wumpus

Napalm removes roughly half the issues of pressurizing a fuel (leaving only the HTP pressurization) and effectively serves as the combustion chamber. I'd check* to see if it is lacking protection from boiling too fast compared to normal "rubber" hybrids, but it certainly greatly reduces the problem set. HTP appears ideal for a white paper. I've yet to hear an explanation on why we could obtain it when nobody else has managed it (with even more available resources). * this is a huge problem in that it should be done to prevent wasting time obtaining HTP in the event it doesn't work. Perhaps N20 would be sufficient to test napalm (N2O or O2 should be used at least before obtaining HTP), but eventually you will need a full up test considering it appears to be so rarely used (not sure if it has been tested outside of the tests described in "Ignition!".)

I'm not sure what the cost basis the US military uses to risk its soldiers in combat, but it is far less than the insured cost of a commercial satellite (well, officially. The DoD has done some amazing things in reducing casualties far below what you would see if you used the official number). "Crew rated" issues are largely due to personal nature that NASA and employees/contractors/US citizens feel about losing astronauts and the PR hit it entails. Most of the "cost to space" centers around the fact that it is high R&D, low volume. From the numbers I've seen thrown around, if ULA had their boosters magically returned and Spacex had to expend all their rockets, spacex would still be vastly cheaper. Much of this is thanks to DoD procurement rules (if you've never been on the inside, just expect that you make a standard profit re-selling things with a 10x markup. No kidding, the red tape eats the rest of the profit, but at least much of the money goes to pay employees in make-work stuff), the rest is a completely different attitude in vertical integration and cutting costs (and Musk convincing his employees to work cheap to be part of something so awesome). The last is important: spacex has only launched 1 or 2 reused boosters, but undercut competition on 20+ flights. Making a profit is easy when you don't have to pay the overtime he gets. I'm sure spacex could make a "daily rocket" for 10% or less cost/flight of the Falcon (it wouldn't be a falcon, but something much cheaper to launch). But I doubt even Musk is willing to design the thing until he at least sees the market for a daily launch.

The "just so story" about the development of the 747 was that Boeing knew they could recover R&D costs (just barely, I'd assume) just on cargo routes. Selling to airlines was effectively gravy. I don't think they would develop the 747 for just cargo, but they almost certainly wouldn't have bet the company on hoping that the airlines would buy it in the numbers they did. New Glenn doesn't have such a fallback mode (nor does the A380, but I guess that Euro subsidies* will work). It looks like they are going for the "heavier than spacex" and "political friends who don't want spacex" (and can't justify ULA costs). I can't imagine that Bezos can subsidize more than a launch or two every year, so even he needs customers (and thus cares about economic viability [within a $1,000,000,000.00/year or so mad money budget]. Oddly enough, I've been reading a history of DARPA (written ~2000). One company interviewed, XCOR mentioned that if you want to make a lot of money, look elsewhere. Money is tough in this industry [with the possible exception of ULA and SLS] and that this was for dreamers. XCOR finally ground to a halt a week or so ago. * I assume "plan C" for Boeing was a government bailout in the form of modifying the 747 into a heavy bomber to replace the B-52. I'm sure Boeing executives were tearing their hair out that a 1950s plane was still central to the Air Force. I'm guessing that they've since bought out nearly all the companies making parts, so keeping the old beasts in the air is more profitable. If it wasn't we never would hear the end of just how old those things are.

Working hard to not kibiclick this thread...

It is lower than Skylab and has about the worst possible aerodynamics for staying up (Skylab, thanks to its shear size, was relatively low drag). The op even points out that its drag 'can be considered an aerobraking test'.

