PB666

There are an infinite number of women you could ask out on a date, but how many could you afford that wont also turn you into wreck.

So an earth Year is 12 months and half a year is 6 months. Half a martian year is 11.28 months the average is an easy approximation in months. 8.64 months. The period is determined by a, the major axis. P = 2πa1.5/[mu]0.5 It takes half the period of a transfer orbit to go from its periapsis to apoapsis. atransfer = (aearth + amars). Therefore transfer Ttransfer = π(aearth/2 + amars/2)1.5/[mu]0.5 = 22,700,000 secs = 8.52 months. The lowest natural transfer from Earth would occur close to its periapsis to the martian periapsis (a diifuclt proposition), it better to plan targets years in advance to match the martian periapsis (since its orbit is more accentric than earths) by doing this one increases the dV requirement by 30 m/s but lower the transfer time to 7.79 months. There is a semi natural transfer that can be done. If we pretended that we could get folks easily to L1 or L2 (we can't and it would not be worth the added dV) you can shave about 2 million km off the average transfer time. In this case you again target the Martian pe. This would take 7.6 months. The problem with this orbit that both require movements at right angles to the direction of travel first. But on the other hand during the departure days on earth speed is substantially higher than average transfer velocity (both sun relative) and likewise speed at Mars is substantially higher than speed just out side of SOI. In addition you lose the benefit of two Oberth-like effcts effects. Unfortunately, the threat sensing software (two types) on my computer report the site as being improperly secured from hacking and block me from using NASA's trajectory browser. I plugged in with a different browser and got it. Its giving the same result that I got, 208 days for the lowest. I tried and got 177 days as the shorted out to 2040 using a cap of 5700 dV. The best being in April of 2033. Using 7000 dV there is one at 3.72 months. Using 8000 dV and filtering for 100 day there is one for 96 days. These are not true Hohman transfers in that the apo and pe of the transfer orbits are not tangential to the orbits of mars or earth at the intersect. These are ;"star trek' transfer. OK so given 6000 dV for the transfer, just a little above that required for a standard transfer to Martian Pe, lets see the best. Mars SPK-ID 499 Orbit Condition Code Size 6779 km Semi-major axis 1.524 AU Eccentricity 0.093 Inclination 1.85° Earth Departure Jul-28-2035 4.29 km/s C3 = 24.6 km2/s2 DLA = -22° 128-day transfer Mars Arrival Dec-03-2035 1.42 km/s* * ΔV to/from a C3 = 0 km2/s2 local planetary orbit.

It should not be the case, polar correction means that everything is changed to Vtan or Vrad . No matter where you are at or what system you used you will always need to roughly gather your Vtan and Vrad . If Earth is the origin of the coordinate system simple calculation. rt0 = SQRT(x + y + z), rt1 = SQRT(x + y + z) then rto,t1' = rt1 - rt0 / (t1-t0) Lets say your Z origin is the equator, X origin is GMT, and Y is at 90' rotation. The latitude component is distance from the plane XY, knowing the radius at that latitude is fairly easy to calculate Z. The longitude in degrees is fairly easily converted to X and Y. X = cosine (latitude) and Y is sine(latitude). GPS gives information in x,y,z but I assume the Russians used their own satellite or ground based navigation systems. Once you have r' then calculating Vtan , (w*r, the circumgeode component of velocity) = SQRT((xt1-xt0)^2 + (yt1-yt0)^2 +(zt1-zt0)^2- rto,t1'^2). A tenth grader can do this geometry. Its basically application of the Pythagorean theorem. If the second stage was seeded it would have been noticing a problem with vectors all along, if it was a initiation problem then it was trying to discover its desired vectors. The next is more complex. But it goes like this. Given mu = 4.98 x 1014, then if you know r and Speed(SQRT((xt1-xt0)^2 + (yt1-yt0)^2 +(zt1-zt0)^2) then you can calculate a=SMA (vis visa equation) and also A'=Vtan*r/2. If you know A' and a you can calculate the period(P), if you know the P and A' then A = P*A'. If you know A and a then you know also b. b = A/(π*a). If you know b and a then you know e = b2/a. If you know e then you know Pe and Apo, l and d. If you know these you can calculate the inclination node between the orbit you are in and the orbit you want. From that you take the mean anomoly of the distance and calculated the true anomoly. Once you have this you simple calculated the time to burn divide by two and burn t/2 before reaching the true anomoly of the inclination node. I think the news article is trying to simplify things. Assuming that the PL-stage were pointing prograde then its likely it quickly determined Vrad. This problem is all about system initialization, if your apriori's are immediate then any corrections that need to be made are relatively simple. For example if you cross the a system boundary going down degrees then you know to convert almost zero to almost 2π or vice versa. The computer program tried to initialize itself base on the apriori's that it had, then it tried to determine the course that it wanted to intercept. So what can happen, this is where I guess, the computer in the stage starts gathering information about its positions and velocities, then it realizes its more off course than its suppose to be and immediately initiates a burn, unfortunately the all-possibilities calculation is unfit for the error-level. Next the gimble on the rocket is too slow, so basically instead of turning say left, it tries to turn right as it is turning is it burning most of the time retrograde. Burning retrograde cause the centrepal acceleration to fall, which means that apparent gravity is higher and the space craft radial velocity begins to decrease and go negative. So by the time it has reached its destination it has now posed to enter the atmosphere and because its speed is much higher than when it left the atmosphere, potentially it is also turned sideways against the direction of motion, parts of the spacecraft disintegrate. Failure ensues. I should also point out that as it turns in the wrong direction, the amount that it needs to turn is increasing from the original prograde so that by the time it reaches where it should have been its now burning at an angle so increased from prograde that the amount of thrust required to stay above safe altitude is probably too low to save the orbit.

