Looking for some Evaluation of this Spaceplane...

[KerbalGuy777]

Hello... I've been working on designing a simple mk2 cargo SSTO. This is what I've come up with so far after some testing: 

https://flic.kr/ps/3UDUwU

It's got good balance, the center of lift stays just behind the center of mass. I've been able to get it to LKO with a max of ~700 m/s of delta-v.  Does that look about right? How much delta-v should this have once in orbit? Also, does anyone notice any design flaws? How could I make it better? Anything I should work on? Any feedback would be great!

PS: Also if anyone could help me, the link above, I tried to click "insert image from URL", but it wouldn't convert the link? Not sure how to paste pictures here. Bran-new to the forum here. 

 

Edited November 1, 2020 by Vanamonde
Fixing link.

[DeadJohn]

If it gets to orbit then it's good

You asked if 700 m/s DV after reaching LKO is "right"? It depends on what you want to do with the plane. Your design looks good for gathering science (you seem to have plenty of cargo space for Science Jr, Goo, and smaller instruments) and for deploying 1.25m satellites. If it flies well, reaches orbit with enough DV for your mission, and can safely deorbit and land, then it's "right".

• Did you get 700 m/s with cargo or empty? Test with the heaviest load you plan to use. Cargo bays so far forward can sometimes force compromises as the balance changes between full vs empty. As an alternative you could swap the cargo bay and a fuel tank; that might also keep the plane more evenly balanced as fuel drains.
• Consider adding a small solar panel on the upper surface of a tank. It will let you keep batteries full during extended length missions.
• If you need to do any docking with this, add a shielded docking port on the upper surface, plus RCS. Radial docking can be tricky, though, As an alternative you could try the other mk2 midbody cockpit, mk2 to 1.25m adapter, and a shielded docking port on the nose.

To show images here you need to provide a link to the file, typically ending with ".jpg" or other formats. One way to do that is to click Flickr's Share button, then click Embed, copy the relevant part of the code, and paste just the link here. For example, your photo's Embed gave me this:

<a data-flickr-embed="true" href="https://www.flickr.com/photos/190856719@N02/50552266403/" title="screenshot329"><img src="https://live.staticflickr.com/65535/50552266403_3dac49d3d7_c.jpg" width="800" height="450" alt="screenshot329"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

I pasted only the highlighted portion into this post and the forum immediately recognized it. I could have pasted it into "Insert image from URL", too.

 

 

 

[KerbalGuy777]

Thanks  DeadJohn for your reply!

8 hours ago, DeadJohn said:

You asked if 700 m/s DV after reaching LKO is "right"? It depends on what you want to do with the plane. Your design looks good for gathering science (you seem to have plenty of cargo space for Science Jr, Goo, and smaller instruments) and for deploying 1.25m satellites. If it flies well, reaches orbit with enough DV for your mission, and can safely deorbit and land, then it's "right".

Thanks! I was just wondering if looking at it, that seemed about right, 700 m/s left in orbit, or should I be able to get it to orbit with more. I was worried because 700 m/s left of delta-v is with a EMPTY cargo bay, with no satellite. I'll test and see how it goes with small sat, but just was wondering if I was flying it efficiently.  But yea, it's a good plane XD

 

8 hours ago, DeadJohn said:

Did you get 700 m/s with cargo or empty? Test with the heaviest load you plan to use. Cargo bays so far forward can sometimes force compromises as the balance changes between full vs empty. As an alternative you could swap the cargo bay and a fuel tank; that might also keep the plane more evenly balanced as fuel drains.

700m/s is with an EMPTY cargo bay.  I'll test it with a satellite and see what I get. I need to get to orbit with enough fuel to at least dock with a refueling station. I'll try swapping the bay and tank if it get's unstable with the satellite. 

 

8 hours ago, DeadJohn said:

If you need to do any docking with this, add a shielded docking port on the upper surface, plus RCS. Radial docking can be tricky, though, As an alternative you could try the other mk2 midbody cockpit, mk2 to 1.25m adapter, and a shielded docking port on the nose.

Will do! I'm trying to get the sat-launching ability right and de-orbit/landing, then I'll see about the docking   thanks for the info about pasting pictures here as well. 

Edited November 1, 2020 by KerbalGuy777

[jimmymcgoochie]

I see only rocket fuel Mk2 and 1.25m fuel tanks and no liquid fuel only tanks for the jets; to me that suggests that you're either carrying excess oxidiser, which is heavy and reduces your delta-V, or are removing oxidiser from some of the tanks, which is inefficient.

I suggest swapping those FL-T800 tanks in the wing roots for Mk1 LF tanks and engine nacelles with the jets on the back of the nacelles and plain old nosecones on the front; adding reaction wheels and/or inline batteries isn't a bad idea either. Get rid of the cockpit completely and replace it with a Mk2-1.25m adapter and a shock cone- one shock cone is more than enough for a pair of Whiplash jets especially with those nacelles I just mentioned to help it out at low speeds, and the extra fuel mass at the front will balance the removal of the cockpit.

I would also rearrange the fuselage sections to be drone core > short fuel tank > cargo hold > long fuel tank, which will help to balance the plane whether it's carrying a payload or not and regardless of how much fuel you've burnt. Weight balance is important for planes because if the centre of mass (CoM) moves behind the centre of lift (CoL) then the plane becomes very unstable and easily flips backwards- just like those little styrofoam gliders or an archer's arrow, mass at the front keeps it pointing the right way.

I also suggest that you either add some airbrakes or configure your elevons to deploy in opposing directions with the brake (or abort) groups to help it slow down in flight.

One more thing- do you need that MechJeb thing on the back? In my experience any probe core (including the Mk2 drone core) has all the MechJeb features (that you've unlocked, if playing science/career modes) integrated into it already so that part is unnecessary. Replace it with a retractable solar panel and add a second solar panel on the top side near the nose, which between them will cover most angles- just make sure the plane doesn't spend too long with its belly towards the sun or you'll run out of power; adding solar panels to the underside is a bad idea as they'll easily cook during re-entry.

[KerbalGuy777]

Thank you jimmymcgoochie!  I'll implement your suggestions and see what I come up with. 

 

[Vanamonde]

I went to your link, then copied the URL from the top of that page into your post. You shouldn't need the insert image method. 

Your plane looks fine to me. In fact, it's better than most of mine. Anyway, I have also moved your post to the craft sharing subforum, and congrats on your plane.