A 41 year mission sounds completely incredible, that's so amazing. And then I read: So in all likelihood we'll never have a space mission sending a physical object outside the solar system. Or are...
A 41 year mission sounds completely incredible, that's so amazing. And then I read:
It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.
So in all likelihood we'll never have a space mission sending a physical object outside the solar system. Or are there any believable theories on how we could achieve that?
There is work underway for an interstellar flyby mission known as "Breakthrough Starshot" - https://en.wikipedia.org/wiki/Breakthrough_Starshot In summary, it plans to use incredibly powerful...
In summary, it plans to use incredibly powerful earth-based lasers to accelerate a fleet of very small light-sail space craft up to ~20% the speed of light, which will get the ships to the Alpha Centauri system in 20-30 years.
It's important to remember that the Voyager probes are just coasting at this point. They don't have on-board rockets (their small thrusters are mostly for attitudinal changes, rather than for...
Exemplary
So in all likelihood we'll never have a space mission sending a physical object outside the solar system. Or are there any believable theories on how we could achieve that?
It's important to remember that the Voyager probes are just coasting at this point. They don't have on-board rockets (their small thrusters are mostly for attitudinal changes, rather than for accelerating). They were launched from Earth with large rockets, then proceeded mostly using the momentum from those launches, plus whatever acceleration they could pick up from planetary fly-bys. Nowadays, they're basically drifting through space (and are, in fact, ever-so-slightly decelerating due to the friction of particles in interstellar space).
However, if we launched a probe that could continually accelerate, that would drastically increase its speed and therefore its travel time. (Working from memory:) I'm pretty sure I've seen calculations which show that a spacecraft continually accelerating at 1g (9.8m/s2) could achieve a near-light-speed velocity in only 1 year, and would be able to get to the Alpha Centauri system, 4 light-years away, in less than 10 years (as measured here on Earth; time dilation would reduce the elapsed time on board to something close to 4 years). That would make reaching the Oort Cloud much more achievable.
Of course, the problem is working out how to continually accelerate a probe. We can't just load it up with enough fuel to burn in in its own rockets, or it would be too massive to leave Earth. It has to have a lighter source of acceleration. There are various theoretical options, like:
firing an Earth-based laser at the probe's light-sail;
having the probe use a Bussard ramjet to scoop up fuel from space to burn;
using an onboard power source which directly converts matter to energy (this might include a hypothetical matter-antimatter reactor).
Noone's going to be building any of these technologies any time soon, but it is theoretically possible to build a probe that continually accelerates and therefore reaches other stars within a human lifetime.
(And I've assumed we don't want the probe to slow down enough to look at interesting things along the way. That's a whole different problem! Although, it's possible to use a Bussard ramjet to decelerate as well as accelerate - if you can figure out how to turn the probe around midway on its flight.)
Plenty of ways to achieve interstellar flight. In addition to the already mentioned Starshot project, there's options like nuclear pulse propulsion (project Orion), where you drop shaped-charge...
Plenty of ways to achieve interstellar flight. In addition to the already mentioned Starshot project, there's options like nuclear pulse propulsion (project Orion), where you drop shaped-charge hydrogen bombs behind a specially armored spaceship to boost it up to 10% of light speed, which could bring it to Alpha Centauri in 50 years, and miraculously, even stop it once it got there.
Or if that sounds a little insane, Project Longshot back in the 80's outlined a probe with a more conventional and controlled fusion-electric drive, that would have been able to achieve just about 5% light speed.
Interesting. Skimming Orion's wikipedia page, it started in the 50s but stopped due to a Cold War nuclear testing treaty in the 60s. Longshot was a followup using fusion technology which doesn't...
Interesting. Skimming Orion's wikipedia page, it started in the 50s but stopped due to a Cold War nuclear testing treaty in the 60s. Longshot was a followup using fusion technology which doesn't yet exist apparently.