I thought that was rather obvious. Dal appears to be frothing at the mouth over this Mars stuff. The MSL CR study was published years ago, no surprises there except that during relatively low sun-spot activity there was GCR obviously higher then expected. Anyone who is thinking of a transfer ship under 50t needs to walk away from the argument now. At least once you get on Mars the CRB is half what it is in interplanetary space. The habitat lander could be buried in Martian substrate for added protection, you could knock the level of exposure down to about a fifth of IPT exposure. I have been presenting examples of interplanetary ships that are in the 200t region, and propulsion systems that can make the transfer, there is a reason for that. IMO we have to get the hydrogen storage and gas recycling done not just to provide fuel for mars landing and, but also to provide a GCR trap. Currently my largest ship gets 2kt into orbit. CGR is not a death nail in interplanetary manned space flight. It can be dealt with (for example placing hydrogen tanks around the crewed areas, more work could be done on design and placement of magnetic fields around ships, etc. The ISS is not a test bed for GR exposure in so much as its a test bed for exposure for microgravity, whose effects may plateau over time. To get to Mars will require more investigations outside of Earths magnetic field. Things like GR sensors implanted under the skin. More sensors added inside of space craft. Attitude based avoidance of GR (including detectors and reaction systems), etc. ITS is a concept, from what I have seen its food for the media and directive for SpaceX to progress, the design is pretty, practicality however dictates design in space. A couple of things I need to correct/opine in this thread. 1. Green leafies can be stored indefinitely at -50'C or below. I anticipate that one thing SpaceX will be able to do is dispatch cargo ships capable of reaching LMO. When a definitive Mars atmosphere aerobraking strategy is worked out such deliveries could be routine. The technology is progressing rapidly. 2. Everyone shows a Mars lander and ascent vehicle (also Lunar lander and ascent). The lander and ascent vehicles may be a separate enterprise. The lander habitats they separately for people to stay in. Just assume that its a two ship enterprise. 3. From my point of view, if the CRB is the biggest problem in interplanetary transfer then you will not ditch your ship landing on Mars, that transfer ship will remain in orbit waiting for the lander. One strategy is that the ascent vehicle provide at least some of the dV to get it back in to LEO. You can carry the utilitarian lander as a package on the transfer ship, but my assumption is that it will remain in Mars SOI. 4. If we are talking about suitability of radiation exposure on Mars, then I think we need to consider the fact that some sort of automated preparation needs to be done (i.e. to the habitat lander) before humans arrive. Otherwise you are going to have humans out trying to lower their habitat and carry tons of sand and rock into the habitat area.

Cool you can have them as a pet in minecraft. poop out building materials.

He can buy it from himself and write it off as a business expense, Purchased 1 large lithium ION battery and a stereo for rocket with a used car attached to it (Space-time wave generating speakers not attached).

If he filled the tesla with xenon gas tanks he could mount some solar panels on it and IOn Hilux could have survived the landing!!!!

They were trying to make their version of a space-shuttle. I went about a football field. It would have worked better if they had used their lucky hilux.

Hes going to park it in the 'restaurant at the end of the universe' orbit, its a drive-in of course.

Yeah, because powerful people never get on twitter and say ..like...shocking crazy stuff...hmmmm

I put 2 kT into orbit, lol.

You have to deflate the tires to 14 PSI before lift-off. And I believe the secondary battery needs to be sealed air-tight, also some ethylene glycol in the windshield wiper fluid or it will boil off. What else its got a big-ass battery, put some solar panels on it and a communication dish and antenna.

Well if inflation created all space, everything could be shrinking as space-time fractures the universe into smaller and smaller parts. The end of the initial inflation may have determined the ultimate size of the universe and subsequent expansion is just a way to stuff everything into it. I have to say that I don't like these analogies. The problem with big-bang divination is that all our basic facts about the big bang come millions of years later when matter cooled enough to create a non-opaque light to travel down. 100s of times larger than the 27 billion light years we can see is speculation. The idea that we could not see the center is equating that the CMBR is the only measure of anisotrophy in the Universe, but there could be other measures. Lets create this logic there cannot be a center because I cannot see anisotrophy at the CMBR. 1. If your visible universe is at the center then you could not see anisotrophy. 2. If the rate of inflation (IOW the in c and not distance) then you might see anisotrophy at most positions, BUT if that radius was 3c (that means the universe is 80 billion ly across in psuedospace-time units) only those obeservable universes closest to the outside might see differences in CNBR, assuming energy pour uniformly into the universe. This is because information on the edge would take 1c * 13.8 billion years to reach observable universe centers that are 2c from the center. We can calculate the interior volume as 4/3πr3 33.8c, while the peripheral volume is 79.2 more than 1/4 th of the observable universes will lack any edge anisotrophy, there are no good statistics that can be made. if the inflation radius is 4c then more than 1/3rd will lack, 5c approximately half. For the argument that there is no center you would have to be in a universe that is close to 1c in radius and observed no anisotrophy. Such a statistical certainty is unlikely. 3. Note all discussions of predicted cohesive size of the universe have been removed from wikipedia (for good reason), there are inflation theories suggesting that the universe is infinite or rolls out on the horizon of the universe and is infinite. So even if you were close to the edge at the beginning of your epoch (your local big-bang) that by the time stuff evolved it would essentially be anisotrophic. In either theory postulating a center is a futile effort since there is almost no way to confirm or deny its existence unless some distortion of the laws of phsyics occurs in a distance related fashion and we could penetrate other comoving space to test this. So that the size of the universe in observable universes size range from a little bit bigger than our own (typologically based science) to gazillion times bigger based on the time in which inflation begins . . . . . .minding that during the time [coughing] that the universe was a quantum space-time singularity time had absolutely no meaning what-so-ever. I repeat that our view of anisotrophy is entirely based on CNBR and we haven't much of a clue as to what is quantum gravity was or its internal stability or how it evolved in the universe including during inflation . . . . .or when time became a useful measure.

As is, the weight is too high, assuming these are gigawatt ranges they might be useful in tugging stuff around, but getting them off the ground has problems at many levels. Keeping the argument short and sweet, in the vacuum of space the scalar size of a heat source is a problem, getting those sizes down is the solution. Fusion has not demonstrated that it can be scaled to the small size.

