Xurkitree

Engines you wish were added.

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1 minute ago, Tyko said:

Love to see "hypergolic" added as a fuel type for engines -

 

Engines could have VAC ISPs around 290-310 - better than monoprop, but not as good as LFO engines.

Engines would be lighter than LFO, but not as light as monoprop.

Fuel would be more dense than LFO so you could make small space probes with more compact tanks without relying on the cheaty Oscar-B tanks. 

How are Oscar-B’s cheating?

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Just now, Fraston said:

How are Oscar-B’s cheating?

They're too compact. They hold over 2x more fuel for their volume than other LFO tanks. 

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1 hour ago, Tyko said:

They're too compact. They hold over 2x more fuel for their volume than other LFO tanks. 

Ah... ok.

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Just now, Fraston said:
1 hour ago, Tyko said:

They're too compact. They hold over 2x more fuel for their volume than other LFO tanks. 

Ah... ok.

I mean, it's cool making tiny space probes using an Oscar engine, I just feel a little bad every time because I know it's not balanced. If they introduced a higher density fuel type for small craft I could have my cool landers guilt-free  :D    

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On 12/2/2018 at 1:01 PM, EchoLima said:

It would be nice to have a 2.5m nuclear engine, and maybe a 1.25m ion engine. 

I'd also like some new ion engines, maybe some like the AFTER in the(I think) Near Future suite.

Edited by HobbitJack
Oops, wrong name

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7 hours ago, Tyko said:

They're too compact. They hold over 2x more fuel for their volume than other LFO tanks. 

Yep, compare with the Dumpling. About the same size, but the Dumpling holds about half the fuel! The dry mass is correct, however.

5 hours ago, HobbitJack said:

I'd also like some new ion engines, maybe some like the AFTER in the(I think) Near Future suite.

I would really like a higher-thrust ion (maybe 1.25m diameter), and for the current one to be unlocked earlier.

Edited by Nebbie

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4 hours ago, Nebbie said:

I would really like a higher-thrust ion (maybe 1.25m diameter)

Nah, 3.75m ion is what we need. :D

I mean, this is KSP. Someone is eventually going to build a several hundred ton monster of a ship propelled solely by ions and make it work, if they hadn't already.

Anyway, being a bit more serious here... how about a dedicated VTOL jet engine?

  • Good static thrust.
  • Good gimbal.
  • Throttles up/down faster than other jets.
  • Gains marginal benefit from airspeed and flames out at transsonic speeds.
  • Suffers very badly from altitude, flaming out just a few kilometers above Kerbin's highest mountain.
  • Prone to overheating if fired for an extended length of time.
  • Possibly limited to radial mounting only?
  • Possibly responds to RCS controls only?

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3 hours ago, Fraktal said:

Nah, 3.75m ion is what we need. :D

I mean, this is KSP. Someone is eventually going to build a several hundred ton monster of a ship propelled solely by ions and make it work, if they hadn't already.

Anyway, being a bit more serious here... how about a dedicated VTOL jet engine?

  • Good static thrust.
  • Good gimbal.
  • Throttles up/down faster than other jets.
  • Gains marginal benefit from airspeed and flames out at transsonic speeds.
  • Suffers very badly from altitude, flaming out just a few kilometers above Kerbin's highest mountain.
  • Prone to overheating if fired for an extended length of time.
  • Possibly limited to radial mounting only?
  • Possibly responds to RCS controls only?

We already have an engine like that. It’s called the Thud.

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48 minutes ago, Fraston said:

We already have an engine like that. It’s called the Thud.

no, not really. The Thud sucks for any atmospheric use really.

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23 hours ago, MrSystems said:

I don't know if that's a great idea. The drawbacks of the current NERV are 1) there aren't enough liquid fuel-only tanks to build a decent rocket and removing the oxidizer from ordinary LFO tanks makes them mass-inefficient, and 2) nuclear thermal engines IRL run on liquid hydrogen which is not as dense as liquid fuel.

