PB666

Here is why I don't like to use ISP [(sec)}. This is going to be a brain teaser. Lets just suppose that we were fed up with the current administration and we elected Prince Harry as president of the US (of course only after he married an American and the law forbidding president to be someone of foreign birth). In an effort to solidify Americans into a single system of governance he made it illegal to use an metric unit in any government operation. So now we are completely adherent on using the Imperial System of measurements as adopted by Americans 120 years ago. So we manage to build a Rocket and the Rocket has four stages and we have weight and thrust (in pounds, a force), and so during ascent we go through the four stages and we are delightfully in orbit. But we are weightless. Remember we are forbidden from using the kg m systems. But we need to find- for a variety of reasons negotiating the earths fluctuating gravitational field, and numerous Oberth effects we intend to perform- the mass of our ship. The ship does have a mass, it has a value in the English system of measurements, what is it? Even 28 years after the units description we see this in the literature Note: that if you find the Wikipedia page where this quote comes from you will find also find the name of the unit. I'm not going to tell anyone, I want everyone to specify in their mind what the unit is and search for and verify that unit. The problem is that even if a 'King' decreed that we use the FPS system, no-one, unlikely 120 years of mass unit definition is going to use the FPS mass unit or be able to communicate with others using that system. We know that mass is important because it specifies inertia. and inertia is an important quality of momentum. And these are two qualities you desperately need to know when you are in an . . . inertial reference frame (kah ching). So why use a unit that is specified for use in FPS, that does not have a 'coherant' mass unit, such that the unit always needs to be multiplied by µEarth / r2Earth,surface when in fact your space ship is now orbiting the sun and about to make an oberth effect on Jupiter, or suppose you want to land a probe on Mars. So where did NASA's spacecraft crash as it did not make the conversion from Imperial to metric units. . . . . . .Mars. The moment that the stage 2 burn ends (i.e. you are now circularized), on the explicit condition that you are using that orbit to propel the ship into space, the most important concern is the mechanical energy Hamiltonian. How much Energy do you need to put into your craft to get you to an exterior orbit from that you specify the dV you need dV = Ve ln (mo/mf) Ve = ISP (m/s) [= ISP * µEarth / r2Earth],surface and Mx = Poundsx / 32 f/s2. Fortunately in this equation the 32 f/s2 in the numerator and denominator cancel, but this is not the case in all equations. Don't bother converting to mass, your final equation will be incoherent (except to an expert in trivia). OTOH, when you are launching you are playing out three different dynamic force vectors. There is the force of gravity, the force of drag, the force of thrust adding the dynamic acceleration in a rotational reference system called 'centrifugal acceleration' (a faux force). Because of the complexity of these the ideal dV required (Sqrt(2(u/2r1 - (Vrot * cos Z)2/2 + (-u/ro-u/r1))) is only part of the equation. Since the ideal dV require can only be achieve by infinite thrust and no drag. The infinite thrust issue is also a problem with burns to escape from orbit, the reason is that δΘ/dT in an LEO = 0.00119 (0.068 degrees) per second, so that if an appreciable amount of the burn can occur in say 5' span it can occur over 73 seconds without much energy loss, and we can use kicks if it is longer. For example if your goal is mars, you need say 3700 dV to get there from LEO, then an acceleration of 50 m/s2 (5g) is required some loss of energy results by burning at 25 m/s2 but the dV required is a magnitude easier to predict from ideal equations relative to launch from Earth. Since in any SME moment the optimal energy efficiency occurs when KE is max, any gain of radius during a burn increases PE at the expense of KE and if under thrust SME. So ideally we want the burn to occur at the lowest radius. The point is that in a launch from Earth the Intergral of thrust as a function of time is a very complex function in which mass is not a primary issue, but once you are in orbit, taking advantage of all the facilities space has to offer requires the definition of mass.

That's why is better for NASA to contract out services, not part's procurement.

But the male sea turtles are very happy.

