Compton discovers an X-ray pulsar; moreoever, it may be a variable X-ray pulsar, a real oddity.
Eutelsat plans to move Eutelsat 1F1 eastward somewhat, giving its beams coverage of the western CIS states. No specific customer named yet.
NOAA-13 checkout underway after launch by Atlas from Vandenberg 9 Aug. [Well, we all know what happened then...]
JPL picks Rockwell and a Hughes/TRW consortium as short-list bidders for Mesur.
Marshall Aerospace begins flight tests of OSC's Pegasus-carrier TriStar.
Milton Thompson dies 6 Aug. Thompson was an X-15 pilot, the first man to fly a lifting body (the M-2), the only civilian selected as an X-20 Dyna-Soar pilot, and (at the time of his death) chief engineer at Dryden.
An unconventional launch bid: Arianespace offers India a three-launch package deal, with the second on Ariane 4, the third on Ariane 5... and the first on Proton! Ariane 4 is so heavily booked that Arianespace cannot offer a launch for Insat 2C early enough, so it has made an agreement with Russia and Kazakhstan to offer Proton instead. Just how this relates to Lockheed-Khrunichev's Proton marketing is not clear, although presumably the Proton for India could be bought through them. Arianespace says it will *not* be offloading existing customers onto Proton; this is seen strictly as a way of acquiring new customers who cannot wait for an Ariane slot. Ariane is booked through the end of 1996 for primary payloads, although some slots are still available for somewhat-smaller secondary payloads.
Meanwhile... Senate Armed Services Committee criticizes lack of any well-defined plan for a new-generation launcher, zeroing funding for Spacelifter and NASP but allocating $30M for some combination of them and upgrades to older launchers. The committee says the situation is difficult: DoD probably cannot afford to keep Titan, Atlas, and Delta all in business, especially since upgrades to them are unlikely to produce major cost reductions, but also cannot afford a massive development program for a new launcher. The committee recommended that DoD look at possible use of foreign launchers. [There is some feeling that this was intended to scare DoD into getting its act together, rather than as a serious suggestion.]
The corresponding House committee retained $54M for Spacelifter and raised NASP from $43M to $79M. It also supplied both $4.88M for DC-X testing and $75M for SX-2 startup, recommending that the SSTO effort be moved from BMDO to ARPA: "If the United States is to regain its international competitiveness in this critically important military and economic area, it must pursue promising enabling space launch technologies that have the potential of dramatic reductions in launch costs".
In another bailiwick :-), NASA continues its own study of future launch needs, in three parts. Part 1 is looking at changes to the shuttle to make it cheaper and more reliable, against the possibility that it will be in service another 40 years [!!]. Part 2 is looking at enhanced expendables taking over about ten years from now, with some sort of manned capsule for manned missions, and the possibility of foreign involvement. Part 3 is looking at more radical ideas [that is, ones more recent than the 1950s], such as SSTO and air- launched TSTO: "[this group] has come up with several very promising options... one feature of this group's report will be the recommendation for a strong NASA technology program over the next several years to put us in a position to have enough confidence to go into a new vehicle program...".
Discovery's engines shut down 3 seconds before liftoff 12 Aug due to a failure in a flowmeter. This will mean at least a three-week delay, since the engines, having lit, must be inspected or swapped out -- they will probably be swapped, since it's difficult to do a full inspection on the pad. This launch attempt had already been slipped from 4 Aug, after NASA noticed that that date would have Discovery aloft during the possible Perseid meteor storm. The latest slip puts NASA in a bind, since it can no longer launch four missions before year end as planned. Columbia was set to fly Spacelab Life Sciences 2 in Sept; Discovery would have been cycled around to fly Spacehab 2, the Wake Shield Facility, and cosmonaut Sergei Krikalev in Nov; and of course Endeavour is being readied for the Hubble repair in Dec. NASA particularly wants to fly the Hubble repair on time while the crew's training is fresh, so the odds are that Discovery's next flight will slip into 1994... which will mean a relatively tight schedule in the first half of 1994.
