How to calculate a rendezvous??

[PB666]

Take a look at Manley's videos that pertain to ascent and kicks. There are a number of reasons why 70k x 70k alt is a bad idea, the smallest orbit one should strive for is 70k x100k where 100k is the launch traj apo and 70k is the end circ point. There are virtually no low altitude targets you cannot achieve that will not either have a pe or apo commence transfer. If the atmosphere curve where larger, or starting atmosphere smaller, it would not be so bad, but drag below 30 puts constraints on horizontal velocity, particularly below 45k and requires more vertical velocity between 20k and 32k. This makes steering to a 70k apo orbit challenging and wasteful (trade off is drag losses versus -radial velocity losses). Of course some of us are probably lowering CoD and may actually have a part lists that justifies this ;^). But the stock part list, shooting horizontal early is going to require a heavier engine for thrust, or some sort of jet based launch phase. This is not a wise early carreer game choice, the conservative choice is to initially apo above 70k.

[Rune]

Take a look at Manley's videos that pertain to ascent and kicks. There are a number of reasons why 70k x 70k alt is a bad idea, the smallest orbit one should strive for is 70k x100k where 100k is the launch traj apo and 70k is the end circ point. There are virtually no low altitude targets you cannot achieve that will not either have a pe or apo commence transfer. If the atmosphere curve where larger, or starting atmosphere smaller, it would not be so bad, but drag below 30 puts constraints on horizontal velocity, particularly below 45k and requires more vertical velocity between 20k and 32k. This makes steering to a 70k apo orbit challenging and wasteful (trade off is drag losses versus -radial velocity losses). Of course some of us are probably lowering CoD and may actually have a part lists that justifies this ;^). But the stock part list, shooting horizontal early is going to require a heavier engine for thrust, or some sort of jet based launch phase. This is not a wise early carreer game choice, the conservative choice is to initially apo above 70k.

That's fun and all, but 90% of my ascents are SSTOs. So... thanks for the sentiment, I guess? In any case, my rockets are usually low TWR to optimize for cost, so my ascent profile is far form the lowest dV possible. And I do like underpowered upper stages with huge mass ratios taking their sweet time to orbit... I usually end up paying way more in gravity losses to save bucks.

Going like you seem to go fro the lowest dV, and most mathematically efficient rocket, while fun and elegant, will end up with you having the same issue Boeing has with the Delta IV: they tried to get the lightest, most efficient launcher possible, thinking that cost was related to mass, and they ended up making the most expensive rocket in recent history. Mind you, to each their own, and I do enjoy seeing how people push the limits in challenges and such. But I've got one of the most cost-efficient space programs out there!

Rune. My engineering attitude is a bit more... soviet I guess?

Edited October 12, 2015 by Rune

[PB666]

That's fun and all, but 90% of my ascents are SSTOs. So... thanks for the sentiment, I guess? In any case, my rockets are usually low TWR to optimize for cost, so my ascent profile is far form the lowest dV possible. And I do like underpowered upper stages with huge mass ratios taking their sweet time to orbit... I usually end up paying way more in gravity losses to save bucks.

Going like you seem to go fro the lowest dV, and most mathematically efficient rocket, while fun and elegant, will end up with you having the same issue Boeing has with the Delta IV: they tried to get the lightest, most efficient launcher possible, thinking that cost was related to mass, and they ended up making the most expensive rocket in recent history. Mind you, to each their own, and I do enjoy seeing how people push the limits in challenges and such. But I've got one of the most cost-efficient space programs out there!

Rune. My engineering attitude is a bit more... soviet I guess?

I don't mistake cost for mass, but if i am going to waste mass, dV i would rather do it on an occupation that at least has some intangible benefit, like gathering infomation or establish useful transiton points, blowing through the mid atmosphere at 5 times the speed of sound might be nice for glowimg red an SR71 blackbird but it is well beyond maximum dynamic stress for the CoD of most real rockets. Seriously when 1.02 came out everyone was complaining why their rockets flipped after launch right about the time they hit M speed, well theres a good reason for that, if you dont want them to flip move the maximum force application point backwards. So SSTO is not really reflective of reality, so I dont think boeing minds the comparison, but if we are talking reality orbits are horizontal and lauches are vertical. If there was a very good reason for a high altitude transition that all space agencies employ, I seriously doubt they would optionally make the transition and simply start with a 45 degree ascent vector that evloves into prograde to minimum altitude. This certainly is possible if your reduce CoD to 0.02. I dont know many payloads that are compatible with this.

The point about the turn is that it is physically a turn, yes if you slow down it might actually roll, but the problem with that, is as you say you pay a cost in t not-orbital which translates into lost thrust. The turn is made after establishing a strong vertical vector for one really good reason, it gets the ship out of alt related drag as it accekerates horizontally accelerating speed related drag.

[Meithan]

That's fun and all, but 90% of my ascents are SSTOs. So... thanks for the sentiment, I guess? In any case, my rockets are usually low TWR to optimize for cost, so my ascent profile is far form the lowest dV possible. And I do like underpowered upper stages with huge mass ratios taking their sweet time to orbit... I usually end up paying way more in gravity losses to save bucks.