Wikipedia links to some related Penn State University research from the 90s: ICAN uses nuclear fission and its obstacles include radiation exposure (requiring space assembly) and the scarcity of antimatter fuel. AIMStar is similar and requires even more antimatter fuel.
Didn't know that all the recent research into particles, matter, antimatter could have direct applications in space travel.
I'm not sure what you mean by "sending a physical object outside the solar system". The Voyagers already achieved escape velocity from the Solar System, it's just a matter of time before they'll...
I'm not sure what you mean by "sending a physical object outside the solar system". The Voyagers already achieved escape velocity from the Solar System, it's just a matter of time before they'll be out.
Admittedly, that's a lot of time, but they aren't exactly very fast, going at around 15 km/s. There exist engines - mostly theoretical, for various reasons - that could put out much more dV. Project Orion, from the seventies, comes to mind: it doesn't require anything more exotic than a huge backplate and a bunch of nukes, and - if we didn't care about nuclear proliferation or fallout at all - it could perform single-stage Earth-surface to Mars.
There are other possible ways that come to mind with current/near-current tech (laser propelled probe? Massively staged normal chemical rocket?) - we won't see many missions of this kind mostly because of the politics/economics of it. It'll be costly, get us nothing "concrete" but scientific data light-lagged by months, over the course of decades to centuries.
I think the implied missing bit is "within a reasonable timeframe".
I'm not sure what you mean by "sending a physical object outside the solar system". The Voyagers already achieved escape velocity from the Solar System, it's just a matter of time before they'll be out.
I think the implied missing bit is "within a reasonable timeframe".
I'll need a definition of "reasonable timeframe", then, besides the aim of that mission (just get out? go there and back?) - anything less than a generation or two is pretty much impossible...
I'll need a definition of "reasonable timeframe", then, besides the aim of that mission (just get out? go there and back?) - anything less than a generation or two is pretty much impossible without Phlebotinium/a century of research.
Maybe if we expanded our "reasonable", but life-extension technologies are not that good yet.
I always assume that, when people talk about (or imply) space missions happening in a reasonable timeframe, they mean they want to see the results before they die.
I always assume that, when people talk about (or imply) space missions happening in a reasonable timeframe, they mean they want to see the results before they die.
When talking about missions to outside the Solar System, I don't think that's a good assumption to make. A "reasonable timeframe", to me, is not "will I be alive to see the results?", but "will...
When talking about missions to outside the Solar System, I don't think that's a good assumption to make. A "reasonable timeframe", to me, is not "will I be alive to see the results?", but "will anyone still be alive to see the results? will they even understand what they are getting?"
Those missions will be measured in centuries no matter what - you'd need to get up to 10% c to stay under 80 years of round trip to Alpha Centauri, and you will not get up to 10% c with our current tech, not for a round trip or "just" a trip not involving lithobraking, AKA "smashing into something bigger to stop". The dV requirements would be absolutely insane - 120k km/s - and not doable with anything we can actually build.
Hell, even with stuff we can't build. Take the Zubrin nuclear salt water rocket - the most over the top, insane engine I can think of that doesn't involve antimatter. It's basically ORION, but the uranium is not inside bombs but inside the fuel tanks, in a barely subcritical solution that hopefully will not start a chain reaction because of the neutron-damping coating of your tanks.
Zubrin then goes on to speculate about a more advanced version of the NSWR, suitable for insterstellar travel. Say that the 2% uranium bromide solution used uranium enriched to 90% U235 instead of only 20%. Assume that the fission yield was 90% instead of 0.1%. And assume a nozzle efficency of 0.9 instead of 0.8.
That would result in an exhaust velocity of a whopping 4,725,000 m/s (about 1.575% c, a specific impulse of 482,140 seconds). In a ship with a mass ratio of 10, it would have a delta V of 3.63% c. Now you're talkin...
As speculative as that is, it still falls much shorter of the 40% c dV budget required for such a round-trip mission, or even just for a mission trying to get to Alpha Centauri - without slowing down - in under a century.
