Question Manned Orion Mission to 2000 SG344

[Siliconaut]

Recently I have been playing with the CEV Orion and I decided I wanted to try a rendezvous with a near earth asteroid as planned for a future Orion mission.

So after a little research I settle on 2000 SG344. It requires a mere 4.8 km/s(according to IMFD, NASA/JPL say 3.4 or so) of delta v and is a likely target for the future orion mission to an NEA as a dress rehearsal for the big trip to mars. So through a tool of Orbit Hangar I installed my very own copy of 2000 SG344 into Orbiter.

Anyway, some real oddities. While trying to find good launch windows. I consulted both JPL's Near Earth Object Program website, the NASA Trajectory Browser website, and the Trajectory Optimization Tool off Orbit Hangar with an installed SPK for SG344.

All three agree that SG344 is the lowest delta v target possible within the NASA manned mission constraints which are:

Less than 12km/s delta v

Less than 420 days round trip mission time

At least an 8 day stay time

Launch window date between 2020-2050.

Anyway. Using all three tools to which all roughly agreed. The best launch window to rendezvous with SG344 within the decades listed was a launch date in early 2028. The final traj I settled on was launch on February 3rd, 2028. It is a 180 day flight time to the rock, a 20 day stay and then a trip back of roughly 6 months.

The problem I have is I don't like the length of the mission. While NASA constraints are a little wider, some sources I have read have stated that NASA would prefer a mission that lasts only 180 days round trip with a 10 day stay time at the rock, as opposed to a 360+-5 day trip with a 20 day stay at the rock.

I'd prefer the 6 month mission myself, and at first I entered in those constraints within the various traj tools, and I found plenty of decent trajectories that would get me to SG344 within 180 days. Some within 45 days with delta v's in the low 5's.. it wasn't a big deal according to NASA in theory. But things got complicated once I got into Orbiter and started messing around in IMFD.

The tools chosen for the job are the ORION CEV placed atop a Velcro Rockets SLS downloaded from Orbit Hangar. The OBH SLS is basically just a slightly souped up Saturn V using 4 massive SRB's around a common core. Really all I'm interested in is the upper stage(which I did A TON of testing with various modern stages to try to find the one with the oomph necessary to get me to SG 344). Which after insertion into a 400km parking orbit leaves me with 134k kg of fuel and 6.8 km/s of delta v. That much delta V is enough to get me out of LEO and to the rock with a small MCC at the apoapsis with just a tiny bit left over to start a rendezvous burn. Should I need extra fuel, once the SLS C stage separates from the Orion, I'm left with about 10k kg of a fuel left for rendezvous, station keeping with the rock for 10-20 days plus the delta v to get home. I forget exactly how much Delta V the Orion itself has.. but its certainly enough after sep from the SLS C stage to get home within 6 months, but I haven't gotten this far into the mission yet.

I tried tests with the Velcro Rockets EELV Delta IV Heavy, but it was too shy of Delta V to give me large enough margin for mistakes, which happen alot with me. So I had to settle for a fictional rocket that was just slightly more powerful than what we have today. It is roughly what the Modern SLS is planned to have in 2018.

Anyway some of the problems I have been having:

1)IMFD refuses to give me a decently low delta v launch window that agrees with NASA/JPL trajectories with round trip time constraints of 180 days:

NASA/JPL and the Trajectory Optimization Tool all have no problem finding me 6 months round trip mission times with a 10 day stay at the rock. But when I load up Orbiter, type in the dates of the launch window as NASA gives me in IMFD.. then I get these wild delta v estimates in the 10-12 km/s range and the position of the rock doesn't agree with where NASA/JPL says it is supposed to be. It is really wierd but..

if I place in trajectory dates of one way flight times of 180 days or greater from Earth to SG344.. then everything matches up to within a 24 hour tolerance level between NASA's estimates.. JPL's estimates and IMFD. Then IMFD has no problems providing me with a tejractory that matches almost exactly with the dates that NASA and JPL have given me for a manned rendezvous to SG344.

