Is the Kerbal X still so capable in Latest KSP (1.1) version

[Orc]

Hi all

 

Recently started playing the full version of the game. In my search for more economical ways of reaching the Mun and beyond I took a ride on the Kerbal X (See:  http://wiki.kerbalspaceprogram.com/wiki/Kerbal_X ).

 

The wiki page says it should be possible to get the Kerbal X to the Mun's surface and back home if you are careful with your fuel. I thought I was a reasonably decent pilot. Maybe I'm not. The best I can do is to get the Kerbal X lander stage back into Mun orbit before the fuel runs out. Even just orbiting the Mun can be challenging. I've modified the design to free up a little extra mass (swapped out the  LV-T45s with LV-T3s saving 1.5 tons) and changing the Mk2 capsule for a Mk 1 (saving about 3 tons). The best I could do with that design was get the capsule back into Kerbin orbit (and not a stable one, the Mun would swing by and gravity whip the stranded capsule away after a couple of orbits).

 

Am I a bad pilot or is this design no longer so good? It is a sweet ride to orbit.

 

Thanks and regards,

Orc

 

[Tatonf]

Hi.

According to the KER, the Kerbal X rocket have 6428 m/s (vacuum).

According to the delta-V map, you need :

- 3400 m/s for LKO

- 860 m/s for reaching the Mun

- 310 m/s for a 14 km orbit

- 580 m/s for landing (perfect suicide burn)

- 580 m/s for LMO

- 275 m/s for going back to a 25 km Kerbin periapsis (empiric result from my game)

The sum of this is 6005 m/s. It means that you have a 6428-6005 = 423 m/s margin.

Those 423 m/s can very easily be lost during 2 phases :

1) Going to LKO. Depending of your piloting, you might lose several hundreds of delta-V if you're doing a bad gravity turn

2) Landing on the Mun. If you're not doing a perfect suicide burn, you can also lose a good bit of delta-V.

Now I'm going to try doing this, because I still haven't done it.

 

EDIT : Testings have been done. The results are :

1) It is theorically possible to put the Kerbal X in LKO with 3100 m/s. I've done it with a bit less than 3200 m/s. Parameters are : 60 m/s, 15° flip, orbit achieved at 40 km.

2) Due to it's high TWR (~10), the lander is capable of doing a quite good suicide burn. I've done it with 630 m/s

3) At the end of the mission, I had 600 m/s remaining.

Conclusion : Your piloting needs improvement.

I would also add that replacing the LV-T45 with LV-T30 change the delta-V of your ship from 6428 m/s to 6419 m/s according to KER. The main reason is that the gain of mass is counterbalanced by the loss of Isp (the LV-T30 are less efficient than the LV-T45).

As for the change of capsule, it might be a good idea, but you might consider adding a heatshied, because the Mk-1 pod is less heat tolerant than the Mk1-2 pod. In my test, the Mk1-2 pod have been able to do a successful one pass reentry without exploding.

If you need any advise on a specific part, i'll gladly help you.

 

EDIT 2 : This experiment left me with a thought : what could I do with the 600 m/s left ? The answer was : going to Minmus !

 

Edited April 22, 2016 by Tatonf

[FullMetalMachinist]

4 hours ago, Orc said:

Am I a bad pilot or is this design no longer so good? It is a sweet ride to orbit.

Not trying to be harsh, but it's your piloting. I've taken the KerbalX to Duna and back .

I did have to make one modification to it. I added two of the radial drouge chutes and removed the useless monoprop from the command pod, but other than that it was all stock. 

It took some pretty careful planning, I had to get a gravity assist from Ike and aerobrake to capture, then I needed another gravity assist from Ike on the way home, and I ran out of fuel just as I finished the final correction burn into Kerbin's atmosphere. 

My point is, it should be very doable to land and return from the Mun, and easier from Minmus. 

[Norcalplanner]

It's been a long time since I used the KerbalX, but I recall it has a pretty high TWR and can therefore benefit from carrying more fuel. Try adding a bit more fuel to each of the stacks and see what happens, making sure to add tanks symmetrically on the side stacks. Should be pretty to get a few hudred more m/s of delta v, which it sounds like is all you need.

