R.A.P.I.E.R. versus Turboramjet? Surprise, surprise

[Mikki]

​This is a Airbreathe, allround Performance comparison Test

Same Aircraft (Spaceplane, its native idea is ramjetdesign)

Target Orbit is 80x80 LKO.

45tons Payload aboard.

Pics taken at Liftoff, 7500m, 15000m, 25000m, 50000m, 70000m, Orbit insertion, Payload undock (If Possible...).

The MK3 SSTO has two Twinboars to achieve final orbital velocity (Exception made for KerikBalm...)

All Flights at optimised Ascend flown, as good as possible (At least 2 Runs to Check...).

Post your Comments, what do you think?

Turbo Ramjet

http://imgur.com/a/r4emd

R.A.P.I.E.R.

http://imgur.com/a/pMTeR

​RAPIERSPIKE (Invention of Communitymember)

http://imgur.com/a/itdnc

R.A.P.I.E.R.s only (TwinBoar off, Raps in )

http://imgur.com/a/eHB0y

R.A.P.I.E.R.s only (Two engines off, now 24)

http://imgur.com/a/92Otx

R.A.P.I.E.Rs and Turboramjets... (no Questions left for me...)

http://imgur.com/a/BDgak

I was wondering how one could not even achieve Orbit, the other has some 750oxidizer left...

And the other one creates crazy phantomkrakenforces...

Finally one other had successfull Payload undock... my first Rapieronly SSTO!!!!)

Aerospike test obsolete... LFO only...

Rapiers seem good so far, but still not much dV left...

... yeah after the last Test i must say... WOOOOOOOOOWWWWWWWWWWWWWW...lots of dV left

Edited May 29, 2015 by Mikki
... adding more Tests... hang on;), Threadtitle simplyfied

[heng]

Uhhh, do a third one with Levelord's RAPIERSPIKE invention!

Seems like that should increase efficiency a bit even more...

Nice ship!

[Mikki]

Uhhh, do a third one with Levelord's RAPIERSPIKE invention!

Seems like that should increase efficiency a bit even more...

Yes, a third test will be done with... the crazy RAPIERSPIKE

hang on guys

DONE: added RAPIERSPIKE

Edited May 28, 2015 by Mikki
done

[Teilnehmer]

Is your ascend profile the same for turbojets and rapiers?

[KerikBalm]

All Flights at optimised Ascend flown, as good as possible (At least 2 Runs to Check...).

Post your Comments, what do you think?

...

I was wondering how one could not even achieve Orbit, the other has some 750oxidizer left...

And the other one creates crazy phantomkrakenforces...

#1) your flight profile seems decidedly not optimized, climbing too fast, with too little speed on the rapiers

That is one of the most inefficient ascent profiles I've seen aside from people just starting to play... your circularization burn should never be that much.

#2) You don't simply switch turbos for rapiers... those twin Boars are dead weight on a rapier spaceplane.

Your rapiers have more Isp than those twin boars, and since they are also rocket, you don't need dedicated rocket engines.

Replace the twinboars with an orange tank+ triple/quad coupler sporting more Rapiers.

More rapiers in place of the twin boars = more airbreathing thrust, and you'll get more dV while in airbreathing mode, plus more dV in rocket mode since Rapiers have slightly better Isp

[Mikki]

Is your ascend profile the same for turbojets and rapiers?

Hi there

This is simply a test to show that Engines need a design that fit their specifications...

To me its clear that the 12ton of Twinboar engines are "dead" Weight for the Modeswitchers...(But nice 4000kn Thrust, Time is sometimes the key...)

While ascending i had to fire the Twinboars for about 200dv at 12500m, because the Rapiers simply do not thrust as like the Ramjets...

And still... flighttime is fuel consumption Time, i had to decide to get the Plane out of the Soup as fast as possible...

This Deltarocket system is also based on Ramjets from scratch... i does not mean other engines are useless.

(The Plane is simply too heavy for Rapiers, as you say, KerikBalm, Twinboar off, Raps in, gonna try...)

I am gonna strap the aerospike engines now...and see what happens .

Edited May 28, 2015 by Mikki

[KerikBalm]

flighttime is fuel consumption Time, i had to decide to get the Plane out of the Soup as fast as possible...

