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Found 6 results

  1. A while back, I was leading a project to begin making and launching a small sounding rocket. Using my limited knowledge I created several documents to help educate the rest of my team which I thought might be nice just to show you all and see what is thought of it. Unfortunately, the project has been suspended indefinitely (I expect forever), due to the joy we like to call Coronavirus. As you can tell, I'm not exactly an expert, so a lot of information within there may not be 100% accurate. What you're going to see are the works I tried to make, so that rocketry is accessible for everyone. On a happier note, Project Origin, one of the documents you will read, is being taken on by me as a personal project, where I'm going to build up skills to develop a fully autonomous Sounding Rocket, and hopefully at some point a space capable rocket. For now though, enjoy.
  2. I'll keep this a brief introduction (because it's late here) and then maybe add to this post later... Having recently been reading up more about Aerospike Rockets, including coming across this superb article by The Everyday Astronaut: https://everydayastronaut.com/aerospikes/ I got to thinking about ways that Aerospikes could be made more useful (and potentially, gain a really solid edge over normal rockets- I think an accurate conclusion is that, on their own, Aerospikes are just a *little bit* better than normal rockets for atmospheric stages, but not really worth the extra R&D effort if their additional usefulness can't be demonstrated more convincingly...) One technology that is also, similarly, is just a *little* better in atmosphere, but not really worth the effort to fully develop right now, are air-augmented rockets (aka "Ducted Rockets", aka "Ejector Rockets/Nozzles" or "Rocket Engine Nozzle Ejector (RENE)" and related to "Ejector Ramjets" and multi-cycle applications like "Rocket-Based Combined Cycle (RBCC)" engines...) https://en.m.wikipedia.org/wiki/Air-augmented_rocket Now, one technology (Ducted Rockets) occurs entirely UPSTREAM of the rocket nozzle, whereas the other technology (Aerospikes) is a nozzle design- and doesn't have any particularly requirements upstream of the nozzle, other than an unusual (toroidal-shaped for Toroidal/Plug Aerospikes like the J-2T, a bunch of small rockets with seoarate combustion chambers and normally-shaped throats in a line for Linear Aerospikes like the XRS-2200/RS-2200) throat design in some cases, which is one of the sources of the heat issues that aerospikes have. By the way, here is some more background in the XRS-2200 in case it helps. Please note that, once again, the linear aerospike is s NOZZLE design- there are no special requirements for the many small combustion chambers that line the aerospike: http://heroicrelics.org/info/aerospikes/xrs-rs-2200.html So, I got to thinking, what if an air-augmented rocket (of the design type where you have a rocket combustion chamber empty into a mixing chamber with ducted air, then the mixed gases are ejected through a typical rocket throat and into the nozzle...) were combined with an aerospike nozzle instead of the usual bell-nozzle? I'm not just suggesting combining these two technologies for the heck of it: one of the MAIN problems with aerospikes is managing heat transferred to the throat and nozzle of the rocket from the exhaust-gases. Air-augmented rockets have cooler exhaust gases. Let me repeat this: air-augmented rockets eject a cooler exhaust gas mixture than do conventional rockets. Because the gases from the rocket combustion-chamber are mixed (diluted) with cooler air from an air intake system- which may be hot due to compressive-heating, but not NEARLY as hot as the gases of a rocket combustion chamber normally are- you get an exhaust gas mixture that isn't nearly as hot as you normally encounter for a rocket of similar Thrust. (Air-augmented rockets eject a larger mass of gases more slowly, with much of the mass coming from the atmosphere rather than the combustion chamber. Thus the exhaust is both cooler and slower-moving, but the EFFECTIVE ISP is *HIGHER* as you burn less fuel to get a given Thrust...) Since Aerospike Nozzles struggle with heat issues, ejecting a larger volume of cooler and slower-moving gases would be desirable- ESPECIALLY as Aerospikes become easier to keep cool at larger sizes (note that the size of a nozzle is based on the Mass Flow Rate, so air-augmented rockets normally have larger nozzles) due