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Delta-Cheese

I need a SSTO 101 class

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Hello! I am currently working on some SSTOs, the only problem is I have no ideia what I'm doing...

What I really want is a rocket/spaceplane that can carry probes in to orbit, fuel for stations, or small station parts in a very efficient manner (meaning I can return it). How do I do this?

Please, if possible give me a little SSTOs 101 class. What do I need for a SSTO? And how should I fly it? After that I shall work on a actual SSTO and I will post the picture here to see what you guys think!

Ignore all english mistakes please...

And may the power of cheese be in your favor!

Edited by Delta-Cheese

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Spaceplanes are fun.

-Use MechJeb or KER for Delta V readouts. If you want to LKO(70x70 orbit), you want 2.3km/s of Delta V with ONLY rockets.

-Try RAPIER engines for your first one. They give quite the thrust at altitude.

- For the first few flights, have small cargo, getting bigger until you can't make orbit.

Flight:

This is a universal rule. Pitch according to engine thrust. If you're seeing that (airbreathing) engine thrust is declining, pitch down. Pitch up so as long as you are still accelerating. At around 10km in altitude, make sure to stay level(ish). In this altitude of the ascent, you need to milk as much speed as possible from your engines. After thrust begins declining, wait until you're speed starts to lose acceleration. When that happens, activates rockets and continue ascent as if your a rocket that did an early gravity turn.

Reentry: Don't go in nose-first. Do whatever to bleed speed before you get in the thicker air.

Looking forward to see your designs!

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SSTOs 101

Some general pointers:

  1. Less is more, MOAR BOOSTERS will not help you here
  2. Use your action groups, manual switch your rapiers and close all intakes when in rocket mode
  3. Struts and fuel lines are not your friends, fuel lines are unnecessary for jets and rapiers anyway
  4. If it isn't doing 100m/s as it passes the control tower, I doubt it's going to orbit today
  5. Airbrakes are worth their weight in gold, oriented correctly they are invaluable for keeping the center of drag to the rear and the nose up during reentry
  6. DO NOT spam intakes, use only one ram or shock cone per airbreathing engine

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There are some good tips above, but to add to that:

1) Minimize drag. This really matters for a space plane since your main challenge is breaking the sound barrier. Every stack should start with a shock cone, and end with an engine.

2) Minimize engines. Atmo engines are dead weight in space, so if you want to go anywhere beyond LKO you want to keep it to a minimum (if you do not need to go beyond LKO it instead increases payload fraction.)

3) Read some guides. Goslash in particular has some good information on appropriate lift and such if you look around.

4) Carry a small amount of lf + O even with a nuke powered plane, a burst from the rapiers on stored oxygen does wonders for getting your AP up.

Flight profile is:

1) Best pitch where you are still accelerating until you are at 10k to 12k

2) Level off and get to the point where you are no longer accelerating.

3) If you have not yet broken the sound barrier, dive a little bit to get there (which is what the 12k is for, it lets you break mach 1 while diving slightly.)

4) If you still do not get there, temporarily turn on any extra engines (like nukes) to get a little extra thrust (even RCS if you have it, this is the hard part which you should throw everything you have into.)

5) Start a minor climb once you are rapidly accelerating.

6) Accelerate to at least 1000m/s on air, you want to be closer to 1200m/s if you can manage it. As you near top speed turn on nukes if you have them.

7) Pitch up a bit, when you start slowing down pitch up more and switch to stored oxygen (until it runs out if you have nukes, enough to hit your desired AP if not.)

8) Circularize.

Reentry is simple with wings even without airbrakes (I do not use them, and never have problems.) You should be at maximum pitch up, let drag level you out against all forces you can muster (unless you are not suffering heat much and want to reenter faster, which I do in most cases to save time.)

Also, to reiterate what was said above as it is super important. NO STRUTS. Do not even think about it until you can easily make an SSTO and are building something very heavy.

Edited by cerberusti

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What's so bad about struts?

DRAG IS THE KING!!! Struts cause significant drag --> struts are inefficient.

(Also low part count is quite important since game performance is quite bad...)

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Now for an ascent profile:

  1. Go supersonic shortly after takeoff
  2. Pitch up into a 25° to 30° climb and maintain about Mach 1.1 to 1.5
  3. At about 7 to 10km, pitch down until your prograde marker is at 15°
  4. Set throttle to full, and hang on to your buttcheeks
  5. You will breach 19km at well over 1200m/s
  6. Engage rockets or switch mode on your rapiers
  7. Pitch up to 20° and burn until AP reaches target

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Air breathing engines (as well as RAPIERs in rocket mode) drain fuel evenly from all tanks, regardless of crossfeed or staging. What this means is that you don't need any fuel lines anywhere ever and that fuel will drain from your payload if you have any, so be sure to lock your payload fuel before launch!

Also if you are having trouble landing if you land on the field next to KSC, you get 98% recovery for a much much easier landing.

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Sure? It seemed to respond pretty well.

I'm only going on my recent experience in building my first SSTO spaceplane. At 20km and 1200m/s I started to lose control, with the craft wanting to go into a flat spin and then backflip. It was solved by the addition of forward canards (pitch) and a much larger tailfin positioned further back (Yaw).

If that's not your issue, then where are you struggling? Not enough dv?

- - - Updated - - -

Sure? It seemed to respond pretty well.

I'm only going on my recent experience in building my first SSTO spaceplane. At 20km and 1200m/s I started to lose control, with the craft wanting to go into a flat spin and then backflip. It was solved by the addition of forward canards (pitch) and a much larger tailfin positioned further back (Yaw).

