Terminology Question: SSTO and Drop Tanks

[Tassyr]

So I've made what I THINK is a pretty good SSTO spaceplane. But it involves two small drop tanks under either wing full of LF. Does that technically invalidate the SSTO name? (Trying to settle an argument.)

[Hodo]

So I've made what I THINK is a pretty good SSTO spaceplane. But it involves two small drop tanks under either wing full of LF. Does that technically invalidate the SSTO name? (Trying to settle an argument.)

Technically yes. If you drop any part of the craft prior to achieving orbit it is no longer a Single Stage To Orbit craft.

Now if you can achieve orbit and then you drop those tanks you are fine, but if you can do that why do you need drop tanks.

[Tassyr]

Technically yes. If you drop any part of the craft prior to achieving orbit it is no longer a Single Stage To Orbit craft.

Now if you can achieve orbit and then you drop those tanks you are fine, but if you can do that why do you need drop tanks.

Well, reducing mass for orbital maneuvers, and for reentry so I don't have to lug the tanks around, perhaps. Well damn. So it's just a spaceplane, then.

[eddiew]

Two stage spaceplanes are perfectly viable, particularly early on And of course the primary reason for an SSTO is cost saving; if you're only dropping some cheap tanks, rather than expensive engines, then your spaceplane has done an admirable job ^^

[Tassyr]

Two stage spaceplanes are perfectly viable, particularly early on And of course the primary reason for an SSTO is cost saving; if you're only dropping some cheap tanks, rather than expensive engines, then your spaceplane has done an admirable job ^^

Actually the way the tanks are designed they have tiny parachutes for themselves- so in theory EVERY part can be retrieved...

[KerikBalm]

Well, reducing mass for orbital maneuvers, and for reentry so I don't have to lug the tanks around, perhaps. Well damn. So it's just a spaceplane, then.

I've made many SSTOs that get to orbit, and *then* decouple something.

Most of the time, its a payload... I almost never take my SSTOs anywhere but LKO (exception: Laythe, Duna when using modded atmospheric propulsion).

I made a spaceplane for duna that used "electric fans" to fly around duna at <300 m/s, and a LV-N to get to orbit around Duna.

Obviously that plane wasn't going to SSTO from Kerbin...

So I added Rapier engine pods to it, and SSTO'd it to LKO, decoupled the pods, and fired the LV-N to send it to Duna.

The rapier engine pods had probe cores on them, and I deorbited and recovered each one.

It was a fully reusable SSTO spaceplane.

Single stage *TO ORBIT* ... I stage/decouple/undock all I want once I reach orbit, and still call it a SSTO.

I include provisions for recovering the things discarded in LKO, but if its not worth it, then you might as well discard them earlier.

[eddiew]

Ohw, then Stage Recovery is your friend! Although sometimes the cost of the chute minus the hit of recovery isn't worth it and you're better off binning them

Seen some good designs that use SRBs for the kick to orbit too; very cheap to let go of on the edge of the atmosphere.

[Hodo]

It was a fully reusable SSTO spaceplane.

Single stage *TO ORBIT* ... I stage/decouple/undock all I want once I reach orbit, and still call it a SSTO.

I include provisions for recovering the things discarded in LKO, but if its not worth it, then you might as well discard them earlier.

I dont think anyone is arguing the point, I said all that in the second post on this thread.

[KerikBalm]

Well, I was re-iterating your point by explicitely pointing it out in the name.

It seems the OP was arguing that point, since this thread was to "settle an argument"

[Alshain]

Technically not an SSTO if it drops them before orbit, but there is nothing wrong with a Two Stage to Orbit either. I wouldn't fret over whether your creation fits into a terminology, just make sure it does what you want it to do.

[Empiro]

Two stage spaceplanes are perfectly viable, particularly early on And of course the primary reason for an SSTO is cost saving; if you're only dropping some cheap tanks, rather than expensive engines, then your spaceplane has done an admirable job ^^

Fuel tanks (even empty ones) are quite expensive, and most fuel tanks have higher cost to (dry) mass ratios than almost all the engines in the game. You're definitely better off trying to save fuel tanks if possible.

[Jarin]

Yeah, if you're doing a multistage spaceplane, it may be best to use cheap SRBs for the needed kick instead of dropping any sort of LFO-equipment (engines or tanks).

[Alshain]

Unless you are using mods. Then add StageRecovery and slap some parachutes on those tanks.

