wumpus

The only reason you would want to bore a tunnel on Mars is if you really needed a deep (100m?) living space. Look at road building (on Earth). Deep trenches are almost always preferable to tunnels. A basic Earth-made structure (the habitats suggested by NASA) covered with adobe (as the OP said) would be much easier until you needed vast amounts of adobe above. As far as "nuclear boring" (especially non-fission), I suppose that NASA could obtain a neutron bomb and use it to bore out an extremely large space easily (like an underground test). I suppose that the radiation levels (after a year or so) of those underground tests are tip-top-secret (Andrei Sakharov is said to have figured out how to build a bomb based on isotopes from the Bikini Islands), but some "safe after n years" might be possible to find out. How cratered is Mars? I know it has an atmosphere and wind, so craters aren't eternal like on the moon, but I also know that Curiosity (or similar) rovers have gone into craters so they can't be that rare. I suspect that building a dome over a crater can give you that much more living space (even martian gravity might make a second story too expensive, not sure).

Commercial satellite launchers wouldn't want such a thing. You'd be surprised how often NASA science probes tend to have to wait years for a launch. My guess is that once the thing is up and in space, it is that much harder to cut the program. The other big issue is if the payload is in the Van Allen belts for two years. What type of shielding do you need, and could you put the whole thing into GTO (or escape velocity) if you didn't have all that shielding? Another thing to remember is that two years to GTO is two years to the Moon (and L2) or three years to Mars. Having bulk fuel (read solid/hybrid/other long term rockets)/cargo ready and waiting at those locations (for roughly the cost of LEO) changes things a bit (like forget the BFR and go to Mars using a bunch of Falcon Heavys).

"Old hands" of missile/rocket design tend to complain about solid rockets' tendency to explode. It might not be high enough to prevent even the most expensive satellites (about 1% per launch), but did at least contribute to one lost shuttle. From what I understand, controls and inspection to get SRBs up to this level of safety tends to pump the price up to liquid rocket levels. Orbital/ATF uses them, but only military surplus (obviously a cheap way to get a booster). As far as I know, the KSP SRB prices are lowered to improve the game, but don't really reflect reality (there's also the issue that while you [almost always] can't throttle liquid rockets like you can in KSP, you preset the thrust of an SRB to change over the launch. The shuttle did this to keep either the G forces down and/or limit the aerodynamic pressure on the orbiter (it couldn't throttle the SSMEs). This annoys me as I am one of the bigger SRB fans in KSP.

Note: if your inclination change is expensive (usually after you botch the angle, but sometimes you want to launch two or more satellites on one booster with different required orbits), the most efficient time to fix it is during your circularization (raise PE to the correct height) burn. My understanding is that real rockets launched from Canaveral to an equatorial GSO often will go excessively high (beyond GSO AP), change the inclination from Florida's to the Equator, then reduce the orbit and circularize (not sure the exact order). Since Kerbal Space Center is on the equator, you never had to do this for single satellites (assuming you matched the orbit on liftoff).

I'm having trouble understanding what the OP is suggesting and trying to do, but it looks like increasing the thrust. Once upon a time there was something called onion staging. The idea was similar to asparagas staging, but included many stages burning through all at once, and then jettising them at once. The idea was to maximize TWR. Before 1.0.x and the aero pass, it made absolutely no sense: you could simply attach all the engines (or simply use larger ones) to the last stages jettisoned and simply ejected each fuel tank as it emptied (since you have exactly the same amount of thrust and less mass (due to jettisoned empty fuel tanks) you will always have both a higher TMR* and higher delta-v than strict onion staging. It might make more sense now (you may have drag issues with the larger engines), but I suspect that a better means would be to break up the engines and the fuel tanks. You always want to jettison the tanks when empty, but it appears you want to manually control when to jettison the engines. I *think* this will do what you described better than using extra fuel lines, but don't know how much drag it will add. * this assumes you didn't explicitly use an adapter to add engines. It also assumes the same number of radial decouplers (typically shown in onion staging, but personally I would just attach two and then simply attach all the boosters to each other).

