Need help, on 25th try. launching a BACC booster

[Elfmaze]

I'm still in the first stages of the game. I have a mission set that is to launch a BACC booster and test in orbit. I am also trying to test a LV-909 engine on the same orbital flight. I have given up on testing the seperation 1 and any goo type canisters. I'm still limited to 30 parts.

I have the first two tiers unlocked (five total green blocks) And I have the science to unlock advanced rocketry(Fl-T800 might help)

Closest I've gotten is a small comand pod with fuel tank and LV-909. with the BACC de-fueled under. Four radial decouplers to dump the booster rockets, and eight FL-T800 fuel tanks mounted to LVT-45 engines.

That gets me 26 of 30 parts. SO I could add another fuel tank to the stacks, But it doesn't seem to get me very far.

I can get the rocket to 100K meter apogee but can never finish the orbital insertion burn before running out of liquid fuel. I don't believe I can burn the BACC untill established in orbit. Plus I de-fueled it to save weight.

The current plan was to get to orbit: Use the BACC to drop the Periapsis below 75K: dump the boosters and BACC to reenter: Reestablish good orbit with LV-909; Retroburn to re-enter.

Any other ideas?

[Elfmaze]

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1) Remove the aero shrouds. That'll get you 4 parts and lose some dead weight.

2) Replace 2 of the engines (preferably all 4) with LV-T30s.

See how it looks then...

What's your velocity at apoapsis?

Best,

-Slashy

*Edit*

I built a copy, and with my changes (plus removing the monopropellant from the capsule) it's about 100 m/sec short of LKO.

Does it have to go to 100km, or is 72x72 okay?

If 72x72 is alright, I can defuel the T-200 most of the way and use the LV-909 to deorbit.

Would that satisfy your test?

The BACC test Needs 93K to 102K. I made another one splitting the boosters into two stages. I also moved the LV-909 to the bottom of the stack instead of on top. I tried to use the LV-909 to finish orbital insertion and adjust the orbit for the BACC and LV-909 test but I think i'm goin gto have to shut down the engine and RE engage it through a stage to finish the mission? Also the BACC cannot maneuver in space. My plan to use it to deorbit are having some issues.

[GoSlash27]

- - - Updated - - -

1) Remove the aero shrouds. That'll get you 4 parts and lose some dead weight.

2) Replace 2 of the engines (preferably all 4) with LV-T30s.

See how it looks then...

What's your velocity at apoapsis?

Best,

-Slashy

*Edit*

I built a copy, and with my changes (plus removing the monopropellant from the capsule) it's about 100 m/sec short of LKO.

Does it have to go to 100km, or is 72x72 okay?

If 72x72 is alright, I can defuel the T-200 most of the way and use the LV-909 to deorbit.

Would that satisfy your test?

- - - Updated - - -

Using the same vehicle, I was able to establish a 75x75 orbit, test the BACC (empty), and deorbit using the LV-909.

Changes:

-Removed the fairings

-Swapped the engines to LV-T30s

-Removed the monopropellant

-Unloaded the T-200 tank to 10%

-Set throttle limiter on the LV-T30s to 80%

Unfortunately, splashdown was at 7.9 m/sec and was just hard enough to destroy the LV-909 and tank.

HTHs,

-Slashy

[Elfmaze]

hitting about 1030 at apoapsis. I have a tiny bit of fuel left in the boosters and can't establish the orbit even at 75K with the staged rocket. Maby this is not possible?

[Elfmaze]

cool i'll try it. But need a bit higher for BACC test. maby I can oblong the orbit and test it at the high phase?

- - - Updated - - -

1) Remove the aero shrouds. That'll get you 4 parts and lose some dead weight.

2) Replace 2 of the engines (preferably all 4) with LV-T30s.

See how it looks then...

What's your velocity at apoapsis?

Best,

-Slashy

*Edit*

I built a copy, and with my changes (plus removing the monopropellant from the capsule) it's about 100 m/sec short of LKO.

Does it have to go to 100km, or is 72x72 okay?

If 72x72 is alright, I can defuel the T-200 most of the way and use the LV-909 to deorbit.

