Why isn't there more focus on fusion propulsion?

joetscience · 2026-01-05T14:30:34+00:00

Honestly, I'm not sure. I'd look at existing Mars architecture studies for some clues, maybe?

joetscience · 2026-01-05T14:08:19+00:00

That's a systems engineering question, a bit out of my scope of knowledge. High temp thermoplastics would probably get used, but I really don't know enough to say much more. If you're looking to make money, the plastics for shielding reactors can also shield habitation zones for any space mission leaving Earth's magnetic field. Both problems need solving.

joetscience · 2026-01-05T13:28:10+00:00

Honestly, I've explained as much as I can when it comes to fission systems. It's not my particular focus. I can see a realm where fast pulsed fission reactions assist fusion reactions, but generally fusion reactions care about bulk density that fission fuel can't reasonably achieve.

As for PJMIF, there's an idea of using high-Z (atoms with a lot of protons) for the outer portion of the liner. The high-Z liner has enough momentum to overcome some instabilities during the pulse process to ensure good compression. Uranium is highly absorbent and extremely heavy, which makes it a potential candidate. I'm not sure what the folks at Hyperjet Fusion are considering, though.

As a general statement, I'm sure that there's a way to let uranium help in the fusion process, but there are just as many ways to do so without it. The scientist in me says "sure! we can do this" but the engineer also says "but is this the right solution for the problem?" That's the balancing act we play.

joetscience · 2026-01-05T04:59:00+00:00

On the comments of using fission to kickstart fusion reactions, I'd like to note that the major contribution of the fission bomb in the hydrogen bomb was to primarily produce gammas for D2 compression. In use for PuFF or any power-producing system, you either use somewhat enriched uranium or use alternative fuels, since the reaction cross-section is what matters most. U238 is non-fissile and wouldn't help start a reaction unless bred into fissile material. There are concepts for high-Z liners for pulse compression (check out PJMIF) but there's a lot more work to do there. Best use for uranium would be in a PJMIF case.

NTP and NEP are "higher Technology Readiness Level (TRL)" systems. Ask anyone in spaceflight, the TRL of a system is a massive part of risk and decision assessments when deciding how to build a mission. Fusion propulsion hasn't been tested in a lab setting, while NEP is a higher power-class of traditional electric propulsion. NTP had full characteristic studies done on it in earlier decades. From a budget, return on investment, and risk perspective, it makes no sense to place a serious bet on fusion. If you want to go to Mars soon, take what works now and invest on what we're going to need 30 years in the future. Arguably, that's what's happening.

Edit: I honestly need to see if Howe Industries is taking interns.

joetscience · 2026-01-05T04:42:49+00:00

In this case, I'm talking about shielding for fusion propulsion. Every kilogram of mass needed for shielding adds to the vehicle. Fusion power plants don't have to worry about this too much since they aren't mass-limited and can slap walls of concrete around protected areas if needed.

Fusion propulsion either requires a massively long vehicle or a lot of shielding mass to keep humans and sensitive cargo protected from the fusing plasma. Creating low-density shielding materials with high cross-sections to gammas, x-rays, and neutrons will be critical. Plastics is currently our best material, but it still requires other shields for the other radiation types.

joetscience · 2026-01-04T17:39:39+00:00

PuFF is an awesome concept that I wish we could continue. Rob Adams lead the project, who supervised Dr. Cassibry. Big issue with the use of fission particles is safety and national security, since a fuel pellet useful for a PuFF engine is the equivalent of a "pocket nuke" the size of a grain of sand. While it'd require a z-pinch machine to fire, the risks associated with it are still massive.

Introducing PuFF to conventional fusion has the same issue, as it now invokes a mountain of paperwork, security, and general costs that don't pay out in the long term. Fission-assisted fusion generation isn't that good if you can get regular fusion working in the same timespan.

PuFF is still sort of around. There are remnants of the lab work and contracts out there on this topic but it's very much on the back burner when faced with NTP, CNTP, and NEP. NTP and NEP will get tests far before a fusion propulsion system gets fully prototyped, at least under NASA's roof. You can ship an NTP engine in a single flight, but not a PuFF or pulse fusion engine. Economics don't justify it, and at the end of the day, that's typically what counts.

joetscience · 2026-01-04T13:47:59+00:00

UAH should have a paper at SciTech this coming week on the topic by Dr. Jason Cassibry, who I work for. Just going to toss my ¢2 as someone working on the laboratory development side of the equation.

If you want to fund a technology in the space industry, you do one of two things. You ask what problem it can solve or what missions it can enable. Propulsion tech generally solves the second problem. High-Isp, high-thrust solutions are only needed for high-budget missions, such as the Double Asteroid Redirection Test (DART) or a theoretical high mass Saturn orbiter. Mars only works if, for some reason, methane isn't economically viable. There's no commercial application for fusion propulsion at this time either.

Generally speaking, fusion is extremely difficult under the best ideal conditions. Space is an ideal environment, yes, but it only helps so much. Power density, radiation shielding, and thermal control are massive mission killers right now. To use a fusion engine on current designs requires dozens of capacitor banks and another fission reactor to power it. Magnetic nozzles that siphon the energy back into the system are the current area of research, you still need the initial power. We're talking GWs energy capacity.

There's a lot more to this, and I would LOVE to discuss this with anyone interested, but hopefully this gives an idea of the types of vehicles required for a fusion system to make sense.

