Comment on [DISC] Houkago, Bokura wa Uchuu ni Madou - Chapter 2
wjs018@ani.social 2 days ago
That Opportunity impression was incredible. The little rover that could! The 90-day mission that lasted 14 years!
However, whenever Opportunity comes up in conversation, it makes me think of it ill-fated (but still incredibly impressive) twin, Spirit. Then, that makes me think of this xkcd and I get sad…
I took a close look at the chalkboard behind her on the first page and I don’t think there is much of anything actually rocketry related on there, just gibberish. The only two things I could pick out is the small diagram of a rocket taking off in the upper right and then the paper attached to the board in the lower left stating their rocket’s specific impulse value is 216 s.
The specific impulse can roughly be thought of as the efficiency of the rocket. A value of 216 s is a bit on the low side, but not bad for a solid-fueled rocket. For comparison, the solid rocket boosters on the Space Shuttle had a specific impulse of 250 s. So, this value seems perfectly reasonable for what amounts to an amateur club that can’t optimize the way that a national space program could.
SatouKazuma@ani.social 1 day ago
Thanks for chiming in on the rocketry stuff. Had you not done so, I’d have been tempted, as an actual aero engineer by background. Of course, should also be mentioned that the SLS solid motors have much more fuel as well. Though, I~sp~ is generally not of that much importance on lower stages, in any case. That’s a better performance metric on upper-stage, and more specifically vacuum engines, since (as you call out) it’s a measure of efficiency, and efficiency doesn’t much matter if you can’t get off the launch pad.
wjs018@ani.social 1 day ago
That’s a good point about I~sp~ not mattering as much lower in the atmosphere. This isn’t my field, but I know enough physics and have played enough Kerbal to know what to look for on the board.
Just a fun aside, while I was in undergrad, we covered the rocket equation in one of my mechanics courses. The textbook we were using was quite old, so a bunch of the questions were about the US/USSR launching rockets at each other.
SatouKazuma@ani.social 23 hours ago
Are you also looking forward to Kitten Space Agency?
wjs018@ani.social 23 hours ago
TIL about Kitten Space Agency. Now I am!