MaxL_1023

The amount of delta-v you need to close an orbit eventually converges to your SOI entrance velocity minus escape velocity, if you are torching it on a hyperbolic transfer. To get the exact value, square your entrance velocity, add the square of the escape velocity, square root that, then subtract the escape velocity, taken at your burn altitude. Circularizing takes about another 500 m\s for Duna.

They are more useful in modded setups, especially when realfuels is involved. Kerolox and Hydrolox suffers from boiloff and the engines have limited ignitions - in those case the puff burns storables and is a restartable engine.

There is a mod which does this (called "orbital decay") - is it possible you have it installed? If you are using CKAN, it may have been recommended from something else and you just "went with the flow" so to speak. Otherwise, your orbit should not change significantly over time unless your craft is inside atmosphere AND you have physics loaded.

What are you using for landing? You need at least 5 KN for every ton of lander to easily land on the mun - any less and you will have trouble slowing down fast enough as you bleed off horizontal velocity. A Lander can mk I, heatshield with ~50 ablator, , FTL-400+Terrier, some batteries and solar panels + science stuff should have enough delta-v to land from Mun orbit, take off, and return to Kerbin (you need about 2k to have a decent margin).

It is difficult, but possible. Your best bet is packing about 4 km/s of delta-v, trying to burn to a 200-300km apoapsis then stage something with ~1000 m/s to pull your PE up.

I would like to see incremental improvements to existing technology. For example, once you finish the rocketry branch, have a 2500 science node open up which gives all engines +5/10 SL/Vac ISP. When you finish the fuel tank branch, have a node which makes all tanks 20% less massive (when empty, not full). Essentially, you unlock the stock tree to give you the parts you need to go places, then unlock improvements which make it easier to get there (or allow more ambitious missions). Nothing too drastic, but a little carrot to reward science grinders without messing up "explorers" or causal players.

I don't think any areas are exactly zero, but a lot are under 1%. As long as you have the large drill you should be fine eventually - it might just take 2 years to refuel!

I would still do it - the configuration you have puts the CoM well above the heatshield. In general, you want it as close to the heatshield as you can get it.

The MPL is very long, so with a heavy pod on the front of it your craft is likely unstable. Your best bet would be to put the pod under the MPL - I know it looks wierd but the mass balances better. You might also get away with putting the whole thing behind a 3.75m heatshield.

How is your rocket shaped? You want it to be stable while pointed retrograde, meaning that a small deviation would create an opposing force. I have never had stability as long as everything behind the heatshield has a gradually decreasing diameter - a 1.25m tank behind a 1.25m heatshield with a pod on top can flip, while the pod by itself will be stable. If you get a stable configuration, the PE height is not a big issue - you can survive a single-shot re-entry and landing using the heatshield. Speed does play a role, influencing how low you get before you bleed off velocity. Too fast, too low will put large forces on your craft and amplify any unstable characteristics. Basically, your craft should be able to re-enter retrograde with no control input at all, besides starting retrograde at atmosphere-top.

Thrust-limiting a large SRB sacrifices delta-v (if you are using a booster + sustainer setup) as you carry solid fuel longer. The sustainer would barely notice if you increase SRB thrust to full, but add more solid fuel to keep your pad TWR identical. If you use a pure-solid first stage, you are alright with thrust-limiting, but the lack of gimbals (or very narrow ones) plus the very high acceleration curve (a SRB stage will often pull 4 or 5 g's just before burnout due to the low ISP) makes a soild stage difficult to execute effectively. Right now almost all of the SRBs are 1.25m in diameter - a stackable solid fuel tank to add fuel to existing boosters (they keep the same thrust/isp/etc.) would help - perhaps unlock it along with the hammer in tier 2 so you can make somewhat customizable boosters. The tech tiers could then be devoted to unlocking more powerful and efficient engines (defined by the base booster type, thumper, kickback, etc.).

I like to put a first stage which is 4 copies of the second stage arranged radially. It works quite well when you need to lift something heavy with only 1.25m parts.