See, I see it differently: Flight time is 6,400/8,000 Isp time.

Even if drag is resulting in only 1/10th of my thrust actually going towards acceleration/inceasing my PE (the other 9/10ths going towards fighting drag), that still leaves me with the equivalanet of 640/800 Isp in a vacuum... which is of course much better than you'll get from a twin boar.

[Mikki]

See, I see it differently: Flight time is 6,400/8,000 Isp time.

Even if drag is resulting in only 1/10th of my thrust actually going towards acceleration/inceasing my PE (the other 9/10ths going towards fighting drag), that still leaves me with the equivalanet of 640/800 Isp in a vacuum... which is of course much better than you'll get from a twin boar.

Hi KerikBalm

I taped a R.A.P.I.E.R.s only together, same weight, same Payload, approximatly same Lift, and it had success.

You know i know youre right, thats why i call it comparison Test ...

My Engineer redux readout has some weird problems with the many tiny engines... bad thing.

The Ramjet/ Twinboar had the most Fuel left. Its still my favour in this Thread.

Greetings

[problemecium]

Mind doing one more test using a turbojet and LV-N combination?

Actually the twin-boars are a bad idea to begin with. They're great near the ground, but in the upper atmosphere or space their low specific impulse will spell doom.

[Mikki]

Is your ascend profile the same for turbojets and rapiers?

The "R.A.P.I.E.R.s only" Test had nearly the same ascendprofile like the Turbo Ramjet/ Twinboar setting.

Very interessting to me too! At 60000m Apoapsis during burn i installed "Prograde" in every Test btw...

Greetings

- - - Updated - - -

Mind doing one more test using a turbojet and LV-N combination?

Actually the twin-boars are a bad idea to begin with. They're great near the ground, but in the upper atmosphere or space their low specific impulse will spell doom.

I think there is no chance, the Time is way to short for the Nukes, and Time is rare firing up 300tons ...

I simply see no way how to do that...

[Temeter]

He isn't wrong, the Twin Boar engine is pretty much a cheaper mainsaill with less efficiency and the same weight.

[Mikki]

He isn't wrong, the Twin Boar engine is pretty much a cheaper mainsaill with less efficiency and the same weight.

Hi, i know why i taped the Twinboar... perfect for this Task. 2000Kn Thrust, nothing else matters here.

The Mainsail has only 1500kn. Time is here more important than Isp or efficiency...

[RuBisCO]

My Xylol has half the weight and 4/5 the cargo capacity. I eventually choose a combination of both Turbo-Rams and Rapiers, the turbo-rams are to provide extra power at lower altitudes and the rapiers to provide higher performance at high altitudes and replace the weight of a dedicated rocket engine. An all Rapier design simply does not perform as well and always requires diving from 12 km down to 9 km to get beyond 600 m/s to get the speed needed for the rapiers to perform, ultimately more fuel is needed to make it to orbit.

http://forum.kerbalspaceprogram.com/threads/123442-Xylol-SSTO-All-stock-space-plane-that-can-lift-36-tons-cargo-to-orbit

[Mic_n]

Time is here more important than Isp or efficiency...

How so?

Unless it's just a matter of "I'm impatient and just want to get it over with" (which is fine if that's how you want to do it), then "not enough time at Ap to circularise" is just another way of saying "my ascent profile is too steep and I'm not carrying enough horizontal velocity". IE it's a symptom of what's already been suggested earlier in the thread. If you're still having to burn once you've passed your Ap, you're wasting fuel you should have burned earlier.

Back in Ye Olden Days you used to be able to circularise a spaceplane orbit with ion engines, and I can't think of a more "time poor" option than that. Admittedly with the new model I don't think that's really viable any more (though I'd love to see someone manage it), but the principle is still the same. The more speed you build up with those delightfully efficient air-breathing engines, the less you need to spend on rockets, the less oxidiser you need, and that beautifully exponential weight saving kicks in more and more.

[problemecium]

If you're so concerned about time, then I agree there's something wrong with your ascent procedure. o_O

[Mikki]

I am gonna make further experiments with this Plane, its a careerproof (safe...) Aircraftdesign, good allroundspecs, good Highspeedhandling, compact size in dimensions, good lowspeedhandling, safely landable...

