OhioBob

Below is a check list that I use for collecting science in the Kerbin system. I find it helpful because I can use it to keep track of what science I've already collected and what new areas I should target. There are actually more biomes around KSC than what I've got listed - each building is now its own biome. http://www.braeunig.us/pics/KSP/ScienceCheckList.pdf In case you are unfamiliar with the "low" and "high" definitions, on Kerbin "flying low" is below 18 km, "flying high" is between 18 km and 70 km, "in space low" is between 70 km and 250 km, and "in space high" is between 250 km and the SOI. On Mun, the border between "in space low" and "in space high" is 60 km, and on Minmus the border is 30 km. The "flying" definition is not applicable to Mun and Minmus because they don't have atmospheres. For the borders of other planets and moons, consult the Wiki. I also recommend that as you collect enough science to unlock a new technology, you should consider unlocking a technology that gives you a new science experiment.

It's easy to make mistakes when working with these kinds of problems. I've often seen people incorrectly compute Isp using a thrust-weighted average (I think I made the same mistake the first time I did it). A similar mistake often occurs when computing average densities. For example, what is the density of a solution containing of 1 kg water (specific gravity = 1) and 1 kg of ethanol (specific gravity = 0.789)? How about 1 liter of water and 1 liter of ethanol?

Thrust weighted. Like so (F is thrust): I think it is more correct to say it is mass flow rate weighted. That is, Isp = (á¹Â1∙Isp1 + á¹Â2∙Isp2 + ...) / (á¹Â1 + á¹Â2 + ...) Note that á¹ = F/(go∙Isp). Therefore, by substituting F/(go∙Isp) for á¹ and multiplying through by go, we get - - - Updated - - - A thrust weighted average would be, Isp = (F1∙Isp1 + F2∙Isp2 + ...) / (F1 + F2 + ...) which is incorrect. I think "mass flow rate-weighted average" is the correct way to say it.

True, scientists can reset experiments. However, I was referring to unmanned missions in which the data is being transmitted.

The marginal rate of return for repeated experiments from the same biome gets so small that I don't think it's worth doing more than twice. Getting those last few points just isn't worth the time and expense. Even doing it twice isn't really worth it unless you can easily access the biome, or if you are returning with new experiments that you didn't have on your first visit. You get far greater return for your buck by visiting new biomes. Of course there are other ways to squeeze a few extra points on a single visit. For instance, if you are transmitting the data back to Kerbin, just run the experiment, transmit the data, and then repeat the experiment until you exhaust the number of points you can get from it. This doesn't work for Mystery Goo and Materials Bay because those experiments are non-repeatable. Also, for unmanned missions, if you plan to return the entire experiment package back to Kerbin, carry multiple copies of the same experiment. And for manned missions, you can mount the experiment on the outside of your pod. Run the experiment once, remove the data, and transfer it to the pod. Run the experiment again and leave the data with the instrument. When you recover the vessel you'll get points for two runs of the experiment. Unfortunately with surface samples you can only return those inside a pod, so, unless you have multiple pods to store multiple samples, you can only do one of those per visit to a biome. I also noted that you didn't mention the GRAVMAX Negative Gravioli Detector and Atmospheric Fluid Spectro-Variometer. Those experiments are also repeatable for extra points.

I've successfully landed Kerbals on and returned them from every celestial body from Moho to Dres. And I've successfully landed unmanned landers on and returned them from every celestial body beyond Dres. The exception being, of course, Jool, but I have dropped probes through its atmosphere. My biggest accomplishment in all that was the manned landing and return from Eve. This was all done in v0.90 stock career mode, just before v1.0 was released. Since v1.0 came out, I've mainly just been running tests and experimenting; really haven't undertaken any big building or exploration projects.

I just derived an equation to allow for a more accurate determination of the heading one must fly to insert into a target inclination. The equation is, Heading = atan[ (Vorb*sin(i)) / (Vorb*cos(i)-174.6) ] where Vorb is the orbital velocity, i is the orbital inclination, and heading is measured from the equator. For example, let's say you want to insert into a 75 km orbit with an inclination of 10 degrees. For a 75 km orbit, Vorb = 2287.4 m/s, and, of course, i = 10o. We therefore have, Heading = atan[ (2287.4*sin(10)) / (2287.4*cos(10)-174.6) ] = 10.82o If we are launching at the target orbit's ascending node, then the heading is northerly; and if we are launching at the target orbit's descending node, then the heading is southerly.

