1.0.2 - Any hope left for SSTOs?

[Radam]

Ive tried it with one of my mk2 crafts. 2 rapiers achieved 1300ms at 25km starting from 20 degree pitch at 5km after breaking the mach barrier. Altho they did blow up from heat a few km later.

Same craft with turbos struggled to pass mach the same way, maybe slightly less. But only achieved 1100ms at 25km from same 20 degree pitch at 5km past mach ascent.

[Mister Dilsby]

I've made a liquid-only SSTO! The key is to thrust to 1200 m/s with a high rate of climb and get the heck out of atmosphere before anything explodes. Full post and album here

Now if you want such a thing to be able to go to Moho, forget it! But it may be possible to scale the concept big enough to carry light cargo to LKO, and be the beginning link in a chain of orbital/surface LH2 mining operations that will truly conquer the Kerbol system.

ETA: Rune beat me to it, posted a couple of pages ago on this thread.

Edited May 6, 2015 by Kuzzter

[Rune]

Yeah, I remember the posts saying how SSTOs were dead, and here we are musing reusable architectures running on liquid fuel, wings and determination... My back of the napkin calculations show starting the trip with a refill in Minmus requires about 12 turbojets going full blast on the runway. Which gives plenty of room to find the perfect fuel fraction/nukes/jets/RAPIER combo that might bring the number of airbreathers down.

Rune. Assuming a 1mT command pod and a 5mT mining rig. Tight.

[Kuu Lightwing]

You can top up at Gilly, that should leave you with 1,500m/s, plus about 1,500 more that you used to get to LKO, leaving you 3km/s to play with at a significantly lower orbit than Kerbin's. Then again, landing on Moho alone from escape velocity will eat around a km/s, so... maaaybe (if you are a god with transfers and nail Moho just in a node)? A flyby for sure, that should be peanuts.

Rune. Then again, with multiple gravity assists (which I can't plan for the life of me) everything is possible, you could use Moho to circularize at Moho's orbit, and yes I know that sounds wrong. Think what Messenger did.

Well, I'm just thinking about making an interplanetary craft (not necessary an SSTO plane, more like a rather large space station) which uses ISRU refinery and a mining lander to refuel at planets and moons to get everywhere in Kerbol system. I think Eve(Gilly)-Moho transfer would be the hardest, so, I'm interested in delta-v requirement to do that transfer, because if I can make it, I can get everywhere. It's a bit of an off-topic, but do you know how much dV would that cost?

[Sattorin]

Just finished a big project (inspired by KerikBalm's monstrosity) to test my computer's limits. 297 parts, 36 RAPIERs and 4 Nervs.

The result: 2 crew, a full ISRU package, and 2,400 Dv in a 74x74 orbit.

ISRU refueling at Minmus (filling up all the liquid tanks) would give it a lot with which to explore the Kerbol system... if I had the patience for this framerate.

Javascript is disabled. View full album

It can DEFINITELY be made more efficient. I probably had more RAPIERs than I needed and obviously ended up with way more liquid fuel than necessary to reach Minmus.

EDIT: Changed some bad math.

Edited May 6, 2015 by Sattorin

[Mister Dilsby]

Doing a bit better in the no-O2 category: this 20.3t craft built around Mk2 got up with 900dV to spare. Still not where Rune is. Could do better swapping cargo bay for more LH2.

[Rune]

Doing a bit better in the no-O2 category: this 20.3t craft built around Mk2 got up with 900dV to spare. Still not where Rune is. Could do better swapping cargo bay for more LH2.

http://i.imgur.com/4p0jGwX.png

Yup, but don't feel bad about it. We may be in the same weight/powerplant category, but yours is a comfortable family car with all the extras and niceties, while mine is a purebred with nothing spent on anything but performance: I have barely a metric ton in command module, while you have two mT of cockpit and some ancillary equipment, and at the same time mine carries twice the fuel (the craft is, quite literally, a flying fuel tank). We both play by the same physics laws, so whatever I can do, you can too! That's the awesomest thing about KSP, you are always learning

Rune. I'm getting great ideas and data points from this thread!

