R.A.P.I.E.R. engines... do they suck or am I using them wrong?

[Wanderfound]

Vernors rock; all of my planes use them for Mun/Minmus VTOL.

Not sure that they'll cut it on Duna, though.

[Red Iron Crown]

Vernors rock; all of my planes use them for Mun/Minmus VTOL.

Not sure that they'll cut it on Duna, though.

They're massless, just keep adding them until enough thrust is available. You can land a VTOL on Eve by spamming enough of them (Pack a lunch though, you'll be staying a while ).

[magnemoe]

Personalty I found trust in atmosphere as more of an issue than rocket trust, you will basically do the last 100-500 m/s on rockets and here you can manage with an TWR of 0.5 or less.

One of my designs used a turbojet and four 48-7S, this worked better than the rapier as the jet engine has more trust.

Spaceplane plus helps here, my current spaceplanes has one small two seat one with two rapiers, an larger plane with passenger cabin and a double length cargo compartment.

It have two rapiers and two jet engines, 6 ton cargo had lite impact on performance. typical cargo is either life support, food, water and oxygen, parts for testing, 4 return pods for kerbals stranded in orbit or probes.

[Wanderfound]

Personalty I found trust in atmosphere as more of an issue than rocket trust

In thrust we trust.

[Levelord]

In thrust we trust.

That's a signature worthy quote right there.

[Zephram Kerman]

No pre-determined landing spot. Fuel will probably be pretty tight so I'll have to improvise a little once I'm in orbit, I don't think I'll have the luxury of spending fuel to manouver to a pre-determined landing spot Anything below 4000m and not *too* hilly should be fine.

I hadn't thought of vernors yet to slow vertical speed, but I am (or perhaps more accurately, Bill, Bob and Jeb are) painfully aware of the problem of coming in fast

I have a way of dealing with it, but I'll keep that a surprise for when I post pictures

For your inspiration:

This is from 0.22, I think. After about a hundred attempts to land horizontally on Duna, I gave up on that idea. However, the combination of wings, one parachute, and a little bit of VTOL was a real joy. We did a lot of exploring with this little guy.

If you still want to land horizontally, put the parachute about 45° aft of the CoM, and use just a little bit of thrust. This way flies sortof like a parasail. Slow and very maneuverable, it's great for landing in terrain.

[Cirocco]

If you still want to land horizontally, put the parachute about 45° aft of the CoM, and use just a little bit of thrust. This way flies sortof like a parasail. Slow and very maneuverable, it's great for landing in terrain.

Parachutes? Where we're going, we won't need... Parachutes.

Seriously though: using Hyperedit I already tested my plane on Duna under worst-case conditions (with a lot more fuel than it will actually have left, at high altitude and hilly terrain) and I can set her down in a conventional manner (sort of) without any parachutes at all.

The reason why I don't use parachutes/VTOL is because the plane is pretty massive (83 tons on runway) and its CoM shifts a little in flight. I don't know where it will end up exactly so using parachutes/VTOL engines is likely to result with thrust acting on the CoM in a non-vertical manner. Which means plane flips ahoy.

And again, I kinda like the challenge: it's plane so we damn well land it like one.

[Zephram Kerman]

And again, I kinda like the challenge: it's plane so we damn well land it like one.

When you do, I want video! It could be raw and unedited, I don't care. But landing something heavy on Duna, horizontally, without even finding a good spot... "that's impossible" â„¢. So if you can do it, that would be... interesting.

[Wanderfound]

And again, I kinda like the challenge: it's plane so we damn well land it like one.

Ahem:

http://www.smh.com.au/nsw/plane-parachute-gives-near-disaster-a-soft-landing-20140510-zr8uc.html if you're curious about what's going on there.

[Cirocco]

When you do, I want video! It could be raw and unedited, I don't care. But landing something heavy on Duna, horizontally, without even finding a good spot... "that's impossible" â„¢. So if you can do it, that would be... interesting.

I have no idea how to do video I'm afraid :s

I'll take a ton of screenshots though!

[Cirocco]

Made a new thread cause I felt like we were hijacking this one: http://forum.kerbalspaceprogram.com/threads/92618-Landing-a-spaceplane-on-Duna-horizontal-landing-no-chutes

[Hodo]

HTOL. Using parachutes is hard unless you want to land her on the nozzles (which is what I did last time, and it just feels wrong for a spaceplane to do that) and vertical landing is also very hard because it is really hard to determine where exactly the CoM will be when I land: the CoM shifts during flight due to fuel drainage and I have no way of telling exactly how much fuel I'll have left upon arrival.

