Jump to content

lowest TWR to orbit


Recommended Posts

The rules are simple: whoever gets to orbit with the lowest TWR on all stages combined wins

Leaderboard:

@AeroGav TWR: 0.20

P.S. this is my first challenge, don't judge

P.S. 2: there isn't a badge because I'm terrible at photoshopping/creating images 

 

Edited by darthvader15001
Link to comment
Share on other sites

1 hour ago, darthvader15001 said:

thread will close on 7/27/22

Why so short?

Also, you do know that TWR changes as fuel is burned off.  So how and when should TWR be calculated?

It’s easy to build a rocket with an initial TWR of less than 1, which can stroll get to orbit on a single stage.

another thing, are you allowing mods?

Edited by linuxgurugamer
Link to comment
Share on other sites

1 hour ago, linuxgurugamer said:

Why so short?

This challenge will just be a short experiment with challenge-making as it’s my first challenge.

1 hour ago, linuxgurugamer said:

Also, you do know that TWR changes as fuel is burned off.  So how and when should TWR be calculated?

Right click on all the stages and one of the readouts should be twr also ker or mj might have stuff to calculate twr. If using that staging bar thingy, just combine the twrs.

and yes mods are allowed, but no cheats like hyperedit or alt f12

Sorry for being unclear in the op

Link to comment
Share on other sites

I feel obliged to point out that jet engines exist and are a common way to get to orbit with an initial TWR well below 1. There are also motors and propellers which technically have no TWR at all since the game can’t calculate them, which could be used to artificially reduce the average TWR for a spaceplane.

I’m sure I’ve heard of someone using only propellers and ion thrusters to fly an SSTO to Kerbin orbit using some serious physics exploits.

Edited by jimmymcgoochie
Link to comment
Share on other sites

ok then, jet engines and anything in the robotics section are banned.

and sorry  that no one likes this challenge, I'm new to the forums and this is my first challenge:/

again, sorry for the unclear rules :(

Link to comment
Share on other sites

13 hours ago, jimmymcgoochie said:

I’m sure I’ve heard of someone using only propellers and ion thrusters to fly an SSTO to Kerbin orbit using some serious physics exploits.

OndrikB and moar ssto produced a very nice video showcasing a craft like this.

 

Link to comment
Share on other sites

6 hours ago, camacju said:

OndrikB and moar ssto produced a very nice video showcasing a craft like this.

 

Like, I think I am pretty decent at the game, and then I see stuff like this and think to myself "What am I even doing?" :lol: This is mindbreaking

Link to comment
Share on other sites

  • 5 weeks later...

I don't play KSP that often anymore and only saw the thread yesterday.        So here is a belated entry.

Ladies and Gentlemen,  I present the Sloth Ray.

https://www.dropbox.com/s/brtkt4ejf8t10ft/Sloth Ray.craft?dl=0

It has 9 Seats and weighs just under 60 Tons.

It has three Nervs,  One Rapier (only operates in airbreathing mode), and a Panther.

Action Group 1 deploys some elevons that push the nose down a few degrees to stop it climbing above altitudes where the jet engines can work, before we're good and ready.

Action Group 3 retracts said same flaps.

Action group 5 toggles the nukes.  It needs those to get though mach 1.

Action group  9 toggles the afterburner on the Panther.

The TWR that appears on the stock game staging indicators show  the following :

Airbreathing Stage TWR 0.20

At 20km altitude, the NERV stage reports a TWR of 0.24,  getting into the dangerously sporty territory.

 

Of course with the jet engines,  the static thrust rating here is highly misleading.   Their output falls with altitude,  increases with velocity (up to a point) then fall off again as you get faster still.

 

This is what Kerbal wind tunnel says about the air breathing stage.

https://imgur.com/ttXElmK

https://imgur.com/IaM1wcQ

https://imgur.com/pLj7nqo

Flight details hidden in spoiler ..

Spoiler


So in practice,  we get up to about 10km and our TWR is down to 0.15.      We continue to accelerate slowly but more than 70% of our thrust is being swallowed by drag .    So I activate the NERVs and let it climb to about 13km, then nose over to a shallow dive.   This gets us through the sound barrier.    In the next screenshot we're just about going fast enough that the aircraft can gain energy without the help of the NERVs..

https://imgur.com/q0qq4Ws

by mach 2, the Panthers are coming on strong and our thrust to drag ratio remains decent

https://imgur.com/MXJCxza

This happy state of affairs lasts to around 1000 m/s,  the Rapier coming on song at about the same rate the Panther, past its peak, fades.

https://imgur.com/hdeZpez

At this point, although technically still accelerating our fuel gauge is moving faster than the speedo.  So I activate nukes.  I keep the nose down trim in until our total thrust falls below 250kN,  at which point I figure the drag penalty from flying this low outweighs what we're getting out of the airbreathing rapier.    So i hit action group 3 to retract the nose down elevons and we bob up into the upper atmosphere like a champagne cork.       Our lift to drag ratio improves to 3.2 to 1 which is decent for hypersonic flight.  Our TWR is 0.35 to 1 instead of the 0.24 to 1 predicted in SPH hanger, because of the fuel already used getting up to mach 4.

https://imgur.com/X7cSa5x

In another 2 and a half to three minutes , we're in orbit.

Incidentally,  I found out this thing can land on Duna. 

https://imgur.com/h6PLj2E

https://www.dropbox.com/s/7n9fibg2a9cb1ep/FINAL.sfs?dl=0

Here's a save file if you want to land it yourself.   Remember to put RCS on.  "K" key fires the ventral thrusters which help us touch down slower.   Space bar opens the drag chutes which can help it stay straight on the rollout.   The biggest danger is getting sideways and flipping over.

https://imgur.com/5YuZTmc

 

Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
 Share

×
×
  • Create New...