Update: No flight on Friday, but there was a hybrid engine test of about 60 seconds on one of the test stands that reportedly went well.
After a six-month gap in flights, it looks as if SpaceShipTwo will once again fly in the Mojave sky, possibly as early as Friday morning.
On Wednesday, SpaceShipTwo was outside on the tarmac underneath its WhiteKnightTwo mother ship for what Virgin Galactic described as a “dry run” for upcoming test flights. There is a Notice to Airmen (NOTAM) indicating that the Mojave Air and Space Port’s tower will be open early on Friday morning. It’s possible this is being done to accommodate a SpaceShipTwo test flight, although sometimes the tower opens early for other reasons.
If there is a flight tomorrow, my best guess is it will involve a captive carry or un-powered drop test to evaluate modifications that have been made to SpaceShipTwo. But, perhaps they will surprise us with something more ambitious.
Whenever the next flight occurs, it will be the first in a series of increasingly longer flight tests scheduled over the coming months. Virgin Galactic and Scaled Composites hope to complete the flight test program this year, and then Virgin Galactic Founder Richard Branson and his two children aboard the first commercial flight out of Spaceport America in New Mexico before the end of 2014.
Whether they can make that aggressive schedule remains to be seen. Much will depend on the success of modifications made to both ships over the past six months.
The last time SpaceShipTwo was seen in the skies over Mojave was in January. On the ship’s third powered flight on Jan. 10, it fired its hybrid engine for 20 seconds and reached an altitude of 71,000 feet. A week later, it conducted an un-powered glide flight.
And then, to the surprise of many observers, the flights stopped. The vehicles were taken behind closed hangar doors, where lots of things happened.
After Scaled Composites turned over WhiteKnightTwo to Virgin Galactic in February, engineers discovered cracks along the spars that form the backbone of the aircraft’s long wings. The cracks were where the spars were bonded to the fuselage, not in the spars themselves.
Multiple sources said the engineers were quite concerned by the cracks. They didn’t know exactly when they occurred or why. They were also uncertain about whether the proposed fixes would permanently solve the problem. One worrisome aspect what this occurred in WhiteKnightTwo, which is the most mature and supposedly most reliable part of the entire air-launch system.
Virgin Galactic had a different take on the matter. CEO George Whitesides insisted the aircraft didn’t have cracks; instead, these were “adhesive imperfections” resulting from imperfect bonding of the composites. They were easily fixed, they said, and didn’t pose any real performance or safety concerns.
While Virgin Galactic and Scaled Composites were dealing with that issue, SpaceShipTwo was undergoing some some significant modifications. Engineers installed fuel tanks into the vehicle’s wings as part of an effort to get the nitrous oxide-rubber hybrid motor to perform better.
To say the hybrid motor ran rough is one of the biggest understatements of the Space Age. During SpaceShipTwo’s three powered flights, the engine was fired for 16, 20 and 20 seconds each — far less than full duration. Beyond 20 seconds, the engines would have created severe oscillations and vibrations that would have severely shaken up the ship and crew. Fire the engine long enough, and the ship would have been torn apart.
Using helium would stabilize the burn and allow the engine to run longer. It worked on a Sierra Nevada test stand back in December. Virgin Galactic was so pleased with the results of the test that it released of video of it on YouTube. Behold, world: our engine really does work. Pay no attention to all those reports to the contrary.
Well, it sort of worked. Sierra Nevada had used an enormous amount of helium to stabilize the static test; it was much more than could ever be put aboard SpaceShipTwo. So, the engine wouldn’t work as well in flight as it did on the test stand. Nor was it clear whether the engine could get SpaceShipTwo where it needed to go. That is to say, space.
There are actually two definitions of where space begins. The international standard is known as the Karman Line, which begins at 100 km (62 miles). However, NASA and the U.S. Air Force use a 50 mile (80 km) standard for awarding astronaut status, a practice dating back to suborbital flights of the X-15 rocket plane in the 1960’s.
While Virgin Galactic used the 100-km (62-mile) boundary in its marketing material, it guaranteed 50 miles in its contracts with customers. Now, it look as if even with the helium and the longer engine burn, SpaceShipTwo might not be able to reach even that lower limit. That posed significant legal and public relations problems for the company.
So, it seemed that helium was their last hope. But no, there was another. ‘
On May 23, Virgin Galactic announced that it was switching to an alternative nitrous oxide-nylon engine developed by Scaled Composites. They didn’t call it nylon, however; it was polyamide, which is a fancy word for plastic.
Company officials said the new fuel grain burned smoother and promised a higher altitude. They have expressed confidence that the ship can reach 50 miles, thus fulfilling their contract obligations.
Virgin Galactic announced the news on a Friday as Americans and Britons were preparing for a long holiday weekend to honor their brave war dead (Memorial Day) and under appreciated bankers (bank holiday), respectively. This is a classic method of dumping news you don’t want a lot of questions about at a time when few people are paying attention. In this case, the strategy largely worked.
