Ion engines could take us to the solar gravitational lens in less than 13 years
29 comments
·October 26, 2024nielsbot
FTA:
“The paper defined an ideal power plan that can output 1 kW per kg of weight.
This is currently well outside the realm of possibility, with the best ion thruster power sources coming at something like 10 W per kg and even nuclear electric propulsion systems outputting 100 W per kg.”
JumpCrisscross
1 kW/kg is an ideal power plant. Does the paper define a minimally-viable one?
If we beef up the chemical stage, e.g. by launching on Starship and re-fuelling in LEO, can we make do with 100 or even 10 kW/kg?
(Also, to put 550 AU in perspective, Voyager 1 is 165 AU out [1]. At 38,000 mph Voyager 1 [2] travels about 3.6 AU/year [a]. Going straight out, it would reach the Solar gravitational lens in 2131 [b].
[1] https://science.nasa.gov/mission/voyager/where-are-voyager-1...
[2] https://en.m.wikipedia.org/wiki/Astronomical_unit
[a] (38026.77 x 24 x 365) / (9.2956 x 10^7)
[b] 2024 + (550 - 165) / a
perihelions
550 au in 13 years is a mean of 200 km/s—chemical rockets are nothing compared to that.
JumpCrisscross
And that is for a flyby.
We’re not getting to 550 AU with chemical rockets alone. Nuclear, ion and/or solar sails will be needed.
rbanffy
Spoiler: with a good-enough powerplant that's yet to be built.
melling
“Before this decade is out… “
When Kennedy committed us to go to the moon, the first American hadn’t even orbited the Earth.
Previous generations just used to get shit done.
bandyaboot
I could be wrong, but these two things don’t seem like they’re really that comparable. Apollo was certainly a monumental engineering achievement, but did it require that we 100X the state of the art efficiency of some critical tech?
JumpCrisscross
> Apollo was certainly a monumental engineering achievement, but did it require that we 100X the state of the art efficiency of some critical tech?
One order of magnitude in propulsion.
When Kennedy made his “We choose to go to the Moon” speech [1], our most powerful rocket was the Saturn I. Its H-1 engines thrusted at 200k lbf [2]. The Saturn V’s F-1s did 1.5mm lbf [3]. (The Saturn V, similarly, could lift an order of magnitude more mass to LEO than the Saturn I.)
It wouldn’t surprise me to find 100x increases in some material’s performance, et cetera.
[1] https://en.m.wikipedia.org/wiki/We_choose_to_go_to_the_Moon
throwaway19972
Previous generations also had it easy. Generally speaking technological advancement isn't blocked by motivation but by other concerns, namely funding.
Personally, I'd rather fix healthcare if we're going to spend political capital. https://youtu.be/goh2x_G0ct4 remains as relevant as ever
satvikpendem
Common philosophical fallacy: just because we are able to do things in one stage does not mean we can do things in the next.
Of course, I am an optimist, but one cannot relate historical circumstances in the same way. I will be glad if it does happen of course, but I do not expect it to be so based on past performance.
Gooblebrai
I'm genuinely curious. What's the formal name of this fallacy? Never heard of it.
wongarsu
Because America was lagging behind the Soviet Union in space achievements, and the Soviet Union was parading their superior space program to promote Communism.
It's not a generational thing, it's that the Moon landing was a top priority Cold War effort to beat the Soviets and show that Capitalism is the best. This mission in the other hand would be neat but has limited political value. What money were are willing to spend on space will mostly be spent on having a permanent moon base before the Chinese.
JumpCrisscross
> the Moon landing was a top priority Cold War effort to beat the Soviets and show that Capitalism is the best
Capitalism, democracy and a multilateral world order in contrast to the USSR’s ostensibly communist, authoritarian and centralised world order. (All lower case, btw.)
The reason being decolonisation had created a bunch of new countries and both Moscow and D.C. wanted to influence them. That performative element is unlikely to repeat absent another wave of new-country creation.
rbanffy
> and show that Capitalism is the best.
Or so it seemed.
> will mostly be spent on having a permanent moon base before the Chinese.
At least it could be launched from the Moon with a magnetic rail in addition to whatever extra propulsion it could carry onboard.
trueismywork
And Mongols conquered almost whole of Asia in less than 100 years, what's your point?
Mistletoe
> fastaguy88 10 months ago | next [–]
>2.5% of the US GDP ($26 trillion in 2023) would be 600 billion. At its peak in 1967, the Apollo program budget was 3 billion, while the US GDP was about 850 billion. So 0.35 percent. US government spending in 1967 was about 112 billion, so closer to 2.5 percent of the federal budget, not the GDP. Converting to today’s 6,000 billion federal budget, about 150 billion today, or not quite 20% of the defense budget, the largest federal expenditure after Social Security (the defense budget is essentially tied with Medicare).
I’m not sure we want those sort of expenses anymore.
metalman
read "failure is not an option"
SPOILER ALERT
lindburg just shows up unanounced at the cape ,security did not call ahead just escorted him up to the main deck everything stops,he hangs out for a bit,heads on his way and then they get back to work
there might not even be a photo,and so you have to trust that it happened,and in that is a large part of how shit got done,on trust
AtlasBarfed
So fine, use 1960s general atomics tech and do a pulse nuclear drive.
77pt77
We'll have the technology in 10 years.
Just like 20 years ago.
m3kw9
Then you have to develop new comms that can travel that far with enough bandwith for photos. The lag could be a week or so. Or you do relays which is equally difficult in a different way
marcosdumay
Just had to do the calculation.
With 3.5% enriched uranium, about 1/8 of that mass on the power supply is fuel.
Yeah, it's not impossible. But nuclear reactors aren't usually anywhere near 7 times heavier than their fuel.
Tuna-Fish
I would assume such a high-performance system uses bomb-grade material.
perihelions
All space nuclear fission reactors use weapons-grade uranium—they'd be impractical otherwise.
marcosdumay
Hum... You can make things about 20 times better by enriching the uranium more.
But then you'll get into severe storage and control problems. And that thing has to work for 13 years, untouched. There's a maximum somewhere on the middle.
Anyway, I don't think reactors on earth are anywhere close to 140 times the mass of the fuel either. And they don't have to use radiative cooling.
For those who don't want to watch a video to understand what a "solar gravitational lens" is: https://en.wikipedia.org/wiki/Solar_gravitational_lens