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SanderB

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    KASA "Preferred Vendor" challenge #2 is up!

    in KSP1 Challenges & Mission ideas

    Posted · Edited by SanderB

    I've made another attempt, the launch vehicle cost 15,810$ after subtracting the cost of the satellite. 14,103$ was recovered on the launchpad (this counts as on KSC grounds, right?). The Satellite was off by 7.1° according to KER. The cost of 1 launch is approximately 141.03$ from the launch vehicle (dividing 14,103$ of the recovered vehicle by 100). The cost of the fuel and the extra equipment on the satellite is 1,707$. The total cost of the mission I think is 1,848$. 100k divided by 1,848$ is 54.11 raw points according to my calculations.

    http://youtu.be/qKEOh-TmY_M

    Edit: Another attempt with the same vessel but this time fully stock: I think performance was the same, although I did not land precisely on the launchpad, I still landed on the flat KSC grounds.

    http://youtu.be/YTobNl570_g

    KASA "Preferred Vendor" challenge #2 is up!

    in KSP1 Challenges & Mission ideas

    Posted · Edited by SanderB

    Hi Slash,

    I'd like to call my company Eight Corners Inc.

    Fully stock, recovering your 1st stage on KSC grounds is nearly impossible without a lot of dV and in my opinion involves a lot of luck of which I wasn't having any today (having tried about 10 times to do a landing with about 300m/s dV remaining before deorbiting to the grounds with a rocket shaped 1st stage and getting within a 100km stretch each time.)

    KASA "Preferred Vendor" challenge #2 is up!

    in KSP1 Challenges & Mission ideas

    Posted · Edited by SanderB

    I've made a shot at this. The main launch vehicle in the VAB costs 5,151$. the fuel 734$.

    I'm not sure how 99% recovery works in this challenge but if recovery = recovering anywhere on kerbin then the cost of the 1st stage is 51.5$ plus 734$ from fuel. The 2 additional parts on the satellite are 180$. The total cost of launch is then 965.5$. I believe points then are 100,000 / 965.5 = 103.57 Points.

    If 99% recovery = on the launchpad then the cost is 2,027$ because the 1st stage was still 66.3% recovered. Points then probably are 100,000 / 2,027 = 49.47 Points.

    Click for video of the launch.

    There was plenty of dV left on the stage and the positioning was off by about 5°, this probably cancels out any bonus. I realize I didn't fast forward 6 hours, but I hope that the difference in timing between peri and apoapsis prove that the satellite is stable.

    Making orbital rendezvous less laborious

    in KSP1 Gameplay Questions and Tutorials

    Posted · Edited by SanderB

    The first 10 min or so of

    deal with an equatorial rendezvous.

    The most important things I can think of are knowing how long it takes for you to reach orbit and how far ahead of KSC you are when you do reach orbit. If you have KER, add up the burn times of every stage until the cumulative dV reaches 3,3km/s or so. Based on that you can decide how far back the target needs to be behind KSC for you to properly time your launch.

    Then, while launching when you get within 100km of your target you switch the navball to target navigation so you see your relative velocities, and you push your relative retrograde-velocity marker on to your anti-target marker as close as you can, while monitoring your closest approach until they minimize. The retrograde-velocity marker can be pushed by burning on the far-side of the anti-target marker.

    At the same time you need to track your distance and the amount of distance you will traverse to cancel out your relative velocity with the V^2/2A formula ((relative) velocity squared divided by double your acceleration) so you don't let your target overshoot you.

    As long as you don't need to burn more than 30° away from your retro velocity marker you don't lose more than ~5% of your total mission dV.

    And just practice and practice. You need a lot of practice.

    2nd demonstration video, demonstrating the relative velocity anti-marker approach in particular.

    Belly landers for airless muns?

    in KSP1 Gameplay Questions and Tutorials

    Posted

    it is possible tilt a vehicle up 30-45° degrees with a few nanonewtons of upwards thrust (at the furthest point from the center of gravity) if only the main landing legs are directly under the center of gravity. With some fuel transfers between tanks and again center of gravity being over a pair of landing legs, it is possible to do this. All a rocket would need is a single thruster (RCS or otherwise), torque wheels, or center of gravity shifting through fuel transfer. Once the rocket is tilted 10° or more is should be a fairly simple procedure to turn around in whichever direction and go full thrust on any low or non-atmospheric body.