In describing the fuel change, Virgin Galactic George Whitesides said the switch was no big deal, merely a switch from one well-performing fuel to a better performing one.
“Frankly, we had good performance from both of them, but as we look for the final range of test flights, we decided to go with the polyamide grain….It basically is the same cartridge,” Whitesides said of the hybrid rocket motor. “You just plug it in, and you connect the plumbing in a slightly different way.”
This was true, in the sense that all the hard work of modifying the ship with wing tanks and new plumbing had already been done. However, the main challenge is testing a new engine in flight along with all the modifications required to make it work.
Those modifications include the new wing tanks. One will contain helium, which will be used at the end of the burn to dampen out the shutdown.
The other tank will contain methane, which will be injected at the start of the burn to heat up the fuel. Although the plastic fuel burns smoother than the rubber kind, it takes more heat to get started. If the plastic doesn’t burn properly, you can get what is known as a hard start. That could lead to what folks in the industry refer to as “a bad day.”
With confidence in the new rocket motor and the repairs to WhiteKnightTwo, Virgin Galactic officials have laid out an aggressive flight test schedule for the remaining five months of the year.
“We expect things to happen fairly rapidly now, with the caveat that we’ll need to respond to little things that might come up in the test flight program,” said Virgin Galactic Commercial Director Stephen Attenborough. “We’re not driven by deadlines, but we have an achievable pathway to fly Richard [Branson] by the end of this year.”
Whitesides has talked about flying only a “handful” of flight tests before declaring the ship operational and placing the boss and his two children on board. He also has said that he plans to be aboard one of the later flights to prove to Branson that the ship is safe. Branson, in turn, will be doing the same to prove that same point to Virgin Galactic’s 700 passengers, Whitesides said.
There is a lot of concern among sources I’ve talked with over whether this flight test plan makes sense. A handful of additional flights for a vehicle designed to carry well-heeled passengers paying up to a quarter million dollars apiece is not very many. To be safe, you generally want to fly the hell out of an experimental ship before you declare it operational.
Sources also report that the plastic engine had been a longer-term project intended for installation in the second version SpaceShipTwo, which is now being assembled. Its use has been moved up, meaning there has been less time for testing.
A rocket engineer I know summed up concerns about the engine and Virgin Galactic’s safety culture succinctly:
New, lightly tested thrust system with two new additional failure modes. A carrier aircraft that’s structurally unsound. An altered SS2 airframe, not proven in test flight. The real possibility of having to perform a dead-stick landing away from the runway. An oxidizer [nitrous oxide] with a particularly nasty failure mode. A company that stores its flammable trash next to a huge N2O [nitrous oxide] tank. No external oversight.
Further, there isn’t a lot of time between now and the end of the year to complete all these tasks. Virgin Galactic has to finish flight testing in Mojave, move its operations down to Spaceport America in New Mexico, and learn how to fly out of there. This latter issue is not trivial; anyone who has seen flight test operations at Mojave knows how much planning and coordination is involved. The folks in Mojave are pros at it by now.
Ultimately, there is concern that Virgin Galactic and Scaled Composites will push SpaceShipTwo too fast and too high too quickly, which could result in an accident during flight test. Or, they will rush through testing successfully and miss something significant that will come back to bite them during commercial flights.
Virgin Galactic officials dismiss these claims. Safety is the North Star of the organization, they say, and they will broach no corner cutting that will compromise safety.
At this point, you are probably asking: so what if Virgin Galactic doesn’t meet its deadline? They’ve been working on this for 10 years already. All their schedule predictions have been way off. What’s behind the rush to fly the Bransons to space this year? What’s the harm of delaying the flight to 2015?
Potentially a lot. Most of the funds for this project have come from the government of Abu Dhabi through Aabar Investments, which has contributed $390 million. Sources say the deal — signed five years ago this month at the Oshkosh Airshow in Wisconsin — expires at the end of the year. The agreement contains a milestone under which Virgin Galactic must fly Richard Branson into space in 2014. Otherwise, there is no obligation from Aabar to continue funding the program.
A loss of funding could be devastating to Virgin Galactic. Sources say the company is in talks with Google about investing because it needs additional money. The deal reportedly involve an equity investment in Virgin Galactic and funding for the LauncherOne small satellite rocket.
Virgin Galactic officials have strenuously denied they are under any deadline to fly Branson to space this year while refusing to comment on reports of a deal with Google.
“There are a couple of other points that I discussed with some of you, firstly concerning rumors of an end of the year deadline for commercial operations/Richard’s flight which, should it be missed, would see aabar withdraw its funding,” Attenborough wrote to a group of ticket holders earlier this year. “This is completely unfounded.”’
The next five months will be very interesting. The flight tests will prove whether the new engine can get SpaceShipTwo safely to space. The future of Virgin Galactic rides on the answer.