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About Starman4308

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  1. If you're looking for thrust in a liquid motor, the two key variables are going to be specific impulse and propellant density. Specific impulse counts because you get more impulse per kilogram of propellant moved into the combustion chamber. Density counts because you can get more kilograms of propellant into the combustion chamber. The practical propellants with decent Isp and high density are either solids (primarily ammonium perchlorate composite propellant), or the major hypergols (hydrazine, MMH, or UDHM as a fuel, dinitrogen tetroxide (NTO), mixed oxides of nitrogen (MON), or inhibited red fuming nitric acid as the oxidizer). The impractical king of this is the aforementioned mercury-based rocket motor, which has terrible Isp but makes up for it in overwhelming density. As to the original question, of what you want in an on-orbit interceptor, that would basically mean MMH/NTO or MMH/MON. Reasonable specific impulse, storable without complicated insulation/refrigeration equipment, does not have tons of mercury, and there already exists a wide variety of RCS motors for the stuff, etc. The primary issue is that it's an on-orbit interceptor, meaning you're locked into a specific orbital plane. This dramatically reduces your options.
  2. At least with Bon Voyage v0.14.8 on KSP v1.7.3, there's an issue where, on picking a target on the map, latitude and longitude are mixed up. This leads to lots of "path not found" errors, as there's a nontrivial chance that you're trying to enter a latitude of greater than 180 degrees. It's possible this only occurs when selecting a site of longitude 180-360 degrees; I forgot to test that. EDIT: The temporary workaround is to enter lat/lon manually.
  3. I get the opposite behavior (right is preferred) in Surviving Mars. The degree to which I do not care about this "bug", though, cannot be overstated.
  4. You can certainly make a complicated hydrocarbon mix. With enough effort put into it, you could probably make something that matches the RP-1 specification. The major question is: why? The RP-1 specification is the way it is because it is (relatively) easy to make it from a feedstock of petroleum. If you don't have access to petroleum, though, it would be needlessly complicated. There are valid reasons to try to get bigger hydrocarbon chains than methane. More extended chains can be made with more of the easily available CO2 than difficult-to-acquire hydrogen. More likely, however, you're going to see something that isn't RP-1, but a new specification of "a mix that can be readily made from CO2 and hydrogen".
  5. First: I am seriously enjoying this conversation.There is a minimum of talking past each other. The fundamental issue I see with SLS is that it can't practically do any of the big missions (e.g. ARM, lunar landings, Mars) without developing the technologies that obsolete the whole concept of SHLVs (e.g. LEO assembly, tugs). Ares V, possibly coupled with a proto-COTS instead of Ares I (I fully agree on Ares I being a poor idea), was big enough to at least do single-stack lunar landings to compensate for its presumably slow cadence. If any single thing should have been preserved from Constellation, it's the Ares V, instead of its awkward smaller cousin the SLS. *I don't actually know what cadence was projected for Constellation. I could be wrong, but I suspect it would've wound up being similar to SLS. I'd also argue that there's some sense in proposing the Ares I. It fulfills the purpose of separating crew from cargo, and would have been a reasonably cheap way to get the astronauts to space. Later studies by the Air Force indicated "hold on, the SRB exhaust will murderdeathkill any abort", and SRBs are in general probably less safe, but it wasn't an insane idea... just a sub-optimal choice that was fortunately cancelled before astronaut lives were risked on the thing. Also (despite my name: I swear I had this screen-name long before FH ever flew), I'm pretty skeptical of the Starship/Superheavy. There's a chance it might work, but I'd rather not bet the farm on it anytime soon. What I would argue is that, between FH, New Glenn, and Vulcan/Vulcan Heavy, there's a pretty solid chance we'll be able to throw some heavy-duty modules into space with commercial LVs. With the immense flaws in SLS, I'd rather go for missions based on assembly of mid-sized modules on multiple commercial HLV launches than continue pouring money down the SLS drain. Developing LEO assembly and/or tugs would also fit well into the mandate of developing new technology to promote the commercial sector. EDIT: And OmegA. Everybody always forgets about OmegA, even me. Finally: I'm given to understand SRBs are really not the greatest choice for LVs period; LRBs are quite cost-competitive. What they do do is keep around institutional knowledge on how to build Totally Not ICBMs. For a purely cargo SHLV, on which astronaut lives didn't rest, I'd be willing to live with SRBs courtesy of that... though my inner KSP player wants to swap those out for Pyrios boosters.
  6. The response to that would be "why human-rate it?" I've never seen a convincing reason why the people have to go up on the same can as the cargo. Human-rating the cargo can makes the cargo can more expensive, and putting people on the cargo can means putting humans closer to unnecessarily large quantities of highly energetic propellant and complicated LV. On top of that, an LEO taxi could be built on very well-proven commercial medium LVs, instead of needing a very low-flight-rate vehicle that's harder to ensure the reliability of. We should have had Commercial Crew a long time ago.