As mentioned above, you wouldn't want a mirror made from silvered glass (which has a nice insulating layer of glass above a tiny mirror layer that heats up). A more effective defense is to make the target shiny (any polished metal, aluminum should work well) and rotating. This is easier when trying to force a laser to blast N-1 missiles and force at least one missile through. One thing to remember is that in [US] military terminology, a "gun" is operated by a crew. "We" already have "laser guns", but nothing like what Han Solo might strap to his hip. Considering the US Navy has some large ships powered by nuclear reactors, they aren't terribly worried about the amounts of power needed (note: I think the ships that have these laser aren't nuclear powered, but they still have big engines). Ships also aren't as concerned with cooling (I know the Navy, at least recently, used water-cooled heat exchangers for their electronics). There was supposedly some work on an "X-ray laser" back in Reagan's "Star Wars" project. Somehow it was supposed to detonate a nuclear explosion and then use the X-rays (or simply heat/pressure) to get coherent X-rays. This may have been pure bunk to get the Soviets on a useless path, because I've never heard of it since.

While I suggested this near the start of the thread, the video points out that you only gain a few percent efficiency. That said, small rockets need all the efficiency they can get. Problems include launch permits on top of mountains, cost of strapping a rocket onto an airplane (easy if you are an air force and using small rockets. Hard for anyone else), and shear size of payload if using weather balloon assisted launch (see theregister.co.uk's "project LOHAN"). Pi in the sky might be pretty necessary if you want GPS. From memory, that appears to claim features "not allowed" in US commercial GPS systems. Uncle Sam isn't too happy about his GPS system being used by non-US/NATO manufactured missiles.

You then need either launch clamps or TWR such that TWR of N-1 engines <=1 (which might do wonders for aerodynamics, but I have to wonder if low TWR is remotely efficient for pressure fed rockets). I don't think that launch clamps are so much an issue as strengthening the structure such that they can hold the force in the opposite direction as the typical case.

If you go that route you might as well end up replacing HTP with LOX (assuming you are confident in ground lighting, less sure about the second stage). While I'm not confident in saying LOX is safer than HTP, it is quite more available. I'd also consider LOX+Alcohol: lose a few Isp for a ~1000C temperature difference. If you switch to LOX, I can't say whether HTP (+catalyst) would make a good igniter, I don't think it is commonly used. On the other hand, I suspect that professional igniters are out there in the "I do not work with these chemicals*" fame. * http://blogs.sciencemag.org/pipeline/archives/category/things-i-wont-work-with <- recommended for most who enjoyed 'Ignition!'.

Computers can be shielded [seriously. How can size be an issue for the things], and crews and ion speeds will never mix (thus the whole point about lifting stages. With kerbal magic these would simply be fuel tanks, but expect to be limited to fully fueled stages for the foreseeable future). I think the big question would be the microwave power receivers (may have to be tube based) and ion engines. Historically, the issue has been solar panels, but there are almost certainly ways of getting around that, but I have to wonder what the next worst issues are.

Sometime after playing KSP I became convinced that anything that needed to go to Mars should be powered by ion thrusters. Note that for crewed flights this can involve docking with multiple pre-positioned chemical boosters (positioned via ion tugs) and doing a burn that doesn't require all stages present (sic semper tyrannical rocket equations). The elephant in the room turned out to be the Van Allen belts and their effects on solar radiation. Since any tug moving from LEO to escape velocity will spend nearly all its time in the Van Allen belts (and nearly all ion engine craft are simply boosted to escape velocity chemically), a naive solution appears disastrous. Other solutions include nuclear power (probably a good idea for VASIMR, but that is a completely different solution), and I'm now wondering if beaming power via microwave might be a better solution. Ideally the power would come from a high orbital satellite (high enough not to worry about being eclipsed at night) but it would presumably start with ground stations. Fortunately, there exists a surprising amount of research on this (although mostly power point and research/government white papers) going the other way (sending space power to Earth), so most of the issues should be obvious. Any ideas if microwave antennas can handle the Van Allen belts better than most craft?

While this looks great, just how are you going to convince a gel to maintain that particular shape, much less convince the convince the oxidizer to mosy over to the fuel and ignite with it. It looks like some sort of baffle (extreme high melting point) will be needed, with a (mostly downstream) carefully engineered design to regroup the combustion pressure outward. The hybrids I've seen are long and similar to SRBs, with nearly all the combustion happening in a tube. I'm curious why you abandoned this design for something with much more drag.