" Instead, the computer decided that the spacecraft had been 360 degrees off target and dutifully commanded its thrusters to fire to turn it around to the required zero-degree position. " lol, do I need a job, I just finished programming that exact issue. If query is between 0 and π/2 and subject is between 3π/2 then add 2π to query and calculate else just calculate. =IF(AND(RC[-15]<=0, RC[-15]<=(PI()/2),RC[-1]>=(3*PI()/2)), ABS(RC[-15]+2*PI()-RC[-1]),ABS(RC[-1]-RC[-15])) [This is in Excel cause my visual studio license has expired] That particular equation was to determine if the space craft was traveling prograde by looking at dx, dy per dt (dz had to be projected to equator). First it had to determine the radial direction of velocity vector, then compare it with an ideal prograde vector for that position, if it was closer to the ideal prograde vector, then it was considered to be prograde (and cartesian coordinate mapping then used prograde assumptions), otherwise is was considered to be retrograde. From that point on the circular velocity (in x,y,z coordinate system) and radial velocity can be extracted. A smarter and simpler solution is just to make a course change at Northern geographic pole, since they were spitting distance from it, and then make a correction turn at the equator after they were nearly in orbit. Making a course change at the equator 'greatly' simplifies the math and course change. EDIT: I should point this out for the general audience. If you trigger a flight navigation system with no other information other than the desired vectors, then presumably that flight system gathers information from satellites and other spacecraft systems, and then goes through an initiation by which it can then use Markov Chain Ramer–Douglas–Peucker chain analysis or the like. But the problem in initiating the system lies in a couple of facts. (for simplicities sake an initiation process does not need a Markov chain simply because the velocity and acceleration vectors can provide enough confinement in the first pass that testing vectors are not neccesary). That traveling close to a zero point you either need to convert to 2π from zero or zero from 2π but for velocities and accelerations its much more complicated. The vectors for prograde and retrograde are +/- π/2. For instance if your position is radius Px = 4525 km, y = 4525km from earths center and the prograde direction vector is such that Arcsin(pY) = ArcCos(pX) [There are ussually two solutions for arcsin and arccos but only one solution that they match] is +/- π/2. The angle for positiion direction is π/4 in this exemplary coordinate system, and the ideal prograde circular velocity has a direction vector of 7π/4. Lets say that you add a radial or normal vector that bring a rotation of more than π/4 to the velocity vector and want to know the angular distance, the proper |distance| is between π/2 and π/4, but the answer might appear to be 5π/4 to 6π/4. This occurs because sine and cosine functions are a waveform that stretch from negative infinity to positive infinity and that wave form -2π = 0 = 2π = 4π = 6π. But when you are trying to set a course you want to use the set of values that give the lowest difference. So in the case above I can raise the ideal prograde direction vector or lower the observed vector by 2π, but not both, and recalculate. But if you add the correction and it is not needed you will over correct. So in the above code snippet I first test to see if the ideal vector is in a 'trouble' spot and see if the actual vector is a reciprocal 'trouble' spot, If all these conditions are met, then perform the alteration of the ideal vector and calculate, otherwise just calculate the distance. This is not a general correction one wants to make, unfortunately, it needs to be done in the confines of each calculation. This is a known issue so I am not describing something new. So if you miss making this correction in a single calculation you may end up making at >370' turn when you only wanted to make a 10' turn. A similar situation occurs in Aircraft, if you are flying along a course and you are told make a right turn [of say 270]. If you throw the heading into the autopilot quickly it will turn left by 90 degrees and some ATC is going to be upset as hell at you. If your flight computer had ears it would know to make a course correction of 135 degrees and another one of 135 before the first solution is achieved. One problem I should note is that different programming languages use different internal function calculations, and this is a platform problem more than a software problem, so if a computer is capable of producing negative direction vectors from basic trignometry functions that will affect how the answer is provided. Therefore the platform needs to be tested in a wide variety of circumstances to see how it performs.

Quantum gravity caused everything, almost. I think [Coughing] came from an alternative universe. At least the way I understand this, A quantum space-time singularity of infinite energy density (meaning that the energy level was so high that no coherent means of measurement was effective). As described by one energy theorist the protouniverse was so hot that it was cold. This means there is no hv, no matter, no sub atomic particles, nothing, except a super-energetic quantum gravity point. As we see from observations of distant stars space-time distortions (waves) carry energy over very great distances, so we understand that there should be a particle that carries energy, these are so-called scalar energy. But for our current universe to exist that point particle needs to be spread out into something that creates our space-time. This had to be a very energetic process given our observations of space-time distortions. Where the uncertainty comes into the argument is this, during the process in which a largely 'quantum' space-time universe ends and something resembling our Universe with strong-force, electromagnetism, . . . . . . there may have been additional energies that poured into the universe as the intense quantum state dissipated/fractured. THere has been proposed an intermediate field between quantum singularity and space-time called the inflaton field. Without being two critical its an intermediate state of cosmic gravity in which no dimensions exist to the current state where space-time exist. We know however that space-time has a ubiquitous Higg's field in it with a non-zero vacuum state (The particle associated with the field is tremendously energetic). Therefore energy must invade space-time. Or alternatively space-time cannot be produced if energy is also not added to the system. As stated above, a quantum gravity singularity gives rise to inflation which gives rise to space-time. For this to happen scientist to create a phase transition to true vacuum. In this Universe, I should say, particularly since Heisenberg, nothing is ever true, we only at best have perspectives on the truth. There is never anything that is truly a vacuum in all sense of the emptiness of space. To simplify this we can think of the Inflaton as being quantum vacuum 'pre'-space but with a huge energy potential. With any huge unsustainable energy potential its never possible to deliver a pure outcome such as pure space-time with only higgs feild that propagates . . . . .so in that sense public discussions of pubic grabbing do make some sense. Hope this explains the problem. Actually our only valid perspective is the CMBR, inflation was drafted to explain the lack of overwhelming anistrophy. Once you have inflation you need inflation of something (transitional space-time) from something (quantum space-time).

