MaxSchram

Ladies and gentlemen, aviators, the first documented long range flight was ... errr ... quite successful. I bent the rules somehow and choose a traveling altitude of around 19km, which allows greater velocities and lower atmospheric drag. Nevertheless, it took more than an hour to travel roughly a quarter of the distance when finaly the engines went dry. It defenitively needs more fuel and even higher altitudes, maybe around 25km, to fly a full round. 1st pic is at liftoff and 2nd some random impression on the trip. In the center of the 3rd is the final position and the last shows the traveled distance (red line).

I recognized it earlier in some other posts of various people. You guys keep mixing up velocity and delta-V. The first one is the actual speed you are going, while the latter is a velocity change. These are two different things, but let me clarify it with an example: If you are in a stable, circular orbit at 100km you have an orbit velocity of ~2245 m/s. To do a Hohmann Transfer to, let's say 200km, you need to apply delta-V of ~73m/s. So your final velocity after that change is ~2319m/s. I know i'm arguing about trifles, but my mathematicians heart hurts so much while reading this. ;D

The 15 minute and the 60 minute challenge are quite similar, but they have different requirements for the optimal solution. What makes them similar is the need for generating as much dV, as fast as you can. Because the longer the time you go on high velocity, the further you go. But the differences come with the limitations of the engines and fuels. You can't get as fast as you want in a given time span. It's about balancing between a long, steady acceleration to a high velocity or a short burst to lower velocity. To illustrate this i made the first two figures below. Each showing the velocity curve of two different rocket configurations. The blue rocket takes a lot longer to accelerate and the burnout is ~1000sec, but the maximum velocity is higher. On the other hand, the red rocket only needs about half of the time to reach max speed, but has a lower end velocity. The area under the curves is the corresponding travel distance - and that is what we want to maximize. So lets take a look at the two graphs: The first one goes up to an hour (3600s) where the area under the blue curve is greater than the area under the red curve. In the second picture, with 15min (900s) to go, the result is inverted and the area under the blue curve smaller. To go even further, intelligent staging is the key. The third picture shows the blue rocket again and a larger black rocket with a second stage added to the blue rocket. It takes the maximal velocity up by ~5000m/s, just by using a (quite larger) second stage to generate some more dV.

47581km I'm sure there is more to get.

While testing around with different propulsion configurations i noticed that your calculation of the specific impulse is not correct. Please don't take me wrong, i'm not sitting here, trying to find bugs and complain about them. I just want that such a nice tool like the Orbital Calculator provides correct results. The formula for the specific impulse at see level is: Isp = Fthrust / (q * g0) With q being the mass flow and g0 the standard gravity. For a standard rocket (Pod, SAS, LFT, LFE) the mass flow is q = 2.2e3 kg / 62.5 s = 35.2 kg/s and the thrust Fthrust = 200kN. Which leads to a specific impulse Isp = 579.19 s, which is alot less than your result. The Tsiolkovsky Rocket Equation to calculate the delta-v value says: dV = Isp * g0 * ln(m0 / m1) with m0 being the initial mass and m1 the mass at burnout. Continuing the former example and setting m0 = 6.3e3 kg and m1 = 4.1e3 kg, the final amount of delta-v is dV = 2439.86 m/s. Btw: You misscorrected your delta-v calculations, it now shows something about 23km/s for the same example

Why don't you finish that experimental launch orbit section in your calculator? It would be really usefull, because often one wants to determine (especially after launch) when, where and at what speed im going to reach apogee / perigee. Also in situations where one wants to change orbit, somewhere between the two hotspots, it could be utilized. But that tools doesn't seem to produce valuable results, no matter what i typed in the fields. In particular the velocity vector isn't clear at all. Do you use some vector notation, or is it an angle relative to the navball (degrees or radians?). I would appreciate further improvements.

Who has read my last posts may has recognized that i like to calculate and simulate things. I also tried it with this challenge and came to the following idea: The only thing that can't be calculated properly is the atmospheric influence and i wanted to get rid of that problem. So i established an orbit, where the orbital velocity exactly matches the delta-v the last stage (Pod, SAS, SRB) would provide. It's at 2053831.93m altitude and 1153.39m/s speed. Than i waited till the spacecraft was, as exactly as i could see, above the space center and burned the SRB. Be doing so all kinetic energy was removed and the rocket was falling towards the target. It didn't hit, but taken the enormous orbit distance into account, it was pretty close. 1st: Launch. 2nd: First orbit at 158km. 3rd: Target orbit after Hohmann Transfer at 2085km (missed the target orbit, but could readjust the speed) 4th: Burning the SRB 20 minutes later. 5th: Atmospheric entry around 40 minutes later at 2904m/s. (space center is near the nav ball) 6th: Impact, with space center in view distance.

