Ares I-X fails to beat weather for opening launch attempt
Ares I-X has seen its opening launch attempt scrubbed, following unacceptable weather conditions over the Pad. A few small gaps in the weather failed to coincide with the continuously realigned T-0s, which was also interrupted by a cargo ship entering the Eastern Range.
Processing Status (Pre-Scrub): *New article will be published for attempt 2.*
At Launch Pad 39-B, technicians and engineers spent the weekend making final preparations for Tuesday morning’s scheduled liftoff of Ares I-X.
Ordnance connections, PIC (Pyro Initiator Controller) resistance tests, first motion, Recovery Systems, and Flight Termination System (FTS) checkouts were completed over the weekend with positive results.
“Ordnance pre-connection system checks; flight and ground NO GO PIC resistance test, first motion test, Recovery System sequence test, Flight Termination System (FTS) open loop test, inhibit tests, hold fire circuit checks, FTS secure flight code load, FTS closed loop test are complete,” notes an Ares I-X status update, available on L2.
Further, “igniter access compartment closeout inspections” are complete as are all post-ordnance installation checkouts with the FTS.
Also, flight door installation on the Solid Rocket Booster (SRB) is complete.
Currently, Ares I-X is powered-down. Power-up of the vehicle and its systems for flight will occur in the initial stages of the countdown, which is set to begin at 1am EDT Tuesday morning.
Currently, there are no technical show stoppers for Ares I-X. In fact, Launch Director – or Launch Authority Team Lead as he is known for I-X – Ed Mango stated in a media Q&A session yesterday that throughout all of the integrity testing of I-X, both at the launch pad and in the Vehicle Assembly Building (VAB), the vehicle has performed “beyond expectations.”
“Usually, when you power-up a test vehicle like I-X for the first time, there are a host of things to go fix and tweak. That simply isn’t the case here,” stated Mango. “Ares I-X has been performing almost flawlessly for us throughout its integrated testing phase.”
In all, nearly every one of the over 700 sensors worked as designed once the system was fully integrated in the VAB. While a handful of sensors did not work as expected, there are still ~711 active sensors on the I-X vehicle – all of which were functioning perfectly as of Saturday.
Therefore, the main obstacle for launching I-X Tuesday morning, as of the writing of this article, will be the weather. Currently, there is a 60 percent chance of unfavorable weather conditions for the duration of the four hour launch window Tuesday.
“Probability of violating launch weather constraints: 60 percent,” notes the I-X processing update on L2. “Primary Concerns: Flight through precipitation and triboelectrification (the production of electrostatic charges by friction).
Recent Ares I-X Articles on NASASpaceflight.com can be found on this link:
In all, the triboelectrification Flight Rule is one that NASA has not concerned itself with for several years, as the Space Shuttle is not susceptible to this phenomenon and most EELVs (Enhanced Expendable Launch Vehicles) are coated to protect against it.
According to the 45th Weather Squadron of the Air Force – the Squadron responsible for monitoring all launch weather rules – Triboelectrification is defined as: “triboelectric charging observed to put aircraft and space vehicles into corona when they fly through clouds containing ice or precipitation in either phase.
“The corona generates radio signals known as P-static (Precipitation static). P-static can degrade the signal to noise ratio of critical communications to the vehicle, especially including the range destruct command link.
“The triboelectrification rule is designed to protect those critical communications links.”
The triboelectrification Flight Rule can come into effect under cloud cover conditions of 5/8 or greater when the clouds are “above the 14 deg F level up to the altitude at which the vehicle’s velocity exceeds 3000 ft/sec,” notes the I-X Weather Launch Commit Criteria.
For Tuesday and Wednesday’s launch attempts, a weather reconnaissance aircraft will determine if any clouds along the vehicle’s flight path (or clouds that are predicted to be along the flight path at the time of launch) pose a concern for this constraint.
Overall, winds are not expected to a problem on Tuesday or Wednesday. However, the I-X weather Launch Commit Criteria (LCC) states that Ares I-X cannot be launched if the surface winds exceed 20 knots.
