Jump to content

Project Alexandria: a history of spaceflight done in Real Solar System

Felbourn

By Felbourn
in KSP1 Mission Reports

 Share

Recommended Posts

Felbourn

Felbourn

Posted
  • Author
Posted

After switching Odyssey to OpenGL I basically just stuck with it, and even used it on new installs that didn't need it. Whatever it is about my system specs, no tests I've run show more than a 5% drop in performance. Usually it's unnoticeable.

Link to comment
Share on other sites
Rune

Rune

Posted
Posted
After switching Odyssey to OpenGL I basically just stuck with it, and even used it on new installs that didn't need it. Whatever it is about my system specs, no tests I've run show more than a 5% drop in performance. Usually it's unnoticeable.

Yup, it was OpenGL. Thanks! The weird thing is, it shouldn't be the memory limit, because I had a lot of leeway, considerably under 3.5GB in most crashes... I run almost no texture-adding mods just for that reason (KAS, KIS, and roverdude's LS, basically), and let me tell you I was usually just waiting for a crash instead of closing my games 80% of the time. Of course it still loads much leaner this way, no doubt about that, about 1.9-2.2GB by the time I load a game, 1.5GB of the title screen. Still, some lagginess in anything UI-related is apparent. Or maybe it's because KSP has been running for five hours now. :cool:

Anyhow, spread the good word in your youtube videos. KSP is much more unstable out of the box than this, frequently crashing even stock installs after a few scene transitions.

Rune. And it's still stable at only 2.5GB of RAM usage after five hours! Yay! :)

Link to comment
Share on other sites
pack_rtr

pack_rtr

Posted
Posted

Only is you haven't found about it already, I found this launchers pack and I thought it was ideal for Project Alexandria but at a later date.

http://forum.kerbalspaceprogram.com/threads/78741-1-0-3-Launchers-Pack-V-5-2-Payload-Interfaces-small-changes

It includes the Falcon I, the Atlas V, as well as the Delta II rocket.

Also, when will you update your Alexandria repo? I want to see that space center!!!

Link to comment
Share on other sites
Felbourn

Felbourn

Posted
  • Author
Posted

In '62 the United States launched Mariner 2 to Venus. I could look up the delta-V of the flight, or I could do the work myself. This project is about doing the work myself, or else I'd have used Realism Overhaul instead of researching all the rockets myself, so.... I'm going to do the math for the delta-V needed to reach Venus as well!

First we need to know how fast we're travelling before we start moving, and then we need to know the delta-V to get into orbit.

We'll begin from LC-12 which is 28 degrees north, and therefore the Earth is 35,410.272 km in circumference there. It takes 86,400 seconds to rotate once, so we are travelling 409.84 m/s when we start.

I'm not sure what altitude we went to first. Let's assume roughly 250 km. I'm assuming this was not a direct ascent since the Agena was fired twice, so the second burn had to be the escape burn. For a liftoff cost we need the desired orbital velocity and then we'll subtract the starting velocity.

That speed is sqrt(GM/r) and GM is 3.986E+14. Earth radius is 6373.45 km at 28 degrees. I got the radius by doing this in Excel:

=A1*SQRT((A2^4)/(A1^4)*((SIN(RADIANS(A3)))^2)+(COS(RADIANS(A3))^2))/SQRT(1-(1-(A2^2)/(A1^2))*(SIN(RADIANS(A3))^2))

I used A1 = 6,378.14 for equator radius, A2 = 6,356.75 for polar radius, and A3 = 28 degrees.

This is not the real radius for the entire initial orbit, but it should be close enough to what we need for the liftoff up to the second Agena burn. It's also more precise than we need anyway!

So orbital velocity needs to be 7908.27 m/s using sqrt(GM/r).

Minus 409.84 gives us 7498.43 m/s as a cost.

There's also a gravity drag and atmospheric drag cost to a liftoff. Gravity will vary as we gain altitude. We start around 9.8067 m/s but it'll drop to 9.4365 by the time we reach orbit. We'll start 90 degrees to gravity at the start, but we'll be going 45 degrees very quickly (around 6.873 m/s), and eventually 0 degrees when we stop. Gravity losses will therefore change over time, and thus is more complex math, so I leave it to the reader to figure it out, but I got 1496 m/s. That was about 6.5 m/s for the 230 seconds to reach 0 degrees. Atmospheric drag is pretty low, about 300 m/s depending on the shape of the rocket, launch profile, etc. Add these all together and we get 9294 m/s for liftoff.

The next task is to figure out our escape velocity and orbit transfer velocities. Escape velocity is easy. That's sqrt(2GM/r) and we have those values from above, so we plug them in and get 11,184 m/s.

Transfer velocity requires knowing the orbits of Earth, Venus, and the GM of the sun. We'll use the formula sqrt(GM(2/r-1/a)) for a Hohmann transfer. We start out in August, so the Earth is 1.0116 AU from the sun, or 1.5133E+11 m. Venus is roughly 1.08E+11 m. SMA is therefore 1.2967E+11 m. Using the formula we get a velocity at Earth of 34,206 m/s and 28,604 m/s at Venus.

Using the orbital velocity formula we know the Earth is travelling 29,613 m/s when we leave. The difference between that and the speed we want to go is 4592 m/s. We don't need to pay all of that though. We will have excess orbital velocity as we leave Earth's SOI. Doing sqrt(11184^2 + 4592^2) gets us the true Earth escape velocity we need, which comes out to 12,090 m/s. We'll already be going 7908, so the difference of 4182 needs to be paid.

Adding the base cost to this, we get a total dV needed of 13,476 m/s.

Give or take.

Link to comment
Share on other sites
Felbourn

Felbourn

Posted
  • Author
Posted

Yep, thanks. There are many good Ariane options. I have researched them in the past, and I will do so again in the future. Liquidhype and I have worked together on things, so I am aware of him and his work, and we've exchanged many messages. However, this is way way premature. It's unlikely that I will reach the Ariane 1 first launch sooner than a year from now. The Ariane 5 is likely to be another year after that.

Link to comment
Share on other sites
sp1989

sp1989

Posted
Posted
Yep, thanks. There are many good Ariane options. I have researched them in the past, and I will do so again in the future. Liquidhype and I have worked together on things, so I am aware of him and his work, and we've exchanged many messages. However, this is way way premature. It's unlikely that I will reach the Ariane 1 first launch sooner than a year from now. The Ariane 5 is likely to be another year after that.

This is dedication ladies and gentleman!!

Link to comment
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing
×
×
  • Create New...