Temstar

The movie Hermes had an onboard nuclear reactor to power its engine (VASIMR or regular ion, I'm not sure, but it's certainly a high isp low thrust engine). It's a bit strange that it also had ISS style solar panels to power the rest of the ship since presumably it would be easier to just bring a reactor powerful enough to power both the engine and the rest of the ship, but I guess the artists wanted to show the solar panels so we get a sense of technological progression from ISS to Hermes. Having a reactor onboard raises other issues. For one it would need a lot more radiators than what was shown as per the picture @SargeRho linked. Secondly unless the reactor is ungodly heavy by spacecraft standards it won't have shielding all the way around like a marine reactor. Instead it would use a shadow shield to protect just the structure of the ship. This seems to be the case in the movie as the reactor is located all the way at the back of the ship next to the engine, while the crewed section is on the other end of the ship. So presumably just above the reactor is the shadow shield. Notice how the Hermes on DA by francisdrakex had these funny looking radiators arranged in a triangular pattern? That's so they all remain in the radiation shadow cast by the shadow shield. If you go beyond that limit you will pick up a lethal dose before you can blink. Of course if your ship is protected by a shadow shield then what you don't want to do is go on a EVA out the side of the ship 300m away, or have a manned MAV fly by at similar distance. Both of them would be dead rather quickly.

Unstable in which axis? Roll, pitch, yaw or some combination? Anyway in the first picture, CoM is too close to CoL, move it forward or move CoL back by moving the main wings back. Also, V-tails are always problematic, especially V-tails made from little wing and control surfaces instead of an all moving tail. You're asking two tails (or even worse, two small control surfaces on two tails) to do the job of three with a rather unsophisticated fly-by-wire control that is KSP SAS, so avoid v-tail at all cost. Lastly are your horizontal stabilizers made from four control surfaces, two of which is back to front relative to their normal orientation? That's just asking for trouble. Never do inverted control surfaces unless you really know what you're doing.

The overall and the poking stick probably helped a little bit so the doctor didn't have to touch the patient as much. The mask with the nice smelling herbs in the beak probably not so much, other than the fact that it scared the bejesus out of everyone whenever he went so people are less likely to go up to him and cough in his face.

Yes I can confirm auxiliary lab is just another MPL. What I'm curious about is if you leave this extra MPL attached to the station what happens to the data? With one MPL you can already do the "get data out of experiment result" thing from any part that can hold experiment result. With two MPL which one of them actually get the data?

Most companies would change $10 just for something like Asteroid Day

Said material is held together by the strong force (the same force that holds protons and neutrons together in the nucleus and is the source of fusion and fission, so you know it's really strong!), not electromagnetic force of normal matter. It doesn't even start to soften until it's heated to a point that it's black body radiation is mainly in the UV side of the scale.

No it's actually easier, because body lift can be used to fine tune reentry trajectory. Once you've passed peat heat load you can pitch and yaw your craft so that the lift generated by the body deflects your craft in a direction you want. So assuming you're facing prograde, pitch up to make you land long, pitch down to land short, and yaw to get cross range. Retrograde orientation means controls are reversed. You can see this happening in real life if you observe how an Apollo capsule reenters. It flies with a high alpha reentry to both reduce the peak acceleration by creating lift, as well as give the craft some steering. It achieves this by having an offset CoM and two RCS thrusters than can roll the capsule.

Another method I've seen for safe booster separation is centrifugal separation. Just before booster burn out you start rolling the rocket to build up some rotation. Then once boosters are done you hit stage and they will all fly off at a tangent to the core. You can then de-spin the core. The con is that it cost you delta-V in terms of steering loss, and your rocket becomes spin stabilised around the separation event instead of follow prograde which can cause aerodynamic drag loses.

You don't need to mount the boosters with an angle to achieve aerodynamic separation, you just need to have the decoupler attached to the booster above its empty CoM and when you stage the decoupler will give the booster a kick so they peel outwards like flower petals. Aerodynamic separation works fine for something like two or four boosters around the core. When you have a lot of boosters things can get tricky once you pitch over. The boosters on the side and bottom of the rocket can still separate fine but the ones on the dorsal surface get dicey due to gravity. I still prefer sepatrons for staging.