I only use ISP sec _here_ in discussions. If you read the literature on some of the drives they do specify Ve. But again I mainly focus on ION drives. Don't forget we had a space craft crash into Mars because they forgot to convert between the two systems. If we all agreed to stop using ISP (sec) here and KSP switched also to Ve then we could get away from that .. If wishes were horses beggars would ride. I don't know about that, seems to me that Russians have alot of good material to write about. I seen quite a few Russian movies in years gone by, they tended to handle some pretty heavy subjects.

Note: Just to point out that this was the same administration whose OMB elected to employ the SRB over LFR of the design that destroyed the challenger. Note: Same administration of Watergate and Ellsberg breakin. Not exactly credible. From that report So if we go by that logic, full replacement of shuttle would have occurred in by 2001, at then end of the ISS, certainly . . . . but it did not occur. A couple of points here the shuttle program when it was initiated was not designed to go until 2011. more like 2001. This is just evidence of the Beaurocracies limited ability to respond to problems. And if you read the other risk report, if they had replaced the tiles and reworked the hull a bit, they would have had an evolved shuttle. However, neither replacement or evolution occurred again that is the problem, from a safety standpoint far more important than where you put an escape capsule. No doubt.

There are some pretty legiitimate reasons to delay BFR, namely the Boca-Chica launch facility is at least a year behind schedule.

Yes, but by artificially limiting the launch windows that would not affect other rockets (as much*) *While most rockets would not be affected by low outside temperatures, at some-point high altitude windsheer is dangerous to all craft because it alters the angle of attack of a hypersonic vehicle and can cause those pesky destructive aerodynamic forces that are talked about in the STS51-L 'event'.

Yeah, that's right, there are two, one is ISP(sec) and the other is ISP(v). But if you don't specify its Ve/g (m/s)/(m/s2) = ISP in seconds.

This is one for huantanvirus https://www.ncbi.nlm.nih.gov/pubmed/24287104.(The plague has been a problem in the SW since at least the Pueblo revolt, IIRC, although it may not have been correctly identified). At least the early papers blamed this on human travelers (Asian disease, Asian travelers). < 2000 years ago, at least for the Asian strain. I hope this helps your understanding of our guys' peoples. I can provide more the the same if you like. .

What about off-planet operations, conceptually the cargo version doing stuff in LEO, MEO GTO are local parameters, when you start talking mars you have a different set of parameters . . timing changes....coordinating entry corridors at distances of a couple million miles . . . . . Lets say you choose a point on Mars, you have to choose a burn time and vector in LEO that roughly allows that point (since you are not circularizing) and then correcting velocities to achieve an atmospheric entry that also corresponds to the atmospheric start of the landing phase along an oblique trajectory. The other problem is that both O2 and CH4 burn off over time, he doesn't have to deal with that problem on the overwhelming majority of launches. BUT, agree with the plan, get fuel into orbit.

I think they are still strolling to the hard part of the learning curve, nothing they have done seems to indicate otherwise. To the moment they have just improved on 1960s technology by adding on more computerized step. . . .save some of your fuel, keep a couple of engine starts and reland. The PPO position is open, plays 200 grand per year. I thought about applying. Say I think the problem with NASA is this, they don't want to contaminated Mars until they have investigated the possibility of life on Mars. Since 2024 is unlikely then he has time, he might have to buy into the biological survey to get it done before he tries (handwaving) to colonize.

The plague was never much of a problem here even though Yerseni Pestis did move through the area prehistorically, but we could have. We are in a bit of a different situation, In Europe there were only wolves and no jackel-forms. Here in the SW we had both wolves and coyotes and they tended not to intermix. On top of that most of Europe is above 50' north, so there are few poisonous snakes. The coyote, in and of itself is a 95% rodentivore (although there is some concern that there is admixture with other canids resulting in more wolf-like predators). So if you eliminate the coyote from the system you get spikes. In that late 60s early 70s while birds were still suffering from DDT they decided to start killing coyotes because some ranchers thought they were pests so the put cyanide laced meat out for coyotes (a very bad idea environmentally). And they did drop the population, but since rattlesnakes only eat what they killed their population bounced up and . . . . .Rattlesnake roundups. Rattlesnakes don't eat your cattle, they just hibernate in your barn, in the dresser drawers in your house, in your outhouse . . . .needless to say very inconvenient. And so DDT is gone and coyotes are left to live in peace, mostly. What makes the coyotes useful is that at night they cover huge ranges, often miles from their dens and they travel very quickly and quietly in search of prey.

