KSP Craft File: Kiwi Orbiter

If you play Kerbal Space Program, you inevitably get to a point where sending Kerbal crew members up and down to a space station becomes a mundane drain on your in-game cash and your real-life time and enthusiasm. It needs to be easy for the player, and efficient for the game.

DESIGN PROBLEM: We need a space bus; a commuter service. The standard “Go Up, Move Around, Come Down” mission. It needs to be very cheap, efficient, and undemanding of the player.

DESIGN SOLUTION: The Kiwi Orbiter

screenshot18

The Kiwi Orbiter is a partially-reusuable, low-cost/high-versatility space capsule, designed to take three Kerbals to a circular, equatorial Low Kerbin Orbit (LKO) of 245km, perform several rendezvous and docking maneuvers, then re-enter safely for a landing at Kerbal Space Centre (KSC), with minimum of fuss, bother, hoo-haa, and flap-doodle to the player.

The vehicle is built with precisely the right resources for the mission, meaning the player can fly it by using mouse-clicks only and no planning, construction, or flight control inputs are required! *(MechJeb mod required for some operations).

It is an analogue for the real-life Russian Soyuz TMA in terms of function, but takes more the physical form of a SpaceX Dragon in that it re-enters in one piece without a Service-Module Separation.

HERE is the download link, but please read on for a full vehicle description and mission walk-through.

You MUST have MechJeb installed. Download MechJeb first here.

The ship is designed in game version 1.3.0, and works in 1.3.1 , 1.4.0, 1.4.1, and 1.4.2.


screenshot5

FAQ: Why 245km orbit? Answer: 245km is my standard altitude for space stations. It’s high enough to enable the player to use 1000x time-acceleration to cut down on real-life waiting time for transfer windows. Additionally it is near the border of High Kerbin Orbit (HKO) which is handy if you need to grab extra high-altitude science, and it is a good jumping-off point for transfer burns to Mun, Minmus, or beyond. Your altitudinal needs may vary and will void warranty.

FAQ: Why use a capsule-based space program, when shuttles and SSTOs are the real deal when it comes to reusability? Answer: because spaceplanes are fickle and need to be micro-managed and I really can’t stress strongly enough how much I caaaaaan’t be fucked (CBF). With this capsule program my real-life investment is as low as it can possibly be, while the in-game costs are comparable. For this reason, the Kiwi Orbiter is the backbone of my space program. Every crewed mission, whether to a space-station or to a large inter-planetary ship, begins and ends in one.

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THE KIWI ORBITER

Primary function:

  • LKO crew ascent and descent.

Secondary functions:

  • ferry crew between stations and vessels while on-orbit,
  • emergency lifeboat carried on larger vessels,
  • space tug for construction projects on-orbit,
  • make New Zealand proud.

KEY FEATURES

LOW COST
Send Kerbals to space for only $7,000 per person *(once recovered from landing near KSC).

FEW PARTS
A mere 20 parts *(orbiter only) ensures the next crew rotation doesn’t turn your station into Kraken chow.

SINGLE-RESOURCE SIMPLICITY
Vacuum engines draw from the same large supply of monopropellant as the RCS, all but eliminating the risk of running out of gas for RV and docking. Additionally, refueling is simple and no longer requires any irritating Lf+Ox balancing!

VERSATILITY
When fully fueled and in vacuum, orbiter has 1021m/s of delta-V (dV) (in 780 units of monopropellant). After subtracting for orbital insertion and de-orbit burns, player is left with approximately 300m/s for on-orbit maneuvers – plenty for the average day of wildly inefficient RV and docking!

HANDS-OFF ASCENT
Vehicle flies itself to orbit with one click of the mouse *(using MechJeb mod).

NO MORE DEBRIS
Vessel is precisely fueled and weighted for Main Engine Cut-Off (MECO) and Stage Separation to occur just before achieving positive Periapsis, leaving your planet 100% debris-free and earning the Kiwi Orbiter the
Kessler Tick of Approval™
*(when using recommended ascent profile).

