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Sturgeon

The Kerbal Space Program Total Sperg Zone

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A Mk III SSTO space plane disconnecting from the Exocet Fueling Station in preparation for deorbit burn. The smaller craft are emergency shuttles for the crew of the station. Each shuttle can hold up to 10 Kerbals. I'll be adding an orbital rescue craft for picking up stranded Kerbals on EVA in the near future.

 

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The Mk III, at least until I come up with a better name for it.

 

 

All done in career mode.

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A little bit of high speed NOE action. I am working on a ground refueling station for spaceplanes. The station is complete and functional, I just have to figure out how to transport it over several continents.

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The Mk III Mod 1 is the most recent "general purpose" versions of the Mk III family of craft. Other iterations exist for specialized and testing purposes, but we will go with the specs for the Mod 1

 

Parts: 117
Height: 3.9m
Wingspan: 11.4m
Length: 19m

Takeoff weight: 30.0 tons
Maximum weight: 30.8 tons
Dry weight: 13.7 tons

Liquid fuel capacity: 1395
Oxidizer capacity: 1705
Monopropellant capacity: 390
Electricity: 400 in batteries + 6 RTG units with combined output of 270/min

Power plant: 4x R.A.P.I.E.R. dual mode engines.
Combined maximum output: 700 (open cycle) 760 (closed cycle)
Maximum speed (open cycle) 1600m/s 2030m/s
Maximum altitude (open cycle): 30000m
Low altitude cruising speed (NOE): 190m/s
Landing: easily done in unpowered glide at maximum weight.

The Mk III family of craft is flyable without SAS, but is not recommended for pilots who are unfamiliar with the craft. Because of the shape of the wings, the craft exhibits a negative static stability in rolling. This is only a minor drawback as SAS can easily counteract the roll. However, even with SAS, extreme maneuvers should not be attempted in powerd flight under 130m/s, as the craft can easily oversteer itself. That being said, at cruising speed the craft is very responsive and enjoyable to fly, dodging its way though mountainous terrain with relative ease at the hands of a skilled pilot. At high altitude (+22000m) the craft exhibits a certain degree of instability caused by differential outputs of the engines. Previously this was mitigated though the combined use of the SAS system and RCS thrusters, but the Mod 1 received and upgrade to the action groups to provide greater control to the engines and air intake system, allowing the pilot to reduce the instability. Full details of the specific improvements of the Mod 1 will come later. The Mk III is capable of SSTO, and generally will have 1/6 to 1/4 of its fuel remaining when docking with the Exocet refueling station. To reduce the takeoff weight, a certain amount of oxidizer is left out of the Mk III, but when fully fueled from the orbital station, it is capable of attaining orbit around Duna, and through the clever use of RCS thrusters and aerobraking, can successfully land on Duna. This is, however, a one way trip.

 

The Mod 1 improvements over the standard Mk III are in the areas of takeoff, high altitude flight, spaceflight, craft operation, and landing. For takeoff, the rear landing gear were moved forward by approximately 1m, reducing the takeoff speed from 130m/s to 110m/s. High altitude flight was improved by symmetrically balancing minor external features that were causing a drag imbalance. Refining the positioning of RCS thrusters improved the spaceflight characteristics, specifically while docking, by moving the CoT closer to the CoG. Additional action groups and improvements to existing action groups added in general craft operation, such as the ability to shutdown and activate engines in pairs (inboard and outboard), closing off air intakes, and toggling various utilities from the keyboard. There was not much to improve in the way of landing characteristics. On one occasion, after undocking from Exocet station and performing a deorbit burn, Jeb deadsticked the landing from 130000m onto the runway at the KSC without the use of SAS. However minor the improvements could be, they are very welcome. While the craft exhibits wonderful landing characteristics under ideal circumstances, and even less than ideal circumstances, the dual parachute arrangement cause problems during emergency landings. This was remedied by removing one parachute, and placing the other above the crafts CoG, between the engines. Now, when the chute is deployed, it will pull the nose of the craft upward while drastically reducing forward speed. This should only be done at very low altitudes, because eventually the craft will stall and the nose will once again be pointed at the ground.

 

Mk III Mod 1 maximum weight.

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Mk III Mod 1 dry weight.

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Original Mk III modified for Duna by adding various science gear and a more powerful antenna.

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I was playing around with VTOL capabilities on the Mk II, specifically to improves its non-atmospheric landing capabilities. It was met with limited success. Perfectly capable of taking off from Kerbin in such configurations, landing on Kerbin was very very tricky. It also had a nasty tendency to tip forwards while on struts. The landing gear could withstand the impact just fine, but it was still problematic.

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Avoiding CG shift with Spaceplanes; some initial experiments:

 

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It appears to be possible to eliminate, or at least mitigate the CG shift due to fuel consumption by using fuel ducts.  The design above has five fuel tanks in a line and, this is critical, a plate that blocks fuel flow.  There is one fuel line leading from the center tank to the engine plate so that the engine has fuel, and one duct leading from the tank immediately forward of the center tank and another duct leading from the tank immediately aft of the forward tank both leading to the center tank.

 

Therefore, fuel is taken symmetrically from the aftmost and rearmost tanks first, then the next two, and then the center tank.  No CG shift.

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What I learned from reading the KSP forums is that I'm bad at KSP.  Or perhaps a different way to put it would be that the skill ceiling is higher than I thought.  There's a lot of min-maxing with flight profiles and craft design that I'm just not doing because I wasn't aware of it.

 

think the problem with the R.A.P.I.E.R. is that its TWR is too low.  Since you're using it mainly to get into orbit, TWR is king even at the expense of specific impulse.  There's something called "gravity drag" which is a term I hate, but I suppose it gets the idea across fairly well.

 

A rocket with a thrust-to-weight-ratio of 1 can't perform any work.  Its thrust and weight cancel exactly and it just hovers.  A rocket with a TWR of 3 isn't 50% more powerful than a rocket with a TWR of 2 on liftoff; it's twice as powerful because it has twice as much available acceleration after you subtract the opposing force of gravity.

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What I learned from reading the KSP forums is that I'm bad at KSP. Or perhaps a different way to put it would be that the skill ceiling is higher than I thought. There's a lot of min-maxing with flight profiles and craft design that I'm just not doing because I wasn't aware of it.

I think the problem with the R.A.P.I.E.R. is that its TWR is too low. Since you're using it mainly to get into orbit, TWR is king even at the expense of specific impulse. There's something called "gravity drag" which is a term I hate, but I suppose it gets the idea across fairly well.

A rocket with a thrust-to-weight-ratio of 1 can't perform any work. Its thrust and weight cancel exactly and it just hovers. A rocket with a TWR of 3 isn't 50% more powerful than a rocket with a TWR of 2 on liftoff; it's twice as powerful because it has twice as much available acceleration after you subtract the opposing force of gravity.

Man, I can't even into transfer orbits properly. I am a ksp peon.

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The Mk V, a lighter weight, less expensive alternative to the Mk III. It was built primarily as a test bed to compare the RAPIER engines to turbojets+rockets, and I have discovered that spaceplane design and flight paths play a larger roll than what engines you use to get to orbit. The turbojet + clusters of small rockets failed to achieve orbit, whereas the RAPIER has been able to do it consistently and with sufficient remaining fuel for deorbit burns.

 

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