Going like you seem to go fro the lowest dV, and most mathematically efficient rocket, while fun and elegant, will end up with you having the same issue Boeing has with the Delta IV: they tried to get the lightest, most efficient launcher possible, thinking that cost was related to mass, and they ended up making the most expensive rocket in recent history. Mind you, to each their own, and I do enjoy seeing how people push the limits in challenges and such. But I've got one of the most cost-efficient space programs out there!

Rune. My engineering attitude is a bit more... soviet I guess?

While I love SSTOs, I just find they take too long to get to orbit. They're very low-cost-to-orbit, granted, but an SSTO launch takes 5x as long as a standard rocket ascent, and the launch profile is more complicated. And regarding cost, I have a family of recoverable-single-stage-plus-SRBs rockets that don't fare too bad price-wise compared to SSTOs.

For instance, my Titan Heavy launch vehicle (the central stage lands on parachutes) can put 36 tonnes in LKO (75 km orbit) for 32k funds (less than 1000 funds per tonne). An SSTO with that capacity will certainly be cheaper, but not by a huge deal (btw: do you have an SSTO capable of that payload? how much does a launch cost? All I've built is a light SSTO with a ~2 tonnes payload capacity).

[Der Anfang]

While I love SSTOs, I just find they take too long to get to orbit. They're very low-cost-to-orbit, granted, but an SSTO launch takes 5x as long as a standard rocket ascent, and the launch profile is more complicated. And regarding cost, I have a family of recoverable-single-stage-plus-SRBs rockets that don't fare too bad price-wise compared to SSTOs.

For instance, my Titan Heavy launch vehicle (the central stage lands on parachutes) can put 36 tonnes in LKO (75 km orbit) for 32k funds (less than 1000 funds per tonne). An SSTO with that capacity will certainly be cheaper, but not by a huge deal (btw: do you have an SSTO capable of that payload? how much does a launch cost? All I've built is a light SSTO with a ~2 tonnes payload capacity).

Your SSTOs are about as good as mine. If I am lucky, I can get 3 tonnes into orbit. I still don't know how to make a proper SSTO using the MK III parts, as they are a bit funky to work with and are very heavy. o-o So yeah, light SSTOs for me it is, as well.

[Rune]

While I love SSTOs, I just find they take too long to get to orbit. They're very low-cost-to-orbit, granted, but an SSTO launch takes 5x as long as a standard rocket ascent, and the launch profile is more complicated. And regarding cost, I have a family of recoverable-single-stage-plus-SRBs rockets that don't fare too bad price-wise compared to SSTOs.

For instance, my Titan Heavy launch vehicle (the central stage lands on parachutes) can put 36 tonnes in LKO (75 km orbit) for 32k funds (less than 1000 funds per tonne). An SSTO with that capacity will certainly be cheaper, but not by a huge deal (btw: do you have an SSTO capable of that payload? how much does a launch cost? All I've built is a light SSTO with a ~2 tonnes payload capacity).

Hum. Let's take the Longsword, which you can grab in R-SUV and check out yourself. That will take 36 mT up, and quite a bit more, actually. In fact, I have been able to manage >50mT of payload out of it, but that takes time as you say to make the slow ascent... about 15 minutes instead of 5 (far from five times, and most of it with hands off the keyboard, browsing and stuff as it builds speed to go transonic). The bird is about 200k√ to put on the runway, six times the cost, but then again, fuel costs are about 7,000√, which is almost a fifth, incidentally. And a runway landing means 100% recovery costs, every time, which I find impossible to do with rockets (granted, >90% recovery is still very good and doable). So of course it's a trade between game time and funds. But if you enjoy flying planes (as I do), it is a profitable one.

Rune. I do use rockets when I'm volume-constrained, but then again, half the fun is to work around that.

[Meithan]

Hum. Let's take the Longsword, which you can grab in R-SUV and check out yourself. That will take 36 mT up, and quite a bit more, actually. In fact, I have been able to manage >50mT of payload out of it, but that takes time as you say to make the slow ascent... about 15 minutes instead of 5 (far from five times, and most of it with hands off the keyboard, browsing and stuff as it builds speed to go transonic). The bird is about 200k√ to put on the runway, six times the cost, but then again, fuel costs are about 7,000√, which is almost a fifth, incidentally. And a runway landing means 100% recovery costs, every time, which I find impossible to do with rockets (granted, >90% recovery is still very good and doable). So of course it's a trade between game time and funds. But if you enjoy flying planes (as I do), it is a profitable one.

Rune. I do use rockets when I'm volume-constrained, but then again, half the fun is to work around that.

Very nice SSTO spaceplane, Rune, color me impressed. Definitely surpasses my design ability (I know because I spent three hours last night trying to design an orange-tank spaceplane and repeatedly failed to get it anywhere near orbit).

OK so the rocket vs. spaceplane margins are not as bad as I first suggested, but they're still there. Using MechJeb's landing predictions, I usually land my recoverable rocket stages within 2 couple km of the pad, with >95% recovery value. And yeah there's the volume issue, too. I've launched monstrosities without a hitch: as long as they fit in the fairing (and those 3.75 m base fairings are huge) and I can strap some struts to it, there's no problem.