NASA/APL Interstellar Probe Mission Architecture | Hacker News Reader

NASA/APL Interstellar Probe Mission Architecture

interstellarprobe.jhuapl.edu

60 pointsdivbzero21 comments

The engineering study has 30 pages of general relativity calculations, whimsically asking how the mission architecture would change if the solar system had a black hole. Bit unexpected.

https://interstellarprobe.jhuapl.edu/uploadedDocs/papers/588... (appendix 11.2.2.1, "Relativistic Oberth Maneuver")

Thanks, that was a fun read and could be an exercise or two in a course on general relativity. I was just astonished about the references to Wikipedia, Stackexchange and Wolfram (apparently Mathematica). Maybe this was actually written by a grad student...

peak speed: 7 au/year, so time to half way to P. Centauri is ~19k-years

(I realize this proposed probe has a much shorter lifetime, but was curious)

I wonder why these probes don't have a ion-motor stage, the RTG isn't powerful enough or light enough, I suppose. Would need a fission-powered engine to beat a chemical stage.

Power looks to be the issue. A single one of the NSTAR engines used on Dawn uses 2.1-2.3 kW; even with the improved next-generation RTGs this design assumes, you'd need a bunch of them to be able to use ion propulsion.

Don't you usually have a battery you charge using the rtg's, so that you can deliver some real power when you need to do a manouvre?

Not to the best of my knowledge; even with battery backup, ion engines have so little thrust that spacecraft with them use a very different style of orbital maneuvers than craft with chemical engines. This [1] answer on Space Stack Exchange discusses how Dawn entered Ceres orbit using the normal thrust of its ion engines.

[1]https://space.stackexchange.com/a/6665/13208

Peak exit speed: 33.2 km/s.

I can’t help but think maybe the way to do an interstellar probe like this would be project Orion.

Exit speed of 7 AU/year is ~0.00011 c by my calculations. Hardly seems worth it. I imagine it will be overtaken by something a lot more sophisticated launched a few decades later.

And it in turn by another probe, which in turn...

Not to be too dismissing, but what are the odds that part of the impetus for this is to find something to use the SLS for?

Apart from that, I really do wish that my (millenial) generation had our voyager, our pioneer, etc. Perseverance (which I always found a bit of a cringe name relative to spacecraft of the 20th century, but i digress) and Curiosity and a few others are nice, but something, and I get a feeling that it's not just me, that there is this terrifying fear that gen x'ers and millenials just aren't as good as their ancestors. And the interstellar probe sort of adds to that fear, given it's not doing anything radically new relative to even 20th century spacecraft (similar science equipment, similar RTG, and so on).

/rant

They seem interested in using Starship for it as well. The main website page links to this article: https://www.scientificamerican.com/article/spacexs-starship-...

Juno, Curiosity, Perseverance, James Webb. A trickle.

But the torrent is coming, and then the flood. It will make Apollo look like kindergarten. Musk wants Starship to have 1000 launches per year in about one decade from now. Maybe it's not going to that, but right now we are reading about 3 launches in 36 hours [1]. So, a few hundred launches per year once Starship becomes mature does not sound quite crazy.

And there are lots of other rocket companies that we don't hear that much about. Ariane intends to build reusable rockets within one decade. Rocket Lab already flies a reusable rocket, although small compared with SpaceX. ISAR Aerospace plans to test their rocket Spectrum next year. Who knows, maybe one day Blue Origin will be successful too.

A new space age is definitely coming.

[1] https://spaceflightnow.com/2022/06/19/spacex-launches-third-...

Came here to say this - I frequently wonder when (not if) these grandiose NASA et al missions to e.g the moon etc will be overtaken by someone taking a joyride in a commercial space launch.

E.g. NASA finally land their 300 squillion dollar 20-years-in-the-making moon probe, only to find a social media influencer had already had a space picnic at their landing site.

When mass is extremely limited, and launches are rare due to cost, it makes sense to build super-expensive probes, because you're putting all your eggs in one basket, and you want that basket to do everything it possibly can when you get there.

IF Elon gets anything close to the launch rate he wants for starship, all the game theory that goes into the last fifty years of robotic exploration spacecraft design becomes obsolete over the course of a year or two. Need more mass, for fuel or ship? Tank or link-up in orbit. Worries about reliability change, because it's suddenly easier and cheaper to send a half-dozen spacecraft built for one-tenth the cost (or less) than it used to be to send a single super-expensive one.

You still need to pay for the team running the instruments, navigating the spacecraft, and pointing the instruments, but with more craft that are likely more "generic", that will hopefully become a little easier (and thus cheaper), too. One overall need will (I'm guessing, this is out of my field - I'm a space exploration fan) be to upgrade the Deep Space Network to handle more traffic.

> Juno, Curiosity, Perseverance

Were any of these as revolutionary as Voyagar, Pioneer, etc.? Perhaps i'm being a bit illogical here since anything can only be done for the first time once, of course...

> James Webb

Arguably designed and lead not by the >1980 generations.

> A trickle

Isn't that in fact it, or most of it, regarding revolutionary spacecraft?

> A new space age is definitely coming.

I hear the same was said just before the Space Shuttle era, and the thing after that, and about fusion reactors, and...you get the jist.

> but something, and I get a feeling that it's not just me, that there is this terrifying fear that gen x'ers and millenials just aren't as good as their ancestors.

I’m a Gen Z-er, so I’m very aware that my generation could be indicted here as well (time will tell), but I appreciate you sharing this comment for the simple reason that I’ve never heard anyone voice this perspective, despite it’s lurking potentially in plain sight. And this isn’t a blame game, systemic factors are surely at play. Interesting thought, though.

> I get a feeling that it's not just me, that there is this terrifying fear that gen x'ers and millenials just aren't as good as their ancestors.

Probably more accurate to say that millennials and x'ers just don't get the same budgets as their ancestors

Good point, but I do wonder why that is. Less money seems to be available for all public spending these days. Where is it even going to? Social care?

This strikes me as insanely underachieving. In ten years we should be able to do much, much better.

What do you suggest? And at what cost?

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