[Dr. Jet]

For reaching LKO - it's actually around 3200 dV. Gentle turning, so that you end flying horisontally at 50 km is the key. MechJeb is perfect with it, but even by hands its possible. 

As for stock KerbalX - its 6200+ dV is more than enough for single landing Mun trip. Especially if you skip the LMO phase and land directly according to MJ or KER "suicide landing" timer.

P.S. Don't have 1.1 yet to tell you if anything had changed in it. 

Edited March 29, 2016 by Dr. Jet

[Plusck]

7 hours ago, FullMetalMachinist said:

Not trying to be harsh, but it's your piloting. I've taken the KerbalX to Duna and back .

I did have to make one modification to it. I added two of the radial drouge chutes and removed the useless monoprop from the command pod, but other than that it was all stock. 

It took some pretty careful planning, I had to get a gravity assist from Ike and aerobrake to capture, then I needed another gravity assist from Ike on the way home, and I ran out of fuel just as I finished the final correction burn into Kerbin's atmosphere. 

My point is, it should be very doable to land and return from the Mun, and easier from Minmus. 

Wooooh!

OK I decided to take that as a challenge. It's a sandbox save game but I'm pretty sure all the difficulty settings were default. Similarly tweaked with drogue chutes, giving a total dv of 6419 m/s according to KER.

Got back with 109 m/s on a 27km Kerbin Pe. Messed up often: excessively elliptic orbit to start with, so had to warp forward 6 years to get a transfer to Duna that aligned with it; ultra hard landing on Duna after 4 tries, failed to reconfigure my staging sequence on the way back to destroyed my main chute and landed (hard) on drogues... Short album here....

Though I actually think that these mess-ups (particularly the first one) helped me with saving a little fuel, enough to make the difference.

[RA3236]

You should actually try Minmus first - much lower dv requirements than the Mun and it also has more science.

You shouldn't be seeing any changes in craft performance, especially since the only change to do with crafts are wheel physics. Dv and atmospheres are the same.

[Geschosskopf]

FWIW, I took the Kerbal-X to Mun and back in 1.1 yesterday, totally stock, flying by eye.  It was actually the 1st time I've ever flown it so I didn't realize at first it was asparagus (which I don't do myself) so I carried some empty side tanks for a bit during accent.  Still, it did get to the Munar surface and back to a safe landing, just barely, without trying to be too efficient.

Because this was a totally clean stock install, I don't have any numbers to give you but the flight went like this:

• Reached a 75km orbit with about 1/4 of the core tank left.
• Used the last to the core stack and a bit of the lander tank to transfer to Mun.  This was a free return trajectory with a Munar Pe of 15km, retrograde on the far side.
• Burned retro at Pe to hit the surface just on the light side of the terminator, without bothering to establish Munar orbit.
• Semi-sucide burn for landing.  Wasted some fuel landing due to the extremely high TWR of the lander by this point making it to back up several times even with tiny amounts of throttle, plus the extreme gimbal of the Poodle making it hard to kill horizontal velocity.  Landing legs also had animation issues but worked.
• Took off into a 25km Munar orbit.  By this point, the lander had very, very little fuel left.
• Transfer back to Kerbin with Pe set at 17km to be sure of landing directly from Mun transfer.  At the end of this burn, the lander had about 20 units of fuel left in the tank.
• Burned last drops of fuel as soon as I hit the atmosphere, then staged the lander.  Noticed with some surprise that the Kerbal X's Mk1-2 pod does NOT have a heat shield.  However, it survived this rather harsh reentry no problem.  Battery depleted early in descent but capsule did not tumble.  Was able to open the chute at about 2500m altitude.

So there you are.  You can get to Mun and back in the Kerbal X in 1.1.  Just barely.  You could probably stretch the "just barely" into "with reasonable confidence" with better flying, better instrumentation, or automation.