Not to worry, Einstein set this up by arguing that everywhere in the Universe is relative, and because if we look to the edge of the visible we only see local anistrophy its simply easier to conclude we are at the center and not. The argument has everything to do with quantum gravity (that handwaving model problem that no-one seems to have a clear answer to). Space-time is the product of something [black box] that took us from a very ambiguous thing to our present ambiguous location. Here is how the fairy tail is supposed to work Once upon a time, but precisely a time when time did not exist, the universe was very small, so small in fact that it had no dimensions, it is the geometric point. But this then made it a quantum singularity. As we know from other studies of quantum states things can be in many places at a time and time can actually go back and forth. The universe was in this state for an immeasurable amount of time and its exact position could have been anywhere, in fact everywhere in the universe (and no I have not gone back to my 70's time machine and found some unused mushrooms lying around). For a reason that remains unclear this existence became unstable, some have surmised that energy had poured into this protouniverse. . . . .that the particle was quantum gravity . . . .and after reaching some threshold (like nuclear fission) . . .that particle decayed at its quantum position(s) creating an inflationary wave. As the instability stabilized inflation slowed to almost a stop (given the uncertainty of how quantum gravity currently works we are left saying. . .) and space-time magically appeared. This creates the problem of the discussion, depending on who you listen to and what version you believe the quantum gravity particle contained all the energy in the known universe or energy poured into the universe as that particle transformed into its current state. Making matters more difficult we cannot connect the quantum gravity particle of today's universe to space-time and so there are opinions about this. Despite what has been said here, it goes unmeasured, on its curving affects on space and time. But suppose you had a time machine and you could go all the way back to the moment that inflation ended and you had a special pair of glasses that could see the universe, could you see the center. Probably not, in fact you would be more likely to know that you were on inflation's boundary than at the center. The reason for this is at the quantum scale, things can travel faster than the speed of light, and since at the very beginning of the universe much of the universes energy was in a quantum space-time singularity its decay was superluminal in nature (this argument is somewhat tainted by the fact that the universe was too unstable for light to exist). This means that within the inflation boundary just about everything in the universe sees a horizon that is just about uniform in every direction, no matter which way you look. Secondarily, no single observer can see more than about 1/20th of the universe (could be much much less). If you were at the exact center of inflation you will pretty much see the same thing that you would see if you were close to the edge of inflation. What we get out of this is that relative motions in the universe cannot travel faster than the speed of light . . . .except . . . . . .if they are in a different co-moving space-time reference frame (this means very far away). So that if something that is so far away from you that you cannot see it can be moving away from you at super-luminal speeds, the problem is you will never detect this . . . .you will only ever detect things moving away approaching the speed of light but never more than. This minor detail of the relativistic view of the universe means that people (physicist, tv, etc) replaced "Universe" (an intangible thing) with observable universe (something we pretend we can see all of) . . . and in the observable universe, by its very definition, everyone is at the center. There is some factual basis to this also, since gravity and light cannot travel faster than the speed of light, the physical existence of things moving superluminal with respect to us will never affect us, we are essentially forever ignorant of their existence and vis-versa. So how do we make this distinction work . . . In the beginning there was a quantum space-time particle and it was the universe, while if you has a magic quantum time watch and could stop it, it had a center, maybe. But that is immaterial to the point of veiw because what matters is the center of inflation. This quality is not measurable because their is no way to fix the universe and also measure the inflationary sphere, All distal surfaces on the inflationary sphere in space time are always too far away to be measured (thats why it was a big bang and not a small bang). Looking from the inside. . . .As it decayed the cohesive universe decayed into a spherical evolutionary gradient of observable universes (remembering that observations require space and time), since we live in a space-time universe we cannot observe the state of the quantum universe and since its center is a quality of that state, it cannot be simply observed. That which cannot be observed or inferred is assumed by science not to exist. See I answered the question without really giving an answer.

