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Old 04-14-2008, 05:48 PM   #61
francisdrake
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Mickey,
I am sorry not to have any trajectory information of the Ares 1.
With the prior configuration I tried to fly manually the same profile as you assume (that is target and hold 20° inclination until the trajectory rises again).

With the reduced power of the J-2X I try to get more horizontal speed out of the 1st stage by inclining down to 15°. During 2nd stage burn I don't want to drop too far, so I point up to ~42° to null the vertical speed, coming back to horizontal gradually. At the end of the burn I try to get a reasonable vertical speed so the burnt-out second stage climbs at first and then falls back into the Pacific. If this insertion orbit is too circular I tend to hit the American west coast or the Rocky Mountain area (something I would try to avoid )

Lateral adjustment is required for launches due east also. The trajectory of the rendezvous vessel will usually not pass directly overhead, so a little adjustment is necessary.
_______

Concerning the 10% 'Orbiter bonus' on the engine power and ISP:
dV is very precious in real world rocketry, so precise steering is required to reach the goal. When 'eyeballing' a launch with standard Orbiter instruments, only very experienced pilots will reach orbit. The remaining 90% may become frustrated because they can't even make it to orbit. To increase the playability Martin uses a little extra margin in his Atlantis shuttle:

< quote from Orbiter SDK >

const double ORBITER_MAIN_ISP0 = 5000.0;
const double ORBITER_MAIN_ISP1 = 4000.0;
// Vacuum and sea-level fuel-specific impulse for orbiter main engines [m/s]
// using H2/O2 (hydrogen/oxygen)
// The correct ISP0 is about 3532 m/s!

</ unquote >

I am not quite sure on the 3532 m/s (seems a little low, might be a typo from 4532), but the real ISP is definitely not 5000 m/s. Currently I am taking his approach as a reference. If we can ensure that most pilots can reach orbit by providing them a method or autopilot not requiring a 'bonus' then I will omit it, but please understand that playability for me is even more important than bare realism

PS: Antonio, thanks for your kind offer to use your meshes and data again.
Will gladly use them, saves me a lot of work on the launcher!
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Old 04-14-2008, 06:06 PM   #62
Urwumpe
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Quote:
Originally Posted by simcosmos View Post
 I'm not an aerospace professional but suspect that things might not be as easy and as-apogee-free-of-constraints as just changing the pitch program for the AresI first stage (also when having in consideration other eventual first stage recovery considerations for this specific launcher configuration, some CEV abort scenarios, etc). Recovering the 5 segment SRB used on AresI might not be as 'easy' as recovering current SRB used in STS or when comparing with 5 segment SRB being used in heavy lifter configurations, but again, I'm not an aerospace engineer. As a side note, loosing recoverability might also be additionally interpreted - in some circles - as loosing the recovery system mass itself.
Well, I am also no full aerospace engineer - I just work on getting my diploma as computer scientist with specialization on spaceflight technology. Specialized aerospace engineers here learn more about the details, my kind of people learn all information needed for being able to develop software for spaceflight applications and understand the informations real aerospace engineers get us.

So, on your question if this is really this simple:
Depends on where you work - for NASA, things are pretty simple.

You have a virtual "basket" of entry conditions which define that the parachutes will be able to open. If the parachutes open, they will quickly reach terminal velocity. The key element in these calculations is the dynamic pressure, which depends on velocity and altitude. Other important elements are the gradient of dynamic pressure (if it increases too fast during landing, the parachute might not open or get damaged), the altitude difference from command for parachute deployment to reaching terminal velocity (more important for capsules which need fast opening parachutes during emergency - stages have a simpler mission). Another factor for optimizing the landing systems of the first stage will be the altitudes of the deployments. The higher you deploy, the stronger is the effect of high altitude winds on your landing location.

The parameters of the ballistic flight phase of the first stage after staging are only interesting as secondary factor for NASA - they want to know where the stages splashdown, but they don't need to optimize this distance. That's what Russian rocket designers currently have to do. They need to hit a zone which is only a few dozen km long, which can mean that they have to use a less optimal trajectory and stage mass ratio.