Try fins to help stabilize it while in the atmosphere. Also keep the angle of attack as small as possible. I find that setting SAS to 'prograde hold' during the brief period when it is most unstable helps to keep it from flipping out of control.

When you say "angle of target" I assume you mean inclination. Inclination is the angle between Kerbin's equatorial plane and the plane of the orbit. What you need to do is go to the map view and watch for the moment when the launch site rotates into the orbital plane of the target. This happens twice per day. I do this by (1) first clicking on Kerbin to center it in the map view, (2) moving the map view around until I see Mun's orbit edge on (Mun's orbit is the same as Kerbin's equatorial plane), and (3) rotating the view left or right until I see the orbit of the target edge on. Once you see both orbits edge on, they appear as two intersecting lines. You want to warp ahead until the launch site moves to a point where it lies along the line of intersection of the two planes. There are only two places on opposite sides of Kerbin where this happens. Once you're at one of those two points, you want to launch in either a slightly northerly or southerly direction so that you insert your spacecraft into the same orbital plane as the target. By looking at the map view you can see whether you need to launch north or south. If the target's orbit crosses the launch site moving north to south, then you want to launch in a southerly direction, and if the opposite is true, then you launch in a northerly direction. How much north or south depends on the inclination of the target. The angle of your launch vehicle's flight path in relation to the equator should be roughly equal to the inclination of the target. For instance, if the target's inclination is 10 degrees, then you want to rotate your launcher as soon as it leaves the launch pad 10 degrees, either north or south as required, and then pitch over (actually yaw over) so that you're flying at an angle of 10 degrees in relation to the equator. This should put you into an orbital plane that matches that of the target. You'll probably still have to make a small plane change adjustment, but with practice you can get very close. I said that your rocket's flight path "should be roughly equal to the inclination of the target" because you actually have to account for the fact that you have an initial due east velocity of about 175 m/s due to Kerbin's rotation. You therefore have to over compensate a bit and fly at an actual heading a little greater than the target's inclination. This correction is small for low inclinations and can be ignored in most cases. However, for high inclinations, such as a polar orbit, the correction can be several degrees. For example, to launch into an orbit the flies directly over the north pole, it is necessary to launch along a heading that is 4 or 5 degrees west of north. The delta-v depends a lot of the design of your launch vehicle and payload, so there is no simple answer. However, if you just want to know how much extra delta-v it takes to launch into an orbit other than a non-inclined prograde orbit, that's easy. A zero inclination prograde orbit is what you get when you launch due east from Kerbal Space Center. You get a free ride of about 175 m/s when you do this because of Kerbin's rotation. If you launch due north or due south, you don't get any free ride from the planet's rotation, so you have to make up that missing 175 m/s with your launch vehicle. Thus the delta-v required to reach orbit goes up 175 m/s. If you launch due west, you are now fighting Kerbin's rotation. Not only have you lost the 175 m/s free ride, but you are now moving 175 m/s in the wrong direction. The delta-v required to reach orbit is now 350 m/s greater than a due east launch. Computing the free ride that you get from Kerbin's rotation involves vector mathematics, but it is approximately equal to 175*sin(A), where A is the azimuth of your flight path, measured eastward from north.

First step is to decide what the mission objectives are. I then determine a ÃŽâ€v budget and select the payload essentials needed to complete the objectives. I then determine what mission mode/vehicle configuration will allow for the most efficient completion of the mission. I then build essentially "top down" or, more correctly, I design the last surviving part first. For instance, this might be the reentry/recovery capsule at the end of the mission. I make this part as small as possible while including only the essential crew and/or data that I want to recover. I then work backwards by next designing the propulsion needed to bring the capsule back to Kerbin, and so on. The last thing I design is the first stage of the launch vehicle. For the launch vehicle itself I will often reuse a previous design if I'm launching a spacecraft of similar size. However, the spacecraft/payload is usually uniquely designed for the specific mission, though I do borrow ideas from previous designs. I only use rockets, so I have no design methodology for spaceplanes. - - - Updated - - - Using pre-built subassemblies for my launch vehicles is exactly what I did prior to v1.0. However, those old designs are no longer ideal with the new aero, so I've scrapped them. I now mostly custom build my launch vehicles, though I may eventually design a new fleet of stock launchers. Even though each launcher is custom built, I do follow a set of guidelines in regard to such things as TWR, etc.

