Problem TransX giving retrograde vector. Crashing with Earth.

[Raumfahrer]

Hi, I spent some time reading and I couldn't find the answer I am looking for, so here I go:

I am trying to get from LEO to the Moon using Transx.

Why from LEO? Because I am using the Deepstar vessel which cannot land on the surface http://www.orbithangar.com/search_quick.php?text=deepstar&submit.x=-1189&submit.y=-144

I have docked to it a standard DG and a Raven Star XR2, my plan for now is to go to the Moon and get into lunar orbit.

The problem I am having and can't resolve is that after I plan my trip with transx the DV vector seems to point just across the Earth or retrograde, the result is that I have not enough thrust to accomplish such a route before falling into Earth's atmosphere. My orbital plane is already aligned with the Moon's so in the maneuvre the only variables I touch are prograde velocity and lauch date.

What could I be doing wrong? is this may be some beginner frequent problem?

In my searches i couldn't find an answer, so I guess I am failing at some basic step. Any ideas?

Thanks in advance for your help.

If it's of any help here it is the scenario file: View attachment Deepstar RV2 y DGS Acoplados.scn

 

[DutchPlayer]

Can you tell step for step what you are doing? And post the values of the variables?
Or you can try to update transx, to version 3.16 (im not sure, i cant check it, because im not at home where my computer is)

Hopefully I can help you further

 

[statickid]

Did you wait for the time to decrease to zero?

---------- Post added at 10:24 AM ---------- Previous post was at 05:34 AM ----------

Here is your scenario. The Deep Star has "weak" (realistic?) thrusters. TransX is calculating the amount of time that you will have to start burning before you get to the location I marked "A" so that half of the burn will be completed when you get to A. It just so happens this is about a quarter orbit, therefore, you are being directed to what will be prograde in the future, but is now pointing at the ground.

There is a way to do this, but you can't follow the instructions that TransX gives you directly, so, in a way, you can't use TransX for this particular maneovre in this particular ship. I HIGHLY recommend just raising your orbit up. For example you can raise it up to 1 Earth radius or so, then you can use TransX, but it will still be difficult. You really have to fly the Deepstar in a different way than small speedy ships.

 

[Raumfahrer]

Can you tell step for step what you are doing? And post the values of the variables?
Or you can try to update transx, to version 3.16 (im not sure, i cant check it, because im not at home where my computer is)

Hopefully I can help you further

Well, taking note of the steps to write them down here, I noticed that I wasn't opening in the second MFD window transx with the encounter data, I was only taking into account the rough app number that the manoevre mode was giving me. This apparently solved my retrograde previous results.

This time transx gave me a prograde course, but the problem was that the route was around 50º prograde, that is from the prograde icon, 50º to the right, pointing away from earth.

I ended up losing to much speed and gaining altitude, reaching the point where the speed started to drop so much that the DeltaV number in the transx bullseye view started to go higher instead of dropping.

I have not time to try now with another scenario and vessel, I will try a standard DG tonight and see.

Here are the steps I followed:

Date: Dec 24 2068 MJD 76739.9890

Orbit:

ApA 422.3k
PeA 422.0k
Vel 7.660k
Inc 5,16º (0º RInc to the Moon)

1- Open TransX in the right MFD
2- Select Moon
3- Click VW
4- Set Manoeuvre mode ON ( here I open transx in the left MFD with the Encounter view to see the min altitude)
5- set prograde velocity to 3.108k
6- set launch date to 76739.9938

I noticed from the start that something was not ok since the green X in the bullseye was moving too much to the left, so I had to make constant corrections with the RCS, making it very hard to warp speed. When the DeltaV started to go higher I aborted the flight.

---------- Post added at 06:27 PM ---------- Previous post was at 06:21 PM ----------

Did you wait for the time to decrease to zero?

---------- Post added at 10:24 AM ---------- Previous post was at 05:34 AM ----------

Here is your scenario. The Deep Star has "weak" (realistic?) thrusters. TransX is calculating the amount of time that you will have to start burning before you get to the location I marked "A" so that half of the burn will be completed when you get to A. It just so happens this is about a quarter orbit, therefore, you are being directed to what will be prograde in the future, but is now pointing at the ground.

There is a way to do this, but you can't follow the instructions that TransX gives you directly, so, in a way, you can't use TransX for this particular maneovre in this particular ship. I HIGHLY recommend just raising your orbit up. For example you can raise it up to 1 Earth radius or so, then you can use TransX, but it will still be difficult. You really have to fly the Deepstar in a different way than small speedy ships.

Wow! Thanks a lot! So the thurst is so weak that transx cannot resolve the route? I will try what you say about raising my orbit but reading what you say I guess I will try first to master the travel with the standard DG, since I am in the learning curve. I had no idea that Deepstar was so hard to fly. I will try again tonight.

Thanks a lot for your help.

 

[statickid]

It is resolving the route correctly, the ship just isn't capable of going directly into the trans-lunar injection from LEO the same way that other ships with higher thrust-to-weight ratios do (usually smaller OR more futuristic/fictional). You have to more actively "shape" your orbit or take a different approach with the DeepStar. In this case an easy solution is to simply start at a much higher altitude, you might even consider parking in a circular orbit halfway to the moon, then doing the TLI.

You may find the Arrow Freighter to be a nice introduction into big, lumbering mother ships.

---------- Post added at 02:09 PM ---------- Previous post was at 11:53 AM ----------

Here is another way to go that's pretty easy, and uses your current scenario. I think you can do it this way without too much trouble.

First, just ignore the transx reticule; use the prograde autopilot instead. Start the burn when trans x tells you to.

It will get you a trajectory that is close to being right, so just rotate it it back a little bit and fly to the moon like normal! Do this right away, the longer you wait, the more fuel it will take.

Do any mid-course corrections and insert into orbit. voila!

 

[Raumfahrer]

Great! thanks statickid! I will try that way, I liked also the option of going to a higher orbit or even half way to the moon and then make the course. It's nice to know that my basic use of transx wasnt the problem. I just did a flight from LEO to the Moon using a standard DG and arrived perfectly.

The Arrow Freighter is not available for download since Dan Steph site is down right? Do you know a place to get it? It looks really awesome.

As a rule of thumb, with the Deepstar, would you suggest to burn prograde first to eject from orbit and then make the course once in travel? For example in a trip to Mars, burn prograde, leave Earth's influence (less than 0.5G) and then make the course? Asumming that fuel is not a problem. (limited fuel unchecked for beginners like me)

thanks a lot!

 

[statickid]

As a rule of thumb the Deep Star's limitations have less impact on planning when you are in higher, slower orbits. Its not that you can't EVER use transx with deep star, LEO is just a really fast, intense place to start. For example if you leave for Mars from a GEO orbit using transx, the problem you are having wouldn't exist because the degrees that you traveled from the beginning of the burn to the end of the burn would be very few. In Leo you have traveled almost 120 degrees around the Earth from beginning to end of the burn!

Think of it this way, if your orbital period is only 90 minutes, and it takes you half an hour to create 3k units of DV, then you will have spent almost a third of the orbit with your engines on.

If your orbit is 24 hours, on the other hand, and it takes you the same amount of time, then you will only travel about 2% of your orbit with engines on, or about 7 degrees.

While it is totally possible to do burns like the first one, doing burns like the second one are much more compatible with the way that TransX works :thumbup: