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Atlas Truss Adapter & Launch Vehicle Details

(all I can find in the Atlas Mission Planner’s Guide and Standard Interface Spec)

David Robinson/543

7/18/08

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173 inch (4.4 m) “Truss” Payload Adapter

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Published Performances [kg] for C3 = -0.5

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Specific Atlas-V 551 Performance for IXO

• Atlas V 551 performance to the nominal IXO 700,000 km L2 orbit (at C3 = -0.5 kg²/s²) is 6305.0 kg

– The payload penalty for using the 5m x 26.5m Long Fairing is approximately 85 kg

– The performance loss equals 10% of the fairings’ mass difference, reflecting the fact that fairings are jettisoned at a low altitude

per (NLS) S. Good AI Solutions, 2006

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NASA Launch Services Program Launch Vehicle Performance Quote – Constellation-X, Goeser

This performance assessment is based on an estimate of launch vehicle capability and does not represent a performance commitment by NASA Launch Services Program or the Launch Service Contractor. Actual performance may decrease due to mission specific requirements and/or fluctuations in launch vehicle performance capability. The performance data provided below is valid only with the ground rules and assumptions that accompany it. Orbit Request: Constellation-X mission requested EELV performance data to a C3 = -0.5 km2/sec2 with an estimated payload mass of around 6600 kg. Performance for the Atlas V configuration should assume a medium payload fairing. The mission is also considering using the 4394 payload adapter. Performance Results: Performance data was estimated for the Atlas V 551, the Delta IV 4450, and Delta IV 4050H (Heavy) configurations. The performance data, provided in the table below, does not account for the mass of a payload adapter/separation system. Once known, the mass for this hardware must be deducted from the data provided below to compute the mass available for the payload. *Separated payload mass = PSW/UL – Payload adapter/Separation system mass Atlas V 551 Ground Rules/Assumptions: - This performance does not include the effects of orbital debris compliance, which must

be evaluated on a mission-specific basis. This could result in a significant performance impact for missions in which launch vehicle hardware remains in Earth orbit.

- 3-sigma mission required margin, plus additional reserves as determined by the LSP. - Launch from SLC-41 at CCAFS (Cape Canaveral Air Force Station). - Performance values assume harness, logo, reradiating antenna, 3 payload fairing doors. - Payload mass greater than 9000 kg may require mission unique accommodations. - Performance provided is payload systems weight (PSW) and does NOT account for any

payload adapter/separation system. The separated payload mass will be the PSW less the chosen adapter/separation system mass.

Vehicle Performance* (kg)

PSW (payload systems weight)/ UL (useful load)

Atlas V 551 6425

Delta IV 4450 5030 Delta IV 4050H

(Heavy) 9780

- 5-meter medium payload fairing. This is a non-standard service and would incur additional costs.

- Performance based on: 6390 kg (nominal NLS payload performance)

+ 80 kg (NLS payload adapter) - 45 kg (performance adjustment for medium fairing. Note that the performance impact is a function of mission orbit targets.)

- 185 km (100 nmi) minimum park orbit perigee altitude. - 185 km (100 nmi) minimum escape orbit perigee altitude. Delta IV 4450-14 and 4050H (Heavy) Ground Rules/Assumptions - This performance does not include the effects of orbital debris compliance, which must

be evaluated on a mission-specific basis. This could result in a significant performance impact for missions in which launch vehicle hardware remains in Earth orbit.

- 3-sigma probability of Stage 2 commanded shutdown, plus additional reserves as determined by the LSP.

- Launch from SLC-37 at CCAFS (Cape Canaveral Air Force Station). - 4450 assumes a 5-meter diameter, 14.3-meter long composite fairing. - 4050H assumes a 5-meter diameter, 19.1-meter long composite fairing. - Composite fairing may require modifications for use with a 4394-5 adapter. - Performance provided is useful load (UL) and does NOT account for any payload

adapter/separation system. The separated payload mass will be the UL less the chosen adapter/separation system mass.