Presumably the whole point of funding them originally was to have this type of thing available. $2M (or so, the wiki doesn't mention the money in the Lunar Catalyst initiative) might be peanuts to NASA, but they did spend it.

Taken from the xkcd "orbiting horsepower" comic, the shuttle itself weighed three times its maximum payload. Part of the reason was to return "whatever", presumably keyhole satellites, to Earth. One of the biggest issues with SSTO is that the designs imply that you take the kitchen sink to orbit every time you want to fly. This is one of the *many* reasons the shuttle never met most of its [official] design goals, especially those concerning cost. https://xkcd.com/1461/ And apropos to the xkcd alt-text, I can't help but wonder if the technology to make the Skylon cost effective isn't all that close to a space elevator (I suspect the SSTO method is harder). Although I have to say that if the Skylon could claw its way out of the atmosphere (presumably in rocket mode) with roughly 4km/s under its belt (2+km/s from velocity [the plus would presumably be done in rocket mode], "2km/s" from aero losses) it would be well on its way to at least making sense (but still requiring a huge number of flights to explain why to develop this instead of SpaceX's working tech).

There have been something like 300 manned space flights (135 shuttle, 128 Soyuz, and a bunch of others according to wiki). The space shuttle is a bad comparison, considering that the first two were the ones that were lost*. As far as "not the first one" goes, it might be awhile before a booster goes 10 for 10 and is retired. I'm guessing that most of the rest will either not stick the landing or possibly be sold as "expendable" (of course, last I heard that might only be an option on falcon heavy). This first one is being retired, so I'd guess that it would be most likely the only "returned falcon" for awhile. * after writing this I remembered I saw the Enterprise in the Smithsonian, and haven't been down to see its replacement. Also not a fair comparison: the Enterprise never went into space, while the "first landed Falcon**" did the full Falcon mission. ** All the planes and spacecraft in the "Hall of Milestones" have proper names (had to look up that the Apollo 11 capsule was "Columbia", the "Eagle" was the more famous name of that flight). Not sure how they would deal with "first Falcon 9 that landed".

Quick google, likely wrong. Still, 2km/s out of 9km/s isn't much (I really should have recognised the number from KSP: 343 is close to mach 1). Anybody know how far you can get a suborbital to go on 2km/s? I'm guessing nowhere close to transatlantic, and that London-China is going to take over 8km/s, but the last time I went googling wasn't too good. But from watching the trajectory while circularizing seems to be short hop, short hop, short hop, almost there, half way around the planet and done!

Notes for 2016: Unkerballed vessels haven't changed: You need to check which instruments need to reset and which can be used again and again (science jr.s need to be reset, thermometers reset themselves). Just keep sending back those results (remember to pack a radio). For kerballed missions: while anyone can remove "science" from an instrument (and store it in a capsule), only a scientist (no xp needed) can reset [some of] the instrument for multiple uses. This is a great reason to bring Bob along. Finally, you might want a capsule on your lander (and not just a command chair). You can't store science in the chair, only a capsule. If you have enough friends in chairs (a leveling mission, perhaps), this might not be a problem but it certainly takes a bigger mothership.

Basically, Skylon shows plenty of issues of why SSTOs are hard (hard to the point of impossible, really). The main point of Skylon is 343* m/s of cheap delta-v (i.e. zero to mach 6). After that, all that "lightweight" heat exchanger is just dry weight to orbit. Remember, we need 9000ish m/s to orbit on Earth, so it makes Skylon's "big point" look a little iffy. * yes, you should add a bit for getting aero losses thrown in "for free" with my fast and loose numbers, but it still isn't that big a fraction of the launch costs. You need way, way, more if you want to build a SSTO out of that.

