General Question XR-5 Mars

[NinjaWeasel]

I'm trying to get an XR-5 to mars, land/refuel and return. I'm trying to go straight from KSC, no stop on the way out. I've loaded up the cargo with LOX (1 tank) and fuel (the rest)... although I can probably drop the LOX since I ditched half the crew and I'm only going with 5 crew members.

My problem is that once I'm approaching Mars, I still don't have enough fuel to do the massive orbit insertion burn. I'm close enough to easily set up an orbit syched with Olympus, but the remaining fuel just isn't sufficient to do the insertion/landing.

Am I doing something wrong, or is this just too difficult with this ship without stopping at Mir for gas?

 

[Wolfer]

I think the XR5 just hasn't enough delat-v to make the trip. You could always refuel at the ISS, Mir or on the moon (as I usualy do).

Also, did you tried to ditch the fuel tanks when they're empty? I know it's not that much, but the more you can shave off the better.

 

[TSPenguin]

You can aerobrake into a mars orbit. This will save you a lot of fuel.
AerobrakeMFD will be invaluable to you.

 

[dbeachy1]

Just set MainFuelISP=5 in your Config\XR5VanguardPrefs.cfg file and you should have plenty of fuel for the trip:

#--------------------------------------------------------------------------
# Main Fuel ISP ("Specific Impulse") setting.  This determines how much 
# main/hover/rcs fuel is burned each second for a given thrust level.
# Higher settings allow longer flights without refueling.  Remember to 
# update the 'LOXLoadout' value later in this file as well so the crew will
# have enough oxygen for the mission!
#
# NOTE: The 'Expert' setting (0) is tuned so that you will need to use your SCRAM engines
# efficiently during ascent to LEO ("Low Earth Orbit").
#
# NOTE: these settings below are calibrated for *minimal payload in the bay*, so if you 
# carry a heavy payload you may have to bump up your fuel setting to the next higher setting.
# The ISP setting for each level is shown in [brackets].
#   0 = Expert    (ISS Only w/expert use of SCRAM engines and expert deorbit/landing)  [13943]
#   1 = Realistic (ISS Only)                [20914]
#   2 = Default   (ISS and Moon)            [25962]
#   3 = Medium    (ISS and Moon w/reserve)  [32981]
#   4 = Medium+   (Moon w/large reserve)    [40000] 
#   5 = Big       (Mars)                    [52922]
#   6 = Huge      (Jupiter+)                [366251]
#   7 = Massive   (Jupiter+ w/full payload) [549377]
#
# The default value is 2 (ISS and Moon).
#--------------------------------------------------------------------------
[COLOR=red]MainFuelISP=5[/COLOR]

By editing the config file you can get all the delta-V you want.

 

[Ark]

How about using a Delta launcher to put a tank of fuel into LEO on your intended orbital plane, then launch and use it to fuel up for the trip?

I experimented a bit not that long ago, it was pretty neat to start the takeoff in the XR5 while a Velcro Saturn automatically launches overhead.

 

[HiPotOk1978]

I have not tried this myself, but you can check out this add-on
[ame="http://www.orbithangar.com/searchid.php?ID=3813"]ReFuel's Morning Star Orbital Refueler V 2.0[/ame]

This addon was intended for orbital refueling of large craft and my upcoming refueling station but you can load as many or as few of the included fuel tanks in the cargobay as you want instead. Dougs most excellent crafts have all sorts of settings such as the ISP modifier that he mentions, but to me that is cheating... If the craft will not do it with default settings, additional add-ons are needed in my opinion. If you try the fuel tanks and they provide enough fuel to get you to Mars, please let me know