Trying to build up speed in upper atmosphere is not so easy as some may think of. Above 20000m is still a lot of drag,

maybe i go an strap some LV-Ns...

I am sure with RAPIERs only its possible to decrease the amount of Engines about minus two, maybe four.

The RAPIER is probably the best overall.

The lifting surface is quite limited on this plane... and its overall drag is huge. Good Thing to compare engine combos.

[Mic_n]

Take a look at some of the SSTO/spaceplane threads if you want some ideas/inspiration...

http://forum.kerbalspaceprogram.com/threads/118470-1-0-2-Any-hope-left-for-SSTOs

http://forum.kerbalspaceprogram.com/threads/123135-RIP-SSTO-long-live-SSTO

It's certainly very different to what it used to be, but still do-able.

[GoSlash27]

Mikki,

What matters in spaceplanes is payload fraction, which directly impacts their operating cost.

If you wish to directly compare each engine type, you need to build aircraft optimized for their engines and compare their payload fraction.

RAPIER designs are getting between 20% and 30% payload fractions. I don't know what the current limits are for turbojet hybrids, but I wouldn't expect them to come close to that.

Best,

-Slashy

[Hobbes Novakoff]

OP, can you embed the images instead of linking? Do [NOPARSE][/NOPARSE].

[herbal space program]

Mikki,

What matters in spaceplanes is payload fraction, which directly impacts their operating cost.

If you wish to directly compare each engine type, you need to build aircraft optimized for their engines and compare their payload fraction.

RAPIER designs are getting between 20% and 30% payload fractions. I don't know what the current limits are for turbojet hybrids, but I wouldn't expect them to come close to that.

Best,

-Slashy

I've been spending a lot of time fooling around with this in the last few days, and for me it seems that 3-4 Rapiers, 1 turbojet, and 1 nuke is the combo makes for the best deltaV on orbit. It seems like with the current atmosphere model, breaking the sound barrier is the biggest hurdle in any ascent profile that's trying to get as much mass/deltaV per ton as possible on orbit. In a 3-hull Mk2 design with 4 RAPIERs plus a nuke, it's always been a long process for me to break the sound barrier and go into the silly thrust zone. I would have to climb to 14km on the RAPIERs at like 290 m/s,then nose down and engage the nuke, hoping that I could hit like 420 m/s and pull back up before getting below 10km. Very tedious and fuel-consuming. Adding one turbojet to the mix dramatically improved the efficiency with which I could get to that point by providing that extra little push at the transition. With 4 RAPIERS and 1 turbo, I was easily able to get a 42 ton craft to the 400+ m/s range on a constantly ascending profile. Keeping the RAPIER/Turbo ratio to 3 or 4 to 1 left enough thrust at the high end for me to get up to 12-1300 m/s surface at 24km with enough climb rate that I didn't burn off all my rocket deltaV getting up out of the soup. Unfortunately, there's no symmetrical way to place 3+1+1 or 4+1+1 engines, so I had to mount the turbo to an empty tank behind the nuke on a decoupler, then jettison it for the circularization burn. Obviously this is no longer technically a SSTO design, although dragging the turbo the rest of the way to orbit, if it were somehow possible, would still have left this ship with close to 4000 dV on orbit. I haven't taken this ship to the Mun and back yet, but I'm pretty sure I'll make it when I try. Landing a big ship like that on just the nuke is pretty costly though. A previous version without the tacked-on Turbo could make Munar orbit and back, but just didn't have enough deltaV to land and get back off.

Edited June 1, 2015 by herbal space program

[Mikki]

I've been spending a lot of time fooling around with this in the last few day,... (...), but just didn't have enough deltaV to land and get back off.

Hi there herbal SP

I am verry interested reading your experience, in the moment i use a 2 R.A.P.I.E.R. per one Turbo Ramjet system, more or less proportionaly.

You are right, the soundbarriers are somehow a horseshoethrowinglike thing, i also tested endlessly heavy planes to put some gear up.

The reason for my engineless mainfuselage design is that i started putting up heavy and wide equipment, with a orbitalstation as dockingtarget in 100x100 LKO. I like to meet up with the station immediatly several minutes after takeoff, or be at least some two handfull klicks away to unload/ dock/ eventually bring down used modules for refunds... The thing with nukes i think is that is not so exact to rendezvous in at least one orbit... but as you say i have to try this system and follow your advice how to start with, thanks alot for your response!