SLOW-BURN ASCENT
Low Thrust-to-Weight Ratio (TWR) and low strains during the atmospheric flight phase make any weighty, complicated and costly launch escape systems unnecessary, thus adding economy. Booster Separation less resembles the fourth of July, and delicate tourists and VIPs are left conscious and with lunch intact.

LIGHTWEIGHT
Due to its small size the Kiwi is very responsive under RCS, easy to dock, and forgiving of mistakes. Its TWR is balanced for both orbital insertion and fine tuning an intercept. Attitude control is more than adequate under reaction wheels alone, saving more RCS fuel for translating and thrusting.

HANDS-OFF RE-ENTRY
Simply arm parachutes and relax! The entire orbiter re-enters in one piece, and can be recovered. No Service Module separation occurs, thus no risks of collisions, explosions, frame-rate issues, or creating debris. Flat solar panels need no retraction, and there are no external antennas.

SAFE RETURN
Heat shield ablator is precisely pared down to the bare minimum (plus 400% safety margin) in order to provide better dV and TWR throughout the mission. Triple parachute system provides step-wise decceleration and soft-landing, without need of player input or conscious Kerbals.

COSTS

Crew: 3
Launch cost: $36,125.
Recovery: ~$15,000 can usually be recovered, assuming re-entry and landing goes according to plan.
Final cost: $21,000 for three Kerbals, or $7000 per Kerbal.

It’s tough to find anything cheaper than that!

PART LIST

Let’s talk about some of the design choices.

ORBITER:

  • Shielded Docking Port. Low atmospheric speeds make launch escape tower unnecessary, and this port is more aesthetically attractive than an open wound clamp-o-tron.
  • Mk1-2 Command Pod (obviously). Provides 3 crew seats, reaction wheel stability, remote comm link. Also functions as reserve battery and fuel tank (with 48m/s dV); both resources are locked off by default.
  • Parachutes. 2x radial main chutes, 1x radial drogue. Only one of the main chutes is necessary, the second is merely for aesthetic symmetry. Quite often to reduce part count further I simply replace one main chute with the drogue, but it doesn’t look as good.
  • Battery and Solar Panels. The largest possible battery is used. Why? Because it makes the electricity supply virtually unlimited. Why do we need near-infinite power supply? Because the solar panels used on the ship are the flat single versions which sometimes don’t generate much power (if, say, you timewarp without facing the sun). Okay then, so why use flat solar panels if they suck? Well, because foldable solar panels are a pain in the neck and are easily broken. So it all stems from that. If the point of the ship is to be ‘hassle-free’, then I’m definitely going to remove solar panels that need to be folded away for protection when it comes time for docking or re-entry.
  • Monopropellant Tank and 2x “Puff” Vacuum Engines. The largest 750-unit yellow fuel tank is used, to fuel vacuum engines and RCS from the same source. The rationale is that while Puff monoprop engines have, granted, a terrible Specific Impulse (ISP) rating, there are other gains to be made from 1) visual clarity when refueling, to say nothing of being distinctive bright yellow and not boring grey, 2) no risk of your Lf+Ox tanks being accidentally emptied or unbalanced as sometimes happens when docked to a Lf+Ox-burning ship with crossfeed unhapp’ly enabled, and 3) the flexibility for the player to perform much, much more translation while on-orbit (i.e. docking, tugboating, more docking, MOAR DOCKING!). More specific dV readouts will follow below, but basically, what you pay for in ISP you make up for in real-life freedom from worries, which ultimately is what this spacecraft is about. It must also be said that the ISP of the Puffs is not so different from that of Lf+Ox engines of a similar size.
  • Mechanical Jeb Control Unit. The entire premise of the Kiwi Orbiter is to provide the player with hassle-free launch and a predictable result every time. It is designed for one mission only: the MechJeb autopilot ascent to 245km. Thus, the craft file will not be provided without the MJ unit attached, and you will need to have the mod installed in your Game Data folder for this vehicle to load in your game. Deal with it.
  • Kerbal Engineer (KER) Flight Computer. This is optional, and the craft file is provided without it.
  • Heatshield. The 2.5m version has had most of the ablator removed, as it was not useful load. The remaining 160 units is approximately 110 units more than I have ever used on even the most aggressive re-entry profiles. NB: the Puff vacuum engines and RCS blocks will often go to temp gauges on re-entry, but never explode when properly pointing retrograde.
  • –Not included: Antenna.– This is not necessary for a commuter bus, not even for remote probe guidance. Add one if you really wish; I recommend the Communotron 16-S to continue the “no-brain-required” design approach.

