Commercial Rockets

VULCAN — USA, 2021?

The United Launch Alliance, having been caught somewhat flat-footed by the new competitiveness in the launch market, and by tensions with Russia which may halt the supply of Atlas V motors, is now putting together a modern rocket of its own to replace Atlas: the Vulcan. Uncle Sam is contributing to the development effort, yet people have been noticing the ULA Board of Directors dragging its feet on fully committing to the project. Hopefully that hesitation is in the past now. The intent is to cut the Atlas’s launch cost in half. They may want even more badly to replace Delta, which they now say is too expensive to make, except for the few who are willing to cough up for the Delta IV Heavy, which is the only Delta model they still offer, and which will probably lose its market once bigger rockets come into regular use. For that matter, once the Vulcan is given a full complement of strap-on boosters, it should pretty nearly match the capacity of the Delta IV Heavy.

ULA partnered with Blue Origin (see the New Glenn article) to use their BE-4 staged combustion methane engine, which may now be ready for full production... or maybe not; a government report just said that issues with the engine may be threatening the readiness of the Vulcan, and therefore risking noncompliance with the federal mandate to stop using Russian engines for national security launches by 2022.

They’re calling this a codevelopment effort, but I have not heard of any engineering contribution coming from the ULA side. Aerojet Rocketdyne was lobbying to have their proposed AR1 engine used instead (and yes, “lobbying” meant they were getting members of Congress to try to put a thumb on the scale in the selection process), but their experience with expensive engines such as those in the Space Shuttle has apparently left them ill-prepared to compete on cost per flight, so they don’t have a suitable motor anywhere near as ready as the BE-4 is... the Air Force has paid Aerojet-Rocketdyne around a quarter billion to develop one, and after years of pressure to stop American companies buying from Energomash, their AR1 replacement still had yet to be test fired. It was to be a fairly direct replacement for the RD-180, being a high performance staged combustion kerosene burner, but it would be two separate engines instead of a single unit with two nozzles. But in the fall of 2018 ULA finalized their choice to use two BE-4 engines instead. Either one would give it a capacity upgrade over the Atlas, but the BE-4 has the edge in thrust, and presumably in specific impulse as well.

The rest of the Vulcan will apparently be a mishmash of existing Atlas and Delta parts, some of which are to be updated later. They are planning to use up to six small solid boosters around the base to augment lift when needed. Though positioned primarily as a replacement for Atlas, which is much more heavily used than Delta is, it might be some Delta IV tooling which gets repurposed to make the Vulcan’s core stage, which is slightly bigger around than the Delta’s five meter diameter. Cost savings relative to the Delta should be huge.

Is it going to be rated for human passengers? Yes. Is it going to be reusable? A little bit. The plan is that the engine section would detach itself from the first stage, reenter with an inflatable heat shield, and descend on parachutes. If all goes well, it would then be snatched up by helicopters before it hits the ocean. If successful, this would be relatively inexpensive to build — a lot less complicated than the Ariane 6 or 7’s winged landing system, and more fuel-efficient than landing the entire booster, though the helicopter operation would certainly have some expense, and losing the rest of the booster would allow it to save only about two thirds of the cost of the first stage. Two thirds isn’t bad, but on the other hand, they aren’t going to put this capability into the first Vulcan version. And that heat shield is going to have its work cut out for it, as the Vulcan booster, like that of the Atlas before it, will get to unusually high speeds and altitudes before cutting the second stage loose. The reentry would take place many times further out to sea than those from, say, a Falcon 9.

The whole program is designed to evolve incrementally away from the Atlas one step at a time; using the BE-4 engines and methane tanks is one big step, but lots of smaller ones will be done later, such as replacing the Centaur second stage, which is undersized for it. They want the new one to be able to remain fueled and active for weeks rather than hours after it reaches orbit. The working name for the new one is ACES, and it isn’t scheduled to fly until 2023. It has a modular design so it can be made in various lengths, with one, two, or four engines. The motor they use would, at least for a while, be some version of the venerable Aerojet Rocketdyne RL10 hydrogen-burner, like they’ve been using all along for their Atlas and Delta second stages, but they might switch to the Blue Origin BE-3U (which has quite a bit more thrust than the RL10).