They basically had to build it [Jamestown] at gunpoint (although getting enough soldiers to point the guns required some amazing leadership). While Mars lacks resources (and the cost to return such means that you couldn't make a profit if the surface of Mars was strewn with gem quality diamonds), the asteroid belt is another story (easier to find the rock you want, and no gravity well).

And also involved some ideas that looked silly in retrospec. When the colonists landed in Jamestown, it was suddenly full of "gentlemen" that couldn't get their hands dirty (unless they were digging for gold). While there is a tiny bit of gold NW of Washington DC (the mine was never profitable), digging anywhere near Jamestown was futile (much to the surprise of colonists used to hearing about gold laden Spanish galleons). Also during the colonial era, "fleeing oppression" likely meant paying by an indentured servant plan before the hangman caught up with you. "Transporting" was a popular punishment with magistrates: it didn't have the resentment of hanging or the cost of imprisonment. It's telling that Botany Bay was established the same year that England accepted the US government. It isn't clear just who would want to live on Mars, and what any other options might be. Most dreamers seem to assume it will be multi-millionaires, but I suspect that in the England-US model, only the plantation owners and shipping magnates followed such a patter (and likely weren't *that* rich when they left England). I guessing that somebody else will be paying for a lot of tickets, and I'm wondering what they expect in return.

I think you have to load the napalm pre-assembly (which makes transportation a nightmare. Just how do you declare "napalm" on your hazardous material list without red flags going up everywhere?). It also makes fueling much more nerve-wracking: leaks are bad. Leaks when fueling hypergolic fuels are disastrous. I'd expect you to stick with the White Lightning (or similar off-the-shelf ammonium perchlorite engine). Sugar rockets are notoriously poor Isp, and it becomes critical at the last stage. First stage use of sugar rockets makes more sense but would likely require careful ignition tricks (explosive launch bolts/clamps or something like a model rockets guide-pole to keep things straight until all rockets are ignited).

http://www.spacex.com/missions There are a huge number of communications satellites in there. I'd be surprised if all the governments in the world could launch as many rockets in 2000-2005. Blue Origin is even less concerned with politics (other than building rockets in Alabama). The big catch is that when you have billion-dollar price tags for launches (see some of the guesses the pentagon pays for a ULA launch), only governments and the odd huge corporation can pay. If the price comes down (or the odd well-heeled space nut wants to pull a D.D. Harriman), then expect it to go to other than government.

My understanding is that there is a bonus for having the MPL on the surface. Of course, if the MPL isn't exactly on the poles it won't be receiving solar power during the night, so tends to have a 50% penalty. So either have your MPL in orbit or landed at the pole.

I'm curious to know if enough would be available to use as an igniter. The whole engine appears to be designed in such a way as you could replace the N2 with NO2 and simply remove the HTP. You would still need an igniter, where HTP would work. This becomes even more important in the second stage where air ignition would likely be a big deal. Are "launch clamps" viable in amatuer rocketry? I'd expect them to be built around explosive bolts holding the thing down, but it would reduce most of the ignition issues of the first stage.

NASA used to launch their "spares". Think Voyage 1 and Voyager 2, various pioneer and viking pairs. This made a lot of sense since the second article build cost a fraction of the first. Presumably cost and computer modeling effectively obsoleted this practice, but I still think it was a good one (and I think essentially used in Opportunity/Spirit Mars rovers). "Use the spares" works great if you have need of more than one type of similar part (and the unique parts are rare and not overly expensive to duplicate) and is a standard means of engineering reliability. Can't say there are obvious ways to use it going to Mars (and it certainly was never designed into SLS) beyond basics such as engines and fuel/oxidizer tanks.

[This might as well be a necro-post for the OP, but as basic principles for the forum I'll include it]. Looking at the actual craft makes this look like a non-option. I think it's a probe, and it also looks like decoupler is on the wrong side of the science jr. (presumably an extremely new player, just sending a probe to Mun). I'd expect two real options: Raise your PE for the "several passes" system. Try coming in both on your heatshield and on your engine (the engine might do better than a heatshield+science jr). Raise your PE for the "several passes" system, then raise your PE to leave the thing in orbit (and send up a recovery ship [including Jeb or Bob if you want the science and don't have a kerbal on board]). You *can* dock with the thing in Munar Transfer Orbit, but Low Kerbin Orbit is so much easier/cheaper.