Plus, I figure it's a plane, so we land her and take off like a damn plane. It's quite challenging in an atmosphere as thin as Duna's, but fun!

I have done a few VTOL lander space planes, and the CoM thing is made a lot easier with 2 mods, TAC Fuel Balancer, and RCS build aid. If you just use one RCS build aid is the best of the two. If you built it right your CoM shouldn't move, or shouldn't move enough to affect your hover stability when in VTOL mode. The biggest thing I have found is all of my VTOLs bring additional RCS, because they will need it on worlds that do not have an air atmosphere. Ones that have oxygen atmospheres I will use the B9 air thrust nozzles for RCS.

And i have built some pretty massive VTOLs.

149 tons.

146 tons.

Went to Ike

240 tons with a 80 ton cargo load capacity in VTOL and 110 ton cargo capacity STOVL.

Again... it took dozens of hours of work to get those designs functional back then, and I am currently working on rebuilding some of them now.

[eataTREE]

My experience has been that they're mediocre jet engines and mediocre rockets, but can be preferable for small designs where there isn't room to stick on dedicated jets and dedicated rockets. Their poor ISP in closed cycle mode is definitely a problem -- try to be going hella fast already in airbreathing mode, so there is less delta-V to burn in rocket mode.

[sumrex]

Meh, they can seem that way at times. Over time my SSTO's have evlolved to carry a mix of engines. What it usually comes down to for me is a slightly different way of assessing my planes. If my planes need more thrust at low altitude I will be more inclined to substitute in some jets. If I am hitting the wall higher up in the ascent profile I will mix in more rapiers or aerospikes. It just comes down to me making a determination at what altitude is the vehicle suffering and which engine at that altitude is the best fit. But concerning your original question the rapier should run through oxider fast at altitude since it sips it at lower altitudes. If it did not it would be the only engine used. The way you need to look at the rapier is that it is an engine type that can provide consistent power through most of the ascent profile. Jets are light and powerful, but hit the wall on average between 25 and 40km altitude; after that they are dead weight which have to be lugged around Kerbin or interplanetary orbits by other engines. Aerospikes provide consistent thrust and are more beneficial at higher altitudes and space, but are inefficient compared to the other engines at lower altitudes.

Of course once you have all that down you may discover occasionally you are so efficient at keeping fuel your plane may become more inefficient lugging around dead weight, but that is a story for another day grasshopper.

Edited September 2, 2014 by sumrex

[cantab]

As a rocket the RAPIER's Isp isn't that bad, a shade lower than the LV-T45 and equal to the .24-buffed Mainsail. Of course it's a lot thirstier in closed-cycle than in air-breathing mode.

[Francois424]

I've tested these engines thoroughly when they came out. Unmodded (and I like to mod the stock parts which I never find a use to) they are a piece I keep ignoring over and over again. Then again, never was a huge fan of SSTO's which are long as hell to get into orbit and eats fuel really quickly when out of air modes.

I prefer using the Ramjet engines with a lot of air intakes when I *do* build an SSTO.

Case and point: With my playstyle, not worth bothering with unless I beef up the efficiency of the fuel part to something like 400 ISP.

[KandoKris]

Rapiers are Cool I love having single engine SSTO's

I have made approx 20 SSTO's with them and countless without.

Yes when they were first put in the game I thought them next to usless but with practice I found that assumption to be wrong. While I still like to do old school SSTO's I now have a fondness for the R.A.P.I.E.R ( Sabre ) engine.

As for being slow to get to orbit that depends on your SSTO design

These 2 will get a 100km orbit in under 5 min

But this take's ages ;

[Wanderfound]

These 2 will get a 100km orbit in under 5 min

Feel like posting a time?

http://forum.kerbalspaceprogram.com/threads/90354-Spaceplane-speed-challenge-shortest-elapsed-time-from-runway-to-orbit

[I_Killed_Jeb]

worked really well for this guy

[qromodynmc]

Interestingly they worked on this plane,Half of the fuel left when I get into orbit.

[MartGonzo]

I noticed something counter intuitive with Rapiers, on a successful flight up to a rendezvous and landing at KSP again I had more oxidizer than fuel left.

so that even though Rapiers eat through oxidizer it makes sense to take some out in the hanger and make the plane lighter.

[tutrakan4e]

Obviously the Rapiers were using no Oxidiser while in the atmosphere.