Squadcast confirms SABRES for 0.23!

[RocketPilot573]

As long as Squad hasn't released any SABRE engine, no one can answer that. In reality the SABRE is an insanely powerful jet engine, especially in big heights. Or at least would be, up to now it was never tested on a real plane.

But that is not the reason why it is so efficient. Because it can basically fuel up in the atmosphere, it's almost like you would launch your rocket with full tanks from the outer rim of the atmosphere. Considering how much effort you need to leave the atmosphere behind, this is just amazing.

I disagree. I think, smaller SSTOs profit much more from SABRE than bigger ones. With a really big plane you can afford to mount multiple engine types without risking your balance or payload efficiency. But for a small ship a single engine that works as well in space as within the atmosphere sounds quite perfect.

Wait, so would the SABRE actually refuel Ingame? (I assume your not talking about intakeair) Also, it has been said that it will have around 350-360 Isp, while the Atomic Engine has 800... So I still doubt that reducing the weight by 1 ton but also hacking the efficiency to pieces will increase the range of small SSTOs.

[GusTurbo]

As long as Squad hasn't released any SABRE engine, no one can answer that. In reality the SABRE is an insanely powerful jet engine, especially in big heights. Or at least would be, up to now it was never tested on a real plane.

But that is not the reason why it is so efficient. Because it can basically fuel up in the atmosphere, it's almost like you would launch your rocket with full tanks from the outer rim of the atmosphere. Considering how much effort you need to leave the atmosphere behind, this is just amazing.

I disagree. I think, smaller SSTOs profit much more from SABRE than bigger ones. With a really big plane you can afford to mount multiple engine types without risking your balance or payload efficiency. But for a small ship a single engine that works as well in space as within the atmosphere sounds quite perfect.

The SABRE doesn't really "refuel" -- it still uses liquid hydrogen and oxygen as propellant. In the atmosphere, it uses atmospheric oxygen like a jet engine. Then at high altitude it switches over to on-board liquid oxygen.

[Monger]

Wait, so would the SABRE actually refuel Ingame? (I assume your not talking about intakeair)

Well, my comment about refuelling is indeed wrong. But still: no idea how Squad has actually implemented this engine.

Also, it has been said that it will have around 350-360 Isp, while the Atomic Engine has 800... So I still doubt that reducing the weight by 1 ton but also hacking the efficiency to pieces will increase the range of small SSTOs.

When you use the nuclear engine you still need an air breather. The SABRE replaces both engines.

Although air breathing engines have quite low Isps, they are still way more efficient than any space engine. I don't remember the right fuel mix, but at least 80% of the fuel mix is air - so, more or less, you only carry 20% of the fuel you are actually using. As long as you are in the atmosphere (which SSTOs are most of the burn time), air breathing engines are far more efficient than anything else, including atomic engines.

Btw. , the corresponding Wikipedia page is really worth reading.

The designed thrust/weight ratio of SABRE is up to 14 compared to about 5 for conventional jet engines, and 2 for scramjets

...

Fuel efficiency peaks at about 3500 seconds within the atmosphere.[4] Typical all-rocket systems peak around 450 and even "typical" nuclear thermal rockets at about 900 seconds.

[DisarmingBaton5]

The designed thrust/weight ratio of SABRE is up to 14 compared to about 5 for conventional jet engines, and 2 for scramjets

...

Fuel efficiency peaks at about 3500 seconds within the atmosphere.[4] Typical all-rocket systems peak around 450 and even "typical" nuclear thermal rockets at about 900 seconds.

While this may be true, from a gameplay perspective that's a bit OP. Remember that this is just a game, not a hardcore simulator.

EDIT: Just skimmed that page, it says the Isp in vacuum is 460s, which is not that high. Not so OP after all?

Edited December 15, 2013 by DisarmingBaton5

[Wahgineer]

Woah woah woah, A4 Pacific http://upload.wikimedia.org/wikipedia/commons/5/5a/Number_4468_Mallard_in_York.jpg and full wiki page http://en.wikipedia.org/wiki/LNER_Class_A4 I strongly disagree with any statement that American steam locomotives are any percentage better than those of Britain.

