PB666

I don't know if nay of these are habitable but here's the appendage to the rest https://www.scientificamerican.com/article/astronomers-haul-in-another-horde-of-kepler-planets/

https://www.bloomberg.com/news/articles/2018-02-15/nasa-is-bringing-back-cold-war-era-atomic-rockets-to-get-to-mars looks like a partial repetition of an old story, but looks like exactly same title so does belong in this necrotic thread.

You should read the scripts behind some of your trusted web pages, its more like 5% content 95% scripting for adds. The lead add for BBC World today had an image with 40 sublink addresses. Some of the more nepharious web scams are fed by click-bait on some of the most trusted websites. Why I don't go to BBC anymore. The website itself has no idea what add is being fed, that is generally fed by google "googlesyndication.com" as google tracks you around and tries to coerce you to buy stuff you don't need. There are services that filter all this stuff out and essentially whitewash your location and identity, like 30$ per year. New groups, Reddit, and groups like this are better forums . . . . Fortunately for most of the poorer Africans their access to the biggest offenders, but there could be advertisements for cigarettes, alcohol or things we may never see. Wikipedia has one advantage of other sources of information, most of its content is kosher, even reddit there is a fair amount of stuff. If wiki is the only service that they can get, they have the best of the internet.

c = 300,000,000 meters per second. Assuming that signal and destination are within 45' then up and down link from a 1000 km orbit are 1,000,000/ 100,000,000 = 0.01 second. It get better on the send because if you are loading something big, it can upload to the satellite and then you only have 1 direction send.

He's a jack of all trades. Just parked a car in trans-martian orbit.

Its showing Spacenet is a provider for my area, almost twice as fast as my laggy DSL connection. Yeah, satellite broadband is here even though I don't need it. Alot of negative reviews on Starband.

For one the cable going to Africa has been cut twice. The problem is that in a very tight supply market, ISPs can charge whatever they want, where as if any joe wants to launch a bunch of satellite he can practically cover every market on Earth. http://www.africabandwidthmaps.com/fibrereach/

Looks like his car insurance rates went up by $0.01 per year.

Things have changed, the has been a major push by non-GMOs to aid in the provision of accessibility services to local market places. You can now literally go on line and buy trinkets from some African in a poor village in the middle of nowhere, it might nt reach you soon, but you will eventually get it (otherwise buy on amazon). This is mainly an East Africa thing, the congo and angola are still pretty off the map.

I am going to realign your logic to fit situations that are more useful. This shouldn't be a problem once SpaceX converts to Metholox since Liquid Methane creates its own head pressure. I don't think spaceX is going to waste any effort on Falcon beyond GTO. They could, of course create a 4 booser S1 falcon 9 rocket (With some S2 redesign) that is capable of sending 25t to Moon intercept, but they have not really expressed any interest in either extending the capability of Falcon beyond FH (due to the recyclability problem of high momentum S1 components), and because their target is Mars. My point is that unless you are sending something on the order of 30t to the moon, its better just to avoid sending men there. A few of points I would make. For station keeping in EM stations, Solar/ION is the way to go . . .no need to worry about engine restarts at all. For non-cryotstic fuels you can use an inflatable baffle that can be deflated when not in use and you can use any gas. The problem with Kerolox is the restarting fluid, but for cryofuels there are engines that us electromechanical turbo pumps (very suitable for the low thrusts seen in space) that can prime using fuel rich mixtures of hydrogen and oxygen (spark) in a preignition chamber. Again the problem with Kerosene is its low vapor pressure. This is not a problem at all with methane, ethane, propane, butane. Alkane Boiling point . . . . . . . . . . . . .Triple Point Press [H2] . . . . . . . 20 K (−252 °C) . . . . . .12 K . . 0.007 atm ISP max ~ 500 .Difficult to contain in space [O2] . . . . . . . 90 K (−182 °C) . . . . . .54 K . . 0.002 atm Methane . .111 K (−161 °C) . . . . . 90 K . . 0.115 atm ISP max ~ 400 Can be liquefied under pressure with traditional low temperature refrigerants using two stage cooling. Ethane . . . 184 K (−89 °C) . . . . . . 90 K . . near vacuum , Can be liquefied with traditional low temperature refrigerants using two stage cooling. Propane . . 231K ( -42 °C) . . . . . . . . . . . . . . . . . . . . . . . . . .Can be liquefied under pressure with typical refridgerants under pressure or low temperature refridgerants. Butane . . . 273 K (O C) . . . . . . . . 134 K . near vacuum. Can be liquified with pressure and passive cooling. Pentane. . . . . . . . 36 'C . . . . . . . . . . . . . . . . . . . . . . . . . . . . Can simply be liquified with pressure. Kerosene . . . . . . .65 'C . . . . . . . . -53'C for aviation fuel. ISP max ~350 With an improvement in performance in space Kerosene can be made more ignitable with the addition of Butane if the fuel is to be stored above -5'C and propane if the fuel is to be stored above -47'C, or ethane of the fuel is to be stored about -93. Pressure can be governed by having a heater on the fuel tank and using solar panels. You might also want an induction type stirring mechanism in the tank. The risks here is that the fuel should be precooled into Space, provided the craft is reasonably shielded from the sun pressure should be easy to maintain. Propane and Butane are commonly used as fuels for vehicles and houses . . . .no problem there.