to scaling-effects from the Square-Cube Law (please see the Everyday Astronaut article and associated content for more on why larger rocket engines are easier to keep cool...) Aerospike Nozzles increase the nozzle-efficiency at higher ambient pressures of a rocket of most any type- meaning you get more Thrust at seal level (higher Sea Level ISP), while they ALSO have superb vacuum ISP (unlike s sea-level optimized bell nozzle: which they tend to outperform even at sea level in terms of ISP: usually by at least 20-30%). The usual drawbacks of aerospikes are issues with overheating that lead to the design of a heavier nozzle (even though an Aerospike is THEORETICALLY lighter-weight than a bell nozzle, you need so much extra mass for dealing with the heat issues they have that your TWR for the engine ends up being lower...) and added design cost/expense as Aerospikes are currently not at full tech readiness for use. In real-life, I'm also not aware of any issues stacking them (like in KSP) since it's not the actual nozzle itself that supports the weight in a stack arrangement- although as Aerospikes are prinarily atmospheric engines it's unclear why you'd ever want to stack them anyways... BUT, the bottom line is that if you combine aeeospike nozzles with Ducted Rockets, you might have fewer heating issues (due to the cooler exhaust), as well as better TWR due to not needing to invest so much mass in solving heat issues, and better ISP than either approach alone... Some details/math: - Ducted Rockets improve Thrust in proportion to the mix-ratio of combustion products and air. For instance, in a 3:1 mix you get, to a first approximation, a doubling of Thrust and Effective ISP (4 times as much exhaust mass, moving a little over half as quickly: due to E = 1/2 M V^2 and the same amount of energy being spread among 4x the mass. Note that this ignores 2 compounding factors: combustion of some of the residual fuel from a fuel-rich primary rocket combustion chamber, which adds a little additional energy, and change in the molecular mixture of the exhaust gases: which slightly decreases nozzle performance vs. a pure HydroLox rocket...) A 8:1 mix triples Thrust/ Effective ISP. - At the same time EFFECTIVE ISP increases (due to getting more Thrust for your fuel use), *actual* ISP based on Exhaust Velocity decreases: due to having slower-moving exhaust. The lower Exhaust Velocity (and pressure) means you don't need (and won't benefit from) as much expansion of your exhaust gases to reach ambient pressure, however, and ideal nozzle length/size is shorter/smaller for the Mass Flow Rate through the nozzle (though higher for the amount of fuel being combusted, as Mass Flow Rate through the nozzle is now many times higher). Large nozzles, low Expansion Ratios, basically. - Aerospikes can very easily achieve some rather impressive expansion-ratios, as they ALWAYS (both at sea-level and in vacuum) expand the exhaust stream to very near the ambient pressure, if large enough (at least, they do better at this than bell-nozzles, particularly at high ambient pressures...) But the more you expand your exhaust, the larger the spike/plug/wedge you need, and the more heating issues you have to deal with: so the lower need for expanding the exhaust of a Ducted Rocket (due to lower exhaust pressures/temperatures leaving the throat of the mixing chamber) is actually *particularly* beneficial for an Aerospike Nozzle, as it saves mass, and Aerospikes struggle with their TWR due to high mass... (lower expansion ratio required --> less nozzle mass needed) - Aerospike nozzles obtain higher ISP and Thrust, but lower TWR, than bell-nozzles (if your ISP and Thrust go up 20% vs. a bell-nozzle, your engine mass might rise 50% with an Aerospike rather than bell-nozzle, for instance...) - Most of the added mass is to deal with heat issues. To reiterate, Aerospikes are theoretically lighter than bell-nozzles, were heat not an issue. - Ducted Rockets also have low TWR's but high Thrust and ISP (TWR as little as 20% of a conventional rocket with similar Thrust, according to Wikipedia... But this is un-cited, and I think the author misunderstood: 5-6x the mass is NOT 20% the TWR if you double your Thrust as well, only about 32-40%...) This "short" prompt has gotten way out of hand, so let me wrap up my idea... Aerospikes increase both Thrust and ISP for the rocket chambers above them by a PERCENT, vs. a bell-nozzle. Keep this in mind... Ducted Rockets have higher base Thrust and lower true (exhaust