The military budget is a jobs program that also keeps a (near bare minimum) level of industrial capacity afloat.
Its why no politician left or right is really interested in cutting it. If you browse open contracts, you'll see they that they overwhelmingly buy rather banal things and spend comparatively little on the "killing people" parts.
What do you think NASA is? NASA is so expensive because it's a jobs program. There's no other reason for Boeing to have factories in so many states for building satellites.
You're not wrong, and no one is turning down NASA contracts, but the scale isn't comparable.
NASA buys mostly highly specialized parts that can be pretty narrow in scope and utility.
OTOH the DoD will buy 150,000 aluminum water canteens, which is probably the only thing keeping the one decent job in Wagatah, Maine from closing. Which happens to be of only a handful of shops in the country with the tooling for this. Wagatah, of course, is not known for it's aerospace engineering. But thankfully water is pretty important for soldiers, and the new design is x% more efficient, so Wagatah gets another 5 years of work, the DoD gets to keep a domestic source of water canteens, and if NASA needs 5 space grade aluminum storage boxes, a company in Wagatah can make them.
Here's a Ken Livingstone quote from the foreword of "Drama Games: For Those Who Like To Say No":
> In the early 1980s, when the GLC (Greater London Council) was trying to save and create jobs to mitigate the impact of Thatcher's recession, we discovered that the most labour-intensive form of public spending was the arts, and so during the five years from 1981 to 1986 we increased spending on arts and recreation from £l6 million to £160 million. Virtually every actor, painter, poet, sculptor and, in particular, community artist was in work, and it made London a much more exciting city to live in. As well as taking orchestras from the Royal Festival Hall to play in the canteen at Ford's Assembly Plant in Dagenham, we particularly tried to reach disaffected youth. It's against that background that I was able to understand Chris Johnston's book. (Oh, and by the way, if you want to know which is the least labour-intensive form of public spending, it is the military.)
Maybe if we stopped pushing insane amounts of money into fossil fuels and the military industrial complex, and instead redirected it into the arts and sciences then, just maybe, we might actually end up with a happier, more employed, more fulfilled, and more equal planet.
This only works if you can force every state to do it, lest naive states be defenseless against those that don't disarm. But any such compulsion would be self-terminating, and thus unstable.
Why not just do it all? Fund the military and the arts and the sciences.
If anything, we've been letting the killing parts languish dangerously for decades - to the point where we may not be able to defend our allies in a serious conflict.
Hmmm, the US is not able to control the Hormuz strait. Iran decides who goes through it. Yesterday Iran shot at a vessel [0]. We can argue the semantics of “control” but I think this whole debacle showed the limits of US military power.
Do you really think the US military was given orders to control the strait, and couldn’t?
It showed limits for sure. But the limits were bluster without the will to follow through (and accept the consequences).
It’s a political and diplomatic catastrophe for an empire in decline. But if control of the strait had been an actual priority, it would have been very achievable. That was never the goal though. The goal was to look stupid on TV, for some reason.
“Make Trump look good” and “control the strait using whatever means necessary” are not compatible.
I agree they can’t make him look good. And I guess we’re agreeing the mission was not actually to control the strait in as a critical military objective .
Hopefully we elect a sane executive next election so we can start figuring out how to keep the executive from fucking over our allies. We can make a lot more of our partnerships with allies into ratchet mechanisms that are far less easily undone.
We have way more rail than the rest of the world. More than China, Russia, and the EU. We have almost 20% of the world’s total rail. But we prioritize freight instead of passenger service.
Those numbers look way off. Are you making the common mistake of ignoring mandatory spending? In 2024 defense spending and net interest were each about 13% of federal spending.
Total government spending in 2024 (at all levels) was about $9.5 trillion. So the military spending of about $950 billion was 10% of that, or $1,700. Interest on federal debt was also about 10%.
It’s worth also looking at what other countries spend on defense. Now that the U.S. is cutting off NATO, France plans to raise military spending to 2.5% of GDP by 2030. Applying that same figure to the U.S. would bring us down to $700 billion in 2024. So you’d pay $1,250 if the U.S. military budget was similar to what France thinks is a good number.
Germany is currently at 2.3% and plans to hit 3.5% by 2029. That’s the same percent as the U.S.
