Trajectory Office backroom

[C3PO]

Put the comm sats into a nice, highly elliptical orbit with their engines, lower apoapse the (hopefully small) required amount, and raise periapse out of atmosphere.

MRO did it the other way around. Capture into a elliptical orbit, and then lower the periapsis to circularize orbit over a longer period.

But you'll still need enough DV in your budget to get into the elliptical orbit. If you plan to skim the atmosphere during insertion, you
WILL need a heat shield.

 

[Lord Wasteland]

I had said, for 30 days to get out of Earth orbit. I am getting this from a 1999 Scientific American article, that detailed it's specifics, approach, and et cetera. Do you guys want me to post the specifics.

 

[garyw]

Nope because we aren't using anything like that.

 

[Lord Wasteland]

Alright, so for the vessel(s) we are using, what kind of transfer are we planning?

 

[Arrowstar]

That has all been worked out (see the previous four pages of this thread). I will be publishing a technical memo in the next few days that describes precisely that. Please be patient with me, it's a busy time of year and I can only get so much done per day.

 

[garyw]

Alright, so for the vessel(s) we are using, what kind of transfer are we planning?

Read the mission discussion thread and the missions list. This has all been worked out and major changes to the missions are no longer being accepted.

That has all been worked out (see the previous four pages of this thread). I will be publishing a technical memo in the next few days that describes precisely that. Please be patient with me, it's a busy time of year and I can only get so much done per day.

Take your time, we have a little bit of time prior to mars missions. I appreciate all your hard work arrowstar.

 

[Arrowstar]

Alright, I need some help from someone who's good with TransX or IMFD. Please do the following:

-Place a DG in a 200x200 Earth orbit with 0 inclination.
-Set the date to 18 July 2018 at 12:00:00.
-Using TransX or IMFD, find a trajectory that gets to Mars on 12 October 2018
-Report back letting me know what the departure dV is

Thanks!

 

[dgatsoulis]

Alright, I need some help from someone who's good with TransX or IMFD. Please do the following:

-Place a DG in a 200x200 Earth orbit with 0 inclination.
-Set the date to 18 July 2018 at 12:00:00.
-Using TransX or IMFD, find a trajectory that gets to Mars on 12 October 2018
-Report back letting me know what the departure dV is

Thanks!

Hi Arrowstar, happy New Year!

The following results are with IMFD.

Departure: 18 July 2018 - Arrival 12 October 2018 - Time of flight: 86 days

dV 7229 m/s for Inc 0 degrees (ecliptic) 23,4393 degrees (equatorial).

dV 7148 m/s for Inc 27,93 degrees (eq) with a LAN at 7,68 degrees.

dv 8860 m/s for Inc 0 degrees (eq).

Hope these help
:tiphat:

 

[n72.75]

Hi Arrowstar, happy New Year!

The following results are with IMFD.

Departure: 18 July 2018 - Arrival 12 October 2018 - Time of flight: 86 days

dV 7229 m/s for Inc 0 degrees (ecliptic) 23,4393 degrees (equatorial).

dV 7148 m/s for Inc 27,93 degrees (eq) with a LAN at 7,68 degrees.

dv 8860 m/s for Inc 0 degrees (eq).

Hope these help
:tiphat:

7229 m/s ?

Sounds a bit high.

 

[Pipcard]

7229 m/s ?

Sounds a bit high.

Because you get to Mars in 86 days!

 

[Arrowstar]

Yeah, I was expecting high dV. I think I have an error in my departure tool somewhere, I just need to find it.

Thanks, dgatsoulis!

---------- Post added at 07:47 PM ---------- Previous post was at 11:12 AM ----------

Hi everyone:

I've put online a draft memo that outlines the departure and arrival dates of each Mars mission, the trajectories of each mission, and other considerations. Can I get extra sets of eyes on this document? Comments and constructive criticisms are most welcome. In particular, there are action items listed at the end of the memo that I'd like others to think about. Also, items listed in yellow are those items I was just guessing at.

Get the memo here.

Thanks!

 

[dgatsoulis]

Just went through the memo, excellent job Arrowstar.
Everything seems fine and I agree with you, we need to discuss the OFMM 20 departure date, because with the current plan, it will get to Mars 4 months after the human mission.

One thing I don't understand is why "the DSCS vehicles have 2017 km/s of ΔV available."
With an emptymass of 780kg , fuel 1497,54kg and an exhaust velocity of 3092 m/s , the available dv is 3313,25 m/s. Am I missing something here?

 

[Pipcard]

One thing I don't understand is why "the DSCS vehicles have 2017 km/s of ΔV available."

It was from the add-on's description.

 

[dgatsoulis]

It was from the add-on's description.

Thanks, I hadn't noticed it. Still 2017 m/s of dv is not right. Even in the scenario provided with the DSCS, on which the tanks are half full, the dv is 2081 m/s.

 

[Arrowstar]

So how much dV do we have? 3313 m/s?

Any suggestions on how to deal with the fuel ship departure/arrival dates?

 

[dgatsoulis]

Yes the dv is 3313 m/s . I did the calculation again and also checked with BTC 2.0 . The result was the same.

As for the fuel ship, there are two ways to deal with it. Either place it on a similar free return trajectory or push the date of departure back to the second launch window. I recommend the later because of the dv expenditure, but it's up to Gary to decide.

 

[River Crab]

One thing I don't understand is why "the DSCS vehicles have 2017 km/s of ΔV available."
With an emptymass of 780kg , fuel 1497,54kg and an exhaust velocity of 3092 m/s , the available dv is 3313,25 m/s. Am I missing something here?

I'm sorry, poor wording on my part. This is not the mass of the fuel, rather, the mass of the entire vehicle when fueled. Here is the calculation.

 

[dgatsoulis]

@River Crab

The calculation you posted is of course correct, but in the addon you have this:

Which gives a dv of 3313 m/s

 

[Arrowstar]

As for the fuel ship, there are two ways to deal with it. Either place it on a similar free return trajectory or push the date of departure back to the second launch window. I recommend the later because of the dv expenditure, but it's up to Gary to decide.

We can push it back (and I've considered it), but if we do that, we're going to have fuel sitting in Mars orbit for a very long time. Typically I'd be worried about boil-off, but I suppose we can hand wave that away. The other consideration, of course, is that the 2015/2016 window is going to be pretty full if we add this launch then. I've been spacing flights three days apart, which means we'll have two solid weeks of launches. Can we sustain that launch rate (or should we just hand wave that away, too)?

Gary, your thoughts?

 

[River Crab]

@River Crab

The calculation you posted is of course correct, but in the addon you have this:

Which gives a dv of 3313 m/s

Oh my, I really smegged up there :facepalm:
Thanks for the catch, this is why the version number is less than 1.0. Will fix this ASAP.