So, unless you have already useful information on the planned recovery systems for the Ares I, we are stuck with the Shuttle SRB recovery system, just scaled up for the higher landing mass. So, we can also assume that it has similar demands on the conditions for opening each kind of parachute.

Which are pretty low - if I remember correctly, two open parachutes out of three are already considered good for "intact" landing. If you can speak of intact landing at all in the case of segmented solid rocket motors.

If they want to use the same parachutes for the boosters of the Ares V (which could be mildly economic), the range of entry conditions could be pretty large. You could easier assume +/- 10% in the stability of the parachute system, than for the ISP of a rocket motor.


But anyway, it is your add-on. I can tell you how engineers might think and what implications a change of one parameter could have on the real thing - but I can't predict the future and tell you which implication they later accept and which they compensate with other implications. Also, I am just one guy... even if I save the time which gets lost in meetings, conferences and making presentations, I can never calculate so many implications as a team of NASA engineers at the same time.

Also simple is a pretty relative term. A simple ascent trajectory problem for the basic spaceflight course might already be a unsolvable problem for 90% of the orbiteers, who can enjoy life without EVER thinking about it.
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Old 04-17-2008, 04:14 PM   #63
francisdrake
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Tried yesterday to make it Ummu compatible, but no joy . My old VC++ 6.0 will not link the Ummu library. As I have currently not the time (and broadband connection) to download the free compiler and set up a new working environment I will concentrate on other design issues.
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Old 04-17-2008, 04:58 PM   #64
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Quote:
Originally Posted by francisdrake View Post
 Tried yesterday to make it Ummu compatible, but no joy . My old VC++ 6.0 will not link the Ummu library. As I have currently not the time (and broadband connection) to download the free compiler and set up a new working environment I will concentrate on other design issues.
Can't you ask somebody else to download it for you? If you are really native of Austria, all that prevents me from sending you a DVDR would be my lack of a DVD-recorder in my PC...
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Old 04-17-2008, 09:58 PM   #65
francisdrake
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Hi, I guess I will download the free compiler soon, but not now.
In the meantime small tedious work goes on, like the hatch animation,
new CM thruster, update docking port, etc.
Still have to clean up some textures, and code as well

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Old 04-17-2008, 10:08 PM   #66
Mission_CDR
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I have a question? will it just be the CEV? or will there be an updated CLV, CTV, and other related vehicles?
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Old 04-17-2008, 10:48 PM   #67
Zatnikitelman
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Wht are those larger thruster things near the bottom on the wedge things? Those some kind of backup TEI system?
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Old 04-18-2008, 05:28 PM   #68
francisdrake
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The idea is to use the old LSAM and Ares V (CaLV) and put it into the CEV package, so you can fly a moon mission.

The larger thrusters a the bottom are called auxillary thrusters. These are backup thrusters in case the main engine fails. They are of the same type as the larger Shuttle thrusters (R4D), originally developed for the Apollo SM and LM.
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Old 04-18-2008, 09:29 PM   #69
Kyle
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Well, its second to best. Anyways, for the VC, do you have the skills to make the interior detailed? I.e Maybe some MFD's that are shown inside the Default Atlantis, Some Buttons that don't do anything, or something around that?
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Old 04-19-2008, 07:48 AM   #70
francisdrake
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Default Next beta version available

Beta-testes are invited to download the next version:
http://home.arcor.de/francisdrakex/d...V-Orion-0f.zip

Major changes are in the reduced performance of Ares 1.
The first stage performance is 'as published', the second stage thrust and ISP were increased by 10%. This leaves less me than 1% fuel at orbit insertion.

Suggested trajectory: During second stage burn pitch up to 45° to avoid loosing too much height. Pitch down when speed increases.

Others: Hatch animation corrected. CM thrusters corrected, but due to asymetrical arrangment rolling induces unwanted pitch. So, when rolling to heads-down for reentry also pitch down to compensate for that.