Funny how people complain about federal debt, when the people complaining benefitted the most from the system. It is your children who will be paying the interest, while the older folk enjoyed a heated economy with high government spending. Economics is just as fundemental as physics. There are conservation laws that cannot be violated. However you can make other people hold the bag.
> There are conservation laws that cannot be violated.
Modern Monetary Theory on line 2 for you!
There is no possible sense in which "economics is just as fundamental as physics": the latter concerns the behavior of the physical world with or without humans in it; the former describes the dynamics of a human created system featuring humans interacting with each other and the physical world.
It's simple accounting. Net money in must be more than or equal to net money out when adjusting for any temporal changes in the face value of the assets. If you use more than you produce, either you are going to have to pay in the future, or in the case of the government, you can die and let your children pay.
Doesn’t sound like those numbers are correct? I doubt out of the total taxes (all taxes, on all levels) 44% went to only pay federal debt (excluding state, city etc debt) and DoD.
That’s just federal spending. $17,000 sounds too high to just be federal taxes, it looks like federal + state/local. Accounting for that, military spending is closer to 10%.
Defense spending in the USA is double what is publicly published
There are all kinds of dark budgets and stuff spun off into "civilian" programs that actually aren't
The published cost of Iran War is like $30 Billion when it is obviously over $100 Billion by experts and that doesn't including replacing all the missiles
TWENTY-ONE TRILLION DOLLARS since 9/11 spent on defense 2001-2021
> imagine how much food clothing shelter for the US and WORLD that would buy
President LBJ proposed his Great Society agenda, which he defined as “a society where no child will go unfed, and no youngster will go unschooled.” It was a war on poverty, touching food, shelter, and education. At that same time, the country also increased its defense spending due to the heightened tension in the Cold War and escalation in the Vietnam War. The country could really do both.
It's like when people comment "This is why the US doesn't have healthcare" around military or war boasting.
No, the US absolutely can afford to have a gigantic military and massive welfare. That's what being the richest country on earth means
But for some reason we spent the past 50 years insisting that we are better off just letting a few individuals direct that wealth instead of making some choices collectively and democratically.
People might come to their senses when the second gilded age once again leaves a third of us unemployed and parents dying in ditches.
>Defense spending in the USA is double what is publicly published
Show your work.
>There are all kinds of dark budgets and stuff spun off into "civilian" programs that actually aren't
How much, though, as a percentage of the federal budget? Also, DoD does a lot of stuff that doesn't involved national defense, like breast cancer research or canal and levee maintenance.
>The published cost of Iran War is like $30 Billion when it is obviously over $100 Billion by experts and that doesn't including replacing all the missiles
Those missiles will be replaced in future defense budgets.
No, not even close. The issue is simply exhaust velocity and reaction mass, that leads us into the tyranny of the rocket equation - in that you have to carry that reaction mass with you and accelerate that mass too. Even if you had magic infinite energy - e.g. it's supplied externally by a laser or similar.
Using the theorized maximum of 31km/s exhaust velocity of project orion (much higher than any current high impulse propulsion technologies) you'd need to have thrown out something similar to 10^42 times the probe's mass out the back at that 31km/s velocity.
That means to accelerate a 1kg probe to 1%c you'd need to start with a spacecraft holding a reaction mass equivalent to a few trillion suns worth of mass.
Hardly seems worth it.
It's all about exhaust velocity - increase that and it scales down quickly. Using the theoretical max of 500km/s of VASIMIR for example means it's only 400x the mass of the probe of reaction mass - but that's still theory and max thrust limits means it'll take the order of millions of years to reach that sort of speed.
And why not accelerate using swing-bys on moons and planets? Of course this gets harder the faster you're already moving, but IIUC Voyager 1 has roughly 0.01% c, and this was launched 50 years ago.
It might help a bit, as you mentioned that Voyager is currently going about ~17km/s, so nearly 0.005% c, so it's already nearly 1/200th of the way there to our target of 1% c.
But then you're at a velocity so far beyond the escape velocity of most bodies you'd need to be skirting stars, then black holes to get anything more, and that's where it dives straight into "sci-fi" rather than anything even close to theoretically possible. How far away even if a body like that? Will this "probe" even survive such an encounter?
So even with that sort of slingshot it's well within the "Estimate Rough Error" of my intial numbers. They're "order of magnitude back-of-the-envelope calculations" of spherical spaceships in an already unrealistically biased to make the numbers smaller vacuum (just reaction mass, no thought of any mass of the engine or spacecraft body itself, or containing the reaction mass itself, or anything like that).