Last time I remember, the U.S. is large enough to fit EUROPE with in its borders. So it isn't that U.S. engines might have been better than English locomotives, they had to be. They had to make 6-day runs across mountains, plains and deserts with stopping points few and far between. They had to cross shoddily laid tracks without derailing (in fact, this is why Americans built their own locos from the start: the British ones where too heavy.). They had to go up steep grades while pulling massive amounts of freight. The largest U.S. steam locomotive, the U.P. Big Boy, is over a 100 feet long. I have never heard of any British locomotive that comes even close. U.S. Locos had to be easily and quickly repaired, hence their lack of complex livery. One standard gauge was adopted universally very early on to increase compatibility. U.S. Locos were almost never built for show, they were designed from the ground up to be powerful, efficient, and practical workhorses, dwarfing their British counterparts both in size, speed, power, endurance, and function.

[KasperVld]

I'm not sure how the discussion went from SABRE/RAPIER engines to steam locomotives, but I suggest we get back to the original topic (and definitely make a steam locomotive topic in the Space Lounge)

[pyrosheep]

Last time I remember, the U.S. is large enough to fit EUROPE with in its borders. So it isn't that U.S. engines might have been better than English locomotives, they had to be. They had to make 6-day runs across mountains, plains and deserts with stopping points few and far between. They had to cross shoddily laid tracks without derailing (in fact, this is why Americans built their own locos from the start: the British ones where too heavy.). They had to go up steep grades while pulling massive amounts of freight. The largest U.S. steam locomotive, the U.P. Big Boy, is over a 100 feet long. I have never heard of any British locomotive that comes even close. U.S. Locos had to be easily and quickly repaired, hence their lack of complex livery. One standard gauge was adopted universally very early on to increase compatibility. U.S. Locos were almost never built for show, they were designed from the ground up to be powerful, efficient, and practical workhorses, dwarfing their British counterparts both in size, speed, power, endurance, and function.

meh.

still 20 times the passenger miles per person in the UK

[Wahgineer]

Sorry kaspervlad, I agree. Sorry about derailing the thread. Any who, back to the RAPIER engine!

[Eric S]

I'm looking forward to seeing it, but unless the Rockomax 48-7S gets nerfed, I suspect that the RAPIER will still be more mass than a turbojet plus a few of those, though it will certainly be more convenient. Those little buggers are just plain OP. I've heard a lot of talk about the RAPIER being overpowered, though at least some of that is probably due to changes that are going to benefit the regular jet and turbojet engine as well.

meh.

still 20 times the passenger miles per person in the UK

Not at all surprising, passenger rail transit just isn't as popular here, the country is too spread out for people to take their time travelling by train. I don't mean just the size of the country, I'm talking the distance between population centers. Get out of New England/the midwest/California, and you start seeing warning signs along the lines of "Next gas, X miles." I used to regularly drive past one that was "Next Gas, 106 miles" when traveling between my parent's home and the college I was attending.

As for commuting within a city, there were some rather active lobbyists a long time ago that convinced most major american cities to rip out their light rail commuter systems and replace them with busses, and that trend has only started reversing in the last decade or two.

[Rainbowtrout]

With my recent plan of SSTOs, or DSTOs (Double Stage to Orbit), these will help loads!

[SlyReaper]

Now that we have the engines, may I be the first to say these bad boys make SSTOs almost trivially easy. I've never managed to do an SSTO before now. With this new engine, I did it on the first try. It's fantastic. I need to fly one of these things to Laythe and back.

[Wheffle]

I'm at work and haven't been able to try out the RAPIERs, but I watched some videos. It seems as though (from the videos) that the RAPIERs don't have the same non-instant thrust build-up issues that the jet engines have. Is this true? This would make my air-breathing VTOL hovercraft a LOT easier to control...

[Whackjob]

I run out of fuel before managing an SSTO. Every single time. I just don't know how to SSTO.

[Hodo]

So the new RAPIER engines... hmmm I cant say I like them yet.

They are small which is good, but they are way overpowered.

175kn in jet mode and 190kn in rocket. They only weigh 1.75 tons. I managed to push a 7 ton test craft with one 1.25m liquid+ox tank to 100km x 100km and still had 220 out of 320 liquid fuel on board. I only used 2 intakes and got to 21km before it HAD to switch over. And the power doesn't die off till around mach 7 in jet mode.

I think I will stick to the heavier B9 SABRE engines for now... but I may find a use for the RAPIER later.

[Van Disaster]

What do you mean never a real world thing?

http://en.wikipedia.org/wiki/NERVA

Yes, that real world thing that's never been plugged into a spaceplane and I'd think is pretty highly unlikely ever to be. KSP has no environmental worries.

[Eric S]

They are small which is good, but they are way overpowered.