    Efficient Landing

    in KSP1 Gameplay Questions and Tutorials

    Posted · Edited by SanderB

    A suicide burn with TWRs below 3 costs about 33% of your dV because gravity is 1. With a retrograde gravity turn (assuming you pitch up bit by bit in order to negate vertical velocity) and a TWR of 1.5 assuming you go for the final vertical descent at 200m has gravity losses of about 15-20%, even though the TWR is low because initially you suffer no losses to gravity and you only really begin to suffer gravity losses later on when your horizontal velocity is lower. This is simply because apparent gravity (that is, actual gravity minus the centripetal acceleration from your horizontal velocity) only begins to exist when you begin to reduce your orbital velocity, apparent gravity is more important than normal gravity for as far as horizontal descents are concerned.

    High TWRs themselves also come with extra costs, because more TWR means that you have higher engine mass and thus less dV or higher launch costs. The savings vs costs of TWR begin to converge at TWRs of about 1.5.

    Naturally, initial TWR (when you begin the burn) is less than final TWR and this needs to be kept in mind when designing vessels with landing costs in mind.

    Pages 8 and 9 of this NASA document may be particularly desireable to read: https://www.hq.nasa.gov/alsj/nasa58040.pdf.

    Achiving Orbit: Continue burn or wait till ap ?

    in KSP1 Gameplay Questions and Tutorials

    Posted · Edited by SanderB

    With a low sea level TWR rocket (between 1.2-1.5) you want to be going 100m/s when you're 10° pitched, 200m/s when 20° and 300m/s when 30° and continuing to pitch over to horizontal as you ascend above 15km and the potential for flipping your rocket is out of the way. Using guidelines like this i always get to orbit with less than 3.4km/s dV, unless I'm trying to launch something that's very draggy or unaerodynamic.

    Aerobraking - when its actually *advantageous*?

    in KSP1 Gameplay Questions and Tutorials

    Posted

    You can quicksave and try different altitudes, or go to higher altitudes than normal and use the aerobrake parts to generate immense drag and turn them off again after you've lowered your speed as much as you needed. You need to be able to control of predict how much you aerobrake. That said, aerobraking is almost free, or at least a lot more efficient than burning almost any kind of fuel.

    Aerobraking and Heatshield Lift

    in KSP1 Gameplay Questions and Tutorials

    Posted

    While craft with similar front-shapes (ie. craft built behind a 1.25m heatshield) will have the same drag, increased mass will mean that deceleration from drag will be reduced due to the increased inertial energy from the extra mass.

    induced drag from lift isn't going to reduce your AP significantly compared to regular drag. One of the benefits of reentry lift is that you can guide your capsule toward a target (such as KSC) and due a much more precise landing. You can use lift to control your trajectory, but if you don't have some way of seeing what your trajectory will look like depending on what actions you take, there isn't a whole lot you can do to do precision aerobraking especially with the lack of knowledge about the exact flight characteristics of your vehicles in stock 1.0.2.

    Command Pod Superheating during launch

    in KSP1 Gameplay Questions and Tutorials

    Posted · Edited by SanderB

    I've been thinking about fairings and it doesn't seem very convincing because their mass is about 20% the mass of the payload, and that is fitting the fairing as tight as I can without clipping parts through it. At 0:51 in my video I show the parachute being at a stable temperature of 310 whereas the mk1 pod at the same point is 610 under almost the same conditions, how does that make any sense? Both parts face into the oncoming air stream, the parachute being smaller maybe should get a little less flux, but as it stands it gets a whole lot less heat flux than anything else even though it is in front of everything else and under almost the same circumstances as the mk1 pod. I don't understand the difference, I'm not convinced that this is merely about going too fast too low in the atmosphere because there is a very significant disparity between the chute and the mk1 pod.

    Command Pod Superheating during launch

    in KSP1 Gameplay Questions and Tutorials

    Posted · Edited by SanderB

    I don't actually see any heating effects. Up to even 70km near orbital velocity the mk1 pod will be at temperatures of 1200-1400° and the conv flux keeps it there all the way. All the while no re entry effects are visible or any glowing of any part. Almost any part pointed straight into the incoming atmosphere I test at the same altitudes and same velocities have 10-100x less conv flux than the mk1 command pod. How is that even possible?

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