[landfish2]

I have been watching. And I have a new design.

Introducing the HotDog - dogger than ever

Javascript is disabled. View full album

some statistics and analysis:

-a resting TWR of 1.4

-very good low atmosphere handling: can pull over 10gs and land on the island runway

-looks cool

resulting in:

700 delta/v at 80x80km orbit with a cargo of 10tons.

performance has of course been sacrificed for looking good

craft file for those interested:https://mega.co.nz/#!ORtlwS4b!MMkJeRtrM05VYBF19iK8HA8iRuCnR4i1217EzGDHszU

[KerikBalm]

I think Eve(Gilly)-Moho transfer would be the hardest, so, I'm interested in delta-v requirement to do that transfer, because if I can make it, I can get everywhere. It's a bit of an off-topic, but do you know how much dV would that cost?

Gilly is so tiny, you can basically ignore its gravity, and just assume one is in orbit of Eve itself (oberth from Gilly is a pitance, gravity drag from gilly is irrelevant)

Its semi-major axis is 31,500 km (ie, thats the average height from Eve).

So... going here: http://alexmoon.github.io/ksp/

Selecting Eve orbit, 31,500 km as the start, and Moho as the destination:

Ejection ÃŽâ€v: 2,355 m/s

Insertion ÃŽâ€v: 1,531 m/s

Total ÃŽâ€v: 3,886 m/s

3886 is much better than going to Moho from LKO (5031)

However, if one were to fill up at minmus, drop PE down just above kerbin, and then do the burn, the difference would be much less than the 1,145 calculated here.

It also depends somewhat on where gilly is in its orbit as you depart - ideally you'd want to leave gilly at apoapsis, so you can cheaply bring you PE down right above EVe's atmosphere and have a higher speed when you do the burn... but then the launch window is more complicated.

If you have ISRU at gilly and moho, you can go to moho and back with a craft that only hasa dV capability of 4km/s

[RobertR]

I have been watching. And I have a new design.

Introducing the HotDog - dogger than ever

http://imgur.com/a/QFfIJ

some statistics and analysis:

-a resting TWR of 1.4

-very good low atmosphere handling: can pull over 10gs and land on the island runway

-looks cool

resulting in:

700 delta/v at 80x80km orbit with a cargo of 10tons.

performance has of course been sacrificed for looking good

craft file for those interested:https://mega.co.nz/#!ORtlwS4b!MMkJeRtrM05VYBF19iK8HA8iRuCnR4i1217EzGDHszU

That thing looks great AND it works?? Reminds me of this

Needless to say I'm a big fan. Thanks for posting the craft file.

I tried building a ssto for the first time since before 1.0 was released today and totally overestimed the number of engines required. Ended up going too fast and ripping the wings right off. Sure I could have throttled down but I wasn't convinced I couldn't just power right through the turbulence. Turns out it doesn't work like that.

Edited May 6, 2015 by RobertR

[landfish2]

I tried building a ssto for the first time since before 1.0 was released today and totally overestimed the number of engines required. Ended up going too fast and ripping the wings right off. Sure I could have throttled down but I wasn't convinced I couldn't just power right through the turbulence. Turns out it doesn't work like that.

In terms of engines I like to run a surface TWR of around 1.5. That seems to work for me

[Slugy]

Posting these two to show the ascent profile I've been using - diving to build speed works nicely, and makes Rapiers very strong ...

First one is a low part count, single engine cargo carrier - 27 parts, 6t to orbit with fuel to spare (570 dV left once cargo deployed, in this flight), ~16t fuelled without cargo, and as it turns out enough fuel to fly a quarter of the way round Kerbin after overshooting the runway a little ...

A similar design, without the cargo bay, is easily capable of 2 trips to orbit without refuelling.

The angle (and size) of the wings is important: it takes off with no input, and flys with no/minimal input, the thrust vector should be close to zero in KER. Also note the climb (then dive) flight path.