 

 

 

[lude]

Just tried it and I managed to get to the mun but saved my landing approach at the wrong moment (I kinda forgot that I don't have KER on the newest)

So I happily smashed a few times into the ground on the darkside until I decided to fly back, only landings that I could do wasted lots of dv due to my naive saving.

When I entered 70k at around 3000 km/s I still had enough fuel to burn the engine for half a minute or so (til ~40k)

I just barely survived the reentry, why does that thing not have a heatshield :E

 

I'm pretty sure that even if I managed to land on mun with a more intelligent maneuver I'd have had problems getting back.

[Warzouz]

I tested it to go to the Mun. It worked well. I came back to Kerbin with grossly the same amount of fuel left

The only thing I notices is the landing struts : The craft was sliding a bit AND the engine touches the ground. Struts suspensions are too weak or the strut is too short.

Edited April 21, 2016 by Warzouz

[WillThe84th]

The Kerbal X is actually a really well designed craft. I'm making a mod that makes Kerbin 637 km in radius  and makes the Mun 3x further away, and the Kerbal X still got there and back. I think you just need to work on your piloting. 

What I do on the gravity turn is I turn over 5 degrees around 3km and continue so that at 15km I'm at 45 degrees. I then continue to turn so I'm on the horizon at about 50-60 km. 

[Mahnarch]

Oh, good. I hadn't checked with anyone else, lately, to compare flight paths.

I usually start to turn E at around 90 m/s and try to be at 45 degrees by 15-17 km.

At 50-60 I'm usually still at 20 degrees above the horizon, but I'm at such a low throttle that I'm usually just using the nozzle to help steer downward to embiggen my orbital loop.

So, I'm within the usually practiced standards, it looks like.

[Warzouz]

On 29/3/2016 at 2:00 PM, Tatonf said:

...

As for the change of capsule, it might be a good idea, but you might consider adding a heatshied, because the Mk-1 pod is less heat tolerant than the Mk1-2 pod. In my test, the Mk1-2 pod have been able to do a successful one pass reentry without exploding.

Nope, you don't need any heat shield on MK1-2 pod inside Kerbin SOI. You don't even need it when coming from Duna (on a proper trajectory). I tested it a lot, it never blew.

I didn't tested the MK1 pod, though.

[Tatonf]

59 minutes ago, Warzouz said:

Nope, you don't need any heat shield on MK1-2 pod inside Kerbin SOI. You don't even need it when coming from Duna (on a proper trajectory). I tested it a lot, it never blew.

I didn't tested the MK1 pod, though.

This is what I said. The Mk1-2 pod is capable of surviving without heatshield, but the author wanted to change the capsule for the Mk-1 one, so I warned him about the heating.

[Warzouz]

3 hours ago, Tatonf said:

This is what I said. The Mk1-2 pod is capable of surviving without heatshield, but the author wanted to change the capsule for the Mk-1 one, so I warned him about the heating.

Ah, my bad. I read too fast.

[Reactordrone]

19 hours ago, Warzouz said:

I tested it to go to the Mun. It worked well. I came back to Kerbin with grossly the same amount of fuel left

The only thing I notices is the landing struts : The craft was sliding a bit AND the engine touches the ground. Struts suspensions are too weak or the strut is too short.

Yeah, there seems to be a problem with the landing legs. The feet are pointing in the wrong direction (unless you're timewarping) so they just sink into the ground.

The parachute is still set to deploy at 500m as well, so that can make the return a little hairy if you don't notice it.

[Warzouz]

4 hours ago, Reactordrone said:

...

The parachute is still set to deploy at 500m as well, so that can make the return a little hairy if you don't notice it.

Well, chutes at 500m for a single pod is OK.

[Tatonf]

Well it might be ok but I swear I got very afraid of ruining the mission because of that. Check the end of the video I posted on my first message, it's very close !

[carlorizzante]

On 3/29/2016 at 2:00 PM, Tatonf said:

EDIT 2 : This experiment left me with a thought : what could I do with the 600 m/s left ? The answer was : going to Minmus !