Aerocapture at Jool is theoretically possible but very tricky. I've done it successfully, but you need a properly designed craft and you have to hit the correct periapsis altitude within a couple hundred meters. Being off just a little bit and you'll explode. The spacecraft needs a low ballistic coefficient, i.e. low mass per unit area of heat shield. I think it's virtually impossible to aerocapture a large massive vehicle, but it can be done with a small probe equipped with an oversized heat shield, such as a 2.5m shield on a small 1.25m probe. Finding the correct periapsis altitude will likely require experimentation, which means it will take a save and several reloads until you get it right. For the one time I did it successfully, the conditions were: spacecraft mass at entry = 2915 kg, heat shield size = 2.5m, entry velocity = 9783 m/s, and periapsis altitude = 196,200 m ±200 m. It's probably easier just to use a different method as described above by others.

The following is something I posted months ago that I think is relevant to the discussion here. This was done prior to v1.0, though that really shouldn't matter.

Slashy, What do you have the SRB thrust limiter set to?

I have the downloaded .zip files for 0.23.5, 0.90, 1.02 and 1.04 but I have only 1.0.4 currently installed.

A few missions back I sent a probe on a suborbital descent through Jool's atmosphere and I had no problem recording and transmitting data from the atmospheric sensor. The problem is surviving entry. I had a relatively small probe and I slapped a 3.75m heat shield on it. Even with that big oversized heat shield, the probe barely survived; it had only a few kg of ablator remaining when it finally settled into a gingerly descent. (edit) FYI, I just looked up my Jool probe and I see that it's total mass was 5055 kg. Using a 3.75m heat shield, that comes to 458 kg/m2. As I said, the probe just barely made it without using up all its ablator. I strongly recommend that anyone attempting this keep their heat shielding loading to ≤458 kg/m2, or else you're likely to go boom! Also note that my descent was started from a low Jool orbit, so the entry velocity was as low as possible. I would have never survived had I attempted an entry direct from a hyperbolic approach. I think the periapsis of my descent orbit was 195 km, but I don't recall what my apoapsis was (probably not more than 500 km).

That's one experiment per type per biome. For instance, a pod can store one seismic experiment from Minmus Flats and another from Minmus Slopes, but it can't store two from Minmus Flats.

Yes, I've though of that. As long as they are clustered together to work as a single unit, the method you illustrate looks like a very inexpensive option. However, I have a couple concerns. First, the 1.25m attachment point looks awful flimsy. Would you typically add struts to strengthen the connection? Second, how does something like that steer without having a gimbaled engine? Are the reaction wheels enough, do you add fins?

I agree that using solids in-line as a first stage can be very economical. I do this frequently for small payloads where I can use a RT-10 or BACC. I have also sometimes clustered 2,3 or 4 SRBs together using stack adapters. Using them radially, however, appears to negates most, if not all, of the cost advantage. The problem is in the way the costs are balanced. A BACC cost only 850, while a TT-70 decoupler and advanced nose cone together costs 1020. Even a cheaper TT-38K decoupler and aerodynamic nose cone costs 840. That's just crazy out of balanced. There is no way the decoupler and nose cone should cost as much or more than the SRB. It's even worse for a RT-10, where the cost of the accessories is more than double the SRB cost. The tests we've performed in this thread seem to show that the only SRB to provide a definite cost advantage when radially attached is the Kickback. More tests are probably needed to confirm, but right now I think the rules for SRBs use might be: 1) In-line as a first stage = YES 2) RT-5, RT-10 & BACC radially attached = NO 3) Kickback radially attached = YES By the way, note that in the post where I reported my launcher w/SRBs results, I wrote So I was indicating that SRBs are cheaper if we can eliminate the costly accessories. I never intended to suggest that SRBs are never economical.

Good. I was hoping it was just an issue in KER and not in the game. I'm planning to do that.