New CM mesh, including windows, seats and dashboard (still very crude).
Astronaut for crew integration (courtesy of DanSteph, thanks!)
Minor changes on meshes and textures.
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Old 04-19-2008, 09:20 AM   #71
Urwumpe
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Ok, from the second test flight (the first failed because I did not get into orbit)

Trajectory: I tried it with my suggested trajectory, which inserted me into orbit with 1% fuel left, though I was still far away from perfect. Pitch over after launch by only about 5° and then do a gravity turn until at about 55° at staging. Vertical speed should be at about 1100 m/s.

After staging and Abort rocket separation, pitch down to 20° and keep it there, unless you have a better feeling than I had about what comes next. first apogee was at 190km, I then let it drop to 150 km, while increasing pitch first to 25° and later lowered it further to establish about 75 m/s vertical velocity at MECO (Apogee = 300 km in my case).

Fuel was displayed as 1% left, I think with some more flight praxis, this could get increased to maximal 2.5%. I still had too many gravity losses on the second stage flight, which I could have avoided. I will try lowering vertical speed at staging to 800 m/s, which should result in a lower first apogee but higher inertial speed at separation.

After that, I did a short navigation phase with Orbit MFD, separated the second stage and coasted away for the next 5 minutes. As the first flight led me directly into darkness, I did not deploy the solar arrays immediately, but instead first made the first OMS burn to circularize my orbit. When reaching the bright side again, I deployed the solar arrays and oriented for the sun.

Trouble Report:
VC mesh is too dark, make the groups to get rendered without orbiters shading, or highly emissive.
Display shows "Separate RM" when you actually want to separate the second stage. This caused some concerns.
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Old 04-19-2008, 11:08 AM   #72
simcosmos
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Quote:
Originally Posted by francisdrake View Post
 
Major changes are in the reduced performance of Ares 1.
The first stage performance is 'as published',
Hummm, Franz, could we do a little of data checking on your dll implementation?

For something like the AresI to work - where I'm defining AresI as having a 5 segment SRB in the first stage and as having a single J-2X US with ~140t propellants or so - the first stage needs to deliver ~1900m/s (~M5.6 to M6, need to check staging altitude vs apogee).

Unless I'm missing something, it seems that your SRB is only burning for ~105s, has a mass of ~80t, total solid fuel amount of ~525t and a max. thrust of 15.33MN.

I believe the values for the 5 seg. SRB should be:
~126s burn time
~105t vs ~626.43t fuel
~15.64MN

I might have other comments but, first things first, it might be better to check a few first stage performance details because the upper stage alone is kind of a single stage to orbit (hehehe, I mean, it does a big part of the ascent work) and if the 5 segment SRB does not provide the expected performance / injection conditions then things get a lot harder when having a single J-2X for the rest of the flight vs ISS inclinations (even with lower mass CEV) or vs Exploration missions (where we can use Earth's rotation but where CEV is heavier). I suspect that know what might have caused an eventual error in performance implementation but would first need extra details about it (we can continue here or by email).

cya,
António

Last edited by simcosmos; 04-19-2008 at 11:14 AM. Reason: the usual... typos, clarifications
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Old 04-19-2008, 11:51 AM   #73
Kyle
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Hmm, Downloading the Beta Version now, Will Report on any bugs that I see.
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Old 04-19-2008, 12:08 PM   #74
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Yes, I agree - the profile of the SRBs is similar to the 4 segment SRBs, not the newer 5 segment SRBs. The 5 segment SRBs use a different fuel, which is more effective and should burn for 130 seconds from what I remember.

New test flight, new data: Vertical velocity at staging 800-850 m/s (40° pitch), first apogee at 125 km, droop to 92 km altitude, orbit insertion into a 250 x -72 km orbit. 2.9% fuel left. My estimates had been too conservative. Needed to slowly increase pitch from 20° to 40° for avoiding dropping too deep into the atmosphere, so I call it still a successful failure.

Last edited by Urwumpe; 04-19-2008 at 01:29 PM.
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Old 04-19-2008, 04:39 PM   #75
Kyle
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Urwumpe, the Ares I Upper stage is not suppose to get you to Orbit. It works like the Space Shuttle's ET, after Sep, you burn again to get a better orbit.
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