These facts tend to balance each other out, though. If you have a more voluminous container carrying a less massive substance, it makes perfect sense that the substance is less dense. And as for these facts being “drawbacks” not really, because the NERV is still one of the best engines in the game, if not the best.

23 hours ago, MrSystems said:

I don't know if that's a great idea. The drawbacks of the current NERV are 1) there aren't enough liquid fuel-only tanks to build a decent rocket and removing the oxidizer from ordinary LFO tanks makes them mass-inefficient, and 2) nuclear thermal engines IRL run on liquid hydrogen which is not as dense as liquid fuel.

These facts tend to balance each other out, though. If you have a more voluminous container carrying a less massive substance, it makes perfect sense that the substance is less dense. And as for these facts being “drawbacks” not really, because the NERV is still one of the best engines in the game, if not the best.

23 hours ago, MrSystems said:

I don't know if that's a great idea. The drawbacks of the current NERV are 1) there aren't enough liquid fuel-only tanks to build a decent rocket and removing the oxidizer from ordinary LFO tanks makes them mass-inefficient, and 2) nuclear thermal engines IRL run on liquid hydrogen which is not as dense as liquid fuel.

These facts tend to balance each other out, though. If you have a more voluminous container carrying a less massive substance, it makes perfect sense that the substance is less dense. And as for these facts being “drawbacks” not really, because the NERV is still one of the best engines in the game, if not the best.

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35 minutes ago, Ozymandias_the_Goat said:

because the NERV is still one of the best engines in the game, if not the best.

Yea, well nuke engines are pretty amazing in RL too. Kerbals don't have the political or safety concerns that limit them in real life. I kind of wish they were further up the tech tree as a balancing factor because once you unlock them there's little reason to use anything else on large spacecraft. 

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5 hours ago, Fraston said:

We already have an engine like that. It’s called the Thud.

The Thud isn't a jet engine, and is super draggy. It's terrible for use in VTOL jets.

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8 minutes ago, Nebbie said:

The Thud isn't a jet engine, and is super draggy. It's terrible for use in VTOL jets.

Its as a joke.

the thud has pretty much all of the limitations that @Fraktal listed, and almost none of the positives.

Edited by Fraston

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And I wasn't thinking of a Thud-style "hangs off the side and points downwards" radial engine. I was thinking of an Ant-style "sticks to the bottom pointing directly outward" engine.

In fact... just now I had the mental image of the VTOL engine being not a freely-attachable part, but being squeezed into a 1.25m/Mk2 fuselage, with the nozzle being on the belly in the middle rather than at the rear.

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23 hours ago, Ozymandias_the_Goat said:

These facts tend to balance each other out, though. If you have a more voluminous container carrying a less massive substance, it makes perfect sense that the substance is less dense. And as for these facts being “drawbacks” not really, because the NERV is still one of the best engines in the game, if not the best.

You misunderstand.  The stock fuel tanks hold 8 tons of LF/OX per 1 ton of fuel tank mass (easy to confirm with the Rockomax 16; the ratio holds more-or-less precisely at all tank sizes).  Using that tank and the appropriate densities (.81kg/L for RP-1, 1.1kg/L for LOX, 0.07kg/L for LH2), we find that the Rockomax 16 has a volume of 8.3m3 and thus would hold only 0.58Mg of LH2. Instead of a 4.6:1 wet mass to dry mass ratio (stock tanks emptied of OX) or a 9:1 wet mass to dry mass ratio (stock tanks modded to hold LF only) or 7.7:1 (stock tanks modded to hold LF only at the correct density for RP-1), you'd have an 8:5 wet mass to dry mass ratio . 

NASA's Space Launch System's LH2 tank has a volume of 2,033 m3 [1] and a dry mass of about 45Mg [2], which would give it a wet-to-dry mass ratio of ~ 4.2. 

