![]() ![]() Basic Design - Atomic Rockets. This section is intended to address some gaps in available information about spacecraft design in the Plausible Mid- Future (PMF), with an eye towards space warfare. Sika manufacture a range of cementitious and resinous concrete repair mortars. · HighPanda How old is you bridge and what is the condition of the deck? This is a concern with concrete girders and no diaphragms between beams at the bridge ends. Poem of the Masses. my smile melts with confusion artisticly enhanced she titty-danced her clients glanced at her mammarily-expansed bust, de-pantsed. It is not a summary of such information, most of which can be found at Atomic Rockets. The largest gap in current practice comes in the preliminary design phase. A normal method used is to specify the fully- loaded mass of a vessel, and then work out the amounts required for remass, tanks, engine, and so on, and then figure out the payload (habitat, weapons, sensors, cargo, and so on) from there. While there are times this is appropriate engineering practice (notably if you’re launching the spacecraft from Earth and have a fixed launch mass), in the majority of cases the payload mass should be the starting point. The following equation can be used for such calculations: Where P is the payload mass (any fixed masses, such as habitats, weapons, sensors, etc.), M is the loaded (wet) mass, R is the mass ratio of the rocket, T is the tank fraction (or any mass that scales with reaction mass) as a decimal ratio of such mass (e. E is any mass that scales with the overall mass of the ship, such as engines or structure, also as a decimal. This equation adequately describes a basic spacecraft with a single propulsion system. Solutions To Concrete Bridge Deck Cracking Back AsianIt is possible to use the same equation to calculate the mass of a spacecraft with two separate propulsion systems. The terms in this equation are identical to those in the equation above, with R1 and T1 representing the mass ratio and tank fraction for the (arbitrary) first engine, and R2 and T2 likewise for the second. Calculate both mass ratios based on the fully- loaded spacecraft. If both mass ratios approach 2, then the bottom of the equation will come out negative, and the spacecraft obviously cannot be built as specified. ![]() Note that when doing delta- V calculations to get the mass ratio, each engine is assumed to expend all of its delta- V while the tanks for the other engine are still full. In reality, the spacecraft will have more delta- V than those calculations would indicate, but solving properly for a more realistic and complicated mission profile requires numerical methods outside the scope of this paper. One design problem that is commonly raised is the matter of artificial gravity. In the setting under discussion, this can only be achieved by spin. The details of this are available elsewhere, but these schemes essentially boil down to either spinning the entire spacecraft or just spinning the hab itself. Both create significant design problems. Spinning the spacecraft involves rating all systems for operations both in free fall and under spin, including tanks, thrusters, and plumbing. The loads imposed by spin are likely to be significantly larger than any thrust loads, which drives up structural mass significantly. This can be minimized by keeping things close to the spin axis, but that is likely to stretch the ship, which imposes its own structural penalties. A spinning hab has to be connected to the rest of the spacecraft, which is not a trivial engineering problem. The connection will have to be low- friction, transmit thrust loads, and pass power, fluids, and quite possibly people as well. And it must work 2. All of this trouble with artificial gravity is required to avoid catastrophic health problems on arrival. However, there is a potential alternative. Medical science might someday be able to prevent the negative effects of Zero- G on the body, making the life of the spacecraft designer much easier. When this conclusion was put before Rob Herrick, an epidemiologist, he did not think it was feasible. The problem is that they [the degenerative effects of zero- G] are the result of mechanical unloading and natural physiological processes. The muscles don't work as hard, and so they atrophy. The bones don't carry the same dynamic loads, so they demineralize. Both are the result of normal physiological processes whereby the body adapts to the environment, only expending what energy is necessary. The only way to treat that pharmacologically is to block those natural processes, and that opens up a really bad can of worms. All kinds of transporters would have to be knocked out, you'd have to monkey with the natural muscle processes, and God knows what else. Essentially, you're talking about chemically overriding lots of homeostasis mechanisms, and we have no idea if said overrides are reversible, or what the consequences of that would be in other tissues. My bet is bad to worse. As the whole field of endocrine disruptors is discovering, messing with natural hormonal processes is very very dangerous. Even if it worked with no off- target effects, you'd have major issues. Body development would be all kinds of screwed up, so it's not something you'd want to do for children or young adults. Since peak bone mass is not accrued until early twenties, a lot of your recruits would be in a window where they're supposed to still be growing, and you're chemically blocking that. Similarly, would you have issues with obesity? If your musculature is not functioning normally (to prevent atrophy), how will that effect the body's energy balance? What other bodily processes that are interconnected will be effected? Then you get into all the effects of going back into a gravity well. Would you come off the drugs (and thus require a washout period before you go downside, and a ramp- up period before you could go topside again)? Spin and gravity is an engineering headache, but a solvable one. Pharmacologically altering the body to prevent the loss of muscle and bone mass that the body seems surplus to requirements has all kinds of unknowns, off target- effects and unintended consequences. You're going to put people at severe risk for medical complications, some of which could be lifelong or even lethal.”This is a compelling case that it is not possible to treat the effects of zero- G medically. However, if for story reasons a workaround is needed, medical treatment is no less plausible than many devices used even in relatively hard Sci- Fi. The task of designing spacecraft for a sci- fi setting is complicated by the need to find out all the things that need to be included, and get numbers for them. The author has created a spreadsheet to automate this task, including an editable sheet of constants to allow the user to customize it to his needs. The numbers there are the author’s best guess for Mid- PMF settings, but too complicated to duplicate here. Rick Robinson’s rule of thumb is that spacecraft will (in the sort of setting examined here) become broadly comparable to jetliners in cost, at about $1 million/ton in current dollars. This is probably fairly accurate for civilian vessels, at least to a factor of 3 or so. Warships are likely to be more expensive, as most of the components that separate warships from civilian ships are very expensive for their mass. In aircraft terms, an F- 1. F- 1. 5, while the F/A- 1. E/F Super Hornet is closer to $4 million/ton. This is certainly a better approximation than the difference between warships and cargo ships, as spacecraft and aircraft both have relatively expensive structures and engines, unlike naval vessels, where by far the most expensive component of a warship is its electronics. For example, the ships of the Arleigh Burke- class of destroyers seem to be averaging between $1. As mentioned in Section 5, some have suggested that the drive would be modular, with the front end of the ship (containing weapons, crew, cargo, and the like) built separately and attached for various missions. This is somewhat plausible in a commercial context, but has serious problems in a military one. However, the idea of buying a separate drive and payload and mating them together is quite likely, and could see military and civilian vessels sharing drive types. This is not as strange as present experience would lead us to believe. It was only during WWII that military aircraft clearly separated from civilian ones in terms of performance and technology.) This simplifies design of spacecraft significantly, as one can first design the engine, and then build payloads around it. One common problem during the discussion of spacecraft design is the rating of the spacecraft. With other vehicles, we have fairly simple specifications, such as maximum speed, range, and payload capacity. WBDG Whole Building Design Guide. This section of the WBDG provides guidance on terminology and integrated planning and development processes to establish an owner's expectations for project scope, budget, and schedule. It also provides guidance on managing the team during the planning, design, construction, and occupancy phases of a project.
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