Yes, talking about ISPs 3000+. But you are confusing two things in the Peewee 36 kg of uranium is brought on board, <0.72 kg of that is actually undergoes a contaminated decay, 35 kg either does not contribute at all to the heat or goes into producing latent heat or simply wasted. The reason ISP is low is because their is relatively poor control of the reaction in NTR. NTR is kind of like someone taking an 12 layer wedding cake, putting it in a giant blender and then handing it off as just as good as a 12 layer wedding cake. All the while everyone walks away from the table . . . .i mean this is what happened to NTR. In a fission reactor, especially fast breeder reactor, the fuel is efficiently depleted of fissile material. The issue is of course how to extract heat in space. Full scale fission reactors are two heavy and need extensive heat dissipation. Smaller scale reactors can use other fuels, like plutonium, which have a much lower critical mass. If NTR could produce impressive ISPs and increase the moment of force associated with optimal fission reaction (not perfect but say 10 fold better), then you might be able to justify its use in space. But as it stands right now an ION drive with 2000 ISP accelerates slowly and you waste half the energy going to orbit if you don't kick, but its still better than NTR because it can muddle through LEO and once it is in interplanetary space its a champion. So the powers-that-be don't see the need for NTRs anymore. If the ISP of an NTR went to 9000, and if the rxn was efficient but did produce a small tail (say 1/4 of a kg) of radioactivity while escaping earths orbit . . . it could be justified (Chernobyl released 3.5t of fuel, but some of this fell immediately into the surrounding area). This is where the political problem comes from. NTRs have the appearance of some Bubbas making a rocket in the fashion that Chrysler used to put big-block V8 (~6.5 liter) lead spewing engines in passenger coupes and then wondered why the company went out of business when oil hit 33 dollars a barrel and there are four door sedans running around getting 30 miles to the gallon.

https://www.nasa.gov/directorates/spacetech/niac/2012_phaseII_fellows_slough.html https://www.nasa.gov/pdf/716077main_Slough_2011_PhI_Fusion_Rocket.pdf

I think their insurance companies are going to do quite a bit of yelling at someone.

Hit "X" key, set course to retrograde, hope your reaction wheels are zeroed out and ready to go, hit "Y". Then of course your are free to sip your vodka.

This argument is a clear case of "a vanablackened cat calling a kettle black". I am not against NTR, I am not an admirer of the current NTR because frankly they suck. Here is why they suck. Except for the fact that no current fissile NTR design is in use and Solar electric propulsion is one of the most popular forms of propulsion. Proof of the pudding is in the eating, and no-one want to eat NTR, it leaves a bad taste in the mouth. NERVA 825 ISP = 8093 m/s. If we assume the nozzle is say 6.7 meters. a = 7,700,000 j = 30,732,000 J/kg 177 MeV is the amount of fission energy in a of 235U. This is 0.0000000000283585 J/235U. One 235U weighs 3.902E-25 kgs. Thats 72,000,000,000,000 J/kg. Lets assume that an NTR rocket has at ION drive efficiency converts 1 kg of Uranium-235 into dead fission products. How much fuel would you need to carry to make the reaction efficient you would need to carry 2364 tons of hydrogen. The big STS orange tank carried 106 t of H2. The peewee project had 36.8 kg of uranium. 9200 m/s Ve. Lets be generous and say 40,000,000 J/Kg. The burn length was 80 sec at 12.5 kg/sec = 10t of fuel. Available power = 36.8 kg (assuming pure U235) * 72TJ/kg = 2.6PJ of Energy available. Of this 400 GJ was used for an efficiency of .015%. If we compare this with solar electric power, the SA power utilization is 0.2 to 0.3, the power efficiency of the drive is .7 to .8 the total Power inefficiency is 14%. In terms of power utilization SEP is almost 1000 times more efficient than NTR. Even if we granted the Uranium235 mass ratio was unenriched at .0072:1 the energy efficiency of Peewee would have been 2.08%. So don't give this BS about ION drives being power inefficient. The NTR rockets are the least power efficient system right now, and it does not really give a spectacular product for the numerous risks and shortcomings. If you could come up with a closed loop fission system (such as a fast breed reactor) at 10% power efficient with a coupled ION drive system would produce a better and safer result than the NTR. At least the Soviets repeatedly placed such reactors in space, NTRs have no space track record at all. . . . .and I don't even like fission electric. The advantage of fission electric over NTR. No need to carry liqH2. Xenon and argon pack quite nicely. Magnesium maybe a future fuel. You could provide a fuel that both blocks radiation and can be used in the ION drive. Fission electric can be shut down if 235U is used as a fuel because its much easier with little weight to reach to approach prompt critical. Its much easier to shield because you are not spewing products into the space your ship is flying through. Solar power can both provide power for ship system and manuevering and low power operations through ION drives when reactor is shut down. The ISPs are much, much better. Remember that the inside skin of the nozzle both slows the gas and cools it down, eventually you will have accumulation.