velocity) ISP than conventional rockets, but higher Effective ISP, while mixing with air (once/if they switch to closed-cycle mode as they ascend to thinner air, which some designs such as RBCC are capable of, they perform similarly to a conventional rocket, but with a lot of extra weight...) When you combine an Aerospike and a Ducted Rocket, you should get an even higher Effective ISP (and less low true ISP) than before at high ambient pressures. For example, if you have 720 seconds Effective ISP at sea level with a HydroLox Ducted Rocket (a perfectly achievable number: you can more than double Effective ISP, and for instance get well into the 500's seconds with SOLID ROCKET BOOSTERS that have been air-augmented...) and you swap the bell-nozzle for an Aerospike- which augments ISP and Thrust at least 20-30%, you should get about 720*1.25= 900 seconds Effective ISP at sea-level with an air-augmented Aerospike rocket (note that TRUE ISP, based on Exhaust Velocity, was only about 180 seconds with a bell-nozzle, and 225 seconds with an Aerospike: but 75% of your working mass comes from the atmosphere, and so Effective ISP is 4x higher...) UNLIKE most airbreathing jets (except SABRE), this is easily a dual-cycle design: you can swap to closed-cycle mode and lose half your ISP at any time... (some Air-Augmented rocket designs are designed to allow you to preserve Thrust by increasing the rate of fuel-consumption proportionally, however...) The Effective ISP in-atmosphere is extremely impressive, and no less than a "normal" Aerospike outside the atmosphere (the RS-2200 was supposed to be capable of achieving 437 seconds on HydroLox, for instance... Not a great deal worse than the Space Shuttle Main Engines, at 451 seconds...) TWR is the main bogey of air-augmented rockets and Aerospikes both. But it's even lower for Ducted Rockets (probably about 30-40% of comparable higher-ISP conventional rockets with a good ducted rocket design, I'd guess around 25:1 - 30:1) than it is for Aerospikes (about 80-90% that of a comparable rocket is likely, once you consider that the RS-2200 was likely over-optimistic in its TWR: which would have exceeded the Space Shuttle Main Engines, at 83:1 vs. 73:1...) The mass penalty for an Aerospike Nozzle would likely decrease with a Ducted Rocket, due to having fewer heat issues. But even if it didn't, increasing that Thrust and ISP 20-30% would still only come at a fixed mass-penalty, attached to a much heavier (ducted) rocket engine. So TWR would fall very little (for a BIG, 20-30% increase in sea-level ISP), and might actually improve for the rocket as a whole (with the benefit of cooler exhaust-gases), by switching to an Aerospike nozzle... This is in sharp contrast to with a normal rocket: where Aerospikes impose a HEAVY (20% or so) penalty to TWR... For instance, let's say you have a standard 1 ton, 1000 kN sea-level Thrust rocket (TWR about 100:1, I will treat g at 10 m/s instead of 9.8 for easier math, as it won't affect the conclusions), 320 seconds ISP. If you make it ducted (air-augmented), mass might increase to 6 tons. Thrust to 2000 kN. TWR has now dropped from 100:1 to 33:1. ISP is now 640 seconds. Now, if you add an Aerospike to that normal (1000 kN) rocket, Thrust might've increased to 1200 kN, but mass to 1.5 tons (TWR now 80:1). ISP at sea-level from 320 to 384 seconds. To add an Aerospike to the ducted rocket, however, would add 2 tons to the mass instead of 500 kg, due to having 4x the Mass Flow Rate (4x the nozzle size), if heat issues were no way alleviated by the cooler exhaust gases, or scaling-benefits (because larger rockets have fewer cooling-issues with their nozzles, up to a certain point, Aerospikes experience less of a mass-penalty relative to Mass Flow Rate as you scale them up...) and you had the same mixture of exhaust-gases. However that last one is a bad assumption we CAN'T make here: the gases of the atmosphere (average MW about 29) are substantially heavier than the gases of a HydroLOX engine (mostly H2O, MW 18). So much so, that even though the Mass Flow Rate is 4x higher, the VOLUME of exhaust gases only increases about 150%, and the nozzle-size needs only go up proportionally. So, 1.25 tons is a more appropriate mass-penalty (nozzle is 250% as large as with the standard rocket, where mass-penalty was 500 kg) even WITHOUT any benefit from larger engine size or cooler exhaust-gases. If the Aerospike adds 20% to Thrust and Effective ISP due to higher nozzle-efficiency, like before, you would get 