I probably should have stated my assumptions - in that "Can we accelerate a probe" I assumed that:
- The "probe" is a significant size - if we define a "probe" as a "Single Ion" then we already do that at CERN and similar pretty regularly - 1kg was my assumption of "Useful Probe Mass"
- "We" - in that "humans" as we know them today, preferably in the realisic age of civilizations as we know them, or even better within the lifetime of a currently living human.
Also there's different levels of "theoretical". VASIMIR has only ever been shown in lab settings, so still "theoretical" as a propulsion technology. something like Project Orion is "theoretical" in that it's never been built, but likely just an engineering effort. IKAROS showed solar sails are "possible", but so many orders of magnitude away from what would be required it'll still be a significant engineering and development effort to even show the same idea at the required scale is possible. Things like lasers as remote energy sources haven't really got off the drawing board. And then at the extreme we have "theoretical" ideas like fusion rockets, which are more "Not show to be /impossible/" rather than anything we could even start at really building today.
And each step along that "further out into theory" path means more risks, and more changes that method is shown to be less useful than really desired.
Is there a short snd simple explanation for how these planetary slingshots work? To me the gravity that increases the vehicle speed on the way to the planet will decrease the speed on the way away. Thanks!
It mostly works because the object you're sling-shotting with is moving relative to the initial origin of the probe - if you can line it up so the object is moving in the direction you want to accelerate in you can get it to "drag" your probe along a bit.
The end result is the probe isn't moving any "faster" leaving the slingshot object than it arrived from that object's point of view, but it may well be faster from the origin reference frame.
The thing is to remember that the bodies you're launching from, and then slingshotting against, are moving very fast relative to each other already. It's like throwing a bouncy-ball against a moving car - when it bounces off it may be moving faster relative to you than when you threw it, but it's actually a lower velocity relative to the moving car's reference frame.
Space sails are super low thrust though, even lower than my VASIMIR example - so will take even longer to reach the desired speed - though they have the advantage of not having to carry the complex and heavy engine I ignored that in the rough estimates anyway.
So by the time they're theoretically close to the desired speed they'll be on the other side of the galaxy at least, even if it took millions of years to get there at the much slower average speed.
You can't use a solar sail for this, but if you use lasers, you can get a few newtons / GW of incident laser power. Sci-fi stuff but if you can make a very very light reflector that can somehow be cooled (microscopic IR dipoles come to mind), and a very very focused and powerful laser, you can go a long way. Not sure what the purpose of moving a thin metalized foil at a fraction of lightspeed would be, though :)
Yeah, many of the theoretical solar sail ideas fall down on what I consider a useful "probe" is, and what it can mass. As mentioned in my other comment, if you define the "probe" to be "a single particle" we /already/ do this all the time in particle accelerators. But it's clearly not a useful "probe" I believe the original thought experiment implied. A few hundred grams of super thin solar sail material is still very much in the "Not A Probe" definition in my mind.
Plus even the best laser dispersion quickly gets significant at the distances required to give the sail the time to accelerate at such a low thrust.
One idea that stuck out to me was an array of giant thin solar powered spinning metal Crookes radiometers magnets in a line to make a railgun-like launcher. Materially cheap to do.
Before someone mentions IBM's (completely BS) "sub-nanometer circuitry": it isn't nearly sub-nm, except if you look at it from one particular way. The real estate is still many nanometers in dimension. The gates aren't even sub-nano; gate-to-gate interactions are, kind of.
> Can we swap the US Military and NASA budgets for just one year please?
It would be nice.
There is a pretty well known interview of Admiral Grace Hopper by David Letterman, where she talks about her famous "nanosecond" and explaining (to Generals) why it takes so long to get a message to a satellite. https://www.youtube.com/watch?v=oE2uls6iIEU (As an aside, Grace was a name she lived up to in a way few others could, if you have never seen that interview it is well worth a watch!)
The valuable and well understood lesson is that latency is tyrannical, and unavoidable. The only real customer for "data centers in space" is spacex for war fighting. You don't want that data, and it's analysis going back around the world. You don't want to put compute close to the front lines, and you certainly cant deploy it for the kinds of "special operations" that the US has been doing for the last two decades.