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~3200 dV left in LKO, 2 Rapier + 1 nuke spaceplane: similar "up then down fast" flight path, with a little help from the nuke as it makes tops out the first time. Wing angle/position needs a small tweak with this one - but it works

Javascript is disabled. View full album

[Wanderfound]

Identical designs, apart from swapping the central engine from a Turbo to a RAPIER.

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Turbo wins on this run, but it's hard to tell how much of that is due to piloting.

[quasarrgames]

Just a reminder that precoolers be crazy good!

[GoSlash27]

But surely the fact that the turbo gives out a) at lower speeds and at lower altitudes, how can it make sense to favour one of those over a Rapier? If you're hitting max TWR with a turbo at around 13km, and max TWR with a Rapier at around 16-17km, surely the fact that you've got more power, at a higher altitude will always be more favourable than petering out much sooner? Even if it requires a reduction in vertical speed, or a short period of diving to push through that drag boundary.

To me, at least, it's all about getting as much thrust as high as possible?

Unless of course, you've got some gargantuan monster hauling up a bucketful of drag and/or payload. Maybe I'm just too darn stubborn, but I've yet to find a reason to replace a Rapier with a turbo. And if I'm struggling to make orbit on account of need moar boaster, surely I'm going to need moar boaster at both ends - airhog and rocketry phases - and therefore I'm again inclined to add a Rapier...

However, adding a Rapier requires more mass in terms of ancillary bits like er fuel. But, at least this is useful mass for the entire ascent. A turbojet becomes dead weight beyond around 15km (yes it will still give power but you're way beyond it's peak and while it's helping, surely its contribution isn't that spectacular?)

Of course, I should probably explore options using real rocket engines too...

Well...

The thinking would be that a turbojet can push a much larger mass through Mach 1. I can get RAPIERs to do that around 35 tonnes per engine, but turbojets are much higher than that. Still not sure where the limit is.

So with that extra mass, you could theoretically carry an efficient, powerful rocket and more fuel to feed it. Perhaps enough to overcome the top end limitations of the turbojet. I'm guessing it's not enough, but I may easily be wrong.

Another possibility would be bringing along some turbojets in order to make a weak RAPIER design still exceed Mach 1.

This might allow for heavier RAPIER designs that still hit the same open cycle limits with more fuel. Personally, I'm dubious about this. DV shortcomings are expensive in terms of payload fraction when your spaceplane is generating enough drag to make a fireball...

Best,

-Slashy

- - - Updated - - -

Just a reminder that precoolers be crazy good!

Are they?

I haven't had any luck with them. They just seem to act like more intake area for me...

[Brotoro]

Just a reminder that precoolers be crazy good!

Are they? Can you explain exactly WHY they are good? Are they worth their weight?

I'm not disagreeing... My spaceplane worked after I added them. I just want to better understand WHAT they do.

- - - Updated - - -

Hahahaha! I echoed the Slash man.

[Matrix Aran]

Are they? Can you explain exactly WHY they are good? Are they worth their weight?

I'm not disagreeing... My spaceplane worked after I added them. I just want to better understand WHAT they do.

- - - Updated - - -

Hahahaha! I echoed the Slash man.

You and pretty much every other plane builder out there

[Wanderfound]

As with the nacelles, intercoolers combine a bit of intake with a bit of LF. What's new, however, is that the intercoolers appear to have extremely high heat tolerance, so they make for very good radiators and insulators.

[panzer1b]

Well...

The thinking would be that a turbojet can push a much larger mass through Mach 1. I can get RAPIERs to do that around 35 tonnes per engine, but turbojets are much higher than that. Still not sure where the limit is.

So with that extra mass, you could theoretically carry an efficient, powerful rocket and more fuel to feed it. Perhaps enough to overcome the top end limitations of the turbojet. I'm guessing it's not enough, but I may easily be wrong.

Another possibility would be bringing along some turbojets in order to make a weak RAPIER design still exceed Mach 1.

This might allow for heavier RAPIER designs that still hit the same open cycle limits with more fuel. Personally, I'm dubious about this. DV shortcomings are expensive in terms of payload fraction when your spaceplane is generating enough drag to make a fireball...

Best,

-Slashy

- - - Updated - - -

Are they?