I know.. the obvious solution is to just fly the 1 year long mission with a 20 day stay at the rock instead of 6 months with a 10 day stay. But I want to try these 6 month round trip trajectories NASA plans to use. LOL


2)The final rendezvous maneuver with SG344:

I'm at a complete loss here as to what to do here. SG344 is about the size of an American Football field. It basically has no sphere of influence. There is no orbiting this rock. What one does is set up a heliocentric orbit that keeps one in station next to the rock. It is bascially like what one does to "Orbit" Phobos and Diemos on mars since neither rock(which are MUCH bigger than SG344) has the gravity to provide for a true orbit around it.

Anyway, Sync Orbit MFD doesn't have fine enough resolution for my needs.(which according to mission paramters call for the Orion capsule to keep station X meters from the rock and EVA's performed out of the capsule itself to the rock for sample collections.)

After MANY attempts through IMFD the best I have been able to pull was a fly by at 1+ km/s and 2 km altitude. NASA and JPL says I should be able to arrive at the rock with a .4 to .6 km/s relative velocity.

What would really be useful here would be a docking port on the rock itself. Then it would just be a trivial matter of using the docking HUD to null out the velocities and enter into a perfect station a few dozen meters from the rock itself. But the rock doesn't have a docking port.. so I can't use the docking HUD, docking MFD, etc for the final burn into station keeping.

One solution I have come up with is placing a DeepStar 2.1 lander on the rock and then docking the Orion to the lander itself. That is one solution (but given my obsession with "realism" that requires an earlier mission flown to actually land the deepstar lander on the rock without using the scen editor to "cheat", which is even HARDER than just getting the Orion to the rock and keeping station with it through a 10-20 day heliocentric orbit.

On top of all this I have read that 2000 SG344 might just be an old SIVB booster stage from one of the 1971 Apollo missions. I have decided once I have done this mission with SG344 as a rock. I will try it with SG344 as an old SIVB booster stage, which will probably be near impossible. But it would be cool to rendezvous with an AMSO SIVB stage in heliocentric orbit none the less.

This mission attempt has given me a new appreciation for certain things NASA/JPL has to do technically. I am of the opinion that this mission is MORE DIFFICULT than a Mars mission in some ways. Mars is a giant, monstrous target compared to a 100m rock floating in space, despite the close proximity and low delta v to get there. The technical aspects of setting up a station keeping burn are actually quite challenging, even with all the best of Orbiter's MFD's. Any suggestions would be appreciated.

 

[dgatsoulis]

About the dates and position of the asteroid not agreeing with Orbiter and other sources, are you sure you've imported the asteroid correctly into Orbiter?

About needing a "docking target" in order to null the relative velocity. Why don't you use IMFD's Orbital→Velocity Match program? You can easily target the body you want for station keeping.

Really interesting mission you've got there. Would you mind posting the links to the required addons and your launch scenario?

 

[orbitingpluto]

None of those late 1950's SLSs in the Velcro SLS addon are souped up Saturn Vs, as that SLS was thought up prior to Saturn 1 even being tested; the Saturn V was still a few years off from being proposed, and was a worlds away in design. But, that a bit nitpicky to ramble on about, so I'll stop there.

Anyway, since your using the CEV-Orion, I wonder if you've seen the new Orion francisdrake is working on, or the SLS gattispilot came up with? The SLS Block 2 in gattispilot's pack has less oomph than the SLS BC your using, but not by a lot(LEO payloads: SLS Block2- 130mt, SLS BC- 158mt). If you have a itch to stay up to date with SLS and Orion, both addons should scratch it.

Also, is this asteroid a vessel or a body? If it's a vessel, you could follwing lines to give it a transponder and frequency:

EnableXPDR = TRUE
XPDR = 477

... and I'm pretty sure it'll come up on your docking hud. It's been a while, so my apologies if it doesn't work.

 

[francisdrake]

First of all I find it great you are working on an Asteroid rendezvous scenario! Finding missions for the Orion will definitely improve the Orbiter-experience of near-future spaceflight.

I fully agree with Orbitingpluto, suggesting to use the MPCV-Orion currently under development. It has modern specs (mass, fuel) and a dV of 1.5 km/s.

