General Question Ascent profile help

[Andy632]

Hi there. In my experience Launch MFD's autopilot doesn't always work with certain add-ons. It seems to be a roll of the dice when using it for CVEL-Titans or Velcro, sometimes it does one thing, sometimes another. I've had it roll and yaw to the correct azimuth only to hold at 90 degrees pitch for example. In the absence of an autopilot, I like to fly vertical launcher ascents manually.

I've tried to find information on ascent profiles on the web, with varying success. Does anyone know of any decent sources for ascent profiles that I can use for Titan and Delta launchers, for example? Or a good autopilot add-on lol.

 

[Donamy]

Let me know when you find one.

 

[francisdrake]

For a manual ascent, use the 20-30-40 rule.

First, in the scenario file, set the heading to the desired azimuth. For an ISS-orbit this would be:
HEADING 42.4

Set an MFD to Surface.

Launch.
At approximately 1 km give the launcher a push, so it starts pitching over in a gravity turn.
At 20 km altitude -> pitch 40°.
At 30 km altitude -> pitch 30°.
At 40 km altitude -> pitch 20°.

When the pitch reaches 15° - 12° kill the rotation.
Continue with this fixed pitch until first stage cutoff.

With the second stage level out the trajectory.
Use the values on the SurfaceMFD to control the vertical speed.
To avoid dropping back into the atmosphere you may need to pitch up, before gradually lowering the pitch again.

Set the other MFD to Orbit. Cut the engine when you have reached the desired orbit.
Illustration below:

 

[Eddie C.]

Hi there. In my experience Launch MFD's autopilot doesn't always work with certain add-ons. It seems to be a roll of the dice when using it for CVEL-Titans or Velcro, sometimes it does one thing, sometimes another. I've had it roll and yaw to the correct azimuth only to hold at 90 degrees pitch for example. In the absence of an autopilot, I like to fly vertical launcher ascents manually.

I've tried to find information on ascent profiles on the web, with varying success. Does anyone know of any decent sources for ascent profiles that I can use for Titan and Delta launchers, for example? Or a good autopilot add-on lol.

Well, any decent source for (detailed) Titans/Deltas' ascent profiles is, most probably, classified. You may have a look onto ULA's website and search for the various launchers' user guides. These are specifically noted to be "Approved for public release", therefore my previous assumption.

 

[Urwumpe]

If you know the launchers acceleration at a time, you can also just use a gravity turn for the first seconds of flight. It is often good enough for the complete first stage flight and has the advantage, that it keeps the AOA low.

For calculating a launch profile, the classic way of constructing this by computer is going backwards from orbit to the ground. There are many possible algorithms around.

 

[Andy632]

Thank you for the help, it did come in handy, particularly the Delta IV chart showing time, altitude and velocity.

I now have a problem with the second stage on the Delta (the DCSS, Delta Cryogenic Second Stage). I've been trying to launch into a geostationary transfer orbit. It seems the Velcro EELV addon has the thrust and specific impulse of the second stage correct to real life, but when I get to the time of ignition for second stage burn I'm unable to reach orbit, whatever ascent profile I've chosen, and the vehicle burns up in the atmosphere. I'm no novice, I've tried different altitudes and different vertical speeds at MECO and it's no good. It seems to me the Delta second stage engine is too weak - at least in how it works in Orbiter - ever to achieve orbital velocity let alone GTO velocity.

I wonder if sputnik is around to give an answer... Or in any case any help or similar experiences with the addon would be helpful.

 

[Eddie C.]

Thank you for the help, it did come in handy, particularly the Delta IV chart showing time, altitude and velocity.

I now have a problem with the second stage on the Delta (the DCSS, Delta Cryogenic Second Stage). I've been trying to launch into a geostationary transfer orbit. It seems the Velcro EELV addon has the thrust and specific impulse of the second stage correct to real life, but when I get to the time of ignition for second stage burn I'm unable to reach orbit, whatever ascent profile I've chosen, and the vehicle burns up in the atmosphere. I'm no novice, I've tried different altitudes and different vertical speeds at MECO and it's no good. It seems to me the Delta second stage engine is too weak - at least in how it works in Orbiter - ever to achieve orbital velocity let alone GTO velocity.

I wonder if sputnik is around to give an answer... Or in any case any help or similar experiences with the addon would be helpful.

Hi Andy. Try to use (if not already) IEAT MFD here, where you may be able to adjust your thrust and Isp, or at least to see what your thrust and Isp are. I never used it, so I cannot give more insights here. Also make sure that the 2nd stage ignition takes place at correct altitude, depending of Delta variant. The 2nd stage of the Deltas should have a thrust of about 110kN and enough fuel for about 20 minutes.