Spot 3 launch delayed due to electrical accident during prelaunch tests. Initial inspection has turned up no significant damage, although the satellite will be gone over more carefully and the battery will probably be replaced as a precaution. The likely result is a slip of 2-3 weeks. Spot Image wants it up soon, because of the four tape recorders on Spots 1 and 2, three are dead and one is ailing... which makes it difficult to get images of areas far away from receiving stations.
ITD Space Remote Sensing Center (at Stennis) supplies an interesting composite image of the midwest floods: a pre-flood optical image from Spot overlaid with an ERS-1 radar image of the flooding, indicating exactly what's currently underwater. (Heavy cloud cover has limited optical imaging coverage of the area.)
Magellan control breathes a sigh of relief as aerobraking ends 5 Aug. Total fuel burn was 31.6kg, against 53.2kg allocated, for an orbit change that would have required 900+kg to do by rockets alone. Magellan has suffered no [detectable] damage, and indeed it is running cooler now [just why Magellan tended to overheat is not known, but one guess is surface contamination, and aerobraking may have burned it off]. Most of the fuel consumption was for attitude control (Magellan's thrusters, more powerful than its reaction wheels, were the main attitude-control system for braking passes), and most of the fuel use actually was after the end of braking passes, when the thrusters tended to bat the attitude back and forth after aerodynamic stability was lost; some fuel was saved, after experience accumulated, by turning the reaction wheels back on relatively early. Small amounts were used for correction burns and for the initial and final burns.
The orbit at the start was 8468x172km, and is now 541x197km, a net velocity loss of 1221m/s. The maximum dynamic pressure experienced was 0.4 N/m^2, equivalent to an Earth-surface airspeed of 1.5kt. The highest temperature on the solar arrays was 89.4C (the temperature on the high-gain antenna was higher, but its temperature sensor has died, so the solar-array temperature was used as a proxy). After a slow initial "walk-in" to allow for atmospheric uncertainties, drag was kept more or less constant, requiring slow lowering of periapsis as the braking passes drifted into the "late afternoon" side of the planet where the upper atmosphere is thinner. This required small correction burns, first upward (when orbital dynamics tended to push periapsis down) and then downward (as the orbit changed enough to reverse the effect).
The tricky part of the operation was determining the exact time of periapsis, basic to choosing the right attitude for entry. The normal method was via DSN tracking... but unfortunately that had a turnaround time of several hours. JPL developed two other methods to do short-turnaround corrections: the solar-array temperature generally peaked 30+-3s after periapsis, and measurements of average attitude variation during a braking pass could measure entry attitude error (which showed up as oscillations around the flight direction) well enough to determine periapsis time to about +-5s. On several occasions, these methods gave early warning of atmospheric density variations that required modifying correction-burn schedules.
Apart from the significance to Magellan's own science work, spacecraft designers are much more likely to include gradual aerobraking in mission plans, now that it has been proven workable (on a spacecraft that was never designed for it).
Magellan will start circular-orbit gravity mapping 16 Aug. There is funding for operations through Oct, and Magellan managers are hoping for another 12 months of funding ($7.4M) to complete the gravity work. Doing gravity mapping in low orbit takes a bit longer than in high orbit, because the planet gets in the way more.
Magellan actually has about another 8 years of fuel aboard. Continued operation for light experimental work would cost $5-6M/yr: "our total budget is less than the uncertainty in the Cassini spacecraft's budget". The electronics probably won't last 8 years, mind you, and Magellan has lost two of its four gyros and will be in trouble if it loses another.
One experiment that may be tried is using Magellan's transmitters to illuminate Venus for DSN's receivers. This shows off-beam-axis reflectivity, which would be interesting because Venus has areas that reflect radar back to the sender much more efficiently than is usual for natural materials, and off-axis data might give a clue as to what they are. This "bistatic" radar work requires the right alignment of Magellan, Earth, and interesting areas on Venus. Such an alignment will occur on 6 Oct this year, and several more times in 1994; the use of DSN for this has not yet been approved. Magellan's electronics problems now pretty much prevent it from returning data from its own radar receivers to Earth, but its transmitters still work fine.