It's P for Peta. http://en.wikipedia.org/wiki/Peta-

I really like the last one.

How do you handle the fact, that the SRB + Pod overheats pretty quick outside the atmosphere?

I have a question how you calculate the delta-v values in your stage calculator, because my calculation lead to different values and i want to know where i'm wrong. For a single solid booster your delta-v is 3704.029m/s. My calculations are: Fthrust = 130kN m0 = 1.8t m1 = 0.36t tBurn = 25s The mass is linear in t: m(t) = m0 - t * (m0 - m1) / tBurn The acceleration is: a(t) = Fthrust / m(t) Integrating this from 0s to tBurn leads to the velocity change: vChange = 3632.41m/s, which is significantly lower than your result. Where am i wrong?

My intention was: If there are no mod restrictions, why not make my own broken parts and burn to light speed in no time. The problem is: There are some limitations for the maximum forces which can be applied to connections between parts. The first try was with a modified solid booster, which had a thrust of 1e8kN,a mass of 1t and a burn rate of 0t/s. Connected to a pod (1t) it would reach light speed in ~6sec. But the connection between both parts broke instantly and the pod stayed at launchpad while the booster burned away. I think it reached light speed, but i wasn't there . So i lowered the thrust and ended up at ~2000kN. At this point the pod and the booster stayed together and flow stable. The problem we now have is time: A ship with a mass of 2t and a trust of 2000kN produces an acceleration of 1000m/s^2. This means that this ship has to fly three and a half days to reach light speed. This is doable but impractical without blocking a computer for that time.

I did another one: I used three elliptical orbits, all with perigee at ~66.7km. The first orbit was the targets orbit the other two had a slightly smaller / bigger eccentricity. They were designed in the way, that the sum of both secondary orbits periods matched two times the target orbits period. I also created three different solid booster parts, each producing a exact calculated amount of delta v and burned 0.1 seconds. By using them i minimized adjustment errors during orbit changes. The apogees were: target = 72858m secondary1 = 75196m secondary2 = 70556m The result worked ot pefectly fine,as you can see in the images: 1st: Shot after launch, notice the three colored boosters. 2nd: Decoupling the target. 3rd: After first orbit change, the target slowy starts to get distance. 4th: Rendeuvous after the maneuver and a few burns for closing in. (I actually bumped in it )

I'm not really sure and the proof i've got isn't worth much, but if you guys trust me: I DID IT After thoose pretty depressing last thoughts i went out for meeting a friend. On the way and back i thought about that problem and had the final idea: If i overshoot by such huge distances, why not intentionally undershoot it, establish a lower orbit and than slowly overtake it? For doing so i first did some tests to estimate the maximal view distance, which is about 30km. At this range the pixel flickering is barely spottable, but can be done. I also did some trigonometric math and came to a method for estimating the current orbit position relative to the space center indicator on the nav ball. With the help of this to things i did all the calculation again an gave it it try. I established an orbit around ~55.7km and transfered to an orbit at ~150km. There i recalculated all the values to take the deviations into account, and waited for 146.67 minutes. Than i transfered back, landing behind the target and also 3km lower. I waited another 30 minutes, while slowly closing in. At this time the flickering started to occure. Finaly i lost patience and tryed to burn towards the target, what was a big mistake - and i lost track of it. I'll think about a closing-in maneuver and try it again eventually. At the picture you see the closest point i could reach. I know it's not more than a pixel and is easily done with paint or photoshop but it had the right heading and altitude and got closer.

I simulated the example from my first post in Matlab and also did some acceleration experiments. The result was disillusioning. If only the two transfer velocities for the orbit changes are missadjusted by just 1m/s, the final rendezvous position is missed by over 100km. This is an unclosable gap. Even if we get thoose velocities right, the change isn't instant. While accelerating a simple spacecraft (Pod, LFT, LFE, SAS) with 25% thrust, the transfer orbits apogee is changed by ~5km. This distance is somewhat equivalent to ~5m/s, which is already more than the error in the first example. The only chance to possibly do this, is to fly the maneuver with a minimal orbit difference about less than 5km. The velocity changes are smaller, so they can be adjusted quicker and more easy. But the orbit period differences are also smaller, so it takes for ever to re-sync them. The wait time for the same maneuver with 40km and 45km orbit altitudes would be around 2440 minutes, which is nearly 2 days !!!. I don't do this before there is some time acceleration tool