Would that satisfy your test?

- - - Updated - - -

Using the same vehicle, I was able to establish a 75x75 orbit, test the BACC (empty), and deorbit using the LV-909.

Changes:

-Removed the fairings

-Swapped the engines to LV-T30s

-Removed the monopropellant

-Unloaded the T-200 tank to 10%

-Set throttle limiter on the LV-T30s to 80%

Unfortunately, splashdown was at 7.9 m/sec and was just hard enough to destroy the LV-909 and tank.

HTHs,

-Slashy

[GoSlash27]

cool i'll try it. But need a bit higher for BACC test. maby I can oblong the orbit and test it at the high phase?

It's pretty much on the ragged edge now, but I'll try it and let you know. Apoapsis needs to be 100 km?

Best,

-Slashy

[Torquemadus]

That gets me 26 of 30 parts. I don't believe I can burn the BACC untill established in orbit.

Don't worry! We're sending you BACC To The Future!

This design burns all seven BACC boosters limited to 70% thrust as a first stage. I've tried to avoid using any parts you didn't show in your pic, so I haven't used any struts. BACC boosters burn out too quickly, so I thrust limit them for a longer burn time and add enough to ensure a decent thrust-to-weight-ratio at launch.

I use sepratrons to (hopefully) achieve a clean staging event, delaying the ignition of my second stage until the first stage is clear. Six out of seven BACC boosters are dropped, with the last remaining booster carried to orbit as payload.

At this point, I've now lifted an empty BACC booster into orbit, with fuel to spare to manoeuvre it into an orbit with the correct parameters to complete the contract, whatever they may be. The next step is to edit the staging sequence so that the BACC booster can be "activated" when the correct parameters are met. The fact that I've already burned out the BACC is irrelevant. By editing the staging sequence, I can "activate" it as many times as I like.

You mentioned sepratrons, goo pods and the LV909. I'm not sure what you intend to do with those, but for demonstration purposes, I brought those up as well.

[GoSlash27]

Okay,

It has just barely enough to establish a 75x100 orbit.

I drained the FL-T200 tank completely and then transferred the remaining fuel into it after establishing the orbit.

I had to fly a very precise launch profile to make it work, so there's not much room for error.

If you're still having trouble with it, just let me know. I have one more idea to squeeze a couple hundred more m/sec out of it.

Best,

-Slashy

- - - Updated - - -

Torquemadus,

I may be mistaken, but I don't think he can use the BACCs in his stack because he's testing one in orbit.

Best,

-Slashy

[*Aqua*]

I may be mistaken, but I don't think he can use the BACCs in his stack because he's testing one in orbit.

He can use as many as he like. The test parts are not limited in numbers.

[Torquemadus]

Torquemadus, I may be mistaken, but I don't think he can use the BACCs in his stack because he's testing one in orbit.

He only needs to activate the BACC via the staging sequence. It doesn't matter whether the BACC has been used earlier in the flight or not. The staging sequence can be edited in flight to "activate" the already activated part.

The contract isn't clearly explained, which misleads a lot of new players into thinking that they have to lift the part to the required situation in an unused state. My method lifts a burned out BACC to the required orbit and then "activates" it to complete the contract.

[GoSlash27]

Oh yeah! That just fixed it for ya!

1) Remove the 4 booster stacks and reattach them as pairs.

2) Set their decouplers to detach in 2 stages.

3) Stage pair 1 has their throttles set to 100

4) Stage 2 pair has their throttles set to 50

Leave the FL-T200 empty (don't forget to fill it before jettisoning the remaining boosters).

Launch at full throttle.

Prograde gravity kick at 6km

Maintain centered prograde ball through the gravity turn

67* pitch at 15km, throttle to maintain 1.5G

45* pitch at 25 km, Throttle to maintain 1G

Jettison stage 1 when dry

Establish 75km periapsis

Establish 100km apoapsis

This leaves you all sorts of extra fuel. You can probably bring along the science.

Best,

-Slashy

- - - Updated - - -

He only needs to activate the BACC via the staging sequence. It doesn't matter whether the BACC has been used earlier in the flight or not. The staging sequence can be edited in flight to "activate" the already activated part.