  7. If you really want a Shuttle-derived vehicle with minimal modifications, you would have gone with Shuttle-C. The DIRECT proposal was probably doomed from the start: you're making enough modifications to the baseline design that you would have seen serious modification creep courtesy of politicians... like we got with the SLS. "Why don't we just go with 5-segment boosters? Why don't we go with 4 engines? Why not add an upper stage?". All of which sound reasonable individually, but were guaranteed to funnel more and more money to developing the rocket with no need to actually produce results. With Shuttle-C, the only modification is replacing the Orbiter with what amounts to a tube. Same fuel feed, minimal pad modifications, etc.
  8. While there is a very amusing KSP video to that effect, I was thinking more along the lines of Pyrios boosters, powered by simplified F-1B engines. I see a few issues with that view of things: 1) SHLVs are not generalist vehicles. The commercial sector has generalist vehicles capable of a very wide variety of missions, ranging from COTS/Commercial Crew, to deep-space probes, to mundane weather/communications/navigation satellites well handled. The only thing you need SHLVs for is to make super-heavy missions like manned BEO exploration possible with a minimum of assembly. 2) The SLS is underbuilt for most conceivable super-heavy missions. It can't do a single-stack lunar landing, meaning assembly is required... and if you admit "some assembly necessary", then you run into schedule/tempo issues, and running the mission with commercial LVs starts to look more attractive. An Ares V would've been a semi-decent option: stupidly expensive, but big enough for single-stack lunar landing, giving it a guaranteed SHLV niche, and breathing room to be used for other missions like superheavy probes or assembling a Mars vehicle. SLS sits right in that awkward zone where it's too big for run-of-the-mill tasks, but not quite big enough to have a guaranteed niche. 3) An expendable SHLV was likely a decent choice in the Bush Jr/Obama era, when options commercial HLVs were fairly limited and expensive. Unfortunately, instead of either pressing through on Constellation or cancelling it outright, we got a compromise that mostly just serves to funnel money to Shuttle-era contractors without being a good solution to anything.
  9. Not exactly. If anything, I'm pretty sure higher Isp boosters (with nothing else changed) would produce less peak force on the coupling joints. At launch, a pretty big fraction of the boosters' force is spent accelerating the boosters themselves. As propellant burns off, the fraction of thrust transmitted to the core increases as the boosters become a smaller fraction of the overall mass. If your advanced boosters have the same thrust, dry mass, and full mass, and you change only specific impulse, you wind up extending burn time. With a later BECO, the core stage has burned off a bigger fraction of its mass, so at burnout, the booster/core mass ratio is higher. That said, SLS definitely has a wonky configuration, with underpowered, undersized upper stages, SRBs that burn out too soon for a long-duration sustainer stage, and far too much of the dV pushed onto said underpowered sustainer stage. Realistically, if one had to use the RS-25s as sustainers, I'd probably go for large kerolox boosters, and see about reviving the J-2 as an upper stage engine. Which, now that I think about it, basically describes an uprated Ares V rocket with Pyrios boosters instead of the old Shuttle SRBs. Maybe I have too much of a fascination with reviving Apollo-era hardware, but it's not like there's a lot of choice for SHLV-scale engines unless you go clean-sheet.
  10. 1) There are several reasons why SLS would turn out more expensive than the Saturn V. There was significant political pressure to make the Saturn V succeed and make it succeed fast, where there is no such urgent, pressing drive for SLS. The S-V used relatively simple gas generator engines (F-1, J-2) rather than the insanely complicated RS-25 engine. Its operational tempo was much higher than SLS, and shared an entire stage with the Saturn 1B. The military-industrial complex was not quite as entrenched, and not quite so practiced in sucking every possible drop of money out of cost-plus contracts. 2) It's not like the Shuttle was a roaring success of cost-effective launch either. The best thing that can be said about it is that it was an attempt to push down the cost of space access, whereas no such claim can be made about SLS. 3) Redundant assembly lines are infrastructure. 4) Even though that post of mine you quoted had nothing to do with Starship/Superheavy, it's still nonsensical. There is a very clear business case for it: rapid and total reusability. It might not work. Its operational costs are almost certainly going to be higher than what Musk predicts. But: even if Starship/Superheavy costs 10x more than claimed, it's still cheaper than F9, Atlas V, etc, while clearly having far more capability. SpaceX doesn't even need to come close to Musk's estimates to obsolete anything currently out there save the cheapest light LVs (e.g. Electron). Just because it's not a guaranteed business case doesn't mean there's clearly a business case for it. What you're claiming there would be that Concorde was doomed by economics... if Concorde was actually predicted to be over 10x cheaper, faster, quieter, and safer than its subsonic competition. It might not pan out, but if there was a decent chance you could make a supersonic plane 10x cheaper, faster, and quieter than its subsonic competition... why not give it a try? This is not the SpaceX thread. It's the SLS thread. Your extreme dislike and skepticism of Starship/Superheavy has nothing to do with the trainwreck that is SLS.