- 4450 performance based on : 4630 kg (nominal NLS payload performance)

+ 400 kg (NLS payload adapter, 1194-5) - 4050H performance based on : 9380 kg (nominal NLS payload performance)

+ 400 kg (NLS payload adapter, 1194-5) - 185 km (100 nmi) circular park orbit at 28.9 deg. inclination. - 185 km (100 nmi) escape orbit perigee. Please direct any questions regarding this performance assessment to: Susan Good a.i. solutions, Inc. NASA Launch Services Program Phone: 321-867-3108 Email: Susan.M.Good@nasa.gov

Received 7/23/08

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David,

I returned from vacation this week finding a number of emails which started with yours below. The 4394 PL truss referenced in the Mission Planner's Guide was designed for a specific mission and never flown. The interface to the Centaur for this truss is at a 123" dia BC which makes it a conical-shaped truss. The payload capability for this truss is limited by the capability of the Centaur Forward Adapter (CFA) to which it mounts, and since the truss is conical it imparts a component of its load radially into the CFA. For this truss, we created capability curves of mass vs. cg for the conservative load factors referenced in the Mission Planner's Guide. From your email below I infer that your SV is large, but without knowing the weight or cg location I cannot tell whether the 4394 truss adapter is the one that will work for you. A better choice might be another truss which we designed for a different payload. That truss is ~132" dia at the top and therefore is more cylindrical, and the loading into the CFA is axial. The capability of the CFA is much higher with primarily axial loading.

I can send you jpegs of Pro/E models, sketches or STEP files of either truss. I could also send capability curves, or you could tell us what you expect the approximate mass and cg to be. Let me know what will work best for you.

Thanks,

Mike Dew (303) 269-6377

Received 6/25/08

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David, here are the answers to your questions. Please let us know if you need any more information. Thanks, Cathy _____________________________ Cathy Andrulis United Launch Alliance Payload Accommodation Structures 303-269-6402 NEW 888-981-0364 pager 303-269-6272 FAX NEW

· Bolt hole pattern of the 4,394 adapter to the spacecraft This is documented in the Standard Interface Specification (SIS) Figure 4. Please let us know if you need a copy of this document.

· Position of the payload envelope relative to the SIP (standard interface plane) of the truss. Con-X is a tall spacecraft which may use the 5m medium or large fairing. The spacecraft goes well up into the ogive section of the fairing and so I need to be sure I understand where the payload envelope of the fairing “begins”. See figures 4.1.1-4 and 4.1.2.1-1.

The 4394 truss is 46" high. This adds an additional approximately 21" to the payload envelope height. (The 300.45" dimension

becomes 321" for the 5m medium.) The 3302 truss is 36" high. This adds an additional approximately 31" to the envelope

height. (The 300.45" dimension becomes 331" for the 5m medium.)

· Some words about the separation system. Is it a set of hard points (18?) with explosive bolts and push-off springs?

It could be. The separation system could also be a clampband or frangible joint, depending on the need of the SV. Please note that this separation system will be within the payload envelope.

· We assume there is no CG height limitation or envelope with these truss adapters… is this correct? There is a CG height limitation. The 4394 truss is capable of carrying 13,500lb with a cg height of 225". The 3302 truss is capable of carrying 42,000lb at 225". The full 3302 truss capability is shown in the SIS Figure 10 (the HPC curve).

· Figure 2.5.6-1 says that there is a 213 kg launch vehicle performance penalty for using a truss adapter. Is this essentially the weight of the 4394 adapter and if we used a smaller one like the 3302 size would the weight penalty be less?

Yes. The weight of the 3302 truss is approximately 428lb.

Received 6/26/08

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7/21/08 telecon with KSC with Cheryl Malloy, et al. They advised using this CG Height chart from the “SIS” document. Use the “HPC” line since it represents the truss adapter.

Also per Cathy Andrulis United Launch Alliance

6/26/08.

Atlas 5 Standard Interface Specification document

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Payload CG Height Limits

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Use “Truss” Adapter for no CG Height Limit

Baselining the 4.4m “Truss” Payload Adapter relieves IXO from any Center of Gravity height limitations

(email from Jeff S. 2006 10 03)

Gabe,        

We were unofficially told (and they would never put it on writing) that both the Atlas V and the Delta IV using the 173" truss PAF could handle a CG almost as high as the fairings themselves. An email that I had George Roach send me a couple years ago which was the closest thing we ever got in writing on this matter.  It was more than 6 years ago that I asked the launch vehicle folks @ KSC and they said this was the case but that they could not put it in writing.

Regards,Jeff

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