Of course, most of that article was pretty pointless as far as SSTOs go. The first idea is to add more stages (any kerbal will tell you that "moar boosters" increases payload). A second is cross-feeding (the start of aspargasing), which of course requires at least one dropped stage (and as far as I know, has been abandoned in Falcon Heavy). The funny thing here is that *with* cross-fueling, altitude compensation, and stage recovery (I'm less hopeful about recovering the Falcon Heavy middle stage, with or without cross-fueling), SSTO becomes absolutely pointless. SSTO makes recovery mind-bogglingly harder (compared to Falcon's "just touching space" recovery), and then requires vastly bigger rockets to haul a vastly higher dry payload into space. The only possible advantage in the rocket equation that SSTOs have is that in normal staging, the upper stages count as "dry mass" for the lower stages: with crossfeeding (and altitude compensation) the upper rocket stages would fire along with lower stages and no longer count for dry mass. The only real difference is that the SSTO would haul the "spent" stages all the way to orbit (massive costs) vs. dumping the useless dry weight (and with easier recovery). Note that the only rocket manufacturer working on altitude compensation that I'm aware of is Firefly: http://www.fireflyspace.com/vehicles/firefly-a They use an aerospike (I'm assuming that redesigning a Merlin as an aerospike is non-feasible). Note that they don't use an aerospike in the upper stage so there is no reason for any cross-feed plans (I would assume that pressure fed rockets would be the first to cross-feed: no turbopumps needed). There is also absolutely no attempt at re-use, although that may have to do with difficulties in checking carbon pressurized fuel tanks for stress (presumably the biggest cost of the rocket). There is, of course, no silliness about trying to go SSTOs.

They said "fire" not "launch". Normal PR wouldn't care, but space nerd PR probably made sure the correct words were used for this copy. After all these launches, I wonder how close the damage is to expected models and what they will change with Falcon 1.3 (now that they know at least one datum of real measurement). Of course my real reason for posting is wondering where that Falcon will end up. My first choice would be the Smithsonian Air and Space Museum "Hall of Milestones". Best guess is that this won't happen: it is a hall of "firsts" (the Falcon was a milestone, just not a "first") and the Shuttle claimed most of the firsts in that regard*. It also probably won't fit. I'd even wonder if it would fit in the hall next door (with the V-2 and Skylab mockup), that has the bottom carved out for more room, but still is finite. I suppose that Udvar-Hazy has plenty of room (it is less than a quarter filled), but the thing would probably have to be sideways (and I suspect if would fit sideways downtown). * The recent Musk/Bezos hissy fit doesn't help things. Bezos owns the Washington Post and has a certain PR advantage in DC.

Some notes: I'm pretty sure you should never lower the thrust in your SRBs (unless it's over 4 or something silly). I'll have to get back to this and make a thread on it. It seems to be based on "leftover wisdom" from the old aero model (where 2.1 [fixed] TWR was the ideal) and assumptions about performing a gravity turn. After making an "expensive and cheerful" (i.e. relatively cheap for 7000 m/s delta-v) out of [kicker] SRBs and a nuclear engine I noticed the following: TWR of .4 (or less) isn't going to cut it. It takes longer than 2 minutes of flight between SRB cutoff to apogee to get to orbital velocity. If your C&C rocket is going to get into space with .3-.4TWR, it will do it by burning enough fuel in the second stage to get a TWR high enough. My solution was pretty weird: use 4 kickers attached laterally and make a second stage of a vertically mounted kicker. This added enough delta-v and time to apogee that the .4TWR could get up to speed in the two minutes it had to apogee. I'm pretty sure that by list-price this was cheaper, but serious fans of recovery funds could build a second stage that got to orbit easier, and then could drop near KSC.

I tend to reload to avoid dead kerbals, but at least one time I was stuck with Jeb in a dead capsule (out of electricity, probably) while being batted around by the Mun's gravity. By that time I could dock and rescue kerbals, but doing a docking in under one orbit was (and still is) beyond me. I have no idea how I managed that orbit. I'm also guessing that there was some other issue (perigee was inside the atmosphere and had to recover since no electricity - no deploying parachutes). Most things like that you can simply wait (or time accelerate) out.