Wow, thanks for the demo. Really Jebediah knows how to ride a rocket :-D There are so many details in your video that show me that I've still a long way to go in order to master even the basics!

I didn't understand one thing especially, though. How comes that you put your ship back into Mun's orbit at 45 degrees, and being able to catch up with Minmus that way? Looks like magic to me... :-o

Gotta watch it again

Edited April 25, 2016 by carlorizzante

[Tatonf]

5 minutes ago, carlorizzante said:

Wow, thanks for the demo. Really Jebediah knows how to ride a rocket :-D There are so many details in your video that show me that I've still a long way to go to master even the basics!

I didn't understand one thing especially, though. How comes that you put your ship back into Mun's orbit at 45 degrees, and being able to catch up with Minmus that way? Looks like magic to me... :-o

Gotta watch it again

Actually it was 56°. The thing is that Minmus is inclined by 6° relatively to the Mun. By launching directly into an inclined orbit around the Mun, you can get an orbit that is correctly inclined relatively to Minmus once you escape the Mun. Starting at 21:45, you can see me adjusting the position of the node in order to minimize this inclination, and I ended up with 0.2°.

Having a low relative inclination is important because it's much easier to get an encounter, and it diminishes the cost of the insertion burn. While it's quite marginal here, it's a very valuable thing to know when you aim for Moho.

[carlorizzante]

45 minutes ago, Tatonf said:

Actually it was 56°. The thing is that Minmus is inclined by 6° relatively to the Mun. By launching directly into an inclined orbit around the Mun, you can get an orbit that is correctly inclined relatively to Minmus once you escape the Mun. Starting at 21:45, you can see me adjusting the position of the node in order to minimize this inclination, and I ended up with 0.2°.

Having a low relative inclination is important because it's much easier to get an encounter, and it diminishes the cost of the insertion burn. While it's quite marginal here, it's a very valuable thing to know when you aim for Moho.

I'm sorry, I didn't really understand, haha. So you started at 56º, but how did you end up on the same level of Minmus? I'll watch the video again after dinner.

I've also noticed that you did quite a cool trajectory to get back to Kerbin and used the Mun to do so. And in that case you put the ship on an orbit close to 0º (~90º from an equatorial one). All that is so different from what I've done myself.

What's the name of those techniques (if they have any) so I can go study some material without taking your time with silly questions and eventually come back with better ones? Unless you would like to explain it again in even simpler words, of course.

Thanks so far

[Tatonf]

2 minutes ago, carlorizzante said:

I'm sorry, I didn't really understand, haha. So you started at 56º, but how did you end up on the same level of Minmus? I'll watch the video again after dinner.

I've also noticed that you did quite a cool trajectory to get back to Kerbin and used the Mun to do so. And in that case you put the ship on an orbit close to 0º (~90º from an equatorial one). All that is so different from what I've done myself.

What's the name of those techniques (if they have any) so I can go study some material without taking your time with silly questions and eventually come back with better ones? Unless you would like to explain it again in even simpler words, of course.

Thanks so far

Sorry but I'm myself very noobie actually. What is actually behind this video is a lot of empiric testing with Hyperedit, and I just reproduced what I actually found to be working.

What I know is : if you exit a body's SOI starting from an equatorial orbit and with only a prograde component on your node, then once you exited this body you will have the exact same inclination than it. However, if you start from an inclined orbit, once you exit the body's SOI, your orbit will also be inclined relatively to this body. So I just tested different inclinations, and found out that 60° would give me a 0.1° inclination relative to Minmus.

For Minmus I didn't find any suitable inclination actually (probably because it's too small), but a polar orbit gave me an inclination relative to the Mun of something like 2.2°, which is better than 6°. But the only reason for doing this is to get an easier encounter with the Mun, because the more you're inclined the harder it is to get an encounter.

The cool trajectory that got me back to Kerbin is called a "Gravity Assist", basically you can steel a bit of energy from a celestial body and give it to your spacecraft to accelerate, or, in this case, the reverse. It depends of your trajectory. But once again I am no expert, and you should look at other topics about it.