Also, to do that you'd have to amass ten tons of 2% uranium bromide solution - using weapons-grade uranium - for each ton of payload, including the engine mass. I can imagine the radioactive fragments of the probe-that-was getting there, but not anything getting back.
Stop assuming the probe has to carry its own fuel. There are other theoretical propulsion methods, such as Bussard ramjets and lightsails. There's the well-publicised Breakthrough Starshot...
Stop assuming the probe has to carry its own fuel. There are other theoretical propulsion methods, such as Bussard ramjets and lightsails. There's the well-publicised Breakthrough Starshot proposal which would send ultralight probes to Alpha Centauri in about 30-40 years using Earth-based lasers reflecting off the probes' lightsails.
Remember that @talklittle's initial complaint was that "in all likelihood we'll never have a space mission sending a physical object outside the solar system." [emphasis mine] No, we won't never have a space mission sending a physical object outside the solar system. At some point, we will build and/or invent a propulsion technology which will allow probes to leave the solar system in human-relevant timeframes. That might not happen within our own lifetimes (ironically), but it will happen at some point. Future astronomers will be able to send out interstellar probes and get data about other stars within their lifetimes.
A 41 year mission sounds completely incredible, that's so amazing. And then I read:
So in all likelihood we'll never have a space mission sending a physical object outside the solar system. Or are there any believable theories on how we could achieve that?
There is work underway for an interstellar flyby mission known as "Breakthrough Starshot" - https://en.wikipedia.org/wiki/Breakthrough_Starshot
In summary, it plans to use incredibly powerful earth-based lasers to accelerate a fleet of very small light-sail space craft up to ~20% the speed of light, which will get the ships to the Alpha Centauri system in 20-30 years.
I teared up a bit reading that. Sci-fi becomes science. Thank you for letting me know.
It's important to remember that the Voyager probes are just coasting at this point. They don't have on-board rockets (their small thrusters are mostly for attitudinal changes, rather than for accelerating). They were launched from Earth with large rockets, then proceeded mostly using the momentum from those launches, plus whatever acceleration they could pick up from planetary fly-bys. Nowadays, they're basically drifting through space (and are, in fact, ever-so-slightly decelerating due to the friction of particles in interstellar space).
However, if we launched a probe that could continually accelerate, that would drastically increase its speed and therefore its travel time. (Working from memory:) I'm pretty sure I've seen calculations which show that a spacecraft continually accelerating at 1g (9.8m/s2) could achieve a near-light-speed velocity in only 1 year, and would be able to get to the Alpha Centauri system, 4 light-years away, in less than 10 years (as measured here on Earth; time dilation would reduce the elapsed time on board to something close to 4 years). That would make reaching the Oort Cloud much more achievable.
Of course, the problem is working out how to continually accelerate a probe. We can't just load it up with enough fuel to burn in in its own rockets, or it would be too massive to leave Earth. It has to have a lighter source of acceleration. There are various theoretical options, like:
firing an Earth-based laser at the probe's light-sail;
having the probe use a Bussard ramjet to scoop up fuel from space to burn;
using an onboard power source which directly converts matter to energy (this might include a hypothetical matter-antimatter reactor).
Noone's going to be building any of these technologies any time soon, but it is theoretically possible to build a probe that continually accelerates and therefore reaches other stars within a human lifetime.
(And I've assumed we don't want the probe to slow down enough to look at interesting things along the way. That's a whole different problem! Although, it's possible to use a Bussard ramjet to decelerate as well as accelerate - if you can figure out how to turn the probe around midway on its flight.)
EDIT: Formatting mathematical notation is tricky!
Plenty of ways to achieve interstellar flight. In addition to the already mentioned Starshot project, there's options like nuclear pulse propulsion (project Orion), where you drop shaped-charge hydrogen bombs behind a specially armored spaceship to boost it up to 10% of light speed, which could bring it to Alpha Centauri in 50 years, and miraculously, even stop it once it got there.
Or if that sounds a little insane, Project Longshot back in the 80's outlined a probe with a more conventional and controlled fusion-electric drive, that would have been able to achieve just about 5% light speed.