I assume for any deep-space mission the Orion will be core of a stack of vessels, but not the only one. Main factors are:
- high dV demand, requiring a kick stage and possibly deep-space engines
- space for living through a year-long mission.

Below is a picture of a stack concept:
From right to left, this stack consists of an SLS upper stage as the kick stage, the Orion spacecraft, an ISS-derived hab, two Multi-Mission Space Exploration Vehicles to explore an asteroid (one would be sufficient, the other is needed for counter-balance) and a solar-electric propulsion module.
Based on a 2012 NASA paper.

 

[Siliconaut]

About the dates and position of the asteroid not agreeing with Orbiter and other sources, are you sure you've imported the asteroid correctly into Orbiter?

I used the MPC Database Viewer Exporter from Orbit Hangar:

[ame="http://www.orbithangar.com/searchid.php?ID=1436"]MPC Database Asteroid Viewer and Exporter v2.0.3[/ame]

I thought that myself and checked the elements and everything seems to agree. IMFD has no problems providing me with the exact trajectory NASA and JPL give me as long as it is 180 days long. Less than that it varies wildly.

About needing a "docking target" in order to null the relative velocity. Why don't you use IMFD's Orbital→Velocity Match program? You can easily target the body you want for station keeping.

*slaps head* Duh! All these years of Orbiter and using IMFD and I have never once found a use for the Orbital Tools. I need to RTFM on that for sure. Thanks!

Really interesting mission you've got there. Would you mind posting the links to the required addons and your launch scenario?

Everything is just culled from Orbit Hangar: Here are the links to the NASA/JPL trajectory sites.. these are cool sites:

http://trajbrowser.arc.nasa.gov/

http://neo.jpl.nasa.gov/

Velcro SLS [ame="http://www.orbithangar.com/searchid.php?ID=4178"]Velcro SLS v1.0[/ame]

I just attached an Orion CEV to the biggest baddest SLS in the package, the BC-2025 I think.. LOL

I'll be messing around with this awhile. Gonna try and AMSO it and land Apollo 11 LEM on it eventually.

---------- Post added at 03:47 PM ---------- Previous post was at 03:40 PM ----------

First of all I find it great you are working on an Asteroid rendezvous scenario! Finding missions for the Orion will definitely improve the Orbiter-experience of near-future spaceflight.

I fully agree with Orbitingpluto, suggesting to use the MPCV-Orion currently under development. It has modern specs (mass, fuel) and a dV of 1.5 km/s.

I assume for any deep-space mission the Orion will be core of a stack of vessels, but not the only one. Main factors are:
- high dV demand, requiring a kick stage and possibly deep-space engines
- space for living through a year-long mission.

Below is a picture of a stack concept:
From right to left, this stack consists of an SLS upper stage as the kick stage, the Orion spacecraft, an ISS-derived hab, two Multi-Mission Space Exploration Vehicles to explore an asteroid (one would be sufficient, the other is needed for counter-balance) and a solar-electric propulsion module.
Based on a 2012 NASA paper.

Yah I have tried several stack concepts on this mission and to mars. The problem is finding the proper motor to power the stack. The best stack I came up with in orbiter consisted of a NERVA2 powering an SBB 4.1 Hab Mod, SBB 4.1 Solar Panels and an Orion. It works somewhat. Do you know of any other add ons for building stacks like that?

Thanks for the links. Those are exactly what I was looking for.

 

[Astro SG Wise]

To make it all the more realistic, use these two (Orion MPCV and SLS).

http://www.orbiter-forum.com/showthread.php?t=34499&highlight=System+Orion+Space+Launch+MPCV+Development%3F Space Launch System. You can find the SLS addon in development that gattispilot has been making. I find it to be very realistic.

http://www.orbiter-forum.com/showth...t=System+Orion+Space+Launch+MPCV+Development?
This is the Orion MPCV that people have been reccomending. Sorry for not linking it, , and the spelling errors, my computer is having a few problems right now.

