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Starship: Kerbin to Kerbin


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Starship Intraplanetary Transport System


You nerds will remember a few years ago when SpaceX announced a plan to huck a hundred customers across the world in half an hour. They said they would do it with a fully reusable VTOL ship.

They haven’t done it yet: Can you?


Your ship will have seats, launch vertically from KSP, and land vertically at the Desert Airfield. The ship is fully reusable, so what goes up must come down, intact.

It is also acceptable to run the course in reverse. 

Precision will be difficult to measure, so let’s just say the Desert Airfield buildings need to be in reasonable view.


Superlatives and Awards:

There & Back- Return to KSC on the same tank of fuel. @camacju @ralanboyle

Sniper- Land on the DA Launch Pad. @18Watt

Bargain Airline- Lowest Fuel Cost per Seat @18Watt 134

Entrepreneur- Lowest Launch Cost per Seat @18Watt 4,116

Cheapskate- Lowest Overall Launch Cost @ralanboyle 17,790

Whiplash- Fastest Time: @camacju 7:48

Musk- No Chutes @camacju

Bezos- No movable Aero Surfaces @camacju

Cattle Car- Most Seats (Command Chairs not eligible) @18Watt 32


Pod Ships: 

@camacju Was first to complete with a quick little 2 seater. Leg time was 7:48 earning him the Whiplash award. He also added There & Back, Musk and Bezos awards. 

@ralanboyle Got it done on the cheap in 11:14 with a 2 seater cruise missile. 

@18Watt Went for a bigger ship resulting in better accounting numbers. He slipped 32 kerbals over to the DA in 11:42 and sniped the landing! 

Chair Ships:

Edited by ralanboyle
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You may want to change fuel cost and launch cost to fuel cost per seat and launch cost per seat. Otherwise, single seat designs will be the best way to go.

I think the best way to attempt this is going to be a Rapier powered vertical launch, come screaming in over the desert airfield at mach 6, and airbrake to land vertically. Basically you're half tailsitter plane and half depressed trajectory ICBM.

edit: best as in fast time and low fuel cost. also can probably return to ksc

Edited by camacju
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Here's a quick jet engine powered submission for fastest time. Probably pretty good fuel cost wise too but I forgot to calculate it.


On launchpad


Cruise. This is about 100m/s slower than max cruise but that won't make too much of a difference. Maybe I'll re-fly it if necessary


Steering. The only lift comes from body lift on the air intake so I have to be careful managing lift and drag.


Deploy the service bay and go retrograde to slow down


Landed at 7min 48sec. More than half fuel left means this has the range to go back to KSC.


From subsequent testing when I was trying to get as high a speed as I could. This is pretty fast.

The main point where I lost time was from engine flameout when I was trying to go over the mountains instead of around them. I coasted for a few minutes at 1800m/s until I got low enough to restart the engines, which probably lost me a good amount of time. Staying at low altitude and steering using body lift is probably going to be the best for this.

Edited by camacju
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14 hours ago, Pds314 said:

Someone wanna do the run in a supersonic airliner and see if (in KSP) the economics compete with those? Both in terms of fuel cost per trip and time and capital investment in the vehicles?

That's pretty close to what I did with my hypersonic jet submission. This could pretty easily be scaled up also, and the air intake and cargo bay mass amortized down. Fuel efficiency wise, the Rapier at max speed is probably going to be optimal, just because it's got a high specific impulse and a high top speed.

A few weeks ago, I was talking with Stratzenblitz on his discord server about fuel consumption like this and the conclusion was that a Rapier engine at low altitude on the edge of flame-out would be more efficient than the Goliath design he used, but would probably be harder to fly.

Edited by camacju
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I made a jet powered cruise missile that seats two. It is extremely efficient but not particularly fast. I forgot to take an engineer so I made the second landing without chutes. I did use them for the first landing so I didn't earn the Musk badge. That said, I did make it both ways and got crazy close to the Sniper award. Fuel cost/seat is 192. Launch cost/seat is 8,895.



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  • 4 weeks later...

@ralanboyle, I have two entries.  I'll describe the first entry in this post.

I didn't quite reach Mr. Musk's promise of a hundred passengers, but my ships have 32 seats.  By the way, these are 100% stock entries.

I believe this entry puts me in the running for:

  • Bargain Airline - Fuel Cost per Seat = $134.0625
  • Entrepreneur - Launch Cost per Seat = $4115.9375
  • Cattle Car - 32 Seats!!

The Ship:


I'm calling this one 'Musk 1', I'm not too original with ship names.  It's powered by 6 RAPIERs.  Here's the pertinent stats:

  • 100% Stock game, no mods whatsoever.
  • Launch Cost: $131,710
  • Seats: 32  (two 16-pax MK3 passenger cabins)
  • Fuel Cost: $4290.  (That's cost at launch, not what I used.  Honestly, I used most of it...)
  • Trip Time: 11:40.  A 12-minute trip ain't going to set any records, but still not shabby..
  • Launch cost per pax: $131,710 / 32 = 4115.9375 
  • Fuel cost per pax: $4290 / 32 = 134.0625


The Run:


I launched from the runway because I built the thing in the SPH.  But, I launched it vertically.


