**Lesson Info**

-   **Lesson Number:** FPPD-LL-0052

-   **Lesson Date:** 11-Jan-2001

-   **Submitting Organization:** GSFC (422)

-   **Submitted by:** Michael Comberiate

**Subject/Title/Topic(s):**

Aqua Red Team Review of Launch-related Issues and Concerns

**Description of Driving Event:**

We have prepared a summary of the major issues and /or concerns that we
have had to deal with for the Aqua project regarding our Launch Vehicle
(LV) Interfaces. This is in preparation for the eventual Red Team review
and to accumulate lessons learned that could benefit other missions. We
are launching in CY 2001 on a Delta 7920 two-stage vehicle with 9
strap-on solid rocket motors. This mission required the stretched 10-ft
composite fairing, which is the largest ever used by Delta. Boeing is
the LV contractor and TRW is the Spacecraft (S/C) contractor. The launch
will be from Vandenberg Air Force Base (VAFB) in California, into a
690km polar orbit, with an ascending node \~130pm mean local time.
Details for each of the topics on this chart are available on request.

Below are several of the key issues from this chart, which would be of
general interest to other projects.

**Lesson(s) Learned:**

1.  Helium Permeation: Helium has penetrated vacuum seals and
    deteriorated bearings (EO-1 IRU). Helium molecules are so small they
    go anywhere. Moisture would adversely affect Instrument subsystems.
    Teflon lines are flight qualified for disconnects, but are permeable
    to helium. Helium is always used by Boeing to switch the Liquid
    Oxygen valves and it is vented in large clouds during normal
    operations on the pad, particularly if the mission is scrubbed after
    the Mobile Support Tower has been rolled back.

2.  Tip Off Velocity: S/C separation from LV introduces a tip-off
    velocity that might exceed S/C ability to accommodate without the
    use of thrusters (which we hope to avoid using autonomously). Causes
    are Shock of Clampband Separation & spring-loaded indicator switches
    coupled with S/C cg offset.

3.  Contamination:

    -   Cleanliness at the Launch Site Integrated Processing Facility
        (IPF). All the handling under unusual circumstances raises
        concerns about contamination for our optical instruments. EO-1
        mission has to remove their fairing on stand and found
        unexpected particulate contamination on their exterior surfaces.

    -   Cleanliness in transport: Trucking S/C for 6 hrs from TRW to
        VAFB. Then 25-mile trailer run between IPF and SLC-2 at VAFB.

4.  Fairing Fluroglide: Has been used on the seal between fairing
    halves, but it is identified as a source of debris at Fairing
    Separation.

5.  Target Altitude: Aqua needs to park in a specific orbit location for
    science and ground support.

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a)  Our goal is to enable the final orbit to be phased with Terra and
    Landsat-7 to optimize spacing between ground contacts.

b)  The Delta altitude 3 sigma tolerance is +3.7km/-18km, but it usually
    achieves \<1 sigma

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6.  Target Inclination: Aqua needs weekly opportunities for executing a
    maneuver(s) to obtain the proper ground track error in reference to
    the WRS. Choose a target inclination based on both physical and
    operational considerations.

7.  Cadmium Parts: Boeing accidentally used Cadmium parts, which outgas,
    as new end fittings for our S/C - LV clampband.

8.  Battery Recharging: Can the Flight battery be adequately recharged
    if the launch is scrubbed? Given all the activities required to
    reconfigure the pad and the S/C, there is only a limited time
    between successive launch attempts (24 hours) for this.

**Recommendation(s):**

1.  Helium Permeation: Pressurize sensitive areas with GN2 to lower
    risks: GN2 Purge IRU & AIRS through lift-off; Stainless Steel Lines
    to S/C in general; Teflon Lines in fairing are wrapped in Al, except
    at joints. S/C uses polyurethane lines internally. Special Umbilical
    disconnect for purge lines.

2.  Tip Off Velocity: Separation Latches will restrain S/C for a few
    seconds after clampband separation, when shock has dissipated. Then
    an automatic command cuts a banding cable that releases these three
    latches freeing the S/C. Helium vented from S2 then causes LV to
    back-off. Widened Cant angle for LV He venting to preclude affecting
    the S/C. The residual impingement on the solar array was assessed
    and deemed insignificant.

