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Old 11-15-2018, 09:10 AM   #11
Fred Brackin
 
Join Date: Aug 2007
Default Re: Are TL4 'Rocket-Pack's Possible?

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Originally Posted by Phil Masters View Post
R

Getting any kind of useful control in rocket-powered flight takes you to TL(4+2), pretty much by definition; TL4 black powder rockets burn until they stop (which can mean "burn out" or "explode"). Actually, getting good enough glider control to make safe landings more likely than not probably makes the thing TL(4+1), minimum.
Any TL solid fuel rockets burn at maximum power until they've burned out. A rocket motor you can shut off or regulate the thrust on is a liguid fuel or hybrid pretty much by definition.

Historically, even vaguely reliable solid rocket motors are very late TL6 or more likely early TL7.

Also historically controllable gliders are early to mid TL6 and it doesn't hurt if your name is 'Wright". Before Orville and Wilbur and even for a little while after no one else knew what they were doing in the control department. If you wonder I'm fairly sure that Santos-Dumont had the Luck advantage.
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Old 11-15-2018, 09:12 AM   #12
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Default Re: Are TL4 'Rocket-Pack's Possible?

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I'm 90% sure that these already have (3e) stats in one of the GURPS Alternate Earths books. However, by brain can't sort out if it was Romans, Aztecs, or Ming using them.
There's an actual rocket pack in Steam-tech. Wear asbestos trousers and have an Extra Life handy.
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Old 11-15-2018, 11:46 AM   #13
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Default Re: Are TL4 'Rocket-Pack's Possible?

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I'm 90% sure that these already have (3e) stats in one of the GURPS Alternate Earths books. However, by brain can't sort out if it was Romans, Aztecs, or Ming using them.
That’d be the jactavolantes of Rome Aeterna (AE1). The important stat with them is that the pilots are automatically manumitted with citizenship if they survive a five-year term of service.

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Any TL solid fuel rockets burn at maximum power until they've burned out. A rocket motor you can shut off or regulate the thrust on is a liguid fuel or hybrid pretty much by definition.
I believe that somebody may have tinkered with a solid fuel motor with a cut-off option. Basically a built-in fire extinguisher, in other words. I don’t think it was ever claimed to gave worked.

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Also historically controllable gliders are early to mid TL6 and it doesn't hurt if your name is 'Wright". Before Orville and Wilbur and even for a little while after no one else knew what they were doing in the control department. If you wonder I'm fairly sure that Santos-Dumont had the Luck advantage.
I suspect that Santos-Dumont and others were getting there, but I won’t guess how fast. Respect to the Wrights, who were way out in front of the race, but I don’t believe they were unique geniuses.
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Old 11-15-2018, 11:58 AM   #14
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Default Re: Are TL4 'Rocket-Pack's Possible?

The way you shut off a shuttle SRB in an emergency was to blow the top cap off so you had thrust in both directions. Never actually used.
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Old 11-15-2018, 12:37 PM   #15
Anaraxes
 
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Any TL solid fuel rockets burn at maximum power until they've burned out.
It is possible to vary the maximum over time, though, casting variations on your rocket fuel burn rate and/or area in a pre-planned way. One application is for increasing the range on something like an anti-tank missile, which needs a large boost thrust, then less to maintain cruise, so cutting the thrust after a bit of flight means the fuel lasts longer.

It's also possible to build solid fuel engines with controllable variable thrust. Varying the nozzle throat area can give you around a factor of 10 variation in the thrust. There's also a technique for modifying the fuel burn rate by pressing a catalytic grating (a "heat knife") against it. That plus varying the nozzle area can give you 100:1 thrust ratio.

I suppose those sorts of ideas haven't gotten as much attention or development as they might, because it's so much easier to control thrust with a liquid-fueled rocket.

And of course if we're talking TL4, we're stretching things even to get the rocket pack to fly, without introducing even higher tech chemistry and manufacturing precision. But there's some grounds for technobabble for your genius Gadgeteer if you want it.
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Old 11-15-2018, 01:05 PM   #16
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Default Re: Are TL4 'Rocket-Pack's Possible?

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I suspect that Santos-Dumont and others were getting there, but I won’t guess how fast. Respect to the Wrights, who were way out in front of the race, but I don’t believe they were unique geniuses.
The Wright's advantage wasn't in overwhelming genius though intuiting that they needed to invent the wind tunnel first was very sharp. The advantage was focussed in the area of controlability. The Europeans had better engines but their control surfaces were primitive.
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Old 11-15-2018, 01:15 PM   #17
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Default Re: Are TL4 'Rocket-Pack's Possible?

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It's also possible to build solid fuel engines with controllable variable thrust. Varying the nozzle throat area can give you around a factor of 10 variation in the thrust. There's also a technique for modifying the fuel burn rate by pressing a catalytic grating (a "heat knife") against it. That plus varying the nozzle area can give you 100:1 thrust ratio.
There are also electric solid fuel rockets (TL8) that can be throttled.
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Old 11-15-2018, 01:17 PM   #18
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However, the first answer means that, if you're talking about a cinematic clockpunk game, please feel free to have rocket-launched glider recon and assault forces. Though even there, they should probably all to a man have the Daredevil advantage.
Background for a Steampunk game actually. The campaign is going to be set on one of several habitable moons of a gas giant, and I figure that causes someone proposal for some crazy flying machine tends to get people saying 'Shut up and take my money' instead of scepticism.


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To answer the thread question; if you mean "Build a TL4 glider with a black-powder-rocket-assisted launch", then the answer would be "probably", in the sense that you can gather enough black powder to throw someone into the air, and glider wings that could in principle enable a skilled pilot to get back to the ground again alive. If you mean "Could you do this to any useful effect in a faintly realistic setting?", then the answer would be "aaargh, those poor test pilots and their families". I'm pretty sure that you'd regularly kill off pilots in routine use; the casualty rate in the development process would be... unspeakable. Even by TL4 standards.

Getting any kind of useful control in rocket-powered flight takes you to TL(4+2), pretty much by definition; TL4 black powder rockets burn until they stop (which can mean "burn out" or "explode"). Actually, getting good enough glider control to make safe landings more likely than not probably makes the thing TL(4+1), minimum.
I'm thinking more of a post-jump then a proper launch, and no steering other then maybe control surfaces.
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Old 11-15-2018, 04:34 PM   #19
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Both chemcial rockets and gliders were TL 4 inventions but nether were very advanced in that time period. Most gliders were small models that were difficult to translate to larger sizes due to weight of materials and gunpowder rockets were a bit unstable. Later we worked out engineering principals that let gliders support weight better and with more stability and stabilizers that made rockets burn more evenly but for nearly a century those advances were made with the same technology, it was just a matter of refinement. It could be possible for someone who is just extraordinarily bright with a lot of time to experiment could have made weak but stabilized rockets and lightweight stable gliders that weren't gigantic. without modern engineering concepts like compressed jets or lightweight materials like aluminum primitive jet gliders would just barely have enough power to get a man aloft and would probably only give you about 10 seconds of thrust. Gliders would be man-portable but delicate and bulky, like carrying around a giant dragon kite broken down.
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Old 11-15-2018, 05:36 PM   #20
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Default Re: Are TL4 'Rocket-Pack's Possible?

Personally I figure that someone with access to bamboo and a lot of silk might be able to make a working glider, those materials are noticeably lighter the wood and cloth that they would normally have been made out of.
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