Something else I noticed in doing this is that Kerbal Engineer computes the combined Isp of different engines incorrectly. I don't know what the game does, but if the game computes it the same way as KER, then there's a problem. For example, if you look at the image in post #19 you see that the Isp is given as 211.9 s. Of course this is a little above sea level; in the VAB the sea level Isp is given as 211.4 s. The formula for specific impulse is, Isp = F / (ṁ * go) where F is thrust, ṁ is the mass flow rate, and go is standard gravity (9.80665 m/s2). When we have multiple engines the formula becomes, Isp = ΣF / (Σṁ * go) where we simply have to sum up the thrusts and mass flow rates of the different engines. Let's start with the Skipper. The volumetric flow rate is given in the game as 41.426/s, which gives us a mass flow rate of 207.13 kg/s. We can also compute the mass flow rate from the known thrust and Isp. I doesn't matter whether we use the sea level or vacuum values because ṁ is supposed to be constant and either set of values should give the same result. 568750 N / 280 s / 9.80665 m/s2 = 207.130 kg/s 650000 N / 300 s / 9.80665 m/s2 = 207.130 kg/s So all the math works out and we know the mass flow rate of the Skipper engine. Doing the same thing for the Thumper SRB gives us a mass flow rate of 145.674 kg/s. In my example I have 1 Skipper, 2 Thumper @ 100%, and 4 Thumper at 50.5%. Therefore, we have ΣF = 568750 + 250000 * 2 + 250000 * 4 * 0.505 = 1,573,750 N (sea level) Σṁ = 207.130 + 145.674 * 2 + 145.674 * 4 * 0.505 = 792.74 kg/s And the combined specific impulse is, Isp = 1573750 / (792.74 * 9.80665) = 202.4 s (sea level) So where does 211.4 s come from? Honestly, I don't know. I've tried some different ideas but I can't come up with that number. Just to prove to myself that this isn't some one time thing, I've also tested other engine combinations and have got similar results. The same error occurs in the calculation of vacuum Isp. For my test vehicle, KER gives a vacuum Isp of 248.1 s while my calculations come to 238.7 s. If we are to believe that the Isp figures given by KER are correct, then we get mass flow rates of, Σṁ = 1573750 / 211.4 / 9.80665 = 759.12 kg/s (sea level) Σṁ = 1856000 / 248.1 / 9.80665 = 762.83 kg/s (vacuum) So much for the idea that mass flow rate is supposed to be constant. Not only do these values not equal the supposed ṁ of 792.74 kg/s, they don't equal each other. There is definitely something wonky going on here.

Several comments: 1) The reason you couldn't get my unaltered design to reach orbit is because a full X200-32 tank brings the payload mass to a little over the theoretical maximum. I had to offload a tiny bit of propellant to get it to reach orbit. 2) I agree the fins were going overboard. I thought they could probably be excluded but I keep them in the design only because I included them on liquid-fueled test vehicle. I have since removed them and re-ran the computer simulations. This significantly reduces the cost per tonne of payload, but it is still higher than the all liquid vehicle. (I've edited my previous post to show the new results.) 3) I prefer to keep the reaction wheels in the analysis because they were included in the liquid fueled design to which I'm comparing. 4) I didn't use "Kickback" SRBs on purpose, simply because they are the best option. I wasn't trying build a vehicle that was the pinnacle of performance, I was trying to build a vehicle that fell somewhere in the middle in terms of performance. This was a situation where a few changes resulted in a highly efficient design, but that may not always be the case. 5) When I wrote "it's also likely that a more cost effective SRB design can be found than the sample tested here", the changes I was thinking about were exactly the ones that you made. 6) The main point, I think, is that using SRBs doesn't mean that cost is automatically going to be reduced. It's going to take the right situation and a good design.

There are too many possible configurations to test them all. I personally prefer two-stage liquid fueled launchers, so that is what I tested. I wanted to see what the sweet spot was for TWR in order the get my payloads to orbit as economically as possible. Based on my tests, it looks like I should target a TWR of between 1.2 and 1.5 for my first stage, and be around 1.1 for my second stage. It doesn't look like there is any cost advantage to using solids, though I think they are a good option to augment first stage thrust if you need a little extra oomph. None of this means there aren't better ways to get to orbit. It just means that if two-stage liquid fueled rockets is your thing, then the cheapest way to get your payload to orbit it to load up on fuel, operate at a fairly low TWR, and don't be overly concerned about Δv inefficiency. (edit) My answer assumes you are talking about KSP and not real life.

You got that right. There's almost no limit to what can be imagined.

Hi, Mahone. I'm the creator of the web site to which Red Iron Crown has provided a link (above). I think the Orbital Mechanics and Rocket Propulsion pages contain everything you need, and perhaps more. The pages pretty much speak for themselves, but I'm here to help if you have any questions. I also agree with NielsBohr that the Tsiolkovsky rocket equation (#1.17) and the Vis-viva equation (#4.45) are probably the two most useful equations to master when playing KSP. - - - Updated - - - Kerbal Engineer is a solution, not an answer. It is a shortcut to understanding.

That's a valid point. But then again, one of the advantages of liquids is that we don't need to employ a radial attachment configuration. We always have the option to go to a "Mainsail" or "Twin-Boar" and use an in-line arrangement. With solids the largest option available has a sea level thrust of 594 kN. If we need more than that, we've got no choice but to add moar boosters.