Is single tank to Tylo possible?

[SomeKSPlayer]

Been able to get this thing into orbit with 7.7km/s of deltaV with a relatively high TWR for a nuclear powered craft, the TWR is >1 on Tylo when the fuel levels are below 2100.

Looking at a previous post on this topic it takes 8.1km/s of deltaV to perform this mission with pretty much no margin but I'm sure that "cheating" using the EVA pack can make this possible.

Edited April 17, 2021 by SomeKSPlayer

[camacju]

I'm guessing it's not possible with your current design. By the time you reach Tylo your fuel levels and TWR won't be at the right value.

You're basically trying to do a single stage to Tylo and back design (even though you stage the Rapiers) because of the single tank restriction. And those basically require oxidizer and ions.

In the orange efficiency challenge reboot I had a design that could go anywhere except Tylo and Eve on one orange tank, and I'm pretty sure that you can't do Tylo on one fuel tank. (Hazard-ish had to cheat to do it).  With some aerodynamic tricks you can do Eve on one tank however.

Edited April 17, 2021 by camacju

[camacju]

Update: I tried to get a tank to orbit as efficiently as I could - 10.5 km/s left. With two extra Nervs I could probably get >9.5 km/s remaining, which would add a good amount of margin to your mission. I might try that later.

Craft in VAB. 69.4 tons, with two Rapiers and two Nervs. 35 tons per Rapier is a good amount for an efficient craft that's still relatively easy to fly. I have 34.7 tons per Rapier which is close to that number.

On runway

This craft falls off the end of the runway, where I pitch up to stay level. This pitch gradually goes to zero as I gain airspeed and lift. Normally this high of a pitch causes significant drag losses but drag is lower at subsonic speeds anyway.

I stay near sea level until 600 m/s. Note that I'm pointing completely horizontal here. The wing incidence is pulling me upwards but I want to build horizontal velocity.

Passing 1 km/s, pitched up 10 degrees. I'll level off at about 21 km until the Rapiers' effective Isp drops to 800. In order to do this I compare vacuum delta-v to surface speed since KSP doesn't give effective Isp values. Another way to do this is to look at the thrust/drag ratio.

This is a heavier craft than I'm used to so I have to be pitched up to maintain altitude. This increases drag so I have to turn on the nuclear engines at 1630 m/s instead of waiting another 30 m/s.

Passing 2 km/s

In orbit - 10.5 km/s left

[SomeKSPlayer]

2 hours ago, camacju said:

Update: I tried to get a tank to orbit as efficiently as I could - 10.5 km/s left. With two extra Nervs I could probably get >9.5 km/s remaining, which would add a good amount of margin to your mission. I might try that later.

Craft in VAB. 69.4 tons, with two Rapiers and two Nervs. 35 tons per Rapier is a good amount for an efficient craft that's still relatively easy to fly. I have 34.7 tons per Rapier which is close to that number.

On runway

This craft falls off the end of the runway, where I pitch up to stay level. This pitch gradually goes to zero as I gain airspeed and lift. Normally this high of a pitch causes significant drag losses but drag is lower at subsonic speeds anyway.

I stay near sea level until 600 m/s. Note that I'm pointing completely horizontal here. The wing incidence is pulling me upwards but I want to build horizontal velocity.

Passing 1 km/s, pitched up 10 degrees. I'll level off at about 21 km until the Rapiers' effective Isp drops to 800. In order to do this I compare vacuum delta-v to surface speed since KSP doesn't give effective Isp values. Another way to do this is to look at the thrust/drag ratio.

This is a heavier craft than I'm used to so I have to be pitched up to maintain altitude. This increases drag so I have to turn on the nuclear engines at 1630 m/s instead of waiting another 30 m/s.

Passing 2 km/s

In orbit - 10.5 km/s left

Hmm I went for the brute force jet VTOL approach to get this thing into suborbital trajectory above the atmosphere before circularising using the nukes, would your approach of an SSTO flight style be more efficient? Also when using only 2 nukes the TWR is far too low to do anything with Tylo which is why I opted for 4 with 3 being detachable.