I hadn't really optimized my flight profile yet, but it worked.  I launch with all 6 RAPIERS in closed-cycle.  Almost immediately, I drop the nose to accelerate.  Reaching ~120m/s I switch all 6 to air breathing.  Accelerate in a shallow climb, reaching ~1520m/s before giving a little boost of rocket power.  This one has one Shock-Cone intake, and 6 radial mount intakes.  The radial mount intakes are a huge drag source.


I was aiming for the Desert Launch Pad, but missed it.  The vertical landing is aided by two parachutes on the nose.  During landing, all 6 RAPIERS are in closed-cycle mode (rocket).  I landed 295.5m from the launch pad!  I'm happy with that.  (For now...)


By the way, the distance figure to the launch pad is because I parked a rover right next to the pad.  I (normally) play 100% stock, so I don't have much for targeting aids.  By placing a rover right next to the pad, it gives me something I can target with stock KSP.   Might have been a little more accurate if I had parked the rover ON the launchpad, but then it would mess up my landing.  On this attempt, that wasn't a problem, the rover was never in any danger..


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@ralanboyle, here's my second entry.  I believe I've achieved Sniper status!

Once again, I'm playing 100% stock KSP, with a 32-passenger vessel.  And I hit the Desert Airfield Launch Pad!  On my first try!  Just kidding, it took me hours to figure out how to hit the launch pad.  Holy guacamole, that is quite difficult!

Ship Stats:

  • Launch Cost - $135,910
  • Seats - 32.  (I actually put 32 brave Kerbals on board..)
  • Fuel Cost - $4,922.  That's fuel cost at launch, but I used nearly all of it..
  • Launch Cost per Seat: $4247.1875 (my previous entry did better..)
  • Fuel Cost per Seat: $153.8125 (my previous entry did better..)
  • Time:  11:42.  Again, 12 minutes isn't a record-setter, but I'm still happy with the time.

The Ship:


I made a few changes to 'Musk 1', this one I'm calling 'Musk 2'.  Instead of a single Shock-Cone on the nose plus 6 radial intakes, I'm using 2 Shock-Cones.  Still has 6 RAPIERS.  I have Vernor RCS on the nose and tail for attitude control during landing.  Single large parachute on the nose.  It has an extra 800 units of LF, which worked well.  Launches and lands vertically.


Here's the ship ready for launch.  Again, I'm launching from the runway (vertically) because I built it in the SPH.  It's loaded with 32 Kerbals- which by the way weigh 1.44T (0.045T/Kerbal).  The weight actually doesn't affect performance much at all.  The fuel-tank windows are pinned open for a reason:  I move fuel to keep the COM (center of mass) where I need it for control.  I forgot to put solar panels on, but the Gigantic battery I used had enough for the flight..


The Run:


After countless runs, I figured out a reasonably good flight profile.  Launch vertically with all 6 RAPIERs in closed-cycle (rocket) mode.  Quickly pitch down to accelerate, reaching ~120m/s switch to air-breathing (jet) mode.  Accelerate in a very shallow climb to ~430m/s, then pitch up at about 10-15 degrees.  When the jets run out of steam at about 1500m/s and 24,000m, switch to rocket mode for a boost.  AP was about 43,000m.  That took me all the way to the Desert Airfield.


A successful landing!!  Time stamp shows 11:42.  The distance marker (16.9m) is to a rover.  I parked the rover next to the launch pad so that I would have something to target.  The targeting features of stock KSP are not great, so anything you can do to help is, uh, helpful.


Failed Attempts:


Here's my first 'landing' on the launchpad.  I was using 'Musk 1', the ship from my previous post.  Technically, I did land on the launchpad, and believe it or not- nothing blew up!  Landing on the launchpad is ridiculously difficult, especially with a tall, pointy ship like I'm using.


The next photo looks good, but it's a FAIL, because I was using Infinite Fuel Cheat to practice landings.  So this one doesn't count.  But it showed me that hitting the launchpad is possible, just need to fly better.


Rats!!!  Again, I'm so close!  But, the rocket tipped over.  Once again, at least it's on the launchpad, and nothing blew up.


Well, it's at least close to the launchpad.  And it didn't tip over.  So close!




Sigh.  Nope again.


Success!!!  Finally made it!  'Sniper' award is mine!  One more time, for the record:  Landing vertically on the Desert Launchpad is very difficult.


Couple of notes on how I flew these things:

  • Action Group to toggle RAPIER mode (Air-Breathing vs. Closed Cycle)
  • Action Group to deploy parachute and toggle flight controls
  • Active flight controls confuse the SAS when the ship is flying backwards (during landing).  So when I deploy the parachute, I also de-activate all flight control surfaces.
  • I move fuel to keep the COM where I need it.  The vessel is always on the edge of being unstable.  By moving fuel, I can increase or decrease stability.
  • Final approach to the launchpad is ideally at ~80m/s.  The slower you go, the easier it is to time when to transition to vertical.
  • Once the chute deployed, I could adjust my landing spot by about 70m, using thrust and RCS.  It's tricky to do even that.  
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7 hours ago, 18Watt said:

Active flight controls confuse the SAS when the ship is flying backwards (during landing).  So when I deploy the parachute, I also de-activate all flight control surfaces.

You can right click the control surfaces and set authority limiter to -20 degrees. This makes them work in reverse

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