FIRST STAGE:

  • 18 Sepatrons (Pointing Upwards). Staged with the separator. Okay, this may be overkill, but I want to be absolutely certain that the first stage debris does not reach orbit. Even if the Periapsis is only +1m above the ground, the game will still put it on rails and allow it to continue orbiting. Not on my watch, sonny. Not on my watch.
  • One Orange Tank with “Skipper” Engine. Let’s talk about the Skipper. The Skipper rocket motor is under-powered and useless, right? Well, combined with two boosters, it actually performs perfectly for what this mission requires. As noted above, the ascent is very docile, and majority of the fuel is burned only after a satisfactory ISP rating has been reached higher in the atmosphere. Thus, the use of the Skipper is the number one cost saver in this vehicle. In the configuration I have provided, it has a huge edge over the more expensive Twin Boar or Mainsail rocket motors you otherwise might want to use.
  • 4 Stabiliser Fins. Keeps everything flying in a nice, vaguely pro-grade orientation.
  • 2x “Thumper” Solid Rocket Boosters (SRBs). The two cheap and disposable boosters provide a “just right” amount of thrust in the first phase of the flight. Using them down low in the atmosphere is what allows for the cost savings of the Skipper at higher altitudes, as noted above. NB: They are Autostrutted to Orange tank without need for EAS Struts, and still separate just fine, thank you.

MISSION WALKTHROUGH

Now you know all about how the vehicle is built, it’s time for a walkthrough of the whole mission, with all the technical details included. There are eight steps in the ascent phase.

  1. Pre-launch.
  2. Launch.
  3. Booster Separation.
  4. Max Q.
  5. MECO, Stage Sep, and Vacuum Engines Start (VES).
  6. Vacuum Engines Cut Off (VECO).
  7. VES-2 Circularisation Burn.
  8. VECO-2 Autopilot Disengage.

And later, another eight steps in the descent. But let’s deal with the ascent first.

ASCENT:

1. PRELAUNCH.

  • NOTE: WHILE MECHJEB ENSURES EACH MISSION IS ALMOST IDENTICAL, THERE ARE QUANTUM FLUCTUATIONS THAT CANNOT BE ACCOUNTED FOR AND WILL CAUSE YOUR DELTA-V CALCULATIONS TO VARY.
  • Open MechJeb.
  • Open ‘Ascent Guidance’.
  • Enter ‘245’ in the ‘Orbit Altitude’ box.
  • Check all other MJ settings match those shown in the screenshot (they are all the defaults so you shouldn’t have to change anything at all).
  • Verify crew and staging has not been garbled.
  • Press the ‘Z’ key to go full throttle.
  • RCS disabled.


 

2. LAUNCH.

  • Press ‘Spacebar’ to activate first stage engines and docking clamps.
  • As quickly as possible, click MJ ‘Engage autopilot’ button.
  • Now that the vessel is on its way up, you may press ‘>’ key to use time acceleration as desired.

3. BOOSTER SEPARATION AT MET00:42.


 

4. MAX-Q AT UNKNOWN TIME – Aerodynamic forces are so low that it doesn’t matter.

 


5. MECO, STAGE-SEP, AND VES-1 AT 02:35

  • Sepatrons and Separator will automatically activate through staging. The first stage falls back to Kerbin.
  • The orbiter will tumble a little, and re-orient itself pro-grade.
  • The two Puff vacuum engines will engage, to finish raising apoapsis to 245km.


6. VECO-1

  • Vacuum engines will throttle down and fine-tune apoapsis before cutting off.
  • MechJeb will coast to edge of atmosphere, create a circularisation node of ~250m/s, re-orient the vessel, and engage time-warp.

 


7. VES-2 CIRCULARISATION BURN AT ~12:05

  • Vacuum engines throttle up to raise periapsis.
  • Advanced users may click MJ ‘Disengage autopilot’ at Pe=140km to combine this circularisation burn with a Hohmann rendezvous maneuver. I do this almost every single time.