Note: small active fins can work well until the air gets thin. but larger fixed fins will still work.

If that's not your issue, then where are you struggling? Not enough dv?

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To me, it looks reasonably OK, but I would get rid of those large landing gear. They create a lot of drag. You should also mount the gear right below CoM. It'll make it easier to rotate for lift-off and eliminate any tendencies to veer off the runway.

I can't see how much fuel you have. Might be too little, compared to the total mass of the craft.

There are some really great tips if you read through these threads:

SSTO cookbook.

"simple" rule to build spaceplanes?

Hope that helps.

5cUhiOG.png

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I recreated the craft as best I could from the pictures. And I found a few more things.

  • As RCgothic mentioned the tailfins need to be further back.
  • I can see from the Mass, ~18 t, that you didn't put any fuel in the wings.
  • It'll be much easier get off the runway and fly if you move the CoL closer to CoM.

My version (Craft file) has the small landing gear, so be careful when pulling up from the runway and when landing.

Javascript is disabled. View full album

Launch Instructions

  1. Full throttle, SAS, and Stage.
  2. At 100 m/s lift nose 5° and let the craft lift-off.
  3. When clear of the runway pitch up to 15° and set 2/3 throttle.
  4. At 10 km set Full throttle again.
  5. At 22 km switch RAPIER mode. Press 1
  6. At 30 km start following the prograde marker.
  7. When AP is above 80 km, cut throttle.
  8. Coast to space and circularize.

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  • I can see from the Mass, ~18 t, that you didn't put any fuel in the wings.

I didn't put any fuel in the wings because it never got used (ran out of oxidizer)

My problem was (I think) not enough delta-v, but it may just have been very bad flight skills...

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...

My problem was (I think) not enough delta-v, but it may just have been very bad flight skills...

Your craft is probably more hampered by the big landing gear, than by piloting skills. They have too much mass and drag for a craft that small.

And I'm a bad pilot, too. I don't actually fly the crafts I make. MechJeb Smart A.S.S does. All I do is set throttle, enter what pitch I want and click on Execute. You can see it in the upper right of my in-flight screenshots.

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Hey there, Delta-Cheese--I'm certainly no SSTO expert, but I do like building them and I've gotten all kinds of designs into orbit, so maybe my 2 cents will be helpful? Anyway :) I'm looking at your pictures, and here's what I see.

1) You don't have nearly enough fuel (delta-v). It looks like from the posts you've got this pretty much ironed-out, but my personal rule of thumb in my spaceplanes is about 4-6 km/s dV in the jet engines or airbreathing with dual-cycle engines, and somewhere between 1-3 km/s dV for rockets or closed-cycle mode. KER is a little janky right now, but still pretty good at predicting how things will work. What you want to do is first, set your engines to atmo mode and get enough fuel to hit those numbers. Then, switch your engines over so KER reads them as rockets and add enough fuel to hit the numbers for closed-cycle mode.

2) You have a TWR >1. Not a problem, especially if you're bringing up big cargo SSTOs, but ever since 1.0 and the aero model actually starting to make some sense, you really only need a TWR of around .4-.6. I think my super-heavy cargo SSTO I'm working on has a launch SSTO of about .47. Basically what I'm saying here is you can pack in the fuel without consequence.

3) Like other posters have said, I'm not quite sure how the medium and large landing gear really rate on SSTOs...they're really over-massed for their size, IMO. I'd recommend getting B9 Aerospace--even if it's just for the landing gear, because it really works well in just about any situation, with lots of variance for any kind of craft.

4) You're using the wrong intakes--those radial intakes are great for basic planes and jets, but when you have high-speed, high performance jet engines and SSTOs, you're going to want to use the Structural Intakes, Ram Air Intakes, and Shock Cone Intakes to maximize performance.

5) Question: Are you closing intakes when you switch to rocket mode? That will seriously cut down on atmospheric drag higher up.

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Classic DeltaV problem, it happens to the best. Later, I'll be recording a vid

on building SSTO's.

By the way, try to aim for 2km per second of rocket deltaV. That's enough even for the shallowest of ascents.

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Got to orbit :D
That is great news. Gratz :D

Do you have any pictures to share of this joyous event?

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That is great news. Gratz :D

Do you have any pictures to share of this joyous event?

Unfortunately no... I installed EnvironmentalVisualEnhancements and my screenshots apparently don't work anymore...

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After seeing this thread, I started tinkering around with ssto's.

i have found that the ideal twr for air-breathing/nuke craft to be around 1.5/.54 to make orbit.

I have found these craft to be ideal as you can easily get to LKO with 2.5k ms remaining.

Any one have any twr stats that you find ideal? I'd like to hear what others think.

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After seeing this thread, I started tinkering around with ssto's.

i have found that the ideal twr for air-breathing/nuke craft to be around 1.5/.54 to make orbit.

I have found these craft to be ideal as you can easily get to LKO with 2.5k ms remaining.

Any one have any twr stats that you find ideal? I'd like to hear what others think.

When do you measure TWR for airbreathing engines? At what speed and altitude? I'm never really sure. I prefer using launch-mass per engine, as I find that less unambiguous.

I usually make my designs with target of 25 t / RAPIER, but I've gone as high as 34 t, and as low as 10 t.

For TWR in orbit I don't really set any specific targets. I do try to keep it above 0.25, but 0.5 is less tedious on interplanetary burns.

There's a bunch of RAPIER-Nuke discussion and designs in the SSTO to laythe and beyond thread.

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