Is there a civilian use? Maybe. Ships, oil platforms, and remote locations could all see a use for this, but it isnt going to be that impactful.
Realistically, getting military spend back to more "dual use" applications would be great. We have a LONG history of this in the USA. Tons of Army core of engineers projects. The interstate highway system was born out of a need for better logistics. NASA was about missiles, space was incidental. The US computing industry's foundations fell out of the navy code breaking efforts of WWII. The internet (ARPANET) was a DARPA project to start with. Spread Spectrum and its roots in Torpedos (navy again). GPS, the auto injector (epi pens).
Most of these are far in the past, recently the biggest thing we have gotten out military investments is TOR (and one could argue its in decline).
I think we don't see as much coming out of the modern military because it is grossly mismanaged. It's become reliant on private industry to "innovate" and that has a relentless focus on the bottom line.
Yes it would be nice if we did that spending swap, but it will never happen realistically. I think a change of leadership, of intent could result in far less waste and much more benefit for the American public. We have proof we can, we just need to figure out how and make it happen.
I hope I am not alone in thinking the military needs to be defunded in the USA. Nuclear weapons mean that there is zero strategic threat and any future wars will be regional. Drawdown of oversea bases is long overdue.
They published an official press release on this on the 22nd.
https://rocketlabcorp.com/updates/victus-haze/
Also,the mission to rescue the Swift telescope made news this week.
Soon I'll be seeing a sign for a "Joe's Satellite Repair Service" shop right next to the local autobody shop.
https://www.mos.org/article/space-news-deep-dive-saving-swif...
Here is a good video on the swift rescue mission.
https://www.youtube.com/watch?v=Up0LNTMPnjI Pegasus to the Rescue: 'The Edge of Feasibility' (Alexander the ok)
I remember working with the Pegasus at Caltech in the early 2010s for a tech demo that was never going to launch.
I'm amazed it's still operational.
Joe and Buzz Aerospace Supply
https://www.youtube.com/watch?v=KB-ZCmvFIXo "accents"
https://www.youtube.com/watch?v=keKDA7523_c "Nerdneck"
Can we swap the US Military and NASA budgets for just one year please?
Just one year
It would be AMAZING
Or even what we fund Israel's 2/3 of all their weapons are bought by US
We'd have 10% speed of light probes going outside of solar system already
Well at least Nancy Grace Roman L2 Telescope is launching, hope it goes perfectly
The military budget is a jobs program that also keeps a (near bare minimum) level of industrial capacity afloat.
Its why no politician left or right is really interested in cutting it. If you browse open contracts, you'll see they that they overwhelmingly buy rather banal things and spend comparatively little on the "killing people" parts.
What do you think NASA is? NASA is so expensive because it's a jobs program. There's no other reason for Boeing to have factories in so many states for building satellites.
You're not wrong, and no one is turning down NASA contracts, but the scale isn't comparable.
NASA buys mostly highly specialized parts that can be pretty narrow in scope and utility.
OTOH the DoD will buy 150,000 aluminum water canteens, which is probably the only thing keeping the one decent job in Wagatah, Maine from closing. Which happens to be of only a handful of shops in the country with the tooling for this. Wagatah, of course, is not known for it's aerospace engineering. But thankfully water is pretty important for soldiers, and the new design is x% more efficient, so Wagatah gets another 5 years of work, the DoD gets to keep a domestic source of water canteens, and if NASA needs 5 space grade aluminum storage boxes, a company in Wagatah can make them.
OK so maybe they're both jobs programs, but .mil is bigger and employs more people (almost certainly at a lower per capita cost).
> OK so maybe they're both jobs programs, but .mil is bigger and employs more people
Which is a direct function of its budget not a function of what it does.
> (almost certainly at a lower per capita cost).
DoD is extremely expensive per job due to the longe term benefits, layers of bureaucracy, and sub contractors.
Here's a Ken Livingstone quote from the foreword of "Drama Games: For Those Who Like To Say No":
> In the early 1980s, when the GLC (Greater London Council) was trying to save and create jobs to mitigate the impact of Thatcher's recession, we discovered that the most labour-intensive form of public spending was the arts, and so during the five years from 1981 to 1986 we increased spending on arts and recreation from £l6 million to £160 million. Virtually every actor, painter, poet, sculptor and, in particular, community artist was in work, and it made London a much more exciting city to live in. As well as taking orchestras from the Royal Festival Hall to play in the canteen at Ford's Assembly Plant in Dagenham, we particularly tried to reach disaffected youth. It's against that background that I was able to understand Chris Johnston's book. (Oh, and by the way, if you want to know which is the least labour-intensive form of public spending, it is the military.)