I haven't had any luck with them. They just seem to act like more intake area for me...

turbos are better at lower mach numbers, and are also a little more efficient, but suffer at extreme speeds and become useless there. that said, the combos are i believe easier to work with, and you dont need as much diving profile anymore. That said, unles you absolutely need them, its extra mass and parts that are useless in space. A rapier (even if you use nukes and dont carry oxy) makes more sense, less part count, and at least in my opinion is very very similar in what its capable of.

As for the preecoolers, they have LESS drag then a nose mounted intake, and provide 40 extra LF to power your engines, but suffers from somewhat high mass for what it does (unless you want a structural element that is). it also pulls heat away from stuff very well and radiates it better then most other parts, but it is still not worth it unless you need more intake area, or want to use it as a structural element for appearance or whatever. i use it myself some for nuke mounts though, as it looks really cool when the nuke is clipped all the way inside and all you see is that much cooler jet engine look with blue flames coming out of it. But aside from cases where it looks pretty, it isnt quite a majorly useful part.

[Brotoro]

I'm confused. Are precoolers air intakes? I put mine BEHIND other air intakes. If they aren't air intakes, then why wiuld I care if they have less drag than an intake?

[Wanderfound]

I'm confused. Are precoolers air intakes? I put mine BEHIND other air intakes. If they aren't air intakes, then why wiuld I care if they have less drag than an intake?

They are intakes (stack-mounted, but radial-drawing: they don't need to be at the front of the stack), LF tanks and heat sinks.

[Brotoro]

They are intakes (stack-mounted, but radial-drawing: they don't need to be at the front of the stack), LF tanks and heat sinks.

Wow. I never would have guessed that. Are these supposed to represent some real technology?

[Wanderfound]

Wow. I never would have guessed that.

There's a price to pay for the multi-function: if you consider them just as intakes or just as LF tanks, they're heavy and expensive for what they provide compared to normal intakes and tanks. But when you put it together and add the heatsink property, they can become worthwhile.

[Matrix Aran]

So while I'm still catching up on most of this thread I thought I'd at least share some of my findings. The pictures are of my new Terra Block 1 craft, which I've set up as a crew transporter seeing as I've been running alot of LKO tourist runs lately. I've not equipped it to carry any cargo, just a small service bay to hide solar panels and batteries in which helps cut down on a bit of supersonic drag forces.

I chose the LV-T45 as an experiment to see if it could augment the turbojets as they trail off around 17km. Even with the large tails (I like having the option of pulling silly high G turns in the upper atmo and not flat spinning, sue me) it's reliably getting to a 200km orbit with about 430 m/s in the tank, with a simple point at 10 degrees pitch and hold it there ascent.

Not the world's best performance judging by what I've seen so far in this thread, but for a mid career craft, it's been very reliable.

[Kuu Lightwing]

Gilly is so tiny, you can basically ignore its gravity, and just assume one is in orbit of Eve itself (oberth from Gilly is a pitance, gravity drag from gilly is irrelevant)

Its semi-major axis is 31,500 km (ie, thats the average height from Eve).

So... going here: http://alexmoon.github.io/ksp/

Selecting Eve orbit, 31,500 km as the start, and Moho as the destination:

Ejection ÃŽâ€v: 2,355 m/s

Insertion ÃŽâ€v: 1,531 m/s

Total ÃŽâ€v: 3,886 m/s

3886 is much better than going to Moho from LKO (5031)

However, if one were to fill up at minmus, drop PE down just above kerbin, and then do the burn, the difference would be much less than the 1,145 calculated here.

It also depends somewhat on where gilly is in its orbit as you depart - ideally you'd want to leave gilly at apoapsis, so you can cheaply bring you PE down right above EVe's atmosphere and have a higher speed when you do the burn... but then the launch window is more complicated.

If you have ISRU at gilly and moho, you can go to moho and back with a craft that only hasa dV capability of 4km/s

Thanks! That's still quite a lot though... And for "safety" reasons it would be better to have about 4,500 dV... Yeah, Moho seems to be difficult