  11. SpaceX, ULA, and most likely Blue Origin and Northrop Grumman (with OmegA) can get reasonably large payloads into space for a tiny fraction of the cost of SLS, which is a fairly objective criterion. On top of that, both SpaceX and ULA have well-proven boosters (Falcon 9/Heavy, Atlas V, Delta IV Heavy)... and if you account for the planned cancellations of Atlas V and Delta IV, that literally only leaves SpaceX as a long-term choice with a fully proven booster. Vulcan Heavy, New Glenn, OmegA and the Superheavy booster do not quite yet exist, but are based on well-understood technology. The Starship is highly experimental, but even a fully expendable Starship is likely to cost a lot less than SLS. Even if Starship/Superheavy didn't exist at all, SLS still compares unfavorably to extant commercial HLVs (i.e. Falcon Heavy, Delta IV Heavy), and even less favorably to highly-probable near-future HLVs (i.e. Vulcan Heavy, New Glenn, OmegA). What I'm seeing isn't any objective reason to explain why SLS is a good choice for NASA, but rather a lot of hate for Elon Musk and Jeff Bezos, leading to a dismissal of anything they do... and utterly ignoring ULA and Northrop Grumman. EDIT: Okay, if I'm being honest, there are a few objective factors in favor of SLS... just not enough to outweigh its downsides. Yes, it has more single-launch capability than anything else. Yes, it has a pretty enormous fairing. Yes, it can, with a single launch, transport astronauts to what is technically a lunar orbit. These factors, however, are outweighed by issues like its enormous expense, its slow launch cadence, and the risk posed to astronauts by using such an untested vehicle that still possesses some of the safety flaws of the STS (e.g. a core stack that cannot lift itself without SRBs, enormous SRBs, enormous amounts of highly energetic hydrolox propellant).
  12. "individual contributions obviously vary based on income." As an example, as a PhD student, I pay substantially less. Other than off the cuff rounding $5B/300 million to $15, the only mistake I made was forgetting that children and possibly others don't pay taxes. I can still be furious that my money is going to entrenched fat cat contractors instead of either useful programs... or back into my wallet to buy something I want. That money is not being spent efficiently to obtain something of use to the US; it's going to a questionably useful pork barrel project to keep entrenched contractors happy. Any value the SLS program has could be obtained with less taken from the US population.
  13. NASA gets substantially more than a half cent per taxpayer. About $20 billion per year, for which about $5 billion goes to SLS/Orion. That comes out to roughly $15/year per taxpayer, though individual contributions obviously vary based on income.
  14. Please stop it with the blatant lies. The Falcon Heavy always had a purpose: booster reuse when SpaceX would otherwise need to expend a Falcon 9. There was a business case established from day 1.
  15. The low cadence of Falcon Heavy isn't a limitation of design or facilities like SLS. The limitation there is just a lack of customers. Meanwhile, SLS could not possibly launch more than about once per year without major infrastructure improvements. Also, SLS is not a stopgap. Either you take it at face value as NASA's Plan A, or recognize that it's a jobs program. At its inception, a NASA only SHLV made a little bit of sense due to a lack of cheap commercial HLVs. There was kind of Delta IV Heavy, but that couldn't be man rated. Even at the time, though, SLS was a terrible idea. It uses Shuttle hardware in a fashion best designed to send money to entrenched contractors. Those RS-25 engines were never meant to be expended. The SRBs add danger to the design for little good reason. A clean sheet design may well have been less expensive than this mockery of "hardware reuse". In the current day, it's virtually unjustifiable. Commercial HLVs with a substantial fraction of the capability of SLS are either already present (Falcon Heavy) or soon to come online (New Glenn, Vulcan Heavy) for a tiny fraction of the cost, and more importantly, enough launch cadence for impressive EOR missions. While we don't have a huge deal of experience with EOR... developing that experience would be a lot cheaper than the Shelby Launch System, even if SLS was actually enough for single launch missions. I'm not even counting Starship here, which is a highly experimental vehicle. Commercial expendable or semi reusable HLVs have reached the point of offsetting SLS's single launch capacity. A clean sheet SHLV would have been justifiable a decade ago, but "let's throw away four of the most expensive and complicated engines ever built with each flight" was never a good idea.