Langley researchers report a new method of measuring planetary atmospheric densities, giving more flexibility to aerobraking operations. The normal method is to measure changes in spacecraft velocity due to drag, but this is slow because it requires lengthy tracking to detect small changes. If you look at the attitude disturbances due to aerodynamic torques instead, the spacecraft's own attitude-control telemetry gives rapid results. The two methods agree within about 5% using data from Pioneer Venus and Magellan. The investigators are hoping for considerable data on Venus's atmosphere from Magellan's new low orbit; a bonus is that if Magellan is kept running for a while, it will give data from the low point of the solar cycle, complementing Pioneer Venus data from the 1989 peak. Funding and approval permitting, Magellan may try a "windmill" test, orienting its solar panels like ailerons to induce a slow roll at periapsis (this would be done at normal periapsis, not at the lower aerobraking altitudes). [There was talk of trying to do roll control during aerobraking that way, in fact, although in the end it was deemed unnecessarily risky.]
Mars Observer preparing to enter orbit. [Oh well...]
FAA beginning trials (at Bedford, Mass.) of a system using the standard aviation Mode S data link to transmit differential-GPS corrections to aircraft. Even more significant will be transmissions the other way, with the aircraft reporting not only barometric altitude but also GPS position. This could greatly simplify operation of collision-avoidance systems and the like. The major limitation, right now, is that current airport radars are still mechanically scanned, and they rotate too slowly, illuminating each aircraft every 4.8s, compared to a preferred update rate for DGPS corrections of once every 1.2s. Omnidirectional antennas would have to be used... and that presents possible interference problems, since there is no organized channel-contention procedure for Mode-S transmissions. The current trials are aimed mainly at assessing this problem.
Lengthy article on USAF satellite-observing facilities on Haleakala in Maui. The site has wonderful optical conditions, between high altitude and the location far away from pollution sources. Image of Columbia in orbit, taken by one of the 1.2m telescopes. It's pretty good: you can see the cockpit windows, you could probably tell whether there was someone at the window or not, and the position of the arm is clearly visible. The facilities can also do laser illumination of satellites for work during orbital night, although precautions are needed to avoid the possibility of damaging satellite sensors.
Complications appear in the Express mission, in which DARA is buying a Russian reentry capsule for launch on an ISAS booster as part of a joint German-Japanese research effort. DARA is buying the Russian capsule because the schedule makes it impossible to develop their own in time, and that's where the snags have appeared. There is now some doubt that the Nov delivery date of the capsule will be met, and that might slip the launch from next August -- awkward because Japan has only two short launch seasons due to agreements with the fishermen's union. One problem is that the Salyut bureau managers are used to being in control of missions, and DARA has to keep reminding them that they are just a supplier and DARA is calling the shots on this mission. They would also like to do mission control for the mission, but Germany's position is that this will be done by DLR at Oberpfaffenhofen. For this, DLR needs detailed information about the capsule, and although this is in the contract Salyut signed, they are being slow about supplying it -- probably because the capsule was originally a ballistic-missile warhead.
The pair of Titan Centaurs that have been sitting on the pads at the Cape for nearly two years now are going to go on sitting for a while. The current holdup is the Titan IV failure at Vandenberg, which is a switch; most of the delays so far have been Centaur issues. The Centaur on these birds is the wide-tank Centaur, originally meant for the shuttle but never flown on it, and that makes people nervous, because *this* Centaur is in many ways rather different from the one that has a long and (mostly) distinguished launch history: "this Centaur has never flown". There is also some concern about how Centaur changes made as a result of recent Atlas-Centaur failures affect the somewhat different Titan hardware.
USAF gives Spaceport Florida Authority, the Florida state agency that is trying to encourage commercial spaceflight, $2.15M to modify the Cape's complex 46 -- primarily used for Trident tests -- for use by small launchers based on the Castor 120 (this would include Taurus and some of the Lockheed LLVs). Trident launch capability will be retained, and commercial launch facilities will be self-contained modules wherever possible. The plan is to have the facility ready for use in the Taurus launch of Clementine 2 in 1995.
