Jump to content

Apotheosist

Members
 View Profile  See their activity

  • Posts

    189

  • Joined

  • Last visited

 Content Type 

Posts posted by Apotheosist

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted

    Not trying to sound overcritical of your design or anything (hopefully you didn't take my comments the wrong way). I'm just curious how it would work with more decouplers and a higher center of thrust. Everyone has different design philosophies; I personally dislike carrying around empty tanks any longer than I have to. But like you said, the game in its current state does favor lesser stages.

    Fear not, I did not think you were being overcritical. I am actually very welcoming towards criticism, it helps me get new angles and ideas on things that I could not have thought of on my own. I also try to give constructive criticism to other people on their ideas. Sometimes people do take it the wrong way, but I never mean to be derogative, so when someone gives feedback and constructive criticism to my designs, I am sure they dont mean to be derogative either. It is a good way to learn from one another.

    I am also curious as to what differences would be caused by adding more stages and such, and I like to theorise about these problems mathematically. I'm currently on half of a little investigation into staging, and what effect it has on delta-v compared to the weight of the overall rocket. As you said it depends on the relative weight of the decouplers and the empty tanks. Too many stages and the rocket gets heavy with decouplers. Too few stages and you end up carrying too much weight in empty tanks. It would be nice to have an equation which tells us how many stages we should have to maximise delta-v from a given mass. So that's what I'd like, but I think the maths might be above my level :P

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted

    @r_rolo1, Thanks for the compliments on the lander, I also have always disliked SRB'S, Originally I just had two 1m tanks attached directly to the 3m tanks with fuel lines feeding the 3m tank. However, I needed to add the ASAS for stability, and after I did that it's thrust to weight at liftoff was too low, thus too inefficient for my liking. I considered adding more liquid engines, however I realised I could actually reduce the overall weight of the rocket, even with the ASAS, and have a high enough thrust to weight by using two SRB's. The small SRB's in this version are much better than in previous versions. They actually have a higher specific impulse than any liquid engine I think. They might need rebalancing.

    @Nori, I know what you mean now. However this is just the way I design my rockets. As the fuel tanks empty, the thrust to weight increases gradually, which corresponds to decreasing air density as you move through the atmosphere. I'm not sure what help it would be to have more stages to drop more empty mass. By my design philosophy, in this current version of KSP the optimum number of stages to get to orbit is two or three.

    @liorg, Yeah, I forgot to mention that it's best to shut down the core engine before seperating the six outer boosters, then gently thrusting away from them, to avoid them hitting your centre booster.

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted

    I just don't see how you are getting so much more efficiency, have you moving to a higher Kerbol orbit in that craft to test a rendezvous?

    Also you have no RCS and no control surfaces? Just a single ASAS that I can spot. How can this be controlled in orbit, or are you down to the lander stage at that point? Is your lift and Transition stage combined or do you shed all those 3M tanks and engines before transitioning to another orbit?

    I have not sent my ship into Kerbol orbit to test a rendezvous, but I'm confident it has the required delta-v.

    Control is a little bit of an issue. The first version didn't even have an ASAS, and tended to rotate. So I added the ASAS and it helped keep the craft from rotating. It still requires patience to maneuver, since it has no vectored engines in that stage, only 3 aerospikes.

    I am down to the lander stage once I am in Kerbin orbit. In fact the lander stage does some of the latter burn to orbit. It then also does the burn into Kerbol orbit and rendevous and landing on the planet.

    My lift and transition stage is not combined, once I reach the surface of the planet and I want to come home, I shed those 6 3m tanks and two aerospikes and keep only The center part. The center part uses two SRB's, one Aerospike and one 3m tank in the first stage, then the 1m tank and small vectored engine. I should really show more pictures.

    Here, these pictures show the lift and transition stage (return rocket) seperating and lifting off from the lander/launch platform. There is also an image of the SRB seperation. The SRB's provide a lot of power at liftoff, so there is no real need to thrust with the aerospike while SRB's are burning, or you will just waste fuel pushing through the atmosphere. http://imgur.com/a/qNRlq

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted

    Not a bad design, but you end up carrying around a lot of dead weight when the tanks empty. You could try mounting the engines on the side and stage the lower tanks when they empty. Would probably save you a bit.

    @Nori, You may well have a point that I just can't see. I'm not quite sure I know what you mean about carrying dead weight. Or mounting the engines on the side and staging the lower tanks.

