ION + RAM the 4k ISP challenge!

[EduardoS]

May reaching space be cheap by only using the most efficient engines?

I would like to rank the best ideas based on mission cost for this task, rules are:

1. IX-6315 "Dawn" Electric Propulsion System and J-X4 "Whiplash" Turbo Ramjet Engine only, RCS may be used if your idea requires rendezvous
2. Fully reusable, the entire ship must land on Kerbin, may only consume fuel, decouplers and fairings, do not need to be SSTO but all parts must be recovered
3. Must reach LKO with a Kerbal onboard and 30km/s delta-v left

[ralanboyle]

1 hour ago, EduardoS said:

30km/s delta-v left

...?...

[jimmymcgoochie]

30km/s of delta-v? I’m not sure that’s possible with the stock ion thruster even without lugging the additional weight of an air-breathing jet engine around, let alone trying to get it into orbit. Ion thrusters have a terrible TWR in space and appalling efficiency in atmosphere, making them a bad choice for getting to orbit, and xenon tanks have a really poor fuel fraction which severely limits the total delta-V you can get out of them.

[OutInSpace]

3 hours ago, jimmymcgoochie said:

30km/s of delta-v? I’m not sure that’s possible with the stock ion thruster even without lugging the additional weight of an air-breathing jet engine around, let alone trying to get it into orbit. Ion thrusters have a terrible TWR in space and appalling efficiency in atmosphere, making them a bad choice for getting to orbit, and xenon tanks have a really poor fuel fraction which severely limits the total delta-V you can get out of them.

30kms is within the capabilities of the Dawn and stock Xenon tanks without any drop tanks. However, getting an ion ship with that much vee into orbit using a jet and a Dawn? Probably impossible.

[Pds314]

On 11/4/2020 at 1:37 PM, EduardoS said:

May reaching space be cheap by only using the most efficient engines?

I would like to rank the best ideas based on mission cost for this task, rules are:

1. IX-6315 "Dawn" Electric Propulsion System and J-X4 "Whiplash" Turbo Ramjet Engine only, RCS may be used if your idea requires rendezvous
2. Fully reusable, the entire ship must land on Kerbin, may only consume fuel, decouplers and fairings, do not need to be SSTO but all parts must be recovered
3. Must reach LKO with a Kerbal onboard and 30km/s delta-v left

30... km/s????? I mean, I guess it's doable with enough launches.

Edited November 6, 2020 by Pds314

[EduardoS]

Let me try to explain the purpose of that requirement.

 

The 30km/s can be achieved by putting together two PB-X750 tanks with a Dawn, a (light) solar panel and a command chair, that's supposed to be a minimum payload to orbit, the reason I put it in terms of km/s instead of specifying a payload was to let some flexibility for those who wanted to try it, but I see I just created confusion, the intention is: a payload for deep space exploration which is also recoverable.