For Wednesday, the primary concern for weather violation remains flight through precipitation and triboelectrification; however, the probably of violating those constraints during the four hour Wednesday launch window is only 40 percent.
System Development and Modification Overview:
Standing 327.24 ft tall, Ares I-X is the world’s third tallest rocket, coming in behind NASA’s Saturn V and the USSR’s (Union of Soviet Socialist Republic’s) N-1.
Over four years in the making, Ares I-X represents the first steps of the Constellation Program toward achieving the goal of a reliable, safe replacement for manned access to Low Earth Orbit (with lunar and Martian prospects as well) after the retirement of the Space Shuttle fleet.
Composed of a loaded four segment Solid Rocket Booster (SRB), a fifth SRB segment weight simulator, an Upper Stage Simulator (USS), and a boiler plate Orion Capsule and Launch Abort System, Ares I-X is nearly identical to the current design of the Ares I vehicle.
Because of the Ares I’s unique use of a single SRB as the sole source of First Stage thrust, several unique adaptations to the vehicle’s control system had to be incorporated for the I-X mission.
Arguably the most critical of these adaptations was the addition of a Roll Control System (RoCS) to help the I-X vehicle (and the future Ares I vehicle) maintain its proper orientation during flight.
The RoCS, developed by the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, will execute a “90-degree roll maneuver of the I-X vehicle after tower clear and control roll attitude during flight.”
While the Ares I vehicle – for lunar missions – will not have to execute a roll maneuver after clearing the Launch Umbilical Tower (Ares I will simply “pitch over” for lunar missions and fly due east from KSC), Ares I-X will have perform a 90-degree roll maneuver in order to orient itself into the same position that Ares I will be in during First Stage flight.
Essentially, Ares I’s flight axis will point east while the rocket rests on the launch pad. Ares I-X’s points south due to the need to utilize existing Shuttle hardware for SRB access at the launch pad.
Nevertheless, if Ares I is used to transport crew and supplies to and from the International Space Station, the vehicle will have to perform a roll maneuver in order to orient itself onto a northeasterly flight path.
However, regardless of whether or not Ares I has to perform a roll maneuver after tower clear, the fact remains that the RoCS will be used to prevent the vehicle from spinning along it axis during flight.
This phenomenon, which program and project engineers and managers describe as corkscrewing, is caused by the combination of the “stick” vehicle’s natural tendency to roll around its axis and the multiple protuberances on the skin of the vehicle which create instabilities in the downstream air flow over the vehicle.
While corkscrewing would not be overtly detrimental to the I-X test flight, it would be harmful to Ares I since you do not want your Flight Crew spinning around the center axis of the vehicle during launch.
Corkscrewing of the I-X vehicle would, however, prevent the communication antennas on the vehicle from maintaining proper alignment with ground-based tracking stations.
As such, data downlink could be intermittent – as could communications with the vehicle’s various systems which could pose a potentially significant problem if the need arose to terminate the flight.
To solve this problem, MSFC developed two RoCS pods (Pod A and Pod B), which are located on opposite sides of the lowest segment of the USS on Ares I-X.
Each pod contains two thrusters capable of generating up to 2,250 pounds of force in a vacuum.
The RoCS modules “fire tangential to the skin and at right angles to the roll axis in order to provide a controlling roll torque,” notes an informational sheet from MSFC.
The RoCS will be enabled just after tower clear until just prior to SRB burnout and separation from the USS.
The RoCS components were constructed from decommissioned Peacekeeper missiles and enabled NASA to reduce the cost and development time of a new RoCS – thereby furthering the Ares program and NASA in their desire to use as much heritage hardware as possible.
However, the development of a RoCS for Ares I-X was not the only aspect of the launch system that required adaptation. The SRB required extensive modifications to meet the Ares I (and I-X) specifications.
