ION Planet Hopper [KSP 1.2]

[9t3ndo]

Built a small [KSP 1.2] ION Craft for travel between my spacestations and land save on planets with an atmosphere.

The craft has 4 ION-Engines and 2 small Jets. Electric charge comes from 2 fuel cell arrays.

 

Download v1.1

 

Action Groups:

1 - atmospheric mode (stop Fuel Cells)

2 - ION mode (start Fuel Cells)

3 - Cockpit

Abort - toggle the Fuel Cell Arrays

Spoiler

 

 

Edited September 19, 2016 by 9t3ndo

[Majorjim!]

it looks awesome! How much dv does it have?

[9t3ndo]

Is allrdy a mod released for 1.2 that show me the delta v? EE Redux didnt work for me...

[panzer1b]

This thing looks really cool (alot better then the slew of "real life" replicas everyone seems to be into these days), sadly i cant figure out how to get it to orbit.  Al ascent profiles ive tried result in running out of fuel well before i get anywhere near orbital speeds...

[Qwarkk]

I love the design at the back - the ion engine plume makes it look epic!

[Streetwind]

On 17.9.2016 at 10:20 PM, 9t3ndo said:

Is allrdy a mod released for 1.2 that show me the delta v? EE Redux didnt work for me...

It's a single stage, right? You can easily do the math yourself, then.

I went and downloaded it, loaded it up in the SPH, and removed the capsule support structure. Left me with a mass of 8,744 kg. However, since an external command seat is used, the Kerbal in it has a mass of 93.75 kg, which I'll round to 94 for simplicity. So the final takeoff weight of this craft is 8,838 kg.

There are six 0.625m xenon tanks on the craft, which is 6x 70 kg.

The rocket equation is thus: 4200 * 9.80665 * ln(8838/8418) = ~870.9 m/s of dV.

That is fully loaded, of course. There is 500 kg worth of dedicated LF for the jets onboard. As far as I understand the design, that fuel is for atmospheric flight, from which it cannot return to orbit, so it would always be present for the purposes of adding mass during orbital flight. Unless you specifically removed it, because you knew you wouldn't be going down to a planet. In that case, without the LF present, dV improves to ~924.5 m/s.

Also, the craft consumes up to 1,200 kg of LFO for the fuel cells while running the ions, so it will have a higher dV than it looks at first glance. I don't know off the top of my head how the runtime of four Dawns on six small tanks compares to the runtime of two fuel cell arrays on six Oscar-B tanks. Until I figure that out, I'll guesstimate and say that after all is said and done, you may get around 1,000 m/s of vacuum dV out of this craft.

With that kind of propulsion, it could start in low Mun or Minmus orbit, and safely return to Kerbin. First using the ions to propulsively brake over multiple periapsis passes, then aerobraking the remaining ~200 m/s excess velocity once xenon is depleted. Heck, you may be able to reenter directly at that point. It could also go from Mun to Minmus, or from Minmus to Mun. It's probably just a little short of being able to go from Kerbin to Minmus or Mun and intercepting an orbiting station there, unless your starting Kerbin orbit is already fairly high.

Finally, I agree with the others - it looks pretty darn cool

 

BONUS EDIT: runtime analysis (yes, I was actually that bored )

Ion engine runtime, via definition of Isp: "runs this many seconds at 1 kN thrust with 1 ton of fuel"
- One ion at 4200s, 2kN: 2100s on 1 ton xenon
- Four ions: 525s on 1 ton xenon
- 0.42 tons available: 0.42 x 525s = 220,5s

Fuel cell runtime, via the wiki: 0.02025 volume units of LF per second, oxidizer ratio matches tanks
- Two fuel cells: 0.0405/s
- Six Oscar-B: 6x 18 volume units of LF
- (6 x 18) / 0.0405 = 2,666.66667... seconds

Result: this craft is vastly overstocked with LFO and will barely gain any dV due to consuming LFO during the ion burn time. The fuel cells could keep the ions going for more than twelve times as long as they have fuel available.

Recommendation: replacing four of the six Oscar-B with xenon tanks will improve the orbital dV greatly (>1,600 m/s) while still leaving more than enough LFO to provide power.

Edited September 18, 2016 by Streetwind
Typos, typos everywhere!

[9t3ndo]

6 hours ago, panzer1b said:

This thing looks really cool (alot better then the slew of "real life" replicas everyone seems to be into these days), sadly i cant figure out how to get it to orbit.  Al ascent profiles ive tried result in running out of fuel well before i get anywhere near orbital speeds...

Its no SSTO. More a return Vehicle from a Station in Mun, Minmus and Kerbin orbit. I was a bit bored of the Dream Chaser design and want something with IONs  

 

@Streetwind

thx for the maths, i will change soon as possible the tanks with xenon :-)

[Streetwind]

While you're at it: there's 100 unused units of monopropellant you can remove to save mass... unless you need it for weight distribution. Or maybe you could add a pair of linear RCS ports somewhere for emergency maneuvering Though personally I think every kg saved really benefits this craft, all the clipping makes it quite heavy for its size.

Edited September 18, 2016 by Streetwind

[9t3ndo]

Rework done. Switch 4 Oscar B for Xenons and add 4 Linear RCS Ports backsite. Action Group 1 and 2 start and stop now also the Fuel Cells - Abort still works for manuell toggle.

Download v1.1

Edited September 19, 2016 by 9t3ndo