The thing is, dividing the centre state into two should improve the dry weight to orbit and thus gain you some delta-V. The thing to offset this is that the upper stage engine is a dead weight until staging. It just happened that Nova II's staging have these two effects just about cancelling each other out so combining the two stages back into one neither gained or lost performance. I think rule of thumb for rocket design is that if all your stages use the same fuel, then each of them should contribute about equal delta-V to be optimum. Nova II's upper stage is a lot smaller than the equal delta-V divide for other reasons so it wasn't very delta-V optimum. I know about the all solid first stage then liquid 2nd stage trick and in fact I use it on my go to medium left launch vehicle. It won't really work on 200+ton sized rockets though. By my count a Nova II using all solid first stage will need to fire 30+ kickbacks! Until they give us 2.5m SRBs that's probably too many parts to be worth it. As for tail sitter landing, I find it's mostly water landing that's giving me grief. I can get it to land fine without smashing the engine but inevitable it will tip over and if the stage is tall enough the tanks at the top will be smashed when they hit the water. In any case horizontal landing uses the same number of parachutes as tail sitter and probably need less parts since the landing gears are so robust can you can get away with just three of them, rather than many landing legs.

Are we doing reusable now? Cos that's my speciality.

So a while ago I created the Nova II Ultra Heavy Lift Launch Vehicle. But there was always a bit of nagging thought in my mind that it was a compromised solution. The main reason why the original Nova II had a reusable upper stage was that at the time I didn't think it was possible to recover the entire core stage of the asparagus. The reusable upper stage solved the problem of cost, but also introduced a structural weakness with its thin probe core / reaction wheel section that weakened the rocket and was only partially fixed by strut spam. Then, while working on my fully reusable launch vehicle I came upon a way to recover large rocket stages horizontally: Of course this is a relative small stage, a Nova II core will be more than 3 times as heavy as this, but nevertheless it showed the way forward. Nova IIB Ultra Heavy Lift Launch Vehicle Craft file: http://kerbalx.com/Temstar/Nova-IIB-UHLLV (Craft file contains proofing payload) Specifications: dry weight: 156 tons wet weight: 866 tons cost: √304,039 (including fairing) part count: 163 payload: 230 tons to 75km x 75km orbit payload fraction: 20.58% core stage value (without fuel): √110,299 Cost per ton to LKO: without recovery: √1320 95% average recovery rate: √865 90% average recovery rate: √889 Nova II's original cost per ton was calculated incorrectly because the RHEUS value was double counted, cost per ton to orbit with 95% recover for Nova II should be √1080 per ton. Comparing the two vehicle the Nova IIB has cheaper per ton to orbit, slightly higher payload to orbit, lower part count and greater structural strength by getting rid of the upper stage weak spot. When not using a fairing the Nova IIB can launch a 240+ ton payload, the same payload cannot be launched at all on the Nova II because it will snap the upper stage at its structural weak point. So it's cheaper, stronger, more powerful and less complex. Typical mission profile: Enjoy

Did some KSP purist provoke you into making this thread? Otherwise it seems rather projecting.

You get to operate HUGE, exqisitely engineered machines. How cool is that?

I know that the rules already say vertical launch only, but what about lifting surfaces? Are they allowed?

I vote for inert payload, same additional requirements as the payload fraction challenge - no upside down decoupler or docking port on the bottom of the payload to cheat that little bit of weight. No using Ec from payload either.

I disagree. We are now moving out of the area of rocket design into payload design. When faced with a problem of "I want to put payload to Jool", you can always divide up that problem into two halves of "KSC to LKO" and "LKO to Jool". Of course the upper atmosphere being nearly a vacuum means most rocket's top stage naturally makes a decent injection stage, and conversely if you don't have a dedicated upper stage then payload engines are generally pretty good at getting the payload into a circular orbit from suborbital. But this overlap is more of a happy coincidence rather than hard requirement for rocket design in general. Getting out of LKO to places should always be the job of the payload, even if the payload is "borrowing" the upper stage to do part of its job.

They didn't do it for cost so much. It's more that the Apollo spacecraft was overweight so they had to make up the difference somehow with the rocket. Most of the extra delta-V came from making the 2nd and 3rd stage have a common bulkhead and therefore lighter. But they did have this idea that small improvements could be made to the F-1 engine over time to boost the thrust further so they designed the first stage with huge fuel tanks that could barely lift off. The engines were improved over time hence why the last three flights were able to bring a rover with them. N1 also had the same spacecraft overweight problem, they "fixed" it by superchilling the fuel to make it denser and adding six more engines much to the rocket's detriment.