I like alot the old wingparts and simply dont get warm with the new ones, hm... they look good and all, but give not much choice to assemble.

My priority is allways that the craft is somehow dockable, "careerproof", good landable , safe and has some room for changes in purpose, thats also the reason why some are bit overpowered, i use to detach engines when putting up depleted Modules, and i prefer to do fueling mission separatly with designated "idiotproof" (me is the idiot ...) fuelsstos witch behave i exactly know. Docking mediumsized clampotrons with some 200 or more not allways well balanced tons of Kerbal engineeringwonders is not fun, takes sometimes near half an hour!!

Have a good time

[Red Iron Crown]

What matters in spaceplanes is payload fraction, which directly impacts their operating cost.

If you wish to directly compare each engine type, you need to build aircraft optimized for their engines and compare their payload fraction.

RAPIER designs are getting between 20% and 30% payload fractions. I don't know what the current limits are for turbojet hybrids, but I wouldn't expect them to come close to that.

I've been of the same line of thought, but I'm starting to have doubts. For a recoverable SSTO, dry mass is better than fuel mass because dry mass can be recovered for 100%. I'm starting to think fuel per unit payload mass is a better metric, i.e. a more massive craft that brings the same payload to orbit with less fuel is superior, even though its payload fraction is inferior.

[Mikki]

I've been of the same line of thought, but I'm starting to have doubts. For a recoverable SSTO, dry mass is better than fuel mass because dry mass can be recovered for 100%. I'm starting to think fuel per unit payload mass is a better metric, i.e. a more massive craft that brings the same payload to orbit with less fuel is superior, even though its payload fraction is inferior.

Hm, its matter of purpose... i do not want to go laythe or so with an ssto as it was possible days ago, i never did also.

To me is simply putting up gear to LKO the reason, i dont dump any equipment any more, or at least not so much... (fairings, decouplers etc...).

I fact i try to dump nothing around kerbin, while going further visiting other bodys, dumping equipment somewhere looks sometimes mandatory...

Its kind of a thinking challenge about reasonable ressourceuse..? i really dont know how much or few others reuse, or if they dont mind the cost (done work...) of some hundred kilos Kerbalbugs to go to space each time. Fuel is cheap somehow, dumped stuff is gone... forever, and with it the value once invested. its hard enough to have a crashlanding and loose the half of the funds for a large ssto.

Would be interesting to know exactly how people play this game...

Edited June 1, 2015 by Mikki
...Typo...:)

[ajburges]

I've been of the same line of thought, but I'm starting to have doubts. For a recoverable SSTO, dry mass is better than fuel mass because dry mass can be recovered for 100%. I'm starting to think fuel per unit payload mass is a better metric, i.e. a more massive craft that brings the same payload to orbit with less fuel is superior, even though its payload fraction is inferior.

I'm with you Crown. Staged rockets have better payload fractions than SSTO, but people still choose the SSTO. The efficiency is all about what fraction of launch vehicle (fuel included) funds you get back.

Payload fraction does correlate though, and is much easier to calculate. Also payload fraction is a better metric for single stage to anywhere. Those monsters need to dedicate their payload fraction to fuel their OMS.

Given that funds are balanced for pure rocketry, I tend to be happy with any spaceplane that gets the job done with a forgiving flight profile. I've dabbled with a no oxidizer turbo space plane, but it was a nightmare to balance the anaerobic profile. I had to thrust 30 degrees off prograde for most of the accent to make orbit! Given that some of my body parts have oxidizer storage anyway, I will probably have future nuclear spaceplanes use a RAPIER power plant for easier orbital insertion.

[herbal space program]

So I figured out how to mount both turbo and nuke engines in the middle by canting them outwards, and this is the SSTO I came up with:

Javascript is disabled. View full album

I haven't successfully landed it on the Mun yet, but i should have enough deltaV to make it and back. Based on its performance, I think 4 RAPIERs, 1 turbojet, and 1 nuke is indeed the magic ratio for optimal SSTO performance. I'd love to see all-stock designs that can do better than this one with a different configuration....

Edited June 2, 2015 by herbal space program