I'd stick to drones and existing aircraft. Adding something like the F-35 air inferiority target is just going to cause dead Canadians. The others may work, but are still going to be vastly more expensive than the drone. But still, Sopwith Camel for pilot training and airshows (actually, it is probably hard to fly and better for advanced training)!

First they have to have a proven means to orbit. Then they need the customers. Then they need launch. Only after all that can you really say they are "operational and have all these advantages". The real reason that Falcon 9 will not be able to compete with them (aside from offering "extra space" on other launches) is that the payloads are more like Falcon 1. If SpaceX really cared for this market, they could presumably revive Falcon 1 (note that landing Falcon 9 requires tricks not available in Falcon 1, like "virtually" throttling by a factor of 9 by only burning on one motor on the way down). In the unlikely event that SpaceX cares enough to compete in this market (they don't), there is almost no way they are going to recover a Falcon1 booster. While the designs look good (have to love the idea of a carbon-pressure fed aerospike), there is always the knowledge that powerpoint slides always out perform real rockets. I love how Firefly's (conventional bell) ISP is at least 10% higher than SpaceX's turbopump fed system (and something like 30% higher than their first orbiting engine in falcon1). They also say nothing about ISP at 1bar (much of the point of the aerospike), not that I'd really believe it anyway. I'd have to see them in orbit before announcing Antares dead.

Sopwith Camel. Great for airshows. MQ-1 Predator. A better idea would be to revive the Freewing Scorpion a nearly vertical takeoff and landing aircraft of great simplicity designed (well the idea came from him, Freewing engineered it) by Burt Rutan. Freewing had two issues: they seem to have been into drones at not quite the right time (and couldn't stick around long enough for the gravy train) and they had French backing when the US military was invading Iraq at least partially to take the oil contracts away from French companies.

Under the "did SpaceX kill ULA" thread I claimed that it certainly killed SSTOs (proposals). The rocket equation killed SSTOs. I think fredinno (the poster above me) claimed that I wasn't quite right: a rocket with the first stage of the SLS could presumably deliver a falcon-9 sized payload into LEO as a SSTO. Personally, I think that proves my point. I would happily permanently* send however many falcon second stages into orbit than try to perform the maintenance required to resend all those shuttle engines (a known billion dollar expense) into orbit again. SSTO involves one of two things: magic ISP a poor understanding of the rocket equation (or perhaps confusion with "magic ISPs cause SSTOs" with "SSTOs cause magic"). To understand why SSTOs are such a failure, just install the realism overhaul mods. * permanently means with deorbit and total loss. No Kessler syndrome for me, please.

It wasn't that long ago that SpaceX pretty much admitted that they were never going to return/reuse the Falcon9 (at least for any Falcon <=1.2). I've never really believed that it was a possibility, and thought that the genius of the Falcon was to reuse the 90% of stuff that only barely scraped space and was moving less than half of orbital velocity. Also note that the merlin engine is specifically designed for roughly 10 flights. If you place an engine in the second stage after 9 flights in the booster, there is really no reason to try to recover it (at the painful costs of orbital recovery, not "touching space, yea!" recovery). Building a CH4Lox stage would make tons of sense if they wanted to start small for the BFR engine. My guess is that they would/have developed it but aren't/haven't even considered sticking it into the proven Falcon stack. Sure, that might be a "waste" of engineering. But the costs of making an engine that works on the bench are nothing compared to building an engine and integrating it into a rocket while being reliable enough to bet $60M rockets & satellites and endanger any manned ratings. If by "not working towards this at all" you mean "not considering mucking with the proven Falcon design" I'd agree this makes sense. "here are still maintenance and inspection crews required" The official word is that the Falcon is meant to be gas & go, with the assumption that an actual ride into space proves the thing far better than any inspection routine and that maintenance isn't needed. My guess is that they are finding out if this is true this out as I write this, but we'll see. One thing to remember is that the ISS supply contract is pretty unique: NASA (+ESA and whoever else wants to pay the bills) appears to pay top dollar for cargo that is easily replaceable. Typically such contracts include satellites that are as expensive as the launch. I have no idea if the contractors get multiple tries (Orbital might have wanted to, but I doubt they can afford to blow up another launch site. SpaceX is unique in having an "extra" booster), but it certainly is an ideal contract for sending up reused boosters.