Orbital Sciences shelves plans to spin Orbcomm off as a separate company and sell shares, at least partly to avoid muddying the waters in FCC licensing of the Orbcomm system, which OSC is trying to hasten. OSC has signed final agreements with Teleglobe, a Canadian company that is the world's fifth largest international comsat operator, for financing and operations of Orbcomm. Phase one, mostly funded by OSC, will cover the first two satellites and key ground facilities for $55M. Phase two, $80M mostly from Teleglobe, will launch 24 more satellites. OSC hopes for FCC approval by the end of the year, leading to launch of the first two satellites in the first quarter of 1994 and initial service sales in late spring. Phase two will take place in 1995. Launch of the phase-one satellites (by Pegasus XL) had been set for late this year, but there have been development delays in some items, such as the very lightweight antennas.
Compared to other LEO-comsat projects like Iridium, OSC is essentially gambling that restricting service to electronic-mail delivery, with no voice capability, will buy Orbcomm enough in lower costs and earlier operational status to make up for the smaller market. Some analysts pick it as the single best bet in the LEO-comsat race, because of its low cost and the selection of a niche market. Others caution that they'll have to actually deliver service, not just launch satellites, and this won't come easy for a novel one-of-a-kind system.
Lockheed Skunk Works proposes its own SSTO concept, intended to deliver payload to low orbit at $500/lb (or less) not long after 2000. The "Aeroballistic Rocket" would use a flat lifting-body shape and a linear aerospike rocket engine. [Note: this is not an airbreather.] Payload capacity would be 40klbs, comparable to the shuttle or Titan IV. The vehicle would launch vertically and land horizontally, with a 12-72hr stay in orbit. Initial flights would be manned, but the intent is that routine operations be unmanned.
The linear aerospike ties in well with a wide flat body shape, resembling the X-24 flown 25 years ago, with a near-vertical fin at each "wingtip". Thrust:weight ratio at takeoff will be 1.4, and the vehicle has full engine-out capability, with a failure of an aerospike segment resulting in shutdown of a matching segment on the other side, and diversion into a trajectory that will burn off fuel and return to the launch site. The lift:drag ratio at hypersonic speeds will be poor, below 1:1 due to a very high angle of attack (45deg), but it will be a respectable glider at lower angles (10deg), with an L/D of 5.5-6 for landing. Lockheed claims a unique lower-surface contour that will manage airflow and heat buildup; the underside will be a high-temperature metallic structure, not ceramic tiles (which are seen as heavy and costly).
Lockheed sees crucial issues in an SSTO as being minimal preparation time for a mission (7 days or less), horizontal payload processing, and certification done once per aircraft rather than once per flight. Given these, Lockheed estimates a development cost of $5G and a unit flyaway cost after the first one of $475M. Each flight's consumables would cost about $300k, with each aircraft needing about $250M of spares during a 20-year lifetime. Lockheed says that one aeroballistic rocket could launch 30 times a year, and the $500/lb price could be maintained with as few as 15-20 flights. Costs could go as low as $100/lb with 120 flights per year. [The article also contains some bits of fairly irrelevant propaganda from Scott Crossfield, who is beating the drum for NASP-based airbreathers and sees Lockheed's solution as inferior. I don't see, actually, why AW&ST included his remarks.]
Lockheed gets the spacecraft-bus contract for Iridium: a production run of 125 for $700M+. This had been expected for some time, but the final deal was only recently made.
Editorial urging that the US "stop trying to kludge Freedom and Mir modules into a world space station and play to Russia's strength -- its launch vehicles". AW&ST's suggestion is that Western station hardware be launched on Energia, giving a bigger station sooner (in a higher-inclination orbit), and minimizing program disruption and loss of Western jobs while giving the Russians major station business.
"Every time I inspect the mechanism | Henry Spencer @ U of Toronto Zoology closely, more pieces fall off." | henry@zoo.toronto.edu utzoo!henry