Early SSTOs + Flight Plan

[almagnus1]

So, how much of the tech tree does one need to unlock before making SSTOs is possible?

Also, what's the basic template for flying an SSTO now that the atmosphere has the proper viscosity.

Edited May 5, 2015 by almagnus1

[capi3101]

You'll want Turbojet engines before a traditional KSP spaceplane becomes a possibility; the Basic Jet engine won't get too much above 300 m/s. You'll want to get up to about 20 kilometers as quickly as you can, then level out and begin your acceleration run. At about Mach 4 (somewhere between 1,200 and 1,300 m/s) and at least 30k, switch on your rockets and keep the jets going for as long as you can run them. Spaceplanes with the new soup behave similarly to the way they did in FAR prior to 1.0, so they'll take some getting used to. Expect a new plane design to want to fly backwards the first few times you try it out, and then try to move the Center of Mass towards the nose. Try to balance the plane's fuel load so the CoM's position doesn't shift a whole lot.

1 Turbojet and 100kN of rocket per 10 tonnes, .01 intake per jet, 40 units of both Liquid Fuel and Oxidizer per tonne of plane. When you get RAPIERs, its the same except it's one RAPIER per nine tonnes of plane. Wing-wise, you want enough that your takeoff speed is not much slower than 100 m/s; if you can take off earlier, you'll have too much drag ongoing when you get up to switchover altitude. 125 is optimal, IMHO. I generally base the wing I need off of the mass of the plane and the length of the fuselage; that's a fairly complex set of formulas though. Plan for roughly a 15% payload fraction, the payload being pretty much anything you stick in the fuselage itself.

SSTO rockets...those can be done pretty much repeatably by the time you've got ahold of the LV-T45 engine; they're possible (though tricky) with the LV-T30. Start a pitchover around 5k such that you're at 45 degrees at 15k, and then pitch down to 20 degrees when you're at least 35 seconds to Apoapsis. Hold it there until you're 45 to Apoapsis, then drop to 10 degrees. With 55 seconds to Apoapsis, you want to be burning along the horizon. You'll need somewhere between 3500-4000 m/s of delta-V to make orbit this way, depending on how well you fly it.

Edited May 5, 2015 by capi3101

[eddiew]

...You'll want to get up to about 20 kilometers as quickly as you can, then level out and begin your acceleration run. At about Mach 4 (somewhere between 1,200 and 1,300 m/s) and at least 30k,...

Apologies, capi, but turbojets won't make 20km or 1200m/s anymore, they'll likely fizzle around 18-19km at 1000m/s and you definitely can't make 30km before they die. You've listed a flightplan for 0.90 FAR rather than nuStock 1.0.2 aero

For a stock 1.0.2 spaceplane, turbojets and LV-T45s are enough. Best flight plan involves taking advantage of the raw power of turbojets at low-mid altitudes and essentially take a run up around 10-12km and fling yourself into a ballistic trajectory. It takes a few tries to gauge the right altitudes and speeds for any particular design, but ultimately you want to be passing 19km at about 1km/s on a 20-30 degree ascent. Depending on your TWR, you may have to level off a little around 10-12km and build up speed first, or you may just be able to go for it right off the runway.

It's not too hard to get your turbos to launch you up to 45km with an aggressive ascent, which is a good place for your LV-45Ts to be taking over

[capi3101]

Apologies, capi, but turbojets won't make 20km or 1200m/s anymore, they'll likely fizzle around 18-19km at 1000m/s and you definitely can't make 30km before they die. You've listed a flightplan for 0.90 FAR rather than nuStock 1.0.2 aero

Well, turdbiscuit then. I knew I didn't like the new stock aerodynamics very much...now I've got more reason to switch back.

[Wanderfound]

Turbojets allow much better spaceplanes, but they aren't strictly necessary. You can do it on basic jets, lighting the rockets when the basics conk out. Takes a lot more oxidiser, though.

OTOH, while basic jet spaceplanes are possible, they're very rarely worth the hassle. Charge for the turbos if you want to do anything serious with wings,

[Kosmo-not]

Command pod + parachute

decoupler

stack of fuel tanks

LV-T45

That should do it.

[Slugy]

Command pod + parachute

decoupler

stack of fuel tanks

LV-T45

That should do it.

The simplest approach is often forgotten

If making a spaceplane, and using jets, speed is key (as eddiew said) to get the thrust up - even if that means climbing and then diving to build speed and thrust before a desperate pitch up on your way to space!

[eddiew]

Well, turdbiscuit then. I knew I didn't like the new stock aerodynamics very much...now I've got more reason to switch back.

It's actually not that bad What it's not good at is letting you have any fuel when you get there.

The SSTO showcase thread has been coming up with some pretty good solutions, though the overall consensus is that in-orbit refuelling is pretty much mandator if you want your SSTO to go beyond LKO. There's a few people seemed to have pulled off Mun/Minmus, but I've not seen any Duna or Laythe round trippers yet.

If you really hate it though, nuFAR is already available as a development build, but you'll have to do without the calculations window because most of it just reads infinity or null right now From a brief excursion with it, I found that it made bi-rapier planes work again, but felt very... slippery. Every touch of controls seemed on the brink of putting my plane into a pancake spin. That might just have been lack of a calculations window however - maybe it was actually a really bad design!

- - - Updated - - -

If making a spaceplane, and using jets, speed is key (as eddiew said) to get the thrust up - even if that means climbing and then diving to build speed and thrust before a desperate pitch up on your way to space!

Climb and dive can definitely work with rapiers, which have lower power delivery at low speeds and can struggle to break the mach threshold. Certainly most rapier craft need to fly level to get the speed going, unless they're conspicuously overpowered later in the flight.

Turbojets really deliver a lot of oomph at mach 0.95 though and as yet I've never had problems getting them up to speed Even 1 additional turbojet supporting 4 rapiers on a 50 ton plane (see spoiler above) is enough to make a build go from useless to a powerful beast that nearly tears itself apart in a rush to get out of the atmosphere.

[Kagame]

My definition of SSTO is merely that it take a single stage to get into orbit. Which means that you basically only have to unlock decouplers, LVT-400s, and the Reliant. xD