The contract isn't clearly explained, which misleads a lot of new players into thinking that they have to lift the part to the required situation in an unused state. My method lifts a burned out BACC to the required orbit and then "activates" it to complete the contract.

Ah, cool.

So he's got a couple different options now.

Best,

-Slashy

Edited January 25, 2015 by GoSlash27

[Elfmaze]

Nice! Your rocket kung-fu is better than my kung-fu! I started playing with some BACC boosters last night to reduce parts.

I need to learn a more efficient way to get to orbit as well. Best I know so far is to burn straight up to 7500-10000k Turn to 45* on the 90* axis and burn until my peak hits desired orbit. wait until apoapsis and finish prograde burn to raise periapsis.

Probably not the most efficient approach. I don't know much about holding G's in the gravity turn or throttling down in the thick atmosphere. so still got some more to learn!

I'll give the six pack method a try when I get home, Thanks!

[Elfmaze]

Ran it in my "sandbox sim" the six pack BACC was a PITA to get everything aligned right... The four way snap tool for the decouplers wanted me to have matching boosters on all four sides. So i had to manually place each booster. I also needed two separation boosters on the top of the SRB's or they kept hitting my fuel tanks... BUT it orbits with ease! I'm finding it hard to tune my orbit without the maneuver nodes...

seems holding prograde at apoapsis will distort my orbit and leave me with a high Apoapsis before my periapsis comes up to something reasonable. Guess I need to aim a bit off the prograde marker.

[Acet]

Nice! Your rocket kung-fu is better than my kung-fu! I started playing with some BACC boosters last night to reduce parts.

I need to learn a more efficient way to get to orbit as well. Best I know so far is to burn straight up to 7500-10000k Turn to 45* on the 90* axis and burn until my peak hits desired orbit. wait until apoapsis and finish prograde burn to raise periapsis.

Probably not the most efficient approach. I don't know much about holding G's in the gravity turn or throttling down in the thick atmosphere. so still got some more to learn!

I'll give the six pack method a try when I get home, Thanks!

One important thing that people often forget is to keep the speed below terminal velocity during the early stages of launch.

I have a couple of early stage launch base subsystems I've made mostly from boosters (trying to keep both part count and costs low) and just by changing the Thrust Limit of the boosters in VAB so that during the early stages of launch the speed is kept around terminal velocity, I get huge differences in how far a rocket will go and how big a payload it can take to orbit.

Keeping launch speed at the ideal point between getting out of the gravity well ASAP and not wasting too much energy due to drag is very important, especially when every part, ton and $$$ counts.

Look it up in the Wiki, there are some tables for Terminal Velocity at different altitudes in Kerbin (for example, http://wiki.kerbalspaceprogram.com/wiki/Basic_maneuvers). Also MechJeb has an option in the Ascent Guidance panel to "keep below terminal velocity" which strangely is not on by default.

You might be able to improve that six-pack setup by tweaking the thrust limits to try and keep ascent speed close to terminal velocity. You might be able to reduce it to only 4 BACCs by setting them on lateral decouplers, and using different thrust limit values on paired boosters (say, one pair with 70, the other with 50) so that they are empty at different points of the ascent and you can drop some of the boosters earlier and get more work done (due to less weight) from the energy left on the remaining propulsion units.

I have a pretty simple launch base done like this (4 BACCs in pairs around 1 liquid engine + 2xFL-T400 in the middle to better control speed), which is 12 parts (including top decoupler) and can put 3-5t in orbit (more than enough for an empty BACC).

[Elfmaze]

Mission successful! Got to test the BACC; LV-909; radial parachute; And finished a "return science data from orbit" mission. Very successful! thank-you for the help on this one. Was starting to think it was not possible to get it all done.

Speaking of the wiki, has the site been down lately?

- - - Updated - - -

One important thing that people often forget is to keep the speed below terminal velocity during the early stages of launch.

besides the VSI how do I see my current speed? nav ball speed?