In all, four components of the SRB for Ares I-X were constructed especially for this flight. The Frustum, the Forward Skirt Extension, the Forward Skirt, and the Fifth Segment Simulator were all constructed for I-X.
Of particular interest is the Fifth Segment Simulator. “The fifth segment simulator is unique to the Ares I-X test flight and will be recovered with the first stage booster,” notes an ATK (the company which produces and managers the Reusable Solid Rocket Motor segments) information booklet.
The segment is attached to the top of the forward-most active segment and the lower portion of the forward skirt.
The fifth segment simulator serves to elongate the Ares I-X vehicle to the proper height (equaling that of the Ares I), contains 90% of the electronics and avionics that will be used during the test flight, and simulates the empty weight mass of an SRB motor segment.
The reason the fifth segment simulator does not simulate a loaded segment is because of recovery operations of the First Stage after splashdown in the Atlantic.
It was determined early on that, since the weight of an SRB segment changes as the solid propellant is burned, it would be more advantageous to simulate an empty segment so the SRB would not carry “dead weight” during separation, entry, descent, splashdown, and recovery.
In all, the Ares I-X first stage SRB “will provide primary propulsion for the flight, is a motor from the Space Shuttle inventory, includes a fifth segment simulator to match the Ares I First Stage height, includes new main parachutes, and demonstrates the ability to recover the First Stage.”
The final major system on the Ares I-X is the avionics systems.
Developed by Jacobs Engineering and Lockheed Martin, the I-X’ avionics package is comprised of heritage hardware from the Atlas rocket, modified SRB avionics, new box developments, and Commercial-Off-The-Self (COTS) systems.
Comprised of a Fault Tolerant Inertial Navigations Unit (Atlas heritage), a Redundant Rate Gyro Unit (Atlas heritage), Flight Software (modified Atlas heritage), Ground Communication, Command, and Control System (new development), First Stage Avionics Module (new development), Ascent Thrust Vector Controller (new development), and COTS Developmental Flight Instrumentation, the avionics system is responsible for First Stage and vehicle control from liftoff to recovery.
The system is also responsible for recording data and telemetering that data to the ground via the vehicle’s communication antennas.
The Test Flight:
In all, the Ares I-X test flight is predicted to last approximately 7-minutes (from liftoff to SRB splashdown). However, only the first 2-minutes 2-seconds (or 2-minutes 12-seconds – depending on how long it takes the SRB to burn) of the flight will be “powered flight.”
Countdown for the scheduled 8am liftoff is set to begin at 1am EDT following Call To Stations for the launch team at 12:30am.
The first weather balloon will be launched at 1am and preparations to power-up the vehicle will begin at this time as well.
At 3:30am, vehicle cooling will be removed; the Onboard Navigation Unit will be aligned for flight; and the First Stage avionics module access platform will be retracted.
The Flight Control Team will come on console at JSC at 4am, six more weather balloons will be launched at 4:30am, and, at 5am, Inertial Navigation Unit alignment will be complete.
The Rotating Service Structure will be moved to the “park” position at approximately 5:25am.
Range Safety System verifications, Auxiliary Power Unit checkouts and C-Band beacon transponder power-up and testing with the Eastern Range will commence at 5:30am.
The Vehicle Stabilization System (VSS) will be retracted and secured at 6am, with final pad securing for liftoff beginning around 6:15am.
Final pad evacuation will begin around 7am as well as “range verification of all ‘go-no go’ interfaces.”
The Flight Termination System will be activated and set to ‘safe’ at 7:17am The Countdown will then enter its only Built In Hold at 7:36am at the T-4min mark.
If all technical work is on time, the Launch Authority Team will conduct their final “Go/No Go” poll for launch at 7:46am If all systems and the weather are “go” at this time, the countdown will resume at 7:56am.
If the weather (or any technical aspect of the rocket) is not “go” for launch, the Launch Authority Team has a four hour window in which to wait out the weather or resolve the technical issue(s).
