Open Ion engines to orbit?

[4KidsOneCamera]

This probably sounds dumb, and I think it's impossible, but could you reach orbit using only ion engines?

 

[Kirk_TGM]

With cheat, yes
With no cheat?





idk

 

[4KidsOneCamera]

With cheat, yes
With no cheat?





idk

Cool. I know you can do it with cheats as that is self explanatory. I have tried without cheats and am not sure it is possible.

 

[Horus Lupercal]

Yeah, it's not. A functioning Ion engine (as in with a sufficent amount of power storage/generation to burn long enough to hit LEO) is too heavy to lift itself off the Earth surface

 

[Gurren Lagann]

Yeah, it's not. A functioning Ion engine (as in with a sufficent amount of power storage/generation to burn long enough to hit LEO) is too heavy to lift itself off the Earth surface

Are you sure? I had once built a near-LEO ion rocket on 1:10 scale without cheats! I will show it later, as my phone is currently charging already.

 

[4KidsOneCamera]

Yeah, it's not. A functioning Ion engine (as in with a sufficent amount of power storage/generation to burn long enough to hit LEO) is too heavy to lift itself off the Earth surface

Thanks. This is what I thought, but wanted to be sure!

 

[Horus Lupercal]

Are you sure? I had once built a near-LEO ion rocket on 1:10 scale without cheats! I will show it later, as my phone is currently charging already.

Ya. The challenge has hit here a few times already. No one has managed it in SFS 1:20 scale.

A naked Ion engine only has a TWR of 4.08. Add the 4tons of RTGs you need per engine, or the 2 tons of solar cells and that doesn't give you much spare thrust to add for (admittedly small) fuel requirements and the probe needed to control it. You could bring the weight down slightly by calculation how long you'd need the ions to burn for, how much power that will take and only adding that amount of batteries/fuel as it works out slightly lighter. And the more engines you add to spread the weight of the probe 'payload' between, the more power and fuel and it never stops.

 

[Lt. Snakestrike]

Ya. The challenge has hit here a few times already. No one has managed it in SFS 1:20 scale.

A naked Ion engine only has a TWR of 4.08. Add the 4tons of RTGs you need per engine, or the 2 tons of solar cells and that doesn't give you much spare thrust to add for (admittedly small) fuel requirements and the probe needed to control it. You could bring the weight down slightly by calculation how long you'd need the ions to burn for, how much power that will take and only adding that amount of batteries/fuel as it works out slightly lighter. And the more engines you add to spread the weight of the probe 'payload' between, the more power and fuel and it never stops.

Basically, you can go straight ions, but it isn't useful for a payload.

 

[Gurren Lagann]

I just remenbered that i messed up the scale i mentioned - sorry to dissapoint you guys, but that was done on a 1:100 solar system, and since my memory sometimes corrupts itself, i missed a zero when saying the scale...

 

[Horus Lupercal]

Basically, you can go straight ions, but it isn't useful for a payload.

Not even. In theory, a 2 stage, 3 ion/5 ion rocket with a probe and the small battery 0.5t on top has a decent enough TWR and could reach LEO with 2.05t of fuel. Except that battery contains about 20seconds of power...

 

[Lt. Snakestrike]

Not even. In theory, a 2 stage, 3 ion/5 ion rocket with a probe and the small battery 0.5t on top has a decent enough TWR and could reach LEO with 2.05t of fuel. Except that battery contains about 20seconds of power...

Which is why you start to add more batteries, then more ions and fuel, just fighting with the tsiolevsky equation...

 

[Horus Lupercal]

Aye. With a TWR of 1.3 ish, you'll need about 150 seconds of burn time to get LEO cracked. Which is 300 units per engine at 1.5t.

Infact, give me an hour, i may have got something...

 

[4KidsOneCamera]

Aye. With a TWR of 1.3 ish, you'll need about 150 seconds of burn time to get LEO cracked. Which is 300 units per engine at 1.5t.

Infact, give me an hour, i may have got something...

I am excited to see it!

 

[4KidsOneCamera]

The highest I have been able to get is 7000m up

 

[Horus Lupercal]

Which is why you start to add more batteries, then more ions and fuel, just fighting with the tsiolevsky equation...

Aye. With a TWR of 1.3 ish, you'll need about 150 seconds of burn time to get LEO cracked. Which is 300 units per engine at 1.5t.

Infact, give me an hour, i may have got something...

I am excited to see it!

Cancel my last.

This is pretty much as close as I got...

And thats achieved using every dirty trick in the book, i.e., komodo staging, sharing batteries, partial fuel tanks.

You can either have the right TWR or the right Dv or the right battery power. But not all. And it's sooooo close that it cannot be accidental either, it has to be designed that way.

I could probably break the karman line. But that's about it.

 

[4KidsOneCamera]

Cancel my last.

This is pretty much as close as I got...

View attachment 25119

And thats achieved using every dirty trick in the book, i.e., komodo staging, sharing batteries, partial fuel tanks.

You can either have the right TWR or the right Dv or the right battery power. But not all. And it's sooooo close that it cannot be accidental either, it has to be designed that way.

I could probably break the karman line. But that's about it.

Yeah. I kept running out of power on accent.

 

[4KidsOneCamera]

In the case of it being impossible I find it funny that the subreddit has a challenge for it stating that "the math proves it's possible".

If only they knew the forum.

 

[diakonos]

komodo staging

Now that's one I hadn't heard before, so I searched the forums. I found something about your KDS, but I'm not quite sure how komodo staging works. Can you explain please?