 


8. VECO-2 AT 13:04. 

  • Engines throttle down, autopilot disengages.
  • Player may now assume control of the vessel.
  • Game time elapsed is 13:04, but real-life time elapsed is only 02:27.
  • Delta-V: I have run over 100 ascents and kept data (some pictured below), and found that most times there will be ~770m/s remaining. However some physical time acceleration issues alter the MJ ascent profile and leave only ~690m/s remaining (you can tell this situation is occurring if your boosters explode on separation – no known workaround exists sorry). Another unexplainable quirk in the cosmos will cause the ascent to go more efficiently and leave you with ~810m/s of delta-V. No guarantees!


 

DESCENT PHASE:

1. CHECK SETTINGS

  • Check you have enough fuel! You need approximately 300m/s of dV to complete the recommended MJ-auto landing at KSC. Otherwise the standard “eyeball your burn so your periapsis touches the eastern peninsula” plan may be used.
  • Check your orbit is clear of objects and ready for a burn.
  • Check you have control of the ship i.e. either Pilot on board or Remote control link, with reaction wheels enabled and plenty of electric charge. Ablator, obviously. All the usual stuff.
  • Check fuel tank flow is open.
  • Toggle the engines to ON (action group 1 by default).
  • OPEN MECHJEB LANDING GUIDANCE PROGRAM. Set your landing target for “KSC Pad” and click “set” twice. If successful then target coordinates will appear. Ensure “show landing predictions” is enabled.


 

2. DE-ORBIT BURN

  • Switch to map view
  • Click “land at target”
  • The ship will now time warp up to the burn point, turn and point retrograde, and engage engines..


 

3. DISENGAGE AUTOPILOT!!!

  • This is crucial. You MUST click “abort autoland” when the estimated distance reads 21km from KSC.
  • If you need to adjust it (I usually do) you can do some manual burns either prograde or retrograde, using RCS or main engines as you see fit. The only thing that matters is that your landing prediction is reading an overshoot of 21km, and that you achieve this as quickly as possible after the autopilot disengages.


 

4. DEPLOY CHUTES, ORIENT RETROGRADE

  • You are now free-falling towards the Kerbal Space Center. The 21km overshoot is precisely designed to reduce to zero after entering atmosphere.
  • Deploy your chutes. They are in the staging by default, but you can also do this manually by right-clicking them.
  • Use MechJeb SmartASS (or a pilot if you are super, super certain they won’t lose consciousness on re-entry) to HOLD RETROGRADE.
  • Goes without saying that you need electric charge to run the reaction wheels to hold retrograde. If you are out of charge (how the hell did you manage that?) then you should use remaining RCS fuel.


 

5. RE-ENTRY HEATING

  • Vessel will re-enter the atmosphere and hopefully hold retrograde well enough that nothing will explode and your aiming is not spoiled by aerodynamic lift.
  • The engines and RCS blocks will go to temp guages.
  • Do not panic.
  • Do not touch the controls.
  • Pray to deity/deities.
  • You may time accelerate, but this sometimes causes overheating. Use discretion.


 

6. PARACHUTES OPEN

  • If you’ve done it right, it should look like this!
  • Don’t touch anything.
  • If you really screwed up your approach, this is your last chance to use your engines to land closer to KSC.


 

7. LANDING

  • Easy as pie! Bob’s your uncle, and Val’s your aunt.
  • Sometimes things will explode. Sometimes the heatshield. Sometimes the engines. Sometimes both or nothing. This is the risk you running by landing on terrain – if it really bothers you I suggest changing your approach from “21km” overshoot to “23km” overshoot to ensure you land close to the KSC but in the water.
  • If you’d like to be sure of nothing exploding, you could lighten your impact by burning your engines at the last moment to expend fuel mass and reduce airspeed. But honestly, meh.
  • It don’t get much prettier than that!


8. RECOVERY

  • Click the green “Recover Vessel” button like normal and reap rewards!
  • Thank you for flying the Kiwi Orbiter. We hope to see you again.


 

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