slowing down to the closest star.
Maybe 5-20 years at that system visiting planets and sending probes to each one.

Getting nuclear fuel into space, probably not going to happen so maybe launching it from mars after you set up abilities to make the probe, launcher and fuel at mars.
100-500 in future.

#### Truthseeker007

BANNED
Please provide verifiable proof of that claim or rescind it.

HAARP deals with near vacuum above 43 miles, while all of Earth’s weather occurs within the first 7 miles. At 43 miles the molecules are spread thin and create a plasma, which is what HAARP energizes to facilitate the propagation of microwaves at that altitude.

You got the DARPA google so try using it. I am not going to rescind it when it is true. And even some of the information was in one Trumps relations hands.

So you claim to know how HAARP works? I want verifiable proof that you have even been to a HAARP facility and were there when it was being used. If not rescind it.

#### YetAnotherBob

Back in the early '90's ...
The only difficulty for such a design is, apparently, simply generating enough antimatter fuel! ....
There is also the minor matter of confining the requisite amount of antimatter. Currently, we can contain an amount roughly the same mass as a single bacterium. The amount needed for the 1/10 C vessel you mentioned is approximately 1/5 the mass of the probe plus it's hydrogen fuel. That's It's on the order of ten thousand tonnes. Roughly 100,000,000 years production at currently technology levels. Current confinement times are on the order of a second. for the voyage, it would need to be on the order of a century at least.
We need some massive technological advances to make this thing a reality. We are not quite as close as Leonardo Da Vinci was to supersonic flight.

#### Catastrophe

##### "There never was a good war, or a bad peace."
What may have gone over many peoples' heads is not how quickly you can speed up, but how quickly you can slow down prior to arrival.

dfjchem721

#### YetAnotherBob

What may have gone over many peoples' heads is not how quickly you can speed up, but how quickly you can slow down prior to arrival.
Speed up and Slow Down are both simple Delta V functions. For a trip to another solar system, you have to be able to both speed up at the beginning and slow down at the destination. Stars are similar to planets that way. Moving about in the 'target' system is minor compared to the delta V required for the trip.
What that means for those above who posit a trip at 1/10 C, is a total Delta V of 1/5 C. It's impossible for a chemical rocket, nearly so for a fission rocket, rather hard for a fusion rocket, and slightly doable for an antimatter rocket. It also means a trip of roughly 45 years, one way, plus whatever time it takes to speed up and then slow down.
Refueling at the destination is also a bit of a problem, unless you intend to die there. Hydrogen might be the easiest fuel source, Deuterium almost as easy. Plutonium or Uranium require massive infrastructure, and anti-matter requires a larger infrastructure than Earth presently has.
But you are quite right. Find the total Delta V of the system and then take only half to find the total final speed. After all, you have to stop to make it a trip.
Unless of course you intend to commit suicide anyway when you get there. Then just run into the star or planet at 1/10 C.
Go out with a bang!

#### Catastrophe

##### "There never was a good war, or a bad peace."
"Unless of course you intend to commit suicide anyway when you get there. "

Must be easier and less expensive ways. Also plenty of time to think about changing your mind but not much chance of doing much about it!

#### YetAnotherBob

I have always wondered why we haven't (that I am aware of) developed a retransmission setup for probes sent into deep space? Does anyone know of any projects working towards this goal?

Probes on Mars surface are relayed by orbiting satellites back to Earth. Is this not what you asked for?

#### Catastrophe

##### "There never was a good war, or a bad peace."
In order to reach nearby suns, what is the limit to the speed we can accelerate a probe using gravitational assists or other means?

Why not just radio them and wait at least 8 years for an answer then offer to meet them half way - and wait at least another 8 years for the reply.

If they agree, ask them where they are, and wait another 8 years (at least) for a reply.

Hope you are less than 5 now and doing well with your reading.

dfjchem721

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