[GoSlash27]

Mission successful! Got to test the BACC; LV-909; radial parachute; And finished a "return science data from orbit" mission. Very successful! thank-you for the help on this one. Was starting to think it was not possible to get it all done.

Speaking of the wiki, has the site been down lately?

Aye. Something about a "password reset during server update". They're working on it.

- - - Updated - - -

besides the VSI how do I see my current speed? nav ball speed?

Aye. Nav ball speed.

I don't worry about the exact speed myself. So long as my G meter stays within my launch profile limits, I can be confident that my speed will also be in line.

2G is the limit for vertical acceleration, and it tapers off at a function of 2sin(pitch) as I pitch horizontal in the gravity turn. 1.8G at 80* pitch, 1.5G at 45* pitch, 1G at 30*.

So long as you hit the marks and maintain your G limits, you can be confident that you're squeezing all the DV out of your design you can get.

Once you're past 35km altitude, the terminal velocity is higher than orbital velocity and you don't need to worry about it (although I maintain 1G to simplify things).

Best,

-Slashy

- - - Updated - - -

You might be able to improve that six-pack setup by tweaking the thrust limits to try and keep ascent speed close to terminal velocity. You might be able to reduce it to only 4 BACCs by setting them on lateral decouplers, and using different thrust limit values on paired boosters (say, one pair with 70, the other with 50) so that they are empty at different points of the ascent and you can drop some of the boosters earlier and get more work done (due to less weight) from the energy left on the remaining propulsion units.

A big +1 to all of this.

Serial staging and tweaking the thrust limits of the stages gives a bigger payoff in efficiency than either technique alone.

Tweaking it out is a big pain in the butt, but it pays for itself by allowing you to lift more payload to orbit with less rocket.

Best,

-Slashy

[tsotha]

He only needs to activate the BACC via the staging sequence. It doesn't matter whether the BACC has been used earlier in the flight or not. The staging sequence can be edited in flight to "activate" the already activated part.

This is a critical for parts testing. There's no reason to drag an empty (or even full) BACC to orbit to test. Just make sure you have one still attached to your stack when the test conditions are right. A good strategy for this test is to use the BACC to launch and then complete the orbit with radial engines (assuming you have them) without decoupling the BACC.

In general newer players tend to assume they're under restrictions that aren't really there:

1. Reiterating - you can test a part you used already by selecting "run test" from the right click menu, or, if it isn't available, add an empty stage below it and "stage" it. This saves you tons of dV. An RT-10 test at 30,000 meters requires only three parts - capsule, parachute, and RT-10 (assuming you adjust the throttle to make sure it's going at the right speed at the right altitude). And you can stage it for test purposes when it's still running.
   
2. The part needn't be configured to actually work. By that I mean you can stage an engine that doesn't have any fuel. That never had fuel, in fact - you don't have to wait for Xenon tanks to test an ion engine or air intakes to test a jet engine.
   
3. You can set the thrust limiter to zero so that when you stage it it doesn't actually do anything even if fuel is available. This can be handy if the contract calls for staging a part that's still buried in the stack. You can complete the test without wasting fuel or damaging the part below it, then select "shutdown engine" from the right click menu, change the thrust limiter back to 100%, and move it to the stage where you'll actually need it. This way you can, for example, complete an LV-909 test at 10,000 meters during a Mun shot with an engine you won't actually use until it's time for your Munar descent.
   
4. Take all "Landed at Kerbin" contracts, since they literally cost you nothing in time or money. A "landed at Kerbin" KR-2L contract can be fulfilled with a single probe/capsule and the engine itself. Hit the space bar and recover your craft. There's no fuel so it never goes anywhere and you get 100% salvage on the entire "rocket". But by the same token, read the contract carefully enough to make sure it's actually "landed at Kerbin", since testing a heavy part landed at Ike is a whole different kind of contract you may want to schedule with other activity on the same body.
   

EDIT:

I was able to get this into a 105/72 orbit. Splashed it off the coast of KSC (97.8% recovery) for a net cost of 3767

The thrust limiter on the BACC is set to 69%, and the RT-10s to 54.5%. I doubt this is optimal, but it's close enough to do the job.

Edited January 27, 2015 by tsotha