Maybe if we stopped pushing insane amounts of money into fossil fuels and the military industrial complex, and instead redirected it into the arts and sciences then, just maybe, we might actually end up with a happier, more employed, more fulfilled, and more equal planet.
This only works if you can force every state to do it, lest naive states be defenseless against those that don't disarm. But any such compulsion would be self-terminating, and thus unstable.
Why not just do it all? Fund the military and the arts and the sciences.
Do you think the US needs all of its current military capacity to just deter outside aggression?
Great. Can we change it to just be the non killing part for a few years until the bad project ideas fully die off?
If anything, we've been letting the killing parts languish dangerously for decades - to the point where we may not be able to defend our allies in a serious conflict.
As proven so well during this whole debacle in the Hormuz strait.
Hard to see that as an indictment of military capability when it is so overwhelmingly a reflection of political incompetence.
Hmmm, the US is not able to control the Hormuz strait. Iran decides who goes through it. Yesterday Iran shot at a vessel [0]. We can argue the semantics of “control” but I think this whole debacle showed the limits of US military power.
[0] https://www.npr.org/2026/06/26/nx-s1-5871963/un-agency-pause...
There is a difference between military might and political will.
Going all out on Iran would free up the straight, but also be political suicide for the right.
Do you really think the US military was given orders to control the strait, and couldn’t?
It showed limits for sure. But the limits were bluster without the will to follow through (and accept the consequences).
It’s a political and diplomatic catastrophe for an empire in decline. But if control of the strait had been an actual priority, it would have been very achievable. That was never the goal though. The goal was to look stupid on TV, for some reason.
Re: “Do you really think the US military was given orders to control the strait, snd couldn’t?”
Pretty much. I think US military was given the order to make Trump look good, and they couldn’t (Trump looks weak now, which he completely hates)
“Make Trump look good” and “control the strait using whatever means necessary” are not compatible.
I agree they can’t make him look good. And I guess we’re agreeing the mission was not actually to control the strait in as a critical military objective .
Good thing you don't have that many allies left, so it should make the job easier.
Hopefully we elect a sane executive next election so we can start figuring out how to keep the executive from fucking over our allies. We can make a lot more of our partnerships with allies into ratchet mechanisms that are far less easily undone.
No it would obviously lose its purpose then.
You could have a jobs program that builds infrastructure instead.
That's where we got a whole lot of dams in the American West!
Last that I checked, you guys could use some more trains.
We have way more rail than the rest of the world. More than China, Russia, and the EU. We have almost 20% of the world’s total rail. But we prioritize freight instead of passenger service.
https://en.wikipedia.org/wiki/List_of_countries_by_rail_tran...
The military budget is how the US enforces Bretton Woods. The jobs part is just a nice side-effect of any govt. spending.
Bretton Woods was formally terminated in 1973.
Only in theory. The US still forces emergent countries to trade in USD under the menace of tariffs, staging coups, and military intervention.
We're getting into tinfoil hat territory here.
In 2024, the average American spent about $17,000 on taxes. Nearly $4000 of that went to the DoD, about $3500 went to interest on federal debt.
I think it’s fun to think about it in this way. I personally spend hundreds of dollars a month on war.
Those numbers look way off. Are you making the common mistake of ignoring mandatory spending? In 2024 defense spending and net interest were each about 13% of federal spending.
Total government spending in 2024 (at all levels) was about $9.5 trillion. So the military spending of about $950 billion was 10% of that, or $1,700. Interest on federal debt was also about 10%.
It’s worth also looking at what other countries spend on defense. Now that the U.S. is cutting off NATO, France plans to raise military spending to 2.5% of GDP by 2030. Applying that same figure to the U.S. would bring us down to $700 billion in 2024. So you’d pay $1,250 if the U.S. military budget was similar to what France thinks is a good number.
Germany is currently at 2.3% and plans to hit 3.5% by 2029. That’s the same percent as the U.S.
Funny how people complain about federal debt, when the people complaining benefitted the most from the system. It is your children who will be paying the interest, while the older folk enjoyed a heated economy with high government spending. Economics is just as fundemental as physics. There are conservation laws that cannot be violated. However you can make other people hold the bag.