Or not. They now say that their ACES plans are being scaled back. The new upper stage will now be called Centaur V, and though it will use many ACES ideas to increase its endurance, fuel capacity, and reusability, it will not be a full ground-up redesign. They still say it might eventually be able to do missions with 500 times the duration that the old Centaur could handle.

One odd feature of the ACES is that it would meet its needs for electric power not with solar panels or fuel cells, but with a six cylinder internal combustion engine which burns the vapors from the hydrogen and oxygen tanks. (A piston engine has never gone into space before.) The engine’s heat would be used for keeping the fuel pressurized. It’s part of a system which is designed to eliminate many of the secondary fluids and energy sources which other rockets have to lug around with them to make all the little parts work. I don’t know if this idea will be used in the Centaur V... to me a fuel cell would make a lot more sense.

With a bigger upper stage and six side boosters, they think a Vulcan could hoist up to 36 tons — enough to compete very directly with the Falcon Heavy and the New Glenn. There’s been some loose talk of them making a triple-booster Vulcan Heavy, but no such plan will be pursued for many years yet. If they do build one, it would be a lot more capable than the Falcon Heavy. Even the single-stick Vulcan looks to be fairly competitive with the Falcon Heavy in both capacity and cost... unless SpaceX cuts their prices, which they probably could.

They’re also tackling reusability from another angle. For missions beyond low orbit, rockets usually need a third stage added, but they envision avoiding this by making the ACES or Centaur V reusable, which would give them something they call a “space truck”. A few of them could be parked in low orbit, and the launch vehicle would rendezvous with one, fuel it, hand over the payload, and tell the truck where to take it. After completing the job, the truck could return to its parking place. This would not only save building expendable third stages, it would save the weight of lifting it along with large payloads; you’d only need to lift the fuel. But the fuel is the heaviest part (or to be more exact, the lox is), and this system would be of little use in cases where a lower orbit is the final destination of the payload, as it quite often is... and orbital transfer just isn’t the costly part of the average mission. So this plan might not have much impact for most commercial work, though for lunar or interplanetary missions, this sort of refueling might yield extra delta-V. On the other hand, if you want to bring the truck back to low orbit, that increases the fuel requirement again, so its weight may be no better than sending up an expendable stage.

But it sounds like the real point of ACES is that they are making a long term bet on the possibility that someday they will have a facility for making hydrolox fuel away from Earth, such as at the lunar south pole. ULA has called for the government to work toward this goal, which if achieved would give ACESes the ability to go anywhere.

The Russians, on the other hand, are hoping to build an orbital truck with nuclear-powered ion engines. They’ve had plans for this on paper for about a decade. It would be covered on the sides with big hinged radiators to disperse about three megawatts of heat. They call it the Transport and Energy Module. This would move slowly because it would only have about 18 newtons of thrust, but it would cut the mass of needed propellant down to a tiny amount, like no heavier than the payload. This thing could, like, make repeated trips to Mars orbit and back, or explore asteroids.

Unless the government gets more heavily behind this, I don’t know if ULA will even hold together... they’re laying off workers, though apparently they are still turning a profit. And in May 2018, their machinists’ union went on strike against them. Even if they succeed with this project, a 50% price drop may not save them. Some governmental launch customers, such as the Air Force, have requirements that there be two American providers for any rocket they need, so they might prop up ULA for a while (as they are currently propping up the Delta 4 Heavy though ULA would rather drop it)... but if one of the other startups qualifies, ULA might eventually be out in the cold. But on the other hand, it may turn out that none of the upstarts is capable of building something as good as the Vulcan, and its prices may be reasonable for its quality level. This rocket might end up a real winner. Their Atlas V has been the safest and most dependable large rocket ever built, and if they can continue that record with the Vulcan, it may not matter much that SpaceX underprices them. And Blue Origin’s New Glenn may not be any cheaper, nor ready anywhere near as soon at the rate they’ve been going.

Vulcan 401 (no side boosters): mass 430 t?, diam 5.4 m, thrust 9800 kN, imp 3.1 km/s?, type ZOm, payload 10.7 t (2.6%?), cost hopefully under $5M/t.