Fall out shelters are designed to protect from x-rays and gamma radiation, protection is generally heavy metals like lead. The particle type is photons and relatively low velocity alpha particles. Alpha particles are 4 times as heavy as protons. True GCR are waves of matter traveling at relativistic speeds some have been traveling around in the galaxy for 200 million years. I should repeat, most of what we experience on Earth and the ISS are secondary radiation, that is the electrons have been stripped from the protons and some loss of momentum has already occurred. The ability to detect a neutral matter field traveling at the speed of light is virtually impossible (deBroglie hypothesis) therefore it is necessary to slow highly relativistic-particles in cascades of interactions that steal momentum from the particle. The preference of shielding for deep space is not the same as for use on ISS or in a fallout shelter . . . . these are two very different problems.

Thats true but a spiral orbit can be seen as semi-ciruclarizing at each point in the process, its not key, its just a notation. What is key is adding prograde energy at the less that maximal speed (as close to the tolerable atmosphere as possible), which is profoundly made worse in burns beyond the parabola because the energy in excess of SPE you get to keep as SKE. and that translates as V = SQRT(2*SKE) and so it makes. It is certainly true that if you burn to say r = 10,000, circularlize, then burn again to exit, you will have spent more dV.

There a milliions of pieces of space junk most tiny working their way slowly to decay.

You could greatly lessen this number if you could copolymerize the substrate with a hydrogen rich plastic. Might even be good to have embedded boron, lithium or berylium. The ideal of slowing down cosmic radiation is to have a collision partners which are light enough to take alot of the energy out of the moving particle. If you take out energy they become less relativistic (they age more rapidly) and shower more quickly. Its not just substrate, if you can select from within the substrate the lightest elemental components . . . .hydrogenate these components . . . .one could make the shielding more effective. Short term . you place a Cylinder on the planet, connect it to adjacent cylinders and you bury the center one in as much substrate as the structure can withstand. As you say starting from a fresh crater of smallish size is a good place to start, but in the short term you want quantity is more important than quality. Robotics are the answer here, move, elevate, dump. I don't see storage of hydrogen cylinders on top of the facility as a viable option; not at least until someone can find a source of water that could be used for electrolysis that would exceed the biological needs of a Lunar or Martian colony.