Nah it's not true. TWR depends only how how much of the craft is engine, not on the absolute amount of thrust. So you could just as well have a tiny craft where the ion engine + battery + xenon makes up most of the mass of the craft and you will get decent TWR (for an ion craft that is). Yeah this 500m/s rule is messing with things, it's making us focus on payload instead of launch vehicle because we all know when you make the payload better that dramatically scales downwards towards the rocket due to the rocket equation. I still say we should go for 100% inert payload: no engine, no probe core, no reaction wheel, payload mass in VAB must match payload mass in orbit. Than way we can start to ignore the payload and really focus on the rocket.

But that's what actually happened with Saturn V, it launched with a lift off TWR of 1.16. The thing is fuel is really cheap but engines are expensive, so to minimise cost it makes sense to carry a lot of fuel in the first stage to get as much use out of the big first stage engines as possible, even if marginal delta-V increase with more fuel is decreasing (but remains positive).

Okay fair enough, but it seems like that's encouraging designs that optimize payload delta-V expenditure to as close as to 500m/s as possible isn't it? Because whatever tankage that holds that 500m/s delta-V worth of fuel is payload for free, and that fuel spent is free delta-v as far as the launch vehicle is concerned. Like say a payload made up almost entirely of ion engines and solar panels, plus a little bit of xenon to provide the last 500m/s to orbit. This last 500m/s would have extremely high Isp which then boost the average Isp across the whole launch?

I think I might have conceived a way to abuse the current rule set as it stands, and no it doesn't involve explosive staging. Will try to get the design to work tonight. It's making use of the old "payload vs upper stage" grey area thing again. But yeah seen as you've already made a precedent for rule change, I suppose there's always the opportunity for more rule changes to fix rule lawyering / creative accounting.

Since I'm known for big rockets and asparagus staging it would be remiss of me to not represent the vegetable growers in this challenge $240,050 / 262.50 tons = $914.48 per ton to orbit. Not bad for all liquid rocket right? Let's see, features of this rocket: I carried more payload to orbit than the current top seven entries on the leaderboard combined.

Aerospike is surface attachable which is infinitely more flexible.

I don't think that's very useful way of thinking though. Imagine a big cannon firing at 45 degree angle into the sky. As the cannon ball leave the muzzle it has equal magnitude of vertical and horizontal velocity. At the AP of the cannonball's flight it's vertical velocity component is now zero while it's horizontal component is still the same as when it left the cannon (assuming no drag). The upward velocity has been lost to gravity. Of course the cannonball gained gravitational potential energy equal to vertical velocity component lost. But we all know being 100km above the surface does not mean you're in orbit, only the horizontal velocity component is useful for you to achieve orbit. Similarly when you launch a rocket your engines add both horizontal and vertical speed to the whole vehicle depending on your climb angle. Assuming your aim is a circular orbit, by the time you have entered your target orbit your vertical speed is by definition zero - ie every single m/s of vertical speed your engine has added to your vehicle during its burn has been lost to gravity drag. The only thing that keeps you in your circular orbit is the horizontal speed that your vehicle has accumulated. We know experimentally that launching horizontal on an airless body cost the least amount of delta-V, even with an instantaneous acceleration from a cannon. Thus we know gravity drag is present even when you have instantaneous acceleration followed by coasting, as long as some component of the acceleration is done against the direction of acceleration from gravity. The only way to avoid losing velocity to gravity is to never accelerate against it - ie firing a cannon on mountain top flat, or accelerate a spacecraft against the horizon. But what about launching into an elliptical orbit you ask? Well let me ask you: if you start off in a circular orbit and you want to go into an elliptical orbit (say going to the Mun), which method of acceleration is more efficient? Thrust prograde (and thus against the horizon, since we're starting from a circular orbit), or thrust radial? As for steering loss, imagine a rocket with two engines on two extremes, facing opposite directions. In other words a giant aeolipile: When you light up those two engines the whole contraction will start spinning furiously, but it won't move an inch. So all the work the engines are doing goes into rotating the vehicle instead of translating the vehicle. So that's what steering loss is. Any time when the thrust of the engine is not aligned with the CoM of the rocket, some of the work the engine is doing goes into rotating the rocket instead of accelerating it in a direction. This loss of potential acceleration is steering loss. An aeolipile has 100% steering loss hence it doesn't go anywhere.