2400 kN Thrust, 768 sec ISP (192 seconds TRUE ISP, based on Exhaust Velocity). If mass went up 1.25 tons (worst-case scenario for the Aerospike) and sea-level Thrust/ISP only 20% (conservative end of the 20-30% range) you now have a 7.25 ton rocket, and TWR of 33.1 :1 (only *slightly* worse than 33.3 :1, before). However these are Worst-Case numbers (only a 20% increase in Thrust and ISP, no scaling-benefits, and no benefit at all from cooler exhaust gases). If Thrust and ISP increase 30% (to 2600 kN and 832 sec Effective, with true ISP of 208 seconds) then TWR is now 35.86 :1, HIGHER than before. If the mass-penalty is even a little less than before (due to scaling benefits or the cooler exhaust gases) then the TWR improves further. In short, an Aerospike Nozzle, Air-Augmented Rocket should have better ISP, and quite likely higher TWR, than a normal Air-Augmented Rocket. It should ease some of the design challenges of an Aerospike (mainly, these have to with heat-management, which should be helped both by cooler exhaust and larger nozzle size) and has the same intended uses (to improve atmospheric Effective ISP on a rocket) and so I do expect the two technologies would be complementary- each eases the other's challenges, at least slightly (Aerospikes suffer from heat-related issues due to having more surface area in contact with fuel, Ducted Rockets from low TWR...) Finally, an honorable mention of the uses of these technologies in spaceplanes- which accumulate a lot of speed (important for Ducted Rockets, which obtain higher ISP at higher speeds: presumably due to some effect of the increased mass or speed of the intake air) and spend a lot of time in the atmosphere, but still ascend beyond it: precisely the sort of ascent Aerospikes work best for (not to mention the reduced penalty for high engine mass on a spaceplane: which can reach orbit with overall vessel TWR less than 1 at takeoff, due to relying on Lift/Drag ratio for the initial takeoff, climb, and run for speed...) The high performance enabled by these technologies, and much greater simplicity than proper jet engines (despite using air for working-mass, Ducted Rockets don't burn it: and thus don't face issues with combustion instability at high speeds, as their primary rocket combustion chamber operates entirely like a rocket...)
  3. Kerbal-X Profile : Stefsilver43
  4. What do you think is the most likely contender to be the "next-gen" space travel method? We haven't gone much beyond chemical rockets In the duration of the history of space travel. I think EM drive could be a possibility but at the moment we don't know quite a bit enough about it to utilize it. Tell me what you think will be the alternative to chemical rockets in the comments!
  5. Colonization Has Begun The story of the journey and arrival of various craft at the Jeb, Bob and Bill's new home. Duna. Link at the bottom for full 2560x1600 shots if anyone wants them for a wallpaper or some shiz. Pictures Interplanetary Transfer of my first attempt at a Duna landing. Looks quite good. Bill Jeb and Bob stand proudly on the Duna surface, after about 8 hours of failures. Transfer of the permanent Duna habitat, with apparently a Halo in the background, over Duna. (The habitat is my own slight modification of segaprophet's Torus Hab.) The Hab with Jeb standing proudly atop it + newly landed rover. wait, whats that on left??? ERMAHGERD!!!!!!!! Nostromo, game over man, game over. FACE IT!!! Why aren't you scared Jeb, why? (The Nostromo is an awesome way of getting around the new planets to test for atmospheres and gravity.) Here is a link to the album and the full res screens:http://imgur.com/a/NvVta#0 And here is my other imgur album for KSP: http://imgur.com/a/MXOIp#0 Comments and feedback would be very much appreciated. Also, would love to know how to get spoilers to work?
  6. Following the apparent loss of the last thread, I thought I should make a new one. This is for discussion of model rockets, be they functional or not. I'll kick off with the latest images of my home-made rocket, which I'm beginning to re-build. I've not worked out how to do spoilers on this damn new forum layout, and it doesn't resize images for you, so here are some crappy thumbnail links. Yes, that is a 10p that's soldered into the end. Here is a nice shiny new image of the shiny brass fins. I need moar shiny. Hopefully we'll get more updates on the other rocket projects from the old thread, I loved those!
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