Because when you launch you have to lift against the weight of the vehicle, and thus you can multiple by the weight fuel. Specific impulse is useful when thrusting from non-inertial reference frames, it useless when thrusting from inertial reference frames (like space) Ve is a better choice. Thats why for ION drive systems a more frequent specification is Ve . . it just removes one term from the denominator. Even one level higher is that F = power/C when you talk about photon drives or cannae drives. ION drives, it is often convinient to consider Ev as a fraction of the speed of light, because this tells you basically what your relative efficiency is. For example if you are engaging in interstellar travel you want Ve ----> C (but not reaching C because that is very power inefficient, and the only way to provide that kind of energy is a very efficient matter-antimatter electric generator). Lets say rocket weight 1,000,000 pounds and the ISP is 200 how many pounds of fuel do you need to expel per unit tme to achieve an acceleration of 0.2 g at lift off that grows until half the weight is expelled. 1,000,000 * 0.2 = (Thrust - Weight) such that Thrust is 1,200,000 1200000 / 200 = 6000 lbs of fuel per second. Calculations are pretty simple,

But cats kept the number of flea carriers down. There was a study done in England that found that even house cats that spend time outside that don't eat what the kill, kill something like 800 animals per year. Reduce the number of animals carrying Zoonotic organisms and the time between interactions and you can modulate the growth of the plague. The plague in Europe exhibited some rather peculiar behaviors, rather than tapering after the first major epidemics, for a period of about 150 years is managed to kill 20-30% of the population in episodes of about one per 20 years per area. I will look at the link. So what they are basically arguing is that once the plague gets into human population human lice is better at spreading disease than the rodent borne disease. A counter point however is that we already have a means of spreading Yp from humans, aside from fleas there is also the airborne spread of disease in families which at the time of the plaque as 100% untreated fatality rate as opposed to the 40-60% fatality rate of zoonotic carried disease. And that says alot, the Typhoid Marys of the bubonic world are rodents. But the reason that rodents get blamed stems from the fact that in some cases a counter-selective agent (a toxic drug, a pesticide, . . .) that doesn't eventually kill all of a thing can turn the agent into a resource. This happens relatively quickly with soil-borne bacteria. Rodents are particularly vulnerable because they are near the bottom of the food chain and because of that carrying a bug that is fatal to something that eats you provides kin selection for social animals. Thus if a big mountain lion kills a nice fat rat, it can die from the plaque and before it dies it might transmit plague to its offspring, its mate. It works well unless the thing that is killing you really does not need to kill you to survive. This means if I feed my cat, and the cat goes and kills rats while after making lots of babies (an in a typical case the fleas bail after then animal has died and will bite anything, can't tell if its a good rat until it bite the new host). The cat might die but I am forcing cats into the system (this is a forcing model, that is what drives artificial selection) independent of the prey-rats ability to support a cat economy. So that not all the time are cats eating rats and exposing themselves to disease. A good example is at a port that cats eat fish scraps, they breed, and when ships are in port they catch rats coming on or off the ship. Its really no different from Racoons living in your trees eating your garbage are also going to eat all the pecans when they fruit. So that overtime the ability for rats to communicate disease rapidly falls as life expectancy and density falls. How do you translate this, a predator based active rodenticidal system reduces the initial chance of disease, but if the disease manages to peak, may increase the chance of disease, but this is not so important to the system if the outbreaks are pocketed because this overall prevents the joining of pockets. I

Bulk, you have something very flimsy and bulky that is only stable in space. Imagine a core, say a cube. then imagine creating a lattice around the cube, and as you move away from the cube in two dimension the lattice becomes more an more flimsy as the mass per unit area drops (such as for thin film solar panels).

Well you have to be careful about introducing new wonderful technologies to the medieval Europe, they burned people who kept cats, much to the delight of Yersinia pestis People often credit Columbus with discovering America, both the Basque, Norse, Chinese, Inuit. . . .discovered America before Columbus, what Columbus did was create a methodology for bringing Mexican food to Europe. That would make sense in inverted space.

