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DARPA Launch Challenge


Tyneside, UK
2020 Oct 24
Saturday, Day 298

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The Challenge

The DARPA Challenge was aimed at finding a commercial organisation that was capable of launching a small satellite quickly and repeating the feat within a small space of time but using a different launch location. In the event, DARPA whittled the list down one company, Astra inc.

More detail of the project can be found at the DARPA Launch Challenge website.

The purpose of this article is to examine and explain some of the lesser publicised parts of the 2020 February-March launch campaign.


The Challenge

DARPA described the Challenge as requiring two launches from two locations, with different payloads and different trajectories - all within days’ notice.

It set the initial launch to occur in 2020 and in the window February 17-March 1.

Astra had received notice of the first launch just weeks prior to the event, and exact details for the payload 30 days before. As a reward for success, Astra would receive a prize of $2,000,000 and success was a prerequisite for attempting Launch 2.

The Launch 2 window would be later in March but within days of Launch 1. Astra would be required to deliver a second payload to LEO from a different launch location. If successful, the prize was $10,000,000.

In the event, DARPA narrowed the 'two different locations' down to two different launch pads at the same launch site. Astra chose to operate from the Pacific Spaceport, Kodiak Island, Alaska.

Astra did not meet the deadline for the Launch 1 window. An early technical delay was followed by a number of days when weather conditions prevented lift-off and high level winds and the potential for the ascending rocket to trigger a lightning strike got in the way. Because of the number of days lost to weather, Darpa extended the launch window by one day to March 2.

On March 2 itself, an early hitch pushed launch twenty five minutes into the 20:30 - 23:30 UTC daily window. Countdown proceeded until 53 seconds before lift-off when a call to "hold" resulted from an "off nominal" GNC (guidance, navigation and control) data reading. Astra investigated the problem but, about 30 minutes before the day's window closed, announced that the launch attempt had been abandoned.


Information Sources

Most of the information that follows comes from DARPA and Astra sources. Neither organisation was particularly good with its media handling, often making mistakes, sometimes issuing incorrect information and then not properly correcting errors.


Launch Vehicle

At the start of the campaign the launcher was simply referred to as "Rocket 3.0", following on from Astra's two earlier models of sub-orbital rocket.

Then references to the vehicle suddenly changed to "1 of 3" and parts of the DARPA Launch Challenge website were changed to reflect it but there was no announcement to point it out. Astra later explained it was the first of three rockets it was planning to launch and the name reflected the fact.

Rocket 3.0 is a two-stage rocket with five engines in the first stage and a single motor in stage 2.



Payloads

DARPA presented Astra with three satellites and an additional item of equipment for launch. All were held together by a P-POD Cubesat deployer with the satellites inside and the additional device bolted to the exterior.

Astra's job was to attach the P-POD to the launcher and provide a satellite release signal once in orbit.

All three satellites were Cubesats and fitted into a 3U P-POD deployer. In total, they added to 2.5U, leaving 0.5U of unused space.

Prometheus is a 1.5 U Cubesat belonging to the Department of Defense and reported to carry a tactical communications transmitter/receiver.

Prometheus Cubesats have all been the same size and some have been attributed to the Los Alamos National laboratory. Some have been ascribed a communications task but detailed information is lacking.

The photo, provided by DARPA, shows Prometheus ready to be loaded into the dispenser. It is 15 cm tall and 10 cm square. It has four fold-out solar panels - the hinges can be seen at the bottoms of the two visible sides.


ARCE (Articulated Reconnaissance and Communications Expedition) is described in several places on the Internet as a triplet of 0.5U Cubesats although the formal manifest listd only two.

There is evidence that there might have been an intention to fly three ARCE satellites. First there is the spare 0.5U in the P-POD. Second - the DARPA Launch Challenge website originally said there were four satellites in the P-POD although it only listed three. Enquiries about the contradiction resulted in the website count being reduced to three but without fanfare. Many web news pages still refer to there being four satellites on board, possibly based on the original text.

The ARCE satellites are from the University of South Florida and are described as having the task of testing inter-satellite communications. They ore 5 cm high and 10 cm square at the base. The photo was supplied by DARPA through the Launch Challenge website.


Attached to the P-POD was SOARS (Space Object Automated Reporting System) carrying a radio beacon and transmitter to test passing of information to automated ground-based receivers for use in identifying objects in orbit.

It was bolted onto one side of the dispenser as can be seen in this DARPA photo.



The Orbit

In advance, the orbit was described as sun-synchronous with a suggestion that it was aimed at about 450 km altitude. The Challenge required a satellite to be launched to an orbit between 250 and 450 kilometres and, at one stage, a DARPA representative stated that if Astra reached an orbit above 150 kilometres it would win the initial prize.

None of the payloads demanded a sun-synchronous orbit and a three-hour long launch window is not in keeping with a satellite requiring the precise lighting conditions offered by such an orbit. A launch at the daily window opening would have resulted in a Descending Node at about 09:15 Local Time.

The sun-synchronous requirement was probably set by DARPA as an arbitrary, easily-measured target.


The Mission

The map illustrates the ground track that Rocket 3.0 and then the satellites would have followed. The red coloured sector is the track covered by the launch vehicle while firing. Interestingly most of the initial orbit passes over ocean areas with very little landfall.


One of the DARPA Challenge webcasts mentioned that Astra realised quite late, only about four days before the first launch attempt, that there might be insufficient time to determine whether Rocket 3.0 has reached orbital velocity before it descended below Kodiak Island's radio horizon. An approach was made to the University of Hawaii for assistance which was readily agreed. Presumably the University's Cubesat ground station at The Hawaii Space Flight Laboratory was to be used.

The map shows two horizons, one for each of 250 km and 450 km orbit altitudes. The pass would have centred on about L +15 min and lasted between eight and eleven minutes depending on orbital altitude.


Final Steps

After the launch was called off and the deadline missed, the satellites were handed back to DARPA for return to their owners. Astra has stated that it will continue with its orbital efforts and planned triplet of Rocket 3.0 launches.


Page date: 2020 Mar 3


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