> There are conservation laws that cannot be violated.
Modern Monetary Theory on line 2 for you!
There is no possible sense in which "economics is just as fundamental as physics": the latter concerns the behavior of the physical world with or without humans in it; the former describes the dynamics of a human created system featuring humans interacting with each other and the physical world.
[dead]
Monetary identities can not be violated¹. What you are talking about isn't one of them.
1 - They are also useless by themselves, any rule that actually tells you something will have exceptions.
What are those conservation laws?
It's simple accounting. Net money in must be more than or equal to net money out when adjusting for any temporal changes in the face value of the assets. If you use more than you produce, either you are going to have to pay in the future, or in the case of the government, you can die and let your children pay.
There's no law of conservation of money. It can be pretty trivially created and destroyed. It may not be a good idea, but it's entirely doable.
Doesn’t sound like those numbers are correct? I doubt out of the total taxes (all taxes, on all levels) 44% went to only pay federal debt (excluding state, city etc debt) and DoD.
You have a source to share for that framing of the tax spend?
Although not quite exact, here's spending data for 2024 (https://fiscaldata.treasury.gov/static-data/published-report...) - about 14% of tax dollars went to defence, 0.14*17000=2380.
That’s just federal spending. $17,000 sounds too high to just be federal taxes, it looks like federal + state/local. Accounting for that, military spending is closer to 10%.
You spend that money on defense, not war!
> I personally spend hundreds of dollars a month on war.
Or, put another way, you spend hundreds of dollars a month on not having to learn russian and live as putin's peasant.
Seems like a good deal to me.
The Russians can't even take Ukraine — what makes you think they have a hope in hell of taking the US?
The oceans exist for free.
Defense spending in the USA is double what is publicly published
There are all kinds of dark budgets and stuff spun off into "civilian" programs that actually aren't
The published cost of Iran War is like $30 Billion when it is obviously over $100 Billion by experts and that doesn't including replacing all the missiles
TWENTY-ONE TRILLION DOLLARS since 9/11 spent on defense 2001-2021
* https://ips-dc.org/report-state-of-insecurity-cost-militariz...
imagine how much food clothing shelter for the US and WORLD that would buy
we'd have humans on Mars already with that budget not even knowing now how to stop space-blindness and bone-loss
> imagine how much food clothing shelter for the US and WORLD that would buy
President LBJ proposed his Great Society agenda, which he defined as “a society where no child will go unfed, and no youngster will go unschooled.” It was a war on poverty, touching food, shelter, and education. At that same time, the country also increased its defense spending due to the heightened tension in the Cold War and escalation in the Vietnam War. The country could really do both.
It's like when people comment "This is why the US doesn't have healthcare" around military or war boasting.
No, the US absolutely can afford to have a gigantic military and massive welfare. That's what being the richest country on earth means
But for some reason we spent the past 50 years insisting that we are better off just letting a few individuals direct that wealth instead of making some choices collectively and democratically.
People might come to their senses when the second gilded age once again leaves a third of us unemployed and parents dying in ditches.
>Defense spending in the USA is double what is publicly published
Show your work.
>There are all kinds of dark budgets and stuff spun off into "civilian" programs that actually aren't
How much, though, as a percentage of the federal budget? Also, DoD does a lot of stuff that doesn't involved national defense, like breast cancer research or canal and levee maintenance.
>The published cost of Iran War is like $30 Billion when it is obviously over $100 Billion by experts and that doesn't including replacing all the missiles
Those missiles will be replaced in future defense budgets.
Or hear me out, we improve life here on Earth...
Can we really accelerate any probe to faster than 1% c? Or 2% c?
No, not even close. The issue is simply exhaust velocity and reaction mass, that leads us into the tyranny of the rocket equation - in that you have to carry that reaction mass with you and accelerate that mass too. Even if you had magic infinite energy - e.g. it's supplied externally by a laser or similar.
Using the theorized maximum of 31km/s exhaust velocity of project orion (much higher than any current high impulse propulsion technologies) you'd need to have thrown out something similar to 10^42 times the probe's mass out the back at that 31km/s velocity.
That means to accelerate a 1kg probe to 1%c you'd need to start with a spacecraft holding a reaction mass equivalent to a few trillion suns worth of mass.