They're not way overpowered compared to 0.23 turbojets, just the 0.22 ones you're used to. Compared to the last spaceplane I was experimenting with in 0.22, the RAPIER version took more fuel to get to orbit. The thing is, there have been changes to turbojets and resources (the way IntakeAir gets handled) that have seriously changed the performance of any spaceplane in 0.23, and that's a lot of what people are seeing when they're thinking the RAPIER is OP. Having the dual mode engine is nice, but it's mostly a conveniece, it really isn't going to do that much that a conventional spaceplane can't pull off.

[jshier]

Anyone else see that the Rapier doesn't produce electricity, even in rocket mode? Makes it a bit annoying.

[I_Killed_Jeb]

Anyone else see that the Rapier doesn't produce electricity, even in rocket mode? Makes it a bit annoying.

yep, i think i'm gonna go back to turbojets and rockets for most my planes

[Rainbowtrout]

I have tried it, and it is odd. I rebuilt the Aeris 4A with RAPIERs, and it um... Broke.

[Spatzimaus]

Anyone else see that the Rapier doesn't produce electricity, even in rocket mode? Makes it a bit annoying.

On the other hand, they have much better thrust vectoring than a turbojet. To me, that's a fair tradeoff for the loss of electricity generation in rocket mode. (Besides, what do you really need electricity for on a spaceplane? If you're only worried about the tiny amount used by SAS and such, just stick an RTG on it.)

I said it in another thread: RAPIERs are fantastic for larger spaceplanes (those with 3+ jet engines), where you can replace some but not all of your turbojets with them. My 34-ton plane uses one RAPIER and two turbojets, and it's just a fantastic mix.

[Murph]

I have tried it, and it is odd. I rebuilt the Aeris 4A with RAPIERs, and it um... Broke.

The RAPIER is significantly inferior to the turbojet for the air-breathing part of the ascent. Overall, the Aeris 4A with twin RAPIERs is significantly less capable than with twin turbojets and an aerospike.

Having played around with them extensively, my own conclusion is that the RAPIERs are pretty close to useless in their current form. There might be a niche for them for micro spaceplanes, with just a single RAPIER, but they are just no good for delivering usable payload to orbit optimally. The weight saving over a turbojet+aerospike combination (or turbojet with just about any other small rocket) just doesn't compensate for their poor performance and efficiency in the first half of the ascent. Convenience does nothing to redeem them, as it's easy to swap from turbojets to rockets once you know your plane. Bottom line for me, is that they are underpowered to the point of being useless. People claiming they are overpowered are very much mistaken, and can't have spent enough time properly evaluating turbojets in 0.23.

[Supernovy]

Has anyone tried RAPIER + Turbojets or RAPIER + rockets yet? I wonder if hybrid hybrid propulsion would be better in some form than separate jets and rockets or purely RAPIERs.

[Murph]

Has anyone tried RAPIER + Turbojets or RAPIER + rockets yet? I wonder if hybrid hybrid propulsion would be better in some form than separate jets and rockets or purely RAPIERs.

It's an interesting idea. My gut instinct tells me that they still won't win there, other than in some corner cases. It is certainly worth evaluating.

For me, they need to equal or exceed the performance of the turbojet (both thrust and fuel efficiency) in air-mode, and equal or exceed the fuel efficiency of the aerospike in rocket mode. Yes, that would make the turbojets and aerospike close to obsolete, but that's not actually a problem. Since they are right on the bleeding edge of technology, they should be deep down the tech tree, and probably have a fairly high money cost (once the economy exists). That would keep the traditional choices relevant.

If they were more or less exactly equal to the turbojet and aerospike, that might actually be the correct balance, allowing you to have the RAPIERs as the primary engines, then add either turbojets or aerospikes when you need a little bit more of one or other types of power.

[Spatzimaus]

Has anyone tried RAPIER + Turbojets or RAPIER + rockets yet?

Yes. My 34t spaceplane is a 3-jet design; I replaced the center one with a RAPIER, but left the two outer engines as turbojets. It simply doesn't need more than a single RAPIER's rocket thrust to get to orbit, and I only lose about 5% of my low-atmosphere thrust. I've got the equivalent of two LV-Ns (four radial hybrid ions) for maneuvering in space, but 100kN just isn't enough thrust to get something that heavy to orbit on its own, so previously I'd also stacked on two 110kN radial engines from the HOME mod. The RAPIER allows me to dump those two radials entirely, so I actually saved a bit of mass by switching one jet.

[I_Killed_Jeb]

I wish the jet engine portion of the rapiers were made more powerful, at the expense of worse ISP for balance, or if the thrust spooled faster