There wasn't alot wrong, its just its weaknesses get blown out of proportion by a few idealist. What a boosters true function is to get the launch vehicle away from the launch pad. That sounds sort of redundant, but its not. . suppose you have a perfect rocket, ISP = 500 and the first stage is going to get you to Space, the problem is that in providing 9000 dV required to get to orbit, the launch only has enough thrust to hover over the launch pad for a minute before it starts moving. If a launch vehicle has only TWR = 1, its not going anywhere until it loses fuel. But as the rocket approached MaxQ it really does not need TWR >> 1, otherwise the thrust of the rocket just gets thrown into the structural rigidity of the forward payload. So basically if you have a really efficient rocket, all you really need to do is get off the launch pad with an acceleration at the structural limit of the vehicle, approach about 0.85 M and release whatever boosted you there . . . .take about 15 seconds to pass MaxQ and just go. The ISP issue becomes trivial because, if the Booster is cheap, you're not holding onto the weight but for a minute, the mass of the fuel hardly matters. But if you are going to use a booster to go to >2000 m/s , the ISP is not trivial, and its particularly notable if the SRB is more expensive per kg than alternative boosters. The SRBs weren't cheap, they were expensive, and they were designed to burn much longer than to Mach 0.85 (if they had cut out at 0.85 the challenger disaster would not have occurred and thermodynamic forces would have not torn up the shuttle), and the shuttle would have befitted from having more engines (just not the SS25). The shuttle itself cannot be blamed on the SRBs. The good points of the shuttle program were its flexibility, which many here see as a weakness. But some of the critiques to 'stick' First it could hold up to 11 personnel in an emergency which was basically silly. That wasted weight in the cockpit. The missions should have been scaled back with crews of 4 and a maximum crew capacity of 7. IOW the shuttle tried to do to much of too many things, which could have been scaled back for a viable launch, but not 12 times per year, more like 4 launches per year for specialized missions. Many things the shuttle were doing, like ISS crew and supply missions were redundant with much cheaper launch systems, and having completed the ISS, many of the science missions were redundant in facility with the ISS. The bad point of the shuttle as mentioned was the 'damn' foam and tile issues. Tiles repeatedly fell off the shuttle, including tiles in area that were not exposed to falling foam. So that there was a certain inevitability to the Columbia disaster. If a tile falls off in the wrong place, then craft cannot re-enter until its fixed. The tiles would have continued to be a problem until they designed a different ablation system. @tater posted a comprehensive summary of missions with tile issues over the course of the shuttle program that is worth reading. What is really true about the space shuttle is that the US lost a certain degree of functionality, functionality that was supposed to be replaced by now, but is nowhere near being replaced. The shuttle program was ended to save on cost, but the reality is that the up-and-coming functional replacement systems are not cheap, they are very expensive, and the practices that ran up the cost are still on-going. The only bright spot is that SpaceX has stepped in and it might be able to sort through the supply-inflexible market place weeding out the inefficient players, I suspect the SLS SRBs, once used up, will not be replaced.

FH is heavy buts the rocket itself is not crazy big. The space shuttle uses H2 which drives up the volume of the space craft. Heavy is a cost and Voluminous is a cost. The SRBs on the shuttle while safer in 2010 than in 1986 still do not have a throttle down state short of fuel depletion and therefore can never be made as safe as a 2-component fuel rocket, this is coupled to the fact that solid fuels have ISPs with ISP 2/3rds of LF rockets and 1/2 that of cryogenic. And while the shuttles SRBs were meant to be recycled, it was not an efficient process and really did not save that much money.

There first firing takes out horizontal velocity but is at high altitude. The bell of the M1D engines are engineered, obviously, to withstand the pressure, I have never looked at the speed versus altitude profile of the F9 on return, only on two rockets to first stage separation, so I could not even estimate the horizontal or vertical components of their velocities. Most however separate around 100 km which means at the 2400 to 3000 m/s they are traveling its more space like than atmosphere like. The majorit of their energy is in motion away from the launch pad, to return they have to zero this energy and develope a horizontal component in the direction of the pad. Letting gravity handle the verticle components. The do at least one more supersonic burn and then go transonic before the last burn. In someway the atmosphere helps, fuel rich mixtures are more likely to explode under highpressures in the presence of O2. If they are experiencing very high kPA inside the nozzel and the fuel pump can load the nozzel, it should fire.

I don't know how these ablate or how much structural rigidity they have, you probably would only need a few hundred Pa to inflate them, a light gas like hydrogen would do.

Fr From what I understand the expose outcrops of non-igneous material are generally less densely packed than on Earth, given the presense of large amounts of alkaline oxides its probably not that difficult to drill through them. If you could use High pressure water injection you could remove alot of the binding salts and use rather low tech techniques to debulk. There are forseable problems. 1. The outcroppings are generally not that high in elevation. 2. So you would end up having do dig down, again 10 meters at least if you want 10 meters of protection from GCR and HCR you need to excavate breccia and lose soil, then dig down into the rock, and finally dig sideways. 3. Preferable you want a tunnel 3 to 4 minimal meters in diameter, thats a pretty big tunneling device, very dense and difficult to land on Mars. At least you need a repair station and probably some sort of ultrasonic washing station to get the fine glass off the machine, haul it into a pressurized workshop and then pressurize do that workmen could efficiently repair it safely.