    The tanks that the landing legs are attached to, make a wide, stable base for the lander. The tanks are usually close to empty by the time you land on Kerbin (or potentially, any other planet). This means you have a stable base to land on, which does not weigh very much for the job it does. This lander can land on both land and water without capsising, which is quite important for when you're ready to launch the return rocket. It's a floating launch platform if you happen to land in liquid.

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted · Edited by Apotheosist

    I have the sneaking suspicion Aerospikes are going to get nerfed, they are just too powerful/efficient.

    Also Nova stated that chutes would only slow you to 200-300 meters per second on the desert planet. Which is faster than a dead fall at lower altitudes on Kerbin, so a better test would be a hard landing(no chutes), then add chutes for the actual mission to compensate for the lack of air resistance.

    I agree with you that the aerospkies will probably get rebalanced, and I think they should be.

    The chutes on the craft in the images can't slow it enough for a soft landing on their own, I always need to use some thrust. On the desert planet it would be the same sequence, just that I would require more use of the engines to slow down. I try to use the minimum of parachutes, and make most use of the engines that we already have. The parachutes are just to help control and regulate the descent, and they also provide a hint as to the actual height of the ground; the parachutes open 500m above actual ground level. This is a great help when trying to come to a safe landing using as little fuel as possible.

    The lander part of my interplanetary ship as seen in the images weighs 75.6 tons, The first stage has about 3800 m/s of delta-v (very probably enough for the interplanetary burn and a powered descent on a planet's surface), then the rocket in the middle with the pair of SRB's releases, and it has enough delta-v in its two stages (three if you count the SRB's) to go to the mun and back when flown carefully, (about 7500 m/s delta-v, or less) which should get us home.

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted

    I've seen several people make rockets that could reach LKO, land, reach LKO again, then land on chutes (I made one a while back). But I haven't seen one powerful enough to go to another planet.

    I have already made one powerful enough to go to another planet. Without making use of the fuel bug. And it is not very big. Four large 3m engines and 4 large SRB's on the first stage. Then 3 aerospikes, 2 small srbs, and last stage 1 smallest engine. I designed it as a minimal rocket, using my minimalist design techniques and philosophy.

    It can go to the Mun and back twice. This gives enough delta-v to get to another planet.

    The planetary lander delivery challenge

    in KSP1 Challenges & Mission ideas

    Posted · Edited by Apotheosist

    I am a keen interplanetary spacecraft builder. When I start, I make sure I have the lightest, most efficient possible lander to begin with, because I know the rocket needed to lift it into space is going to be huge. I don't think there is need for so many engines, decouplers and parachutes. My landers usually use 2 parachutes, and I use the engies to help slow the craft down the last few m/s. My landers also tend to include enough fuel to circularize the parking orbit as well as conduct the interplanetary injection burn, this means you only need to put the lander in LKO and it can do the rest. This helps because when you're in low kerbin orbit, lining up for your interplanetary burn, you don't want to have to maneuver a large booster stage. It also avoids creating space junk. It also means that when you arrive at your destination planet, most of the spaceship is empty tanks, which make for useful low density parachute attachement points.

    Personally I think it would be a good idea to redesign the lander. It has far more thrust than it needs, yet it is very complicated and difficult to rig fuel lines to use the extra thrust from those engines to power the booster stage.

    Anyway you asked for a rocket to get this lander into space, so I have attached a craft file with your lander and a booster that gets it into orbit with plenty of delta-v to spare. It is a very simple booster. It may take some time to orient the rocket in space without using the thrust vectored engine. The flight plan I used was also very simple; full throttle, pitchover 45 degrees at 12km, then 90 degrees at 30km or less, then circularize at desired parking orbit.

    Edit: Not sure if it's letting me attach the craft file. Working on it.

    Edit 2: Mybe this will work: http://www./?e7jdwcvbd7epgt7

    Revisiting an old, simple one: The 10 fuel tank challenge.

    in KSP1 Challenges & Mission ideas

    Posted

    I thought the drag values indicated the drag coefficient or something. If you drop two half tanks and one full tank in the atmosphere, they fall at the same rate. I think this explains also why empty tanks fall at the same rate as full tanks. The drag is probably modelled as drag per unit mass. Another example of this would be the big and small parachutes. They both have the same deployed drag value of 500, but the bigger one still slows down your capsule more. This is probably because the bigger chute is 3 times the mass of the small chute, which would give it three times more slowing force.

×
×
  • Create New...