 

[RandomRocket]

I could probably break the karman line. But that's about it.

I've made it to 33 km and 300 m/s of horizontal Velocity before running out of Fuel
Im currently working on 600 m/s of horizontal Velocity

 

[RandomRocket]

The Ionic curse

38.4 km with 429 m/s horizontal top Speed

 

[Lt. Snakestrike]

Cancel my last.

This is pretty much as close as I got...

View attachment 25119

And thats achieved using every dirty trick in the book, i.e., komodo staging, sharing batteries, partial fuel tanks.

You can either have the right TWR or the right Dv or the right battery power. But not all. And it's sooooo close that it cannot be accidental either, it has to be designed that way.

I could probably break the karman line. But that's about it.

Yeah, I might've been thinking of a challenge from 1.35 then. It was possible back then I think.

 

[Horus Lupercal]

**Long Post**​

should change my name to 'Wafflemaster'

I find it funny that the subreddit has a challenge for it stating that "the math proves it's possible"

That's cos other media outlets are full of nuggets wanting .bps and claiming world records, but still haven't managed to figure out how this delta velocity thing works

Now that's one I hadn't heard before, so I searched the forums. I found something about your KDS, but I'm not quite sure how komodo staging works. Can you explain please?

It comes from the name of the rocket I first seen using it. I use it to solve 2 problems, firstly the issue with SFS staging on ridiculously sized multi staged rockets, second to reduce weight spent on engines overall in a build.

The idea is the entire rocket, every engine on board, fires throughout launch. This gives you the TWR you need to get off the ground with the minimum number of total engines on board, lessening your overall dry weight. Each 'stage' then has carefully timed cut outs as the weight drops and required thrust lessens and is dropped away, getting rid of empty fuel tanks and unneeded engines as required, reducing all up mass and dry weight further in flight.

A simple example would be a 2 stage rocket that needs 10 engines to get a TWR of 1.3 first stage, and 4 in the second stage, so you need 14 engines total. Now your options are to spread the 10 launch engines across the first stage and likely a booster pair (6 in the core, 2 on each booster).
How my lizard launch vehicles (Komodo and Salamander) would do it is they'd have 6 in the first stage and 4 in the second, with more fuel. At launch, all 10 engines would fire, generating your required TWR of 1.3 until the main stage runs out of fuel. It's then dropped, getting rid of the 6 unneeded engines as well, but with the 4 in stage 2 still burning.
Even if you offset the weight of the engines you haven't put on with fuel, your dry mass is much, much less because an engine is all dead weight and a fuel tank is only 1/10th dead weight. Your rocket may end up heavier at launch, but more of that will be fuel and because delta velocity only cares about the difference between maximum (which you have more of) and minimum weight (which is now lower), you get more of it from the start.

The down side is they're a bawlbag to design, especially if they have more than 2 layers. Mine have 4, sometimes 5 layers with 4-16 build screens in each layer and getting the burn times to run out in sequence from bottom to top requires some crackerjack maths.

The other plus for me is its modular. I've only used it for ridiculous payloads and I used a version on the smallest to jupiter as well, which actually worked out lighter than the one posted because of the stage attachment, but not the engine numbers.

How that helped in the ion case, was that design wanted z t of fuel, x ions in the first stage and y in the second. My idea was a stage one of x-y ions and sufficient battery power to run just them for the burn time of that stage, but no fuel. Stage 2 would have y ions, sufficient battery power to run them throughout flight and a 5t fuel tank, partial filled to z amount.

The pros were less engines, so less weight, less fuel, less batteries at launch. And, I get rid of the dead batteries as well at staging. I only went for one tank rather than 2 through 2 stages because ions let you do that, and it's less dry weight (.5t rather than 1t).

Cons, power also drains evenly like fuel using ions and unlike fuel you can't do power transfer, so I couldn't drain just the first stage batteries and leave fresh ones on top. Also, even with all this tom-fuckery going on, I still couldn't get the holy trinity to work sufficiently through to LEO.

 

[diakonos]

**Long Post**​

Ah, that makes sense. So every stage functions in principle like a booster, firing from the start until dropped, rather than upper stage engines buried and useless at liftoff until they're activated by staging. I might have to toy with this idea a bit!

 

[Horus Lupercal]

Ah, that makes sense. So every stage functions in principle like a booster, firing from the start until dropped, rather than upper stage engines buried and useless at liftoff until they're activated by staging. I might have to toy with this idea a bit!

Aye, exactly that. And until staging is implimented it is the only way to run enormous upper stages as it takes over a minute to turn the upper half of even the smaller Salamander vehicle

 

[diakonos]

Aye, exactly that. And until staging is implimented it is the only way to run enormous upper stages as it takes over a minute to turn the upper half of even the smaller Salamander vehicle

I realise that I've partially done this already. I always stick to a single build screen per launch, and my heaviest lifter (with DLC) puts about 500t in LEO. (I don't know if that's good or not, but that's not the point!) Anyway, I light a few of the second stage engines along with the first stage.

That gives me better liftoff TWR, but it also makes staging easier. I think it's six Frontiers running from the second stage at liftoff, which means that separating the first stage and lighting up the remaining second stage engines can be done without sending the rocket spinning.

Because it's a simple design and only has two stages, I can also use fuel transfer to advantage by pumping first stage fuel into the second stage from the start. I'm sure that would be unworkable for some of these more complicated staging set ups.