Hardly seems worth it.
It's all about exhaust velocity - increase that and it scales down quickly. Using the theoretical max of 500km/s of VASIMIR for example means it's only 400x the mass of the probe of reaction mass - but that's still theory and max thrust limits means it'll take the order of millions of years to reach that sort of speed.
And why not accelerate using swing-bys on moons and planets? Of course this gets harder the faster you're already moving, but IIUC Voyager 1 has roughly 0.01% c, and this was launched 50 years ago.
It might help a bit, as you mentioned that Voyager is currently going about ~17km/s, so nearly 0.005% c, so it's already nearly 1/200th of the way there to our target of 1% c.
But then you're at a velocity so far beyond the escape velocity of most bodies you'd need to be skirting stars, then black holes to get anything more, and that's where it dives straight into "sci-fi" rather than anything even close to theoretically possible. How far away even if a body like that? Will this "probe" even survive such an encounter?
So even with that sort of slingshot it's well within the "Estimate Rough Error" of my intial numbers. They're "order of magnitude back-of-the-envelope calculations" of spherical spaceships in an already unrealistically biased to make the numbers smaller vacuum (just reaction mass, no thought of any mass of the engine or spacecraft body itself, or containing the reaction mass itself, or anything like that).
I probably should have stated my assumptions - in that "Can we accelerate a probe" I assumed that:
- The "probe" is a significant size - if we define a "probe" as a "Single Ion" then we already do that at CERN and similar pretty regularly - 1kg was my assumption of "Useful Probe Mass"
- "We" - in that "humans" as we know them today, preferably in the realisic age of civilizations as we know them, or even better within the lifetime of a currently living human.
Also there's different levels of "theoretical". VASIMIR has only ever been shown in lab settings, so still "theoretical" as a propulsion technology. something like Project Orion is "theoretical" in that it's never been built, but likely just an engineering effort. IKAROS showed solar sails are "possible", but so many orders of magnitude away from what would be required it'll still be a significant engineering and development effort to even show the same idea at the required scale is possible. Things like lasers as remote energy sources haven't really got off the drawing board. And then at the extreme we have "theoretical" ideas like fusion rockets, which are more "Not show to be /impossible/" rather than anything we could even start at really building today.
And each step along that "further out into theory" path means more risks, and more changes that method is shown to be less useful than really desired.
Is there a short snd simple explanation for how these planetary slingshots work? To me the gravity that increases the vehicle speed on the way to the planet will decrease the speed on the way away. Thanks!
It mostly works because the object you're sling-shotting with is moving relative to the initial origin of the probe - if you can line it up so the object is moving in the direction you want to accelerate in you can get it to "drag" your probe along a bit.
The end result is the probe isn't moving any "faster" leaving the slingshot object than it arrived from that object's point of view, but it may well be faster from the origin reference frame.
The thing is to remember that the bodies you're launching from, and then slingshotting against, are moving very fast relative to each other already. It's like throwing a bouncy-ball against a moving car - when it bounces off it may be moving faster relative to you than when you threw it, but it's actually a lower velocity relative to the moving car's reference frame.
> No, not even close.
10% of C is theoretically possible with a space sail, and lasers.
Will it work? Well we don't know cause we haven't tried.
Space sails are super low thrust though, even lower than my VASIMIR example - so will take even longer to reach the desired speed - though they have the advantage of not having to carry the complex and heavy engine I ignored that in the rough estimates anyway.
So by the time they're theoretically close to the desired speed they'll be on the other side of the galaxy at least, even if it took millions of years to get there at the much slower average speed.
You can't use a solar sail for this, but if you use lasers, you can get a few newtons / GW of incident laser power. Sci-fi stuff but if you can make a very very light reflector that can somehow be cooled (microscopic IR dipoles come to mind), and a very very focused and powerful laser, you can go a long way. Not sure what the purpose of moving a thin metalized foil at a fraction of lightspeed would be, though :)
Yeah, many of the theoretical solar sail ideas fall down on what I consider a useful "probe" is, and what it can mass. As mentioned in my other comment, if you define the "probe" to be "a single particle" we /already/ do this all the time in particle accelerators. But it's clearly not a useful "probe" I believe the original thought experiment implied. A few hundred grams of super thin solar sail material is still very much in the "Not A Probe" definition in my mind.