Once the countdown resumes, the Flight Termination System’s safe and arm devices will be armed at T-3mins 30 seconds. This will be followed 5 seconds later by the arming of the SRB safe and arm device.
At T-2 mins 59 secs, the vehicle will transfer to internal power. Onboard instrumentation recorders will be activated five seconds later.
The Flight Control System (FCS) will be placed into “launch enable” at T-1min 40-seconds and will “go internal” at T-1min 20 seconds.
Also, at T-1min 20 seconds, the Ground Control Station count will begin.
At T-50 seconds, the SRB joint heaters will be deactivated, followed 10 seconds later by the disabling of the gas generator bed heaters.
At T-35 seconds, the FCS will “go inertial.”
The single APU on the SRB will be started at T-28 seconds with a gimbal profile of the SRB nozzle at T-21 seconds.
The ignition and hold down bolt pyros will be armed at T-18 seconds and the Sound Suppression Water system will be activated at T-16 seconds.
The Commander Receiver/Decoder inhibit will be removed at T-10 seconds.
Finally, the hold down bolts will be blown and the SRB ignited at T-0.
At liftoff, Ares I-X will weigh 1.8 million lbs, with the four segment SRB providing between 2.6 and 3.3 million lbs of thrust that will propel the Ares I-X to a height of 130,000 ft.
The SRB nozzle will be gimbaled at Mission Elapsed Time (MET) 0.1 seconds for the “fly away” maneuver (designed to pull I-X away from the launch tower). First motion off the MLP is expected at MET 0.2 seconds.
The RoCS will be enabled and the 90-degree roll program started at MET six seconds. The “fly away” maneuver will be considered complete at MET 20-seconds.
For the first 91 seconds of flight, the RoCS system will be activated every 10 seconds to counter any axial roll of the vehicle. MaxQ is expected at ~MET 50 seconds.
The Flight Control System phase of flight will transition into the separation phase of flight at MET 2 minutes 00.6 seconds.
According to flight timelines, SRB burnout is expected at MET 2 minutes 4 seconds; however, the latest possible time of SRB burnout is MET 2 minutes 12 seconds. As such, all further flight times are based on this no later than SRB burnout time.
The Booster Deceleration Motor and Pyro Initiator Controller will be armed for separation at MET 2 minutes 13.9 seconds with the Thruster Vector Control system commanded to “null” and RoCS deactivated at MET 2 minutes 14 seconds.
The SRB APU will be shutdown at MET 2 minutes 14.5 seconds.
Eight Booster Deceleration Motors will fire at MET 2 minutes 14.9 seconds, followed 0.1 seconds later by First Stage and USS separation. The Booster Deceleration Motors are designed to pull the SRB clear of the frustum and USS.
At the time of SRB and USS separation, the Ares I-X will be travelling at approximately mach 4.76 at an altitude of 130,000 ft. The maximum acceleration force during flight will be 2.48 g.
The SRB tumble motors will fire at MET 2 minutes 18-seconds, inducing a horizontal tumble into the SRB’s profile. This will increase drag on the SRB, preventing recontact with the free flying USS and slowing the SRB down during reentry.
The Recovery Control Unit pyro will be armed at MET 2 minutes 45-seconds.
After coasting to an altitude of 150,000 ft, the parachute system will engage at 16,000 ft (or MET 5 minutes 15 seconds) with the deployment of pilot chutes.
The main chutes will be deployed at MET 6 minutes 15 seconds, brining the SRB to a manageable speed for splashdown in the Atlantic.
The First Stage nozzle will be severed from the SRB at MET 6 minutes 35 seconds, with splashdown occurring ~147 miles downrange from KSC just prior to MET 7 minutes.
The USS will also coast to approximately 150,000 ft before plunging into the Atlantic Ocean at near terminal velocity. The USS is expected to break apart upon impact with the water and sink to the ocean floor.
The SRB will be recovered and towed back to Port Canaveral for inspection, data recorder removal, disassembly, and shipment back to ATK in Utah.