Best engines and fuel tanks for a simple vssto rocket?

[nascarlaser1]

Hi guys!

The title is my question. I want to build a simple vssto rocket for my Kerbals. It does not have to go past Kerbin orbit, I just want to learn about them. What is the best engines and fuel tanks to use for it?

 

Thanks!

[foamyesque]

Depends on how many kerbals you want to launch and whether you're in career or not. If you're just interested in putting a single Kerb into space, use the Mk1 pod, some 1.25m tanks (-8 for the bulk of it, smaller ones to tweak the fuel count), and a Swivel engine.

[Aegolius13]

The Vector might be a good choice due to good TWR and ISP.  But only makes sense if your ship is fairly big, like if you use the three person capsule.  It's expensive, but that doesn't matter much if you intend to recover.

The Dart also seems like an option, but lack of thrust vectoring could be an issue.  

Fuel tanks - there's not too much of a difference.  I'd just figure out how much delta v you need to get to orbit and build from there. If you can get by with all 1.25m parts, that may improve your drag a bit.

[SchwinnTropius]

A Twin Boar and two orange tanks can get up to 25 tons to LKO if flown correctly, although it may be difficult to get enough crewed parts together without it looking awkward.

[nascarlaser1]

Thanks @SchwinnTropius, @Aegolius13 and @foamyesque!

If it helps I am going to try either the mk2 or the mk3 cockpit, and I am in sandbox.

[Aegolius13]

I am a bit confused - are you going with wings and a glider landing (like a space shuttle orbiter with its own fuel tank), or going for a rocket-style that just does not stage?  Guessing the former based on spaceplane parts.  

Anyhow, if you are going rocket-style, the Mk 2 parts generate lift and can be a bit squirrely in verticule launches.  The cylindrical rocket parts tend to be more stable.  But if you're going with wings, obviously you want lift.  

In any event, I suspect that if your craft is Mk 2 or larger, the Vector is the engine for you.  If not enough power... use the bicoupler and add a second one   After all, it is based on the space shuttle engines.

Edit:  Combo of vector and a couple darts is an option too.  You could turn off the vector when the thrust is no longer needed, to benefit from dart's higher ISP in vacuum.

Edited August 19, 2016 by Aegolius13
Added another option

[Plusck]

Assuming you also want to get back to solid ground in one piece:

1.25m parts: parachute, Mk1 pod (monoprop removed), heatshield (with ablator reduced to about 1/4 of the total), stack decoupler, 1x 800 tank, 1x 400 tank, 1x 200 tank, 4x fins (elevon 4s), Swivel.

This will only just get to orbit with careful flying. It's hard to do a VSSTO in 1.25m scale since there are no better rockets with gimbal (not including the Vector, which isn't really intended to be put on a single 1.25m stack and is extremely difficult to control if you do).

2.5m parts: parachute, Mk1-2 pod (monoprop removed), heatshield (with ablator reduced to about 1/4 of the total), stack decoupler, 1x 64 (orange) tank, 1x 32 tank, 1x 16 tank, 4x fins (AV-R8s), Skipper.

Again, that is quite close to the minimum. The advantage with 2.5m parts is you have a lot more leeway. You could make that 2x orange tanks instead and it should be fine. I can't remember what the Mainsail will lift but it can certainly lift three orange tanks (and that's really about as tall as you want to go).

3.75m parts: I don't know what to suggest really, since I rarely use them.

Since you're wanting a single stage to orbit, then any combination of stacks following this basic principle (i.e. a minimum of 1.75 x the tallest tank on top of a reasonably efficient engine) should do. Obviously if you combine different engines, they will run out of fuel at different times, but this is something you can work out with a calculator if you reeally insist on the SSTO part of the requirement. If the aim is just to practice flying, start with the smallest rockets and work up.

Edited August 19, 2016 by Plusck

[GoSlash27]

Nascarlaser,
If you can give me a payload mass you wish to SSTO, I can give you a recommendation for the engine and tanks.

Best,
-Slashy

[Firemetal]

I haven't built VSSTOs but I am sure @NSEP can help you.

[foamyesque]

@nascarlaser1: Please clarify on the kind of SSTO you're after. I was operating on a simple and straight forward rocket SSTO design, with no provision made for landing or recovery.

[Aegolius13]

Just played around a bit with VSSTO concept.  One Dart plus two FL-T800 tanks can get a Mk 1 capsule and batteries/chutes/probe core to LKO with about 700 delta-v left over.  It even starts with a nice reasonable 1.4 TWR.  Despite the lack of thrust vectoring, the capsule's reaction wheel was enough to keep the rocket straight without the need for fins.  (Hold prograde and keeping fuel forward also helped).

I used chutes to do most of the final brake, but it might even be possible to pull of a fancy Falcon-style powered landing.  

Only problem is the Dart is so pointy, I needed a rocket holder on the launchpad.  And as soon as it landed tail-first, the thing fell over and broke in half.  Sigh.  Next time I'll mash the "recover" button.

For the 2.5m size, 1 Mk 1-2 capsule, 1 orange tank and 1 Skipper gets you to orbit with a similar ~700 delta-v.  Looks like the Vector is overkill for this payload.

Edited August 20, 2016 by Aegolius13

[magnemoe]

This is my workhorse for crew transfer, its not an true ssto as I jetison 4 small hard points and basic fins once out of atmosphere 

3 aerospikes, the small service bay store probe, mechjeb, kas and parashutes, it also act as an airbrake on return. 
I lock the fuel in the top tank until bottom start to run dry to keep center of gravity high. 

[nascarlaser1]

15 hours ago, foamyesque said:

@nascarlaser1: Please clarify on the kind of SSTO you're after. I was operating on a simple and straight forward rocket SSTO design, with no provision made for landing or recovery.

I want a rocket that can bring 2-3 (either the mk2 or mk3 cockpit) Kerbals to orbit around Kerbin in 1 stage. I will be using parachutes for landing since my last powered landing ended in complete and utter catastrophe. It doesn't even have to have science on board. I am trying to build a basic space station without any help, and this will be 1 of 3 crew ferries.

[GoSlash27]

nascarlaser,

 The ideal rocket will depend on exactly how much mass you're taking up. Could be anywhere from 2.1 to 4.3 tonnes, depending on which option you choose.

2.1 tonnes is a Skipper with 1 X200-8 and 1 X200-32.

4.3 tonnes is the same with an additional X200-16.

Best,
-Slashy

[nascarlaser1]

14 minutes ago, GoSlash27 said:

nascarlaser,

 The ideal rocket will depend on exactly how much mass you're taking up. Could be anywhere from 2.1 to 4.3 tonnes, depending on which option you choose.

2.1 tonnes is a Skipper with 1 X200-8 and 1 X200-32.

4.3 tonnes is the same with an additional X200-16.

Best,
-Slashy

ok thxs!

[dire]

@magnemoe would you be able to shave off a half a ton if you changed your 2.5 to 1.25 adapter into a 2.5 to mk2 adapter and switched out the hitchhiker for a mk2 passenger module? Then I guess you'd need the mk2 to 1.25 adapter, so your net weight savings might be pretty minimal.

[magnemoe]

1 hour ago, dire said:

@magnemoe would you be able to shave off a half a ton if you changed your 2.5 to 1.25 adapter into a 2.5 to mk2 adapter and switched out the hitchhiker for a mk2 passenger module? Then I guess you'd need the mk2 to 1.25 adapter, so your net weight savings might be pretty minimal.

Sounds smart, an added benefit is that the MK2 passenger cabin is far more sturdy than the hitchhiker.