Oh my, that would opened pandora's box. Why chose fingers at all, you could say Man = 1 and Woman = 0 based on the possession or not of a single digit and watch watch what happened to the lovely christian churches of the 4th century AD. Sure you would have a universal binary system and utter social chaos everytime you need to do some math . . . . . We are endowed with all but universal counting systems (some of the near-sighted probably could not see there toes) and along the way this was extended to the abacus, but as long as folks were playing with their own fingers, there would be normality in the world. (hmmmmm, though I guess that didn't stop the greeks).

Maybe, i'm not sure about this, but maybe they think that if the BFR cannot achieve its 2022/24 goals that it will still be profitable for missions within Earth's extended SOI. So there could be a point if someone says 'we can't do this' then they are doing something else, like providing an assist for asteroid capture missions or refueling someone's gateway. BTW, for the 2022 mission to be useful, all they need to do is get a probe into Mars orbit with mars sample on it, so it could be joined to NASA's mission, in which case you could get someone to pay for it.

I can only imagine the look on this guys chief extraterrestrial engineer when he tells him "I want a city of mars by 2028" The word ambitious is a gross understatement of his plan . . . . but anyway let him try, I can't see the other vaporwares going anywhere.

I actually don't know how two winglets pointing in the direction of oncoming airflow won't twist around.

Umm, tell gregor mendel, once, to Go talk at the British Royal Society. How about convincing the Emperor Constantine to adopt the metric system and at the same time disclose that the earth is approximately 40,000 meters in circumference in all directions. Lets see what else, that the earth is not the center of the universe but that earth does have a center it orbits the sun like all the other planets.

He would have been upset that he did not discover it. Gravity is to newton as quantum entanglement is to Einstein. Newton did not believe there was an actual force acting on objects, but in order for his 'every force has an equal and opposite for working on it (why we can have rockets) something had to be pushing your posterior down on a chair as the chair pushed up on your posterior'. In layman's term the pound is a unit of force, a spring scale of an earlier era is measuring force, not mass, even the balance in the lab is measuring force at some level, there has to be non-inertial force acting on the bottom of the balance in order for it to work, its just less sensitive to gravity than a scale. I am watching these lectures on quantum physics and classical physics and I find it intriguing that they talk about let the math do the work and give your sense a break, but then they turn around and do thinks like say if something appears to be true then it is also true. If a speeding clock appears to slow . . . .. In quantum mechanics explanation of wave/particle duality (which this one teacher says 'this does not exist, its a fault of our language . . an electron is neither a waver or a particle . . its an electron'. Gee what insight, I need to study quantum mechanics to learn that x = x, but the appearance is that you cannot obtain momentum and velocity of a particle at the same time, is not just an appearance, its a reality . . . . . and you never know which you are going to get. But yeah you understand that Newton would have grasp GEneral Relativities curvature of space-time as a good understanding how force can act over the vacuum of space. Things get more freaky at the small scale. The other quip I like is. . .'the wave function is a time function [ Teacher pointing at t, the most important variable in the equation] but its meaningless and pretend it does not exist, you will never use it'. The reason the t in the wave function is ignored is because quantum t in the wave function is in Plank's scale and so period of the wave function is some small multiple of this. I think the thing that would have freaked Newton is the plank's constant and quantum scales, he was very much a unit guy, and if you told him that there was a scale where the very nature of measuring (d,v,t) are useless and the only value is accounting for information coming in and going out of some minuscule system, he might have balked.

They are young so . . . . .but you in the ISS when they some one is bouncing off the walls, they literally would be bouncing off the walls.

Cold? like really cold?

I can just see this some space admin hanging around JSC in the middle of the night watching the cleaning people do shop ' hey friend, would you like to go into space' , a kind of cold hard stare comes back, then a little fear ' . . . . no . . . . no , I don't think so. definitely not'. It reminds me of Garrett Morris and the 3-mile island skit on Saturday Night Live. They really do need young people with low blood pressure and alot of energy to do then. Just convert all the spacemeals to starbucks coffee.