Yes I assume that greenhouse would be an alternative, but under the following circumstances. 1. A genetically engineered crop that is suited for growth under red LED [blue LED fade quickly at high intensity], at elevated biomass accumulation rates 2. the crop is specifically designed to accumulate aliphatic carbon -(CH2)n- (as opposed to (CHO)n) for example palm oil versus cellulose. More O2 3. That some source of H2 production. 4. That access to power is infinite. Again, something I keep repeating, these projects are doable, but feasible as a human endeavor only after sub-terrestrial architecture is in place. If the human isolation projects have shown us anything, its very difficult just to provide enough solar power on Earth to support humans, let alone grow stuff for fuel. So that metric needs to change. ISS works OK if humans are supplied with fuel and food, the second these run out the task involved in getting the ISS to create just its food is a daunting task. Greenhouses, fuel and all this stuff are on a big long IV-fluid feed going back to Earth . . . . . .So who is designing the highly efficient circulator that carries these supplies back and forth to mars (Not ISP 375 but ISP 9000)? Pressure pumps are easier to take care of than centrifuges, and on Mars at night you can use the atmosphere as a low temperature heat sink, not efficient but you can at least produce Dry Ice. There is not enough O2 in the martian atmosphere to waste the effort on, crack the CO2 with H20 or H2 or greenhouses. I actually wouldn't worry about CO, Just find a crop that is tolerant to it and use that crop and greenhouse to remediate it. Aside from that if you have a power supply that gets you into the 'water' zone of Mars, the poles, you can pickup frozen chlatrates of dry-ice water right off the ground. This gets me to a peeve about some Mars logics, some of the posters are treating Mars like a gigantic invisible ocean of Water and Air. Its not, water will be hard to get, and any air you want to use for fuel or living needs to be manufactured. Its much much easier to deal with the pressures, control the temperatures and avoid the HCR-GCR when the living facility is underground, easier to stabilize the water pools.