---------- Post added at 05:26 PM ---------- Previous post was at 05:25 PM ----------

Oh, wait, I did link it.
:lol:

 

[boogabooga]

A few thoughts:

MPC Database Asteroid Viewer and Exporter v2.0.3 came out in 2008.
IIRC, it comes with a database from the Minor Planet Center, which will also be from 2008. That is quite old, as asteroid orbits can be perturbed over time. I suspect that the orbit has been refined since then, and the SPKs and trajectory browser are using an updated orbit. Meanwhile, you have a 2008 solution in Orbiter...
Anyway, I recommend that you follow the directions in MPC Database Asteroid Viewer and Exporter documentation to go to the minor planet center and d/l the latest database.

Something else to try would be Burn Time Calc MFD to rendezvous with the asteroid at a pre-determined distance away from it.

 

[dgatsoulis]

Instead of the MPC VIewer, you can get the asteroid's state vectors (or orbital elements) from JPL's Horizons system and import them into the scenario as a vessel. After doing that, you'll have no problems matching 180 day round trip mission within the delta-v budget constraints. You can also use the same orbital elements to import the asteroid as a celestial body.

Here is one way to do it:

First, find a trajectory within the constraints you want with Nasa's Trajectory browser:

Make a note of the departure date and open JPL's Horizons system.

Click on web interface, use the settings in the pic below and click on generate ephemeris:

You are interested in these 7 numbers, (date, position vector, velocity vector), which you will need to convert into Orbiter format. (JD to MJD -subtract 2400000.5, km - km/s to m - m/s -multiply with 1000 and "right handed" to "left handed" coordinate system, swap the Y and Z values)

Horizons output

2462319.500000000 = A.D. 2029-Jul-02 00:00:00.0000 (CT)
   3.147261108849930E+07 -1.539562200052540E+08  2.829898228715083E+05
   2.761283004782815E+01  5.306608926642870E+00 -5.030156769687598E-03

Converted to Orbiter format:

62319.000000 = A.D. 2029-Jul-02 00:00:00.0000 (CT)
   3.147261108849930E+10  2.829898228715083E+08  -1.539562200052540E+11  
   2.761283004782815E+04 -5.030156769687598E+00   5.306608926642870E+03

Now create the scenario. In the one below, we have a DeltaGlider landed on runway 33 at KSC and the asteroid orbiting the Sun.

BEGIN_DESC
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 62319.000000
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL-01
END_FOCUS

BEGIN_CAMERA
  TARGET GL-01
  MODE Cockpit
  FOV 40.00
END_CAMERA

BEGIN_SHIPS
GL-01:DeltaGlider
  STATUS Landed Earth
  POS -80.705714 28.632274
  HEADING 150.00
  AFCMODE 7
  PRPLEVEL 0:0.500000 1:0.500000
  NAVFREQ 402 94 0 0
  XPDR 0
  GEAR 1 1.0000
END
2000_SG344:2000_SG344
  STATUS Orbiting Sun
  RPOS 3.147261108849930E+10  2.829898228715083E+08  -1.539562200052540E+11
  RVEL 2.761283004782815E+04 -5.030156769687598E+00   5.306608926642870E+03
END
END_SHIPS

Since there is no class "2000_SG344" vessel in Orbiter, you need to create one. Grab the Carina.cfg from Orbiter\Config\Vessels, make the changes below and save as 2000_SG344.cfg in the same directory.

ClassName = 2000_SG344
MeshName = 2000_SG344
Size = 18.5  ;from wikipedia
Mass = 7.1E+7  ;from wikipedia

Now all you need is a mesh, named 2000_SG344.msh, placed in your Orbiter\Meshes directory. The MPC Database Asteroid Viewer and Exporter has several to choose from. You'll want to scale it to the dimensions you want it.(I use MeshWizard for that).
Make sure that you enter the texture you want at the very end of the .msh file (including the .dds extension) and that you convert the MPC texture from .BMP to .DDS and place it in the Textures folder.

All set. Run the scenario and you will be able to target asteroid 2000_SG344 as a vessel. Optionally, you can add a docking port in the .cfg file if you want.

IMFD has no problem finding a solution that matches the one from Trajectory browser

You can easily replace the DeltaGlider in the scenario above, with the SLS stack you are flying.

Hope this helps