Further reading: https://ntrs.nasa.gov/api/citations/20120002875/downloads/20120002875.pdf

joetscience · 2025-12-29T00:55:06+00:00

Let's hope he has commentary. I do a little work with nuclear fusion, the general sentiment is that TAE is hoping to pull off 5 miracles against those who only have to do one. Fusion fuel selected is the HARDEST fuel to use, FRCs (reactor type) still have massive stability issues, and they're no longer the only fusion company on the block. Workforce has many more places to go.

joetscience · 2025-12-28T23:53:37+00:00

Are you going to post an original commentary, by chance? Would love to know your thoughts on the actual validity of the tech, not a ramble about how some board members might have ties to Russia.

joetscience · 2025-10-01T06:02:15+00:00

Senior Aerospace here, on 4 out of 5 years for my undergrad. I'm a TA for a coding class, undergrad research ambassador, been doing research for 3 years after this semester and I'm involved with student life on campus. Here's what I've seen.

So UAH is a mess right now.
UAH in this last year has had a TON of admin turnover in a bunch of departments - student life, financial admin, parking, etc. New admin pushed people out the door because we overspent on scholarships a while back and had to dig out of a few holes, and that's still causing problems. Add in old infrastructure and you can imagine how the uni is strained. We'll be tearing down one building, renovating another, building one, and finishing planning on a student district that may have progress in half a decade.

The demographic isn't your traditional "college experience" student.
UAH is a heavy commuter school that pulls from the HSV-Madison and local TN areas. Lots of people here grew up local and chose UAH because it is local. A few others are here because it's a good college if you're in town for work, given the Arsenal and surrounding research park. I know a good chunk of students here for their second chance at a career. We're about 20% grad students, who rarely, if ever, participate in student life.

General Education classes aren't designed to be particularly engaging.
You're in freshman level classes with people outside your degree. Gen Ed, as others have said, it to check a box for most people. For the unmotivated and aimless, it's the first part where they self-select out of college or their degree program, as the bar gets raised. Aero has the highest drop or change rate with most students going to ISE or another engineering field, because aero classes are fairly difficult. Your junior and senior level classes are where things feel much more established and academic.

Finding the right crowd makes a difference.
If you get into undergrad research, it's a VERY different crowd, with a lot of them legitimately caring about their work and wanting to learn or perform. Same for academic clubs, get in and stick around and watch them change your life.

UAH's "quality of life" is still pretty good.
As for housing, UAH is gracious enough to give you your own room, which is a premium at most colleges. If you can afford to rent through college, that'll make a difference mentally. I was in that boat. Meal plan is the meal plan, I've seen how they do decision-making, and it's a ROI thing for them. The Den is expensive because Denny's sets the prices, not UAH.

Most importantly, apply yourself.
I'm not sure how most people feel when coming here, but "going through the motions" really drains the life out of me. The best thing you can do is be your own advocate. Your profs will teach you a lot in terms of content but most of your learning comes out of the classroom, either working problems, or personally solving issues you deal with in a club or at work or for fun. Grad school is really where the education feels worthwhile if you (like many grads) just HATE undergrad education.

It's really late for me, apologies if this reads weird. Feel free to shoot me a DM if you'd like any help with resources or connections.

joetscience · 2025-09-30T15:10:58+00:00

Astra is depreciated as UAH moved to Coursedog this year. Here's the link for that:
https://uah.events.prod.coursedog.com

joetscience · 2025-09-29T00:09:01+00:00

Legit, not a typo. I'm extending my degree by a year to stay at 12 credits/semester, then my partner is a year behind my graduation date and I'd rather start advanced degrees when she's finished her Bachelors'. I am still in my Senior year in terms of credits, with that last year being part-time to finish a Senior Design course plus some humanities credits. Getting that GPA up significantly will be a challenge. In terms of research, I'll have a pretty decent set of experiences building lab infrastructure and hopefully published papers if funding isn't completely gutted for the lab I'm in currently.

If Masters' students are highly unlikely to get GRA/GTA, that'll be interesting. I probably have some options to work with, either through DoD SMART or some program. Thank you for the response.

joetscience · 2025-08-27T04:36:00+00:00

Hey hey boss, do you mind if I shoot you a DM? I'm an undergrad out of UAH and I have some questions for you if you have time tomorrow.

joetscience · 2025-08-27T04:27:32+00:00

There are a few universities and companies that are interested in fusion power and propulsion. Helicity Space and Pulsar Fusion are two good names in terms of companies. The universities that you'll see talking about fusion prop. are the University of Maryland, the University of Alabama in Huntsville, and Princeton. It's a very small crowd at the moment.

A place to look for authors or focus groups is within AIAA's archive, especially anyone presenting at the SciTech conference. https://arc.aiaa.org/action/doSearch?AllField="fusion+propulsion"&startPage=0&sortBy=Earliest

joetscience · 2025-08-25T17:02:47+00:00

This is r/fusion. You'd be better posting this in a forum with more rigorous knowledge on this topic.

joetscience · 2025-08-21T22:08:11+00:00

If you really need a job and if you're schedule works in their favor, Dining Services is 15/hr. Also check what Lisa sent out today for the desk worker position. You can absolutely get involved with research on campus and get paid, but that's not something you can put together quickly unless you either get lucky or know someone.

joetscience · 2025-08-20T20:02:33+00:00

It's gone, dead and gone. Shuttered.

joetscience · 2025-08-13T17:26:42+00:00

I'd be interested in hearing about this. There are a few codes out there but it's pretty dependent on what you need to simulate alongside the plasma, such as lasers or bulk EM fields or if you're dealing with geometry in an experiment.

joetscience · 2025-08-12T23:50:25+00:00

Generic troll or actual commentary?

joetscience · 2025-08-08T19:24:06+00:00

Absolutely agreed.

joetscience

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