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Comment by walnutclosefarm | Hacker News Reader

It's an interesting idea, and why not write a paper about it and try to get it published? Every academic needs papers with their name on them, and thinking about this had to be fun, if you don't have anything useful to do with your time.

But as an actual scientific investment, in my opinion, it belongs pretty near the bottom of pile of things we should spend our astronomy / cosomology / astrophysics budget on. The cost per unit of new information is just way too large, and the risk of mission failure too high, to justify making it a priority.

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Are you a physicist? This sounds like the opinion of a non-physicist. In physics we usually work on and publish basically any idea possible, just so that we have a full picture of what actually is possible and what the challenges are. Of course it's better if it's practical but that's not a necessity

Trained in physics, computer scientist and engineer by profession, now retired.

My opinion wasn't about the feasibility of this, but rather that of a tax-paying citizen who expects to get value for money spent. I don't see it in this, and I don't really expect the authors imagined they would be describing something that was likely to get any funding attention - the project is too big, and too far out there from an engineering perspective, given the little we'd get from it. So, yeah, I think their writing a long feasibility study is just published paper padding.

But a feasibility study is important scientific work even if it is unlikely to be produced. It could lead to much more realistic or cheaper designs for example

It's not a new idea and there already have been dozens of papers, and entire books (http://erewhon.superkuh.com/library/Space/Spacecraft/Deep%20...), published about using the solar gravitational focus as a lens and sending a spacecraft there. In fact NASA was already funding early mission studies like the Heliopause Electrostatic Rapid Transit System (HERTS) a decade ago.

And not only is it good for planetary sciences, it's good for cosmology too since it enables looking at the truly small scale structure of the cosmic microwave background. A mission to the gravitational focal line opposite some star should be one of the highest priorities.

http://erewhon.superkuh.com/library/Space/Spacecraft/Diffrac...

http://erewhon.superkuh.com/library/Space/Spacecraft/Direct%...

http://erewhon.superkuh.com/library/Space/Spacecraft/Image%2...

http://erewhon.superkuh.com/library/Space/Spacecraft/Mission...

http://erewhon.superkuh.com/library/Space/Spacecraft/Photome...

http://erewhon.superkuh.com/library/Space/Spacecraft/Resolve...

Claudio Maccone's proposal, to put a radio telescope at the solar focal point for SETI or communications purposes, is included as a chapter titled "Radio Links enabled by Gravitational lenses of the Sun and Stars" in the book Communications with Extraterrestrial Intelligence edited by Douglas Vakoch [1].

[1]. https://www.seti.org/book/communications-extraterrestrial-in...

I'm an engineer (current job is designing and building small spacecraft), so forgive me for raining on physicists' dreams, but a huge reason such a telescope is not currently practical is the enormous amount of propellant required to get you there and then station keep to stay focused on a target. The latter is usually glossed over in this concept but it alone blows mission cost out of the water. Would make James Webb look like a cute little project.

If you don't have an active propulsion system for station keeping then you cannot pick targets. Who wants that? Nobody.

This concept is 50 years off at minimum.

That's why the NASA study (HERTS) suggested using an electrostatic solar sail. It's only consumables are the noble gas and/or metal plating of the hollow cathode electron emitters used to keep the craft positively charged.

Actual station keeping +- a few meters once out on the gravitational focal line opposite the target system (which itself is moving) would require some cold gas thrusters that would limit the duration of the mission. But the forces and accelerations required are very small when you're 600 AU out from the sun and even the photon pressure isn't throwing things off anymore.

Yes, getting out there with enough mass for station keeping would be hard and it'd require new methods. Either electrostatic solar sails, or a more traditional H-reversal oberth burn close to the sun.

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