Let's say you have a payload mass of 5 Mg and want 6000 dV with the Nerv (ISP 800s, mass 3.0Mg).  Using Tsiolkovsky's rocket equation, we have:
6,000 m/s = (800s × 9.80665 m/s²) ln [(3Mg + 5Mg + (wet_to_dry_ratio) × dry_tank_mass) / (3Mg + 5Mg + dry_tank_mass) ]

The Mo/Mf ratio in both cases is EXP(6000/7845) = 2.15; the necessary dry tank mass in each case is:

Pure stock: 2.15 = (8 + 4.6x)/(8 + x) || 17.19 + 2.15x = 8 + 4.6x || 9.19 = 2.45x || x = 3.75, which means a Rockomax 32 + a Rockomax 16 + a Rockomax 8 + a T400
Modded stock: 2.15 = (8 + 9x)/(8 + x)  || 17.19 + 2.15x = 8 + 9x ||  9.19 = 6.85x  || x = 1.34, which means a Rockomax 16 + a T400 + a T200.
RP-1 density: 2.15 = (8 + 7.7x)/(8 + x) || 17.19 + 2.15x = 8 + 7.7x || 9.19 = 5.58x || x = 1.64, which means a Rockomax 16 + a Rockomax 8 + a T200
LH2 in KSP stock tanks: 2.15 = (8 + 8/5 x)/(8 + x) || 17.19 + 2.15x = 8 + 1.6x || 9.19 = –0.55x || x = –16.8, which means it cannot be done at all.
NASA SLS equivalent: 2.15 = (8 + 4.2x)/(8 + x) || 17.19 + 2.15x = 8 + 4.2x || 9.19 = 2.05x || x = 4.48, which means a Rockomax 64 + a Rockomax 8

The stage masses in the respective cases would be (8 + 3.75×4.6) = 25.3 tons for pure stock, (8 + 1.34×9) = 20.1 tons for mod option 1, (8 + 1.64×7.7)=20.6 tons for mod option 2, infinity for LH2, and (8 + 4.48×4.2)=26.8 tons for the NASA-equivalent.

In other words, to use LH2 as a propellant we would need specialized fuel tanks for LH2 that have less dry mass per volume than the stock tanks, but the stock game with the oxidizer emptied out of the tanks is a close approximation to real-world LH2 storage efficiencies with respect to nuclear propulsion. 

Sources:
[1] https://www.ukimediaevents.com/publication/845181b9/28
[2] https://www.nola.com/business/2018/12/nasa-moves-huge-liquid-hydrogen-tank-from-michoud-to-huntsville-ala-for-testing.html

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Ramjets and scramjets:
The kind that are dead or lame in performance while under Mach 2 or Mach 4 and have low Isp (2000s, maybe lower) (great tradeoffs for gameplay balance) but can work at far higher speeds than any turbine jet engine. The RAPIER should not be alone as the ultimate stock jet engine for SSTO design. Ramjets and SABRE are in the same situation: experimental aircraft engines that can enable SSTOs irl.

Propfans:
Then you could clone them and change their propellants with just a little MM so they work on Eve and Duna. Mars may not have enough atmosphere for propfans to work but Duna probably does and this should be made available to exploit in KSP. While propfans may seem far from KSP's scope, they're actually very worth considering as an efficient form of propulsion for (likely small) off-world aircraft, specifically drones. A whole lot of people have been begging a long time for this one and imo this is well justified and should happen for KSP 1.7 and be the highlight thereof.

Ramrockets/air-augmented rockets:
Rocket engines with intakes in their bells (look at the Whiplash), enabling them to gain Isp with velocity and do wonders for Eve Ascent Vehicles.

Exotic chemical rockets:
At least one engine that can be very hazardous to use but is fueled by refined material from Eve's Explodium Sea or the dead kraken on whichever of Jool's moons. (Mods exist for both of these.)

 

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I would like an assortment of props, a Vasimr, linear aerospike, scaled up Rapier and nuke, a fusion drive, and an Epstein Drive type engine, but it requires a TON of science and credits to unlock and use, or can only use explodium harvested from Eve. 

Edited by EGB9000

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