Plus even the best laser dispersion quickly gets significant at the distances required to give the sail the time to accelerate at such a low thrust.
Roundtrip Interstellar Travel Using Laser-Pushed Lightsails
https://ia800108.us.archive.org/view_archive.php?archive=/24...
One idea that stuck out to me was an array of giant thin solar powered spinning metal Crookes radiometers magnets in a line to make a railgun-like launcher. Materially cheap to do.
Related, but not exactly what I was thinking of: https://www.centauri-dreams.org/2025/08/05/a-rotating-probe-... The original source I'm thinking of may be lost to time :( I'll keep hunting.
edit:found!
https://www.youtube.com/watch?v=MDM1COWJ2Hc
We have the physics but not the engineering. See the Breakthrough Starshot project for instance
Yes, with lasers or nuclear energy
I think the idea is tic-tac sized probes with nano circuitry (that doesn't exist yet)
accelerated by lasers so they don't have to carry the power source
Obviously stopping is the problem, they can never stop but at some point no need
Before someone mentions IBM's (completely BS) "sub-nanometer circuitry": it isn't nearly sub-nm, except if you look at it from one particular way. The real estate is still many nanometers in dimension. The gates aren't even sub-nano; gate-to-gate interactions are, kind of.
Per new Space Force regulations, we are using F for an adjusted speed of light. We are currently able to achieve 1.48F.
Can we swap the US Military and child care budgets for just one year please?
Just one year
It would be AMAZING
The US gives Israel $3.8B a year (and 2/3 of their weapons are _sold_ by the US not bought). The budget of Nasa is $25B.
But by antisemite math and logic says we’ll get 10% light speed.
Being against military aid to Israel isn't necessarily antisemitic.
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anti-israel-warmongering != antisemite but nice try
US has given Israel over $20 Billion directly since 2023 alone
Since 2023 NINETY THOUSAND TONS OF WEAPONS
Enough already
Israel has universal health care, let them buy build their own weaspons
US must only sell Iron-Dome ONLY, defense only, they are warmongers
> Can we swap the US Military and NASA budgets for just one year please?
It would be nice.
There is a pretty well known interview of Admiral Grace Hopper by David Letterman, where she talks about her famous "nanosecond" and explaining (to Generals) why it takes so long to get a message to a satellite. https://www.youtube.com/watch?v=oE2uls6iIEU (As an aside, Grace was a name she lived up to in a way few others could, if you have never seen that interview it is well worth a watch!)
The valuable and well understood lesson is that latency is tyrannical, and unavoidable. The only real customer for "data centers in space" is spacex for war fighting. You don't want that data, and it's analysis going back around the world. You don't want to put compute close to the front lines, and you certainly cant deploy it for the kinds of "special operations" that the US has been doing for the last two decades.
Is there a civilian use? Maybe. Ships, oil platforms, and remote locations could all see a use for this, but it isnt going to be that impactful.
Realistically, getting military spend back to more "dual use" applications would be great. We have a LONG history of this in the USA. Tons of Army core of engineers projects. The interstate highway system was born out of a need for better logistics. NASA was about missiles, space was incidental. The US computing industry's foundations fell out of the navy code breaking efforts of WWII. The internet (ARPANET) was a DARPA project to start with. Spread Spectrum and its roots in Torpedos (navy again). GPS, the auto injector (epi pens).
Most of these are far in the past, recently the biggest thing we have gotten out military investments is TOR (and one could argue its in decline).
I think we don't see as much coming out of the modern military because it is grossly mismanaged. It's become reliant on private industry to "innovate" and that has a relentless focus on the bottom line.
Yes it would be nice if we did that spending swap, but it will never happen realistically. I think a change of leadership, of intent could result in far less waste and much more benefit for the American public. We have proof we can, we just need to figure out how and make it happen.
I hope I am not alone in thinking the military needs to be defunded in the USA. Nuclear weapons mean that there is zero strategic threat and any future wars will be regional. Drawdown of oversea bases is long overdue.
Durum-burum latency. In fact, internets slowed down compared to 2010s, and CDNs helped only to delay that.
LEO orbit latency is nothing compared to what you lose to stuffing your link with useless web crap.
> Or even what we fund Israel's 2/3 of all their weapons are bought by US
And all of the money the US gives to Israel is earmarked for American products.
Just more American tax dollars going to American defense contractors.
Good spot by whoever noticed it!