3.  Contamination:

    a.  Cleanliness at VAFB IPF and SLC-2W: S/C will be bagged with two
        bags for shipping from IPF to SLC-2W in the Boeing can. MST
        White Room will be at 100k or better with restricted access
        imposed to try to approach 10k levels. It will be cleaned to VC6
        levels prior to our arrival (EO-1 was cleaned to only VC3
        level). An adjustable shroud will be used between levels 5 & 6
        with 10k controls and separately filtered air flow. Personnel
        training imposed on maintaining cleanliness. Continuous
        monitoring of particulate counters with "wipes" and tape lifts.
        More stringent control on cleanliness throughout should ensure
        10klevel. Some concern that S/C is exposed to the white room
        level just before the fairing is installed, after shroud is
        removed. Also, we will take special precautions to ensure that
        any contamination on the outside of the shroud does not fall
        onto the S/C as that shroud is removed.

    b.  Cleanliness in transport: Using Terra Transporter for Aqua, from
        TRW to VAFB. Extra Instrument Bags with custom, non-flight bag
        frames & GN2 purging on route.

4.  Fairing Fluroglide: Not used on Aqua because of contamination
    concerns. Should no longer be necessary given the latest Boeing
    designs, but older fairings still on the shelf might be using it, so
    check into that before accepting your fairing.

5.  Target Altitude: GSFC recommendations accepted by TRW: These are our
    reasons for targeting to 690km instead of 705km:

    a.  Staying below 705 will preclude rotating the spacecraft to do
        retro burns.

    b.  690km will not add launch window constraints. Targeting at 705
        reduces the window to 4 days out of every 16, to maintain EPGN
        contact spacing.

    c.  It will take less fuel to raise altitude than is required for
        lowering the altitude.

    d.  The lower we target the shorter the time between opportunities
        to do maneuvers.

    e.  It optimizes the use of the Delta LV while assuring that we
        don\'t overshoot.

    f.  Probability increases for commanding stage 2 to shutdown (PCS)
        before it runs out of fuel

6.  Target Inclination: 98.167 degrees inclination was chosen to:

    a.  Maintain the mean local time within 1:15 to 1:45 p.m. (ascending
        node) and the beta sun angle within 16 - 32 degrees

    b.  Optimize the initial inclination for a nominal insertion- avoid
        the necessity for immediate correction maneuvers

    c.  Avoid the need to perform maneuvers to increase the inclination,
        when possible (the natural inclination drift is positive, so
        typical inclination corrections are performed to decrease the
        inclination)

    d.  Allow for at least 100 days post-launch before an inclination
        maneuver would be required

    e.  Consider effects of launch dispersions (+/- 0.027 deg)

    f.  Assume a 10-minute launch window

7.  Cadmium Parts: Rather than change the parts again and compromise the
    hardware, the cadmium has been wrapped to preclude outgassing. The
    duration of the concern is only minutes, so this solves the problems
    without adding new issues.

8.  Battery Recharging: Anticipating the possibility TRW analyzed how
    much time will be available in the minimal turn-around for
    recharging. Aqua battery requires a special liquid cooling system to
    be attached in order to not lose capacity during recharge. Our study
    shows that the 6 hours we will have are adequate to return the
    battery to a fully charged state, so that we don\'t lose capacity
    with every scrubbed launch. This info is needed to retain the
    possibility of a second attempt to launch within \~24 hours.
    However, if we cannot charge for at least 140 minutes with our
    battery liquid cooling system attached, then we cannot launch 24
    hours after a scrub.

**Evidence of Recurrence Control Effectiveness:**

1\. Helium Permeation:

2\. Tip Off Velocity:

3\. Contamination Controls at Launch Site:

4\. Fairing Fluroglide:

5\. Target Altitude:

6\. Target Inclination:

7\. Cadmium Parts:

8\. Battery Recharging:

**Applicable NASA Enterprise(s):**

None selected.

**Applicable Crosscutting Process(es):**

Provide Aerospace Prods & Capabilities: Evaluation

**Additional Key Phrase(s):**

Flight Equipment

Ground Operations

Ground Equipment

Hardware

Launch Process

Launch Vehicle

Spacecraft

Transportation

**Can this lesson be included in the International Safety Lessons
Learned (ISLL) Database?** Yes

**Submitted by:** Michael Comberiate

**Mail Stop/Code:** GSFC 422 / 730

**Lesson Author (if different):**

**Phone Number:** 301-286-9828

**E-Mail Address:** michael.comberiate@gsfc.nasa.gov

**Lesson Date:** 01 / 12 / 2001