Don't take what media hype says as truth. The HiPEP system is rated at 24kw weight 10kg and can produce up to 8900 ISP. VASIMR can produce up to 5102 ISP, it weighs tons, and can use 200 kw. If you simply take 8 24kw (.38 m2 x 8 = 3.04 m2 = Circle of radius 0.983 meters) you have better performance than VASIMR at 192 kw. at at least 90% of the efficiency of VASIMR but at 1/100th of the weight. With the weight saved by using HiPEP over VASIMR you can add the weight of theoretical 1000+ m2 of solar panels at 300 w/ meter = >300000 KW. . . . .easily making up any efficiencies you have lost. VASIMR looks like a space ship engine, but its little more than space junk. All electric propulsion are hard and expensive. Even if the Cannae drive for instance is 100 times higher than a photon drive, its power requirement is 3E6 KW per N. You don't use fuel but you have to carry 100 times the weight of fuel you would use in solar panels. I am not knocking ION drives or other handwaving electric propulsion, they have their place. . .(Station keeping and tugging things about) . .but they are not fairy dust or 39 or 89 days to Mars under any known circumstance.

Mercury is much easier to store, but has a lower ISP. Since most NTRs require certain sustained flow characteristics one does not want to employ something like chromium or iron which might gum up the works. For chemical rockets reductants can be anything. For example Fe0 (Cast iron) is a reductant, so is sodium metal. Can you imagine the piping system required to turbopump cast iron. lol. Basic energy. https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf and find the bond energy for Take the energy and divide by the weight. H-H is 436 kJ per mole. O=O is 498 kJ per mole. O-H is 460 kJ/mole. 872 + 498 (it takes 1370 kJ/rxn-mole to take them apart) -----> (1840 Kj/rxn-mole recieved to put them back together) = 470kJ per mole. .004 + .032 kg/mole. This means 470kJ/0.036 kg 13MJ per kg. A joule is a Newton of force accelerated over a length. Suppose a rocket nozzle is 3 meters in length then on can accelerated at 4.3 Ma. T = 0.00118. Ve =5079 ISP(sec) maximum of 517 sec. However this is not what you get from the reaction. Approximately 5-10% of the energy is bled off to run turbo pumps, generators, in H2/02 rockets energy is bled to evaporate the cryoliquids. Then there is heat within the nozzle that is lost and finally there is differential heat in the rocket gas (since the flow from the nozzle is not perfectly laminar). C-H is 4 @ 431 kJ per mole. 2 @ O=O 498.7 -----> C=0 2 @ 749 + O-H 4@460. 3338 - 2724.1 = 613.9 kJ/rxn-mole. (.016 + 0.064 = 0.080 rxn-mole per kilogram) = 7673 Mj/kg. Once again 3 meter nozzle. a = 2.557Ma T = 0.00153. Ve = 3916 ISP is 399. This means that no methane powered rocket can ever produce more ISP than 399 sec. Take note of the fact that CH4 produce more energy per reaction mole than H2, but it adds an additional 0.012 kg/mole of reductant weight and an additional .032 kg/mole of oxidant. . . .its the light weight of the H-H bond that makes all the difference. Benzene or coal are very poor choices for fuel because they both have resonance energy stabilization due to 4n+2 pi orbital arrangement. Also because the C-H C-C ratios are lower. kerosene is some where between Methane and Benzene in terms of performance. Note that gasoline has alot of benzene in it, for this reason it gets lower mileage than diesel fuel. You don't want to use gasoline as rocket fuel, but you could use paint thinner or hexane, pentane, pentanes, butanes, propanes, ethane, and methane. . . .from lower to higher ISPs Hydrogen MAY someday be the choice chemical reductant for long range space craft, but there are many issues that need to be solved. 1st. The weight of fuel tanks need to come down. 2nd. While reducing the weight of tanks, the leakage rate also needs to come down. 3rd. Durable gas refrigeration needs to evolve and the weight needs also to come down. 4th. The weight of secondary containment needs to come down. This may also involve light movable solar shields that protect the cryogenic fuels in flight from latent-heat evaporation.