[eddiew]

Fuel tanks (even empty ones) are quite expensive, and most fuel tanks have higher cost to (dry) mass ratios than almost all the engines in the game. You're definitely better off trying to save fuel tanks if possible.

It's possible I'm ignorant; I never really look at prices, I just sort of assumed that engines are hard to make and expensive, and fuel tanks are easy and cheap xD

[magnemoe]

Technically yes. If you drop any part of the craft prior to achieving orbit it is no longer a Single Stage To Orbit craft.

Now if you can achieve orbit and then you drop those tanks you are fine, but if you can do that why do you need drop tanks.

In 1.0 they might burn up on reentry anyway. I have one setup on a SSTO where it carries air, water and food in under wing tanks like drop tanks.

Smart as its pretty lightweight and its easy to adjust the mix after need hower it would not survive reentry.

Anyway as I see it you can drop stuff after reaching orbit, you drop payload anyway.

[KerikBalm]

I suspect with winged craft in 1.0, it will be relatively easy to keep them high in the atmosphere for long enough (ie due to aerodynamic lift) that it isn't a problem f you just enter at a shallow angle

[Red Iron Crown]

Technically not an SSTO if it drops them before orbit, but there is nothing wrong with a Two Stage to Orbit either. I wouldn't fret over whether your creation fits into a terminology, just make sure it does what you want it to do.

This. I wouldn't get hung up on the SSTO term, if your craft works and is fun to fly then it is a good design.

[magnemoe]

This. I wouldn't get hung up on the SSTO term, if your craft works and is fun to fly then it is a good design.

This, My default medium lifter in 0.90 is an core who return to spaceport with 4 large SRB, Core is an Skipper and 1.5 orange tanks. it can take 20 ton to LKO.

An SSTO rocket with 20 ton capasity would have to use a 24x4 engine and 3.75 meter tanks, fuel cost would be higher and the cost if you fail to bring it back would be far higher.

[Technical Ben]

A "space plane" is as cool as a STTO. A STTO is just a little technical detail. Drop tanks could be recovered and/or really cheap to replace, so would be no worry if your spaceplane is cool still. (Most laws of physics make STTO impractical anyhow)

[Hodo]

A "space plane" is as cool as a STTO. A STTO is just a little technical detail. Drop tanks could be recovered and/or really cheap to replace, so would be no worry if your spaceplane is cool still. (Most laws of physics make STTO impractical anyhow)

Not sure what you mean by STTO, Single Tank To Orbit?

All I build is SSTOs in KSP because the atmosphere isn't anywhere near scaled right for realism. I also run FAR+DRE and have been since 2013 and I rarely have problems with craft burning up or needing drop tanks to achieve orbit. The trick is designing an efficient design that works. If it looks like junk it will fly like junk, if it looks right it will fly right. Simple pilot saying that actually works.

[John FX]

Myself, to contribute my thoughts to your argument, I would say that if you have to stage (or drop parts of your craft with an action group) to get to orbit, it's not a single stage to orbit.

That said, a couple of drop tanks is no biggie but your craft is not technically an SSTO. It's a reusable system though (if your tanks don't burn up on re-entry that is)

[Van Disaster]

I use droptanks with engines on occasionally. StageRecovery won't recover all the cost given I drop them off somewhere above jet altitude and that's a long way from KSC, but the loss is pretty low anyway. Saves completely redesigning the spaceplane, anyway. One day I'll sit down & work out if it's viable for getting spaceplanes to Mun/Minmus economically.

[Hodo]

I use droptanks with engines on occasionally. StageRecovery won't recover all the cost given I drop them off somewhere above jet altitude and that's a long way from KSC, but the loss is pretty low anyway. Saves completely redesigning the spaceplane, anyway. One day I'll sit down & work out if it's viable for getting spaceplanes to Mun/Minmus economically.

I will tell you exactly how I do it with SSTO space planes. I have a refueling station usually at 100km orbit above Kerbin. I have the craft in question launch and dock with the station. It refuels there and waits for its launch window from that point. Then when the time comes I undock and continue on the mission.

No that isnt a small SSTO, it is large enough to haul 25tons into orbit... its just that station is that big. I didnt want to have to deal with refueling it that often.

[Van Disaster]

That does require at least one extra launch on top of your actual launch, though. If you've got a station up and you go through the hassle of rendesvous you might as well transfer everything & use a more economical pure spacecraft.