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Comment by bunderbunder | Hacker News Reader

Surprised to see the photo of the rocket back on the ground, with the nose cone still attached by some sort of rope.

It would appear that the biggest difference between this thing and an Estes rocket is the size?

From a simplistic standpoint, the only difference between the Space Shuttle solid rocket boosters and an Estes rocket was the size.

In reality, a solid rocket motor at this scale is very difficult to manufacture reliably, and with the thrust profile that will provide the performance that you need to reach your goals.

That's not to mention the avionics in this rocket, the materials (carbon fiber laid down by the students), the deployment systems for the nose cone, and the manufacturing of the nozzle engineered to provide adequate thrust through the entire range of atmospheric pressures.

To be fair, though, all of these are solved problems that are easily overcome with budget and outsourcing. Ex. you can buy quality carbon fiber tubes in whatever diameter and thickness you want from multiple suppliers, contract out the nozzle based on existing designs to a CNC milling or titanium SLS printing company, purchase aerospace-rated avionics packages, etc. The impressive part here is that the students seem to be doing a good chunk of these things mostly in-house and with less money than it would normally take.

Sure you can contract out the work, but paying for someone else to make a rocket you launch doesn't really qualify you to say that you did anything. It also doesn't teach you anything, so what's the point?

Most of what you work on in college is solved problems, because college is about learning and not about original research.

At a very high level, yeah, most every rocket is just a tube that's pointy on one and and goes fwoom at the other. But this seems like it might be more similar to an Estes rocket than just that. The space shuttle's solid rocket boosters don't deploy the parachute by ejecting the whole nose cone, which is attached by a shock cord, and letting it drag the parachute out of the rocket's body.

That's really what I was reacting to. That, not only did they get to space, but they apparently got to space using a much more rough-and-ready design than I would have expected. The hacker in me loves that.

Space shuttle is rocket with wings and additional 2 million parts.

Bigger also means they can put more sensors onboard (though you can do quite a bit with Estes). But even the Shuttle SRBs used parachute recovery, although without popping the nose cone.

Biggest difference I can think of is that the SRBs had a gimballing nozzle. From photos on the project website, it looks like fins are fixed too. I don't know the law around it, but guess adding control surfaces would make this into a guided missile!

https://www.uscrpl.com/traveler-iv http://www.uscrpl.com/updates/2019/5/22/traveler-iv

I've done a small amount of model rocketry. My interest in the hobby basically ended once the various old-timers I had access to convinced me that any sort of guidance beyond extremely basic horizon tracking would indeed amount to ITAR controlled missile tech.

My interest ended when I couldn't afford to build the model rocket kits I wanted to build (I was a kid with a very limited budget). When I got older and had money, the lack of any convenient launch sites probably discouraged me from getting back into it.

you're pretty much right on. There's not a whole lot of difference. Where it gets hard is holding it together past Mach 1 and building it in the first place. Misaligning a fin on an estes rocket is no big deal, misaligning a fin on this one would mean near-instant destruction. Also, materials, cardboard isn't going to cut it. At this scale the best option is hand rolled carbon fibre which is an art in its own right.

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