While seagoing battleships didn't make much sense post great-war (pretty much conclusively proven by Mitchel and Pearl Harbor), if you happen to have one of the old girls around (such as the US did during the cold war) it takes an entirely different weapon system to attack one. One captain said that if he was hit by the missile that took out the Scheffield he "would have to repaint were it hit". On the other hand, you really don't want a direct hit "down the hatch" that took out the Arizona. The Almez series apparently doesn't count as (at least according to wiki) Salyut-3 and Salyut-5 were manned, and Salyut-3 at least test fired its guns. A quick glance says Micheal wins (unless somebody copied Micheal and fixed the gun placement issue). Anything more isn't possible with our tech. Anything less likely isn't worth sending into space (and isn't as powerful as a Peacekeeper or SS-20). I had a (wargame? board & counter based) expansion to traveler that was more realistic than you would expect a boardgame style combat system to be called Mayday! The main claim to fame was an inertial system that used counters for where you had been, where you were, and where you would be: thus you could move "where you would be" a number of spaces depending on your acceleration. This solved the usual difficulty of making a system work without any friction.

My understanding is that SpaceX has abandoned the cross-fuel plans for Falcon Heavy. That wouldn't change anything in the air pressure/vacuum calculations of the various staging, just apparently too complicated to stick in the pumps. Note that Falcon Heavy had a weird system where only 1/3 of the engines from each booster would feed one [each] of the other boosters: this may have left the thing carrying empty fuel tanks/dead rockets while the other 2/3 of the fuel tanks emptied. It didn't look like something you would really want in your rocket.

I threw that in after looking for the section and noticing a bit about having meals prepared and of course there would be a wife to do it (and a long-winded explanation as to why). A bit later there was a bit about a proposal that involved finding two 100lb. men for a manned satellite. One commenter suggested that two 100lb. women would be far easier to find. He then proceeded to receive plenty of female fanmail for the comment (no idea about hordes of angry short men "ripped off" of finally getting a chance for glory that doesn't involve the Triple Crown). To be honest, the idea that different times couldn't possibly have different attitudes and people being positively shocked when discovering otherwise goes back more than 30 years (well before anyone thought to warn triggers). I figured that although the math hasn't changed since the 1950s, the writers certainly have and people might get a bit more than they bargained with for their rocket science reading. Still I think it is an ideal book for the KSP player.

After thinking about it some more, I'd guess that the cost in $/kg-to-LEO it would be cheaper to launch a Falcon Heavy, retrieve 2/3s of the boosters (landing the easy ones on land, watching the tough one smack into a barge tilted by waves and fall over). If a falcon9 launch cost is 60-70% booster, then I'd expect that a falcon heavy has three times the booster costs, but similar costs for everything else. You could eat the cost of the booster and still come out ahead due to the much heavier payload (assuming you could find a customer), than even a falcon9 with all (1) booster recovered (and reused). That 30-40% "everything else" cost adds up, and brings most of the euphoria of the landing back to Earth. My guess is that merlin/falcon 1.2 and 1.3 are going to try to chip away at those numbers, now that they are starting to become the high poles in the tent. There was never any reason to take them seriously until now.

I saw this in the "how to play without Asparagus" thread and thought it was too good for just one thread. The other important thing to take away from this is that to a remarkably high degree, designing a rocket means designing a turbopump (fuel pump). I think Scott Manley has stated something like 90% of the engineering comes down to the turbopump, but such things vary so wildly that I doubt you will ever find an "official" number. Just understand that they are by far the most complex part of rocket science and that making your turbopump more complicated is making your rocket more complicated. And making things complicated is the enemy of doing reliable engineering. And while someone pointed out that fire engine pumps aren't the same as rocket turbopumps, I think we can understand that making turbopumps working any harder is a bad thing.