It is not really just that one SRB. The square/cube law alone causes trouble, especially due to the inability to easily cluster engines in stock. If you want to lift a 30 ton LF stack off the pad, you either need to somehow fit 2 reliants under a 1.25m tank, 4 thuds (which are inefficient) , or use radial staging. If you want to use 2.5m parts, you are stuck with the skipper which is too powerful. Think of it this way: Strongest 1.25m lifter engine - Reliant at 216.667 KN (Vector is end-game so does not really count here) Weakest 2.5m lifter engine - Skipper at 650 KN (Poodle is useless on the pad) Strongest 2.5m lifter engine - Mainsail at 1500 KN (Twin Boar is a unique part) Weakest 3.75m lifter engine - Rhino at 2000 KN There is a big ratio gap between 1.25m and 2.5m parts, especially considering that using a shorter tank can let you end up with the same fuel mass on the larger stack. You just can't fit enough thrust on a 1.25m node to lift it all, while a Skipper is a waste of engine mass.

The ratio depends on what TWR you want. If you can get away with a lower TWR on your second stage, you can put more fuel (and delta-v) on it. It depends on what engines you have available, stack size, payload type and ascent profile as well. Generally, I start with the payload, put propellant+engines until it has a TWR of about 0.8-1 for an upper stage, 1.0-1.2 for the middle stage and 1.25 on the pad for the first stage. How the delta-v balances out depends mainly on what engines you have available and your actual payload size.

If you think re-entry is hard now, try it in RSS/RO. Even from LEO your pod can randomly explode (or kill crew due to G-forces) due to a 10m/s delta-v application error. In stock, I have had craft survive coming in backwards (nose forward) due to a design error, and have a parachute be enough to withstand LKO entry on 100% heating. Unless you are doing some hyperbolic or straight-down trajectory you should be fine using a normal heatshield.

Airbrakes let you slow down higher in the atmosphere, where heating is not as large of an issue. If your craft launches inside a fairing, try just using an oversize heatshield with most of the ablator removed. A 2.5m heatshield has 4 times the area of a 1.25m, meaning that you can put a 1.25m pod behind it and slow down much higher up and get an easier re-entry overall.

I would like to see 1.875m parts myself - 1.25m stacks get slightly sketchy if you want to put more than 2-3 tons in orbit, while you need to be near 10 tons to really justify a 2.5m stack.

I would also recommend dropping your near-empty stage early - you would likely lose more delta-v putting in the gear to turn the whole thing than you would sacrifice by staging. (Considering vernors, monoprop, large wheels, etc) Another option which I find works quite well is putting large reaction wheels in large radial stages. They are often the right size (2.5m), and you ditch them when you stage and no longer have enough mass to justify their use. You only haul them for as long as you need them. 0.2 tons is nothing to a 100 ton radial throwaway booster but means a lot when attached to your final payload.

RSS/RO fixes the issue nicely, in that a lander can would never survive re-entry without a lot of extra work and equipment. It is perfect for the moon however.

Hello, I just used an Exokerbol Core Drill on Duna (from DMagic I believe, not sure if stock or not) and it flipped my lander completely - it actually sent it entirely airborne for a second. Is it supposed to push against your craft that hard? My Lander was about 2.5 tons and it was on a narrow base, but you would think if anything a drill would pull you inwards as opposed to the opposite due to the screwing force. Is this known, and if so do I just need a 10-ton class lander? I would have a picture, but trying to F9 crashed my game. I might need a reinstall lol.

The Mk I pod has it (or at least in many Mods it does - have not played pure stock in awhile), so it has an edge over the lander can unless you are really coming in fast (where you would want a heatshield on the Mk I anyways). Considering how heavy the 2.5m heatshield is, removing the requirement from the Mk I-2 would make up most of it's mass deficiency over the other pods.

If the Mk 1-2 pod included a Heatshield it would help. Realistically, neither lander can would survive re-entry and a bolt-on heatshield shouldn't work as well as it does.

Ok - I was including the cost of getting into orbit from the KSC.

An optimal altitude that high does not make much sense - it takes only about 200 m/s more to make a Duna transfer than just the burn to put your AP at the Mun's Orbit, let alone circularizing there than making the transfer again.

To get to Valentine in that new extrasolar mod you would need something like that just to launch a probe core, unless you want to wait hundreds of years.