SSTO Troubles

[funk]

As some already mentioned it's depending on payload, engine combination and fuel fraction. It's possible, sure, but it's inefficient, because you've to take a lot of dead weight with you (rapiers, empty fuel tanks etc). So for my career I usually bring heavy payload to orbit, which can fly by its own or will be pushed by a refuelable interplantery stage.

[AaronLS]

Here's one I was playing with tonight that can escape Kerbin with a Mun gravity assist with lots of fuel to spare. As you can see I brought way more oxidizer than I needed, as it's only use to establish initial orbit. So that's weight that could be used for LF. Not sure why engineer wouldn't tell me remaining delta V (probably my fault). In the SPH I juggled fuel around and estimated the deltaV after obtaining LKO is around ~2000-2500.

I brought a 25t payload in the cargo hold on one test run, so that could be a huge additional fuel for the Nerva if you wanted.

I never use the cockpits. Use a protobododyne inside the cargo bay. If I want to carry kerbals use passenger bays, command seats, or the smallest one seat lander can inside the cargo bay(if you need crew report capability). Had to add a large reaction wheel as well, and disable engine gimbals as they were confused being so close to CoM. I like engines near CoM because the empty plane will be more balanced.

I only use 4 rapiers cause that's all that's needed to finalize orbit. The rest are ramjets and one nerva. Multiple nervas are often bad because they are heavy. When people use multiple nervas, it's usually because they need extra thrust in limited situations. For those scenarios the rapiers will do.

During ascent I run them all and get up to 1300m/s @ ~20k. When I've gotten my apoapsis to ~60k, I'll shutoff the rapiers and only run the nerva for rest of ascent. The nerva isn't enough to circularize, so once I get up to 70k rapiers are turned on again to help circularize.

After I have an orbit, going anywhere else only uses only the nerva. I would never use multiple nervas because they are so heavy. There are only a few situations where you need

One way to use this is to get a payload "half way there", i.e. burn to establish the escape, then release the cargo/probe to continue on it's way. The spaceplane can burn slightly retrograde to stay in Kerbin SOI, and adjust it's periapsis to do airbreaking on return. You can do this same maneuver alot more efficiently with a tug though.

[Goddess Bhavani]

Really nice work, PK! For non-Rapier SSTOs (planes or otherwise) I've had the most success with a turbojet/ aerospike combination. You may also need to experiment with the type/ quantities of air intakes. The ram scoop takes in a lot and the shock cone seems to reduce drag.

One of my favorite "should have been" spacecraft is the Pan Am Space Clipper. With or without the closed wing, it would be cool!

Thank you!

I did go into space after all with this design, after manually adjusting the thrust vector for the rocket engines to point slightly upwards, I guess to counter Mach effects or dynamic CoM changes during pitched up flight. Lesser trim / control surface deflection may have a play in reducing induced drag on the craft, while not wasting time below 20km after accelerating past the point of peak ramjet thrust means I don't waste fuel cruising on the thirsty turboramjets.

I was surprised to see I had 500 Oxidizer left and a bit of excess LF to limp home to an airport after re-entry.

[Val]

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Multiple nervas are often bad because they are heavy. When people use multiple nervas, it's usually because they need extra thrust in limited situations. For those scenarios the rapiers will do.

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http://images.akamai.steamusercontent.com/ugc/445080477298068455/24D17E430DAC3B0F2A5A57C2F90D49461659B2F0/

http://images.akamai.steamusercontent.com/ugc/445080477298067324/47FCECC20024F0FF1D1BA59998A9248263E47616/

http://images.akamai.steamusercontent.com/ugc/445080477298068162/B34D781DA4C032C1645B2F9CBF7B49992E1B3764/

Thanks for the inspiration. I liked the look and concept of your drone transport, especially that last picture, so I created my own.

It's very similar to yours, but has a shorter cargo bay, because otherwise I couldn't get the wet and dry CoM to balance with and without cargo. The tail is also slightly different, because I have 2 side-mounted Nervas, and they'd singe the tail if I made it like yours. And I only have 2 Turbo Ramjets, a bit less wing area and some oxidizer was replaced to make more room for Liquid Fuel.

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Craft file

[Val]

I managed to make a version with a large Cargo Bay, too. Same performance.

Craft file

[KerikBalm]

I just updated to 1.04 and tried out my SSTO for lifting oversize payloads.

I was sticking around with 1.02 because I had put in quitea bit of effort to career mode, and I didn't want to screw up what I had going... in particular an Eve probe at the limits of 1.02 reentry heat - and a lot of things to do* before that probe arrived.

Well, I got all that done, and now I can compare a SSTO before and after the changes.

Before the changes, I had a SSTO that was ~400 tons on the runway, lifting a 101 ton payload (a Duna science station+fuel depot full of fuel maximum width equal to a mk3 fusalage with a 2.5 meter tank on each side... basically 8m wide) to orbit with 46 tons of fuel left inside the SSTO after detaching the payload.

After updating to 1.04, I took the same SSTO with some minor changes (re-made the payload fairing). Apparently taking off the payload and putting it back on messed up the fuel tank settings (or I hadn't saved the changes), because I had a little engine cluster at the back of the payload that redocks with the ssto after payload release... and it didn't work right, the darn rapier drained the fuel from it (I really wish there was a way to change that "drain from everywhere thing, or use action groups to toggle a tanks fuel flow state). My more efficient aerospikes ran out of fuel, although I was able to keep the LV-Ns going. After rapier cutoff I was able to make use of the aerospikes a bit but fuel transfer.

There were also some minor piloting mistakes... anyway, I got the same payload to orbit, but this time with only 31 tons of fuel left on board the SSTO.

Adding leftover fuel to the payload, and ignoring the other mistakes... 147/132 = 1.11... my SSTO was 11% better in 1.02...

Since it got me cool turboramjet effects, and the ability to use nukes without making my entire ship glow red, I'll take it (plus it "feels" more realistic now).

Due to a glitch with the fairing bumping into the payload preventing timewarp(and making the status seem to be landed or moving over the surface), and an evaing kerbal that was meant to bump the fairing away but instead got flung off kilometers away from the craft, and then the craft being completely unresponsive when I switched back to it... I was not able to test re-entry.

Anyway, my SSTO that worked in 1.02 achieved orbit in 1.04 with the same payload it did in 1.02, on the first try... so I'm pretty happy

* lift all my Duna colonization supplies, send them on their way - involved using LV-N tugs and orbital rendevous + multiple aerobraking passes of the tugs to pick up new payload, refuel tugs at Minmus or Mun fuel depots, ISRU to maintain those, launch probes to Jool during the launch window which opened in the meantime, train up a crew of 3 male and 3 female 3 star kerbonauts (1x sci pilot engineer each) to go to the Duna colony... etc

[AaronLS]

I managed to make a version with a large Cargo Bay, too. Same performance.

http://i.imgur.com/XknPAtK.jpg

Craft file

Nice job. I figured it'd need a good bit of tweaking before it was production ready.