The basic theory behind this idea is that at low speed a moving object experiences frictional flow as the mass of the gas a vehicle travels through an atmosphere. If we look at the gas at any moment all molecules are moving around an aerodynamic devise with some velocity in accordance with its distance. The faster an object goes the more turbulent some of those flow elements become. Starting at about Mach 0.85 this starts to change around the less aerodynamic parts, there is a boundary layer that develops and in particular when and object does not conform to the Sears-Haack shape. At about this speed a layer of higher density of gas is found around non-conformant layers at even higher speeds that layer separates. If you watch the F9 launch videos and the humidity of the atmosphere is just right you can see this layer separate from the nose cone and the cone broadens. At the same moment you may see flame from the rocket going the wrong direction, sooting up the side of the rocket. This is cause by supersonic boundary layer separation, In side the boundary the vehicle is basically clinging onto the mass and the flow is non-laminar out some distance. Bow shock off of a blunt body What you don't see is that on the nose cone itself air mass is also accumulating. Air molecules travel at the speed of sound, this is basically the absolute value mean moment of air motion at a given temperature. This means that at any given temperature an air molecule can only accelerate so rapidly. I an attempt to move around the rockets nose cone the gas trys to accelerate but at the speed of sound relative to other local air molecules it cannot. At which point its flow becomes inelastic and it basically piles up as a dense layer on the nose cone. The tip of that layer builds verticle mass on the nose cone with speed. If you build a triangle pointing vertically with on point up the axis, another point touching the side of the rocket at the base of the curvature and the third point touching the curvature, then the sin of angle x hypotenuse(velocity * time) = Mach * time or if speed in is Mach its Sin Θ = 1/SMach . . . . . .Θ = ArcSin 1/S roughly. And everything below the cone created by the hypotenuse gets compacted into the nose cones mass (under the boundary layer), as the layer builds upward molecules accelerate more fluidly outside the layer. If the structure is not designed to take the force (such as the engine on an airliner) the structure will undergo cavitation. In the Sears Haack shape the object has a shape that minimizes the distance of the triangles vertex (verticle) from the skin of the rocket, this causes the flow to become more laminar around the rocket. I should note that there are also oblique shockwaves, but at the altitude on Mars which you will be decelerating through you should not have to worry about these. We can think of it like this, at a certain speed the air behaves like a gas around a structure, above that speed the air starts behaving more like a dense liquid; the degree that it behaves like a liquid is a function of speed and structural design. A liquid has more cohesion than air (you see rain drops stick to the window of a cockpit window) and that liquid has more affection for the object than the air outside of the boundary layer. But as its a liquid if the layer is high enough it can slide off. However, if the object is high enough the 'stuck' gases can slide off before the next gas molecule hits. . . .this is space. So what it means is that as you travel in from space particles are hitting the object and immediately moving out of the way, the layer, if any is very thin. When two molecules stike each other they knock eletrons out of orbitals and create a momentary plasma that glows, these 'chew' at the surface. So that the surface needs a material that sloughs off with these impacts. These molecules can provide lift but that lift is not aerodynamic, there is no Bernoulli's force involved, its like billiard balls striking and reflecting. In this situation if the structural plane is facing the gas flow, it will create maximum drag, but no lift (Imagine the Apollo capsule traveling horizontally, heat shield facing the air flow, as if it is orbiting but inside earths troposphere). If you rotate the plane to 45' (Gasflow ---> \ object) there will be as much lift as drag. The spacecraft will fall less rapidly compared to the verticle plane. If the plane it facing but 30' then it has less that half the drag but most of the force is in lift, so this falls the least slowly. But in horizontal flow through the subMach airspeed you don't want to have the plane of the wing much above 15' because of turbulent flow. Between these (subMach and Orbital speeds at space altitudes) two circumstances the plane can trap gas momentarily and cause the gas (or plasma) to do funny things. For example the plane facing the flow of gas causes the gas to reflect backwards increasing the risk that another gas strikes it, sending it back. That flat plane is expected to build a hot and thicker of layer of gas on its surface (a fire ball). If one grooves the surface like the skirt of a womans dress, the fireballs will flow through the channels. We can constuct the surface (imagine a collection of funnels and tubes) to force the fire ball downward toward the ground and as the fire traveled down the spacecraft would experience an upward force. This behavior would be expected to continue while the spacecraft was above Mach 0.85. Of course you would not want to have funnels and tubes as the increase and mass and the shock forces on the craft would give your engineers nightmares. This image shows that both inelastic and elastic collisions are contributing to the forces. The inelastic collisions create the red glow that is directed by the winglets down the space craft, channelling some of the flow to increase lift. As the static pressure of the atmosphere increases individual particle collisions contribute less and flow dynamics contribute more. This results in the appearance of shock boundaries.

They can't be serious.

I think they were redesigned to increase their saftey margin. There were problems with the classic design. "Report of the Presidential Commission on the Space Shuttle Challenger Accident" Some of the problems were fixed after challenger. If the shuttle were designed today they probably would not be using the SRBs if their intent was to recycle.

Thats what BFR appears to do, by channeling the atmosphere mass into channels you force it to accelerate and compress (at that velocity gas has alot of momentum so the momentum itself creates significant pressure at any speed greater than mach due to boundary effects. This forces gas into the boundary layer and it becomes part of the ships skin and then is released . . . . . .this is work... you are performing work on the gas. But there is only so much work you can do, once the gases mass is the same speed as the ships, thats the most work than you can do, and it needs to be released so that it can be repeated. So there is a theoretical 2 fold possible improvement over a single wing which is less if you consider to channel more gas you have to move gas along the channel. A parachute does essentially the same thing, it has holes to channel air thought the chute, but above Mach Speed you need a rigid structure, flimsy plastics will not suffice. Thats the Mars problem in a nutshell, on Earth terminal velocities are in the 10s of meters per second range, on Mars terminal velocities are in the 100s of meters per second range.

Its correct, but only from the starting radius, if the Pe increases significantly then its more. The key point is that if you burn only at Pe to achieve SOI+ you never have to pay the cost circularizing the orbit, which just before SOI would entail a burn from almost zero velocity to circularize. In a spiral orbit as you increase orbital momentum the speed with which you burn goes down as you rise, and thus simply stated Given a prograde thrust*time of defined total length (in dV) the higher average speed of your burn contributes more energy toward escape than any set of situations where the average speed over all moments of burn is lower.