Interesting. Skimming Orion's wikipedia page, it started in the 50s but stopped due to a Cold War nuclear testing treaty in the 60s. Longshot was a followup using fusion technology which doesn't yet exist apparently.
Wikipedia links to some related Penn State University research from the 90s: ICAN uses nuclear fission and its obstacles include radiation exposure (requiring space assembly) and the scarcity of antimatter fuel. AIMStar is similar and requires even more antimatter fuel.
Didn't know that all the recent research into particles, matter, antimatter could have direct applications in space travel.
I'm not sure what you mean by "sending a physical object outside the solar system". The Voyagers already achieved escape velocity from the Solar System, it's just a matter of time before they'll be out.
Admittedly, that's a lot of time, but they aren't exactly very fast, going at around 15 km/s. There exist engines - mostly theoretical, for various reasons - that could put out much more dV. Project Orion, from the seventies, comes to mind: it doesn't require anything more exotic than a huge backplate and a bunch of nukes, and - if we didn't care about nuclear proliferation or fallout at all - it could perform single-stage Earth-surface to Mars.
There are other possible ways that come to mind with current/near-current tech (laser propelled probe? Massively staged normal chemical rocket?) - we won't see many missions of this kind mostly because of the politics/economics of it. It'll be costly, get us nothing "concrete" but scientific data light-lagged by months, over the course of decades to centuries.
I think the implied missing bit is "within a reasonable timeframe".
I'll need a definition of "reasonable timeframe", then, besides the aim of that mission (just get out? go there and back?) - anything less than a generation or two is pretty much impossible without Phlebotinium/a century of research.
Maybe if we expanded our "reasonable", but life-extension technologies are not that good yet.
Or maybe did they mean "within my lifetime"?
I always assume that, when people talk about (or imply) space missions happening in a reasonable timeframe, they mean they want to see the results before they die.
When talking about missions to outside the Solar System, I don't think that's a good assumption to make. A "reasonable timeframe", to me, is not "will I be alive to see the results?", but "will anyone still be alive to see the results? will they even understand what they are getting?"
Those missions will be measured in centuries no matter what - you'd need to get up to 10% c to stay under 80 years of round trip to Alpha Centauri, and you will not get up to 10% c with our current tech, not for a round trip or "just" a trip not involving lithobraking, AKA "smashing into something bigger to stop". The dV requirements would be absolutely insane - 120k km/s - and not doable with anything we can actually build.
Hell, even with stuff we can't build. Take the Zubrin nuclear salt water rocket - the most over the top, insane engine I can think of that doesn't involve antimatter. It's basically ORION, but the uranium is not inside bombs but inside the fuel tanks, in a barely subcritical solution that hopefully will not start a chain reaction because of the neutron-damping coating of your tanks.
As speculative as that is, it still falls much shorter of the 40% c dV budget required for such a round-trip mission, or even just for a mission trying to get to Alpha Centauri - without slowing down - in under a century.
Also, to do that you'd have to amass ten tons of 2% uranium bromide solution - using weapons-grade uranium - for each ton of payload, including the engine mass. I can imagine the radioactive fragments of the probe-that-was getting there, but not anything getting back.
Stop assuming the probe has to carry its own fuel. There are other theoretical propulsion methods, such as Bussard ramjets and lightsails. There's the well-publicised Breakthrough Starshot proposal which would send ultralight probes to Alpha Centauri in about 30-40 years using Earth-based lasers reflecting off the probes' lightsails.
Remember that @talklittle's initial complaint was that "in all likelihood we'll never have a space mission sending a physical object outside the solar system." [emphasis mine] No, we won't never have a space mission sending a physical object outside the solar system. At some point, we will build and/or invent a propulsion technology which will allow probes to leave the solar system in human-relevant timeframes. That might not happen within our own lifetimes (ironically), but it will happen at some point. Future astronomers will be able to send out interstellar probes and get data about other stars within their lifetimes.