And yet every time they set out to find such 'dark' matter they end up proving that dark matter 'flavor of the day' is not the cause of dark matter. Who said gravity was broken? It should be mentioned that "treating the fictitious forces like real forces" means, in particular, that fictitious forces as seen in a particular non-inertial frame transform as vectors under coordinate transformations made within that frame, that is, like real forces. -Wikipedia Hand and Finch are handing us some humorous physical critique. But if you ever try to calculate an orbit using a Cartesian system you can see why its no laughing matter, the first statement is that the position vector points in the direction of an equally fictitious point mass. But even as we consider energy and gravity, there are apparently as set of n-body nodes that allow passage of objects to areas of our solar system, that if you were in a hurry to go to would cost a considerable amount of dV. They are not violations of space time, but apparently space-time magic. Thus although gravity has been known for quite some time, the connotations of what we know are still being investigated, and we have yet to investigate to any great degree what is going on outside our solar system. But here in lies the problem, we cannot be in every reference frame to test gravity, a force that we admit is fictitious and judge its flavor. One statement of the nature of the Universe in 'that tiniest fraction of a second' was that there was no space and no time, there was no space-time. We could call it quantum space-time, but that might be as fictitious as gravity, because when space and time merge, neither of them make any sense. So then its a quantum state that via something. . . . inflation . . . . . gives us space-time. And more illusive is that in its current state it goes unobserved. The question concerning space is that it might lack observable symmetries at high scales and during transitions (dare it be said because there is the implication of passage of time possibly bidirectional) from higher scales to other scales. The connection of space-time with the early universe may be an inferred symmetry that forces background independence of space-time. As such, although the universe inflated from a point in space, that position become irrelevant in any test that involves space-time (even if it could be inferred). But if we accept the background independence of space-time, then inflation did not occur in one place, but in any place, and a quantum space-time did not exist in a place but in all places. "This and other similar results lead physicists to believe that any consistent quantum theory of gravity should include topology change as a dynamical process." -wikipedia. This is fine up unto the point that the quantum space-time dynamic is undefined and is not easily connected to space-time. As the evaluation of the most important transition in space-time cannot be resolved there is a hanging assumption that we can see enough of space-time behavior at the smallest scale that we can know its behavior is consistent with the larger scale. However some experiments indicate there is much more fluctuation in the gravitational constant than other universal constants one of them was conducted with near zero hv energy. But how does space time behave in the emptiest of empty space, we cannot test because we are highly energetic, do we have a proxy that reports what is going on between the stars and galaxies? We grant Einsteins definition of gravity as a warpage of space-time that exist as a field and propagates at the same rate as other mass-less fields, but this does not in and of itself grant it status as a universal constant. Thus we are left using _our_ co-moving space time, our measures of gravity, as a reference frame and we make the following assumption for right or wrong that: 1. The space we look through has massive or energetic particles in it, some that we cannot observe, that explain the motion of objects by the laws of space-time that we observe here on Earth. 2. That further out the space as we look through it has a force acting on it that is somehow defying space-time as we know it, pressing energetic objects apart at faster speeds. or A mistake was made . . . . (Other than the creation of the Universe, which is generally agreed to have been a bad move). Occam's razor may slice this one quickly and soon. Edit: I should add that we create a "faith" when we believe that the fluctuations in the universal gravitational constant will eventually work themselves out as some sort of experimental or procedural flaws, either these fluctuations are real and have some sort of meaning or something about the experiments that were performed lack some type of fine understanding of space-time.