Of course, there was still the cost. DEC launched the PDP-7 in 1965 for $72k, and Steve Wozniak was excited by its "low price" [this might have been even later after a price drop*]. When his father informed him that the thing still cost more than his house, the Woz would have to go and build his own computer. For something people could buy in a store you would have to wait until about 1977 for the release of the Apple 2 and the TRS-80 (radio shack special. Not recommended). The TRS-80 came with a [blocky-black and white] screen, the Apple plugged into your TV. Not that these were the absolute earliest, but considering how famous the 1975 MITS Altair 8800 was (that you had to solder together, input was manual switches and there was no output screen) at $400, I'm comfortable claiming that the "personal/home" computer era started in 1977. If you just wanted the screen and didn't need to own the computer, hackers had spent at least a decade earlier hacking through the night hours on single-user (no punch card) machines. * My parents bought a house outside of Washington DC around 1972. It was still cheaper than the PDP-7.

If you sorted all "space computer games" by accuracy, you would find a tiny sliver of obscure games just above KSP, and KSP beating the combined sales/downloads of them all by several orders of magnitude. The list should include: Orbiter (KSP started out as "orbiter for dummies") A Saturn V simulator (go through the full checklist every time or crash. Don't expect to get anywhere without reading the manual for weeks) I think this was 2000-2005ish Some rather non-interactive games (no physics engine to cheat at) like Buzz Aldrin's space program. Most of the games below it would have "Star Wars" aerodynamics in space. I'm not sure if Elite: Dangerous has such, but it is certainly the same style game. While Scott Manley does have a fair amount of science videos about "what KSP doesn't teach you about rocket science", so far they haven't exceeded "what KSP teaches you about rocket science" (mainly thanks to time limitations. But eventually they would also get boring). When I step back and look at the game, I'm impressed that things like the Oberth effect and slingshots work in the game (it should be obvious that even with the Newton/Kepler (pre-Lagrange) physics model these have to work, but it is still impressive). When you are comparing KSP to some asymptotic "perfect realism", everything looks fake. Is principia working nicely with RSS/RO yet (I really don't know, but when I get tired of KSP I don't plan on including principia into an RSS/RO stack unless it would cause more bugs to leave it out)?

Sounds like alpha testing (and earlier). Then again, these days we are expecting to ship the beta, so names keep getting pushed back.

I'm really wondering about "just parachute down". Their velocity at staging is roughly the delta-v they (+sustainer) are providing. A good place to start is to divide the stages evenly by delta-v, which means that a "half stage" should either provide 1/4 to 1/3 of the delta-v. I'd have some doubts about it hitting the atmosphere at ~2000m/s, let alone the rest of the flight down. Perhaps a back burn could help things. Expect a few drogues or something like spaceship 1, as the parachute will be heavy enough if it only has to handle landing duty. Landing on land sounds iffy (especially the "flying over land" license), although a fairly hefty aluminum tube on it's side should be able to land in the desert easily enough. Landing on water sounds easier (just have enough empty space above the booster, preferably made of fiberglass) assuming you can get to it by boat, but this lowers the acceptable max-Q the rocket can sustain.

Re-use? As in after launching? We've done the parachute idea to death in the various spacex threads and it appears too heavy (possibly not for side boosters). A pressure fed hypergolic engine wouldn't have the restart and throttling issues that powered landing traditionally has, but you just cranked your control logic requirements up exponentially. You also need some sort of SONAR/RADAR/LIDAR system to measure final altitude. I don't think this system is up to adding spacex-style paddles. Parachute reuse on the side boosters (or possibly something like spaceship one's wings/vanes) might be a plan. It also might require a few more boosters. It also requires land-land flight, and landing legs need to support arbitrary landing sites (presumably any old desert landscape, although you might have some control over the final position if you get in line of site quickly enough).