{"id":44705,"date":"2024-10-04T23:20:20","date_gmt":"2024-10-04T15:20:20","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/ula-hasnt-given-up-on-developing-a-long-lived-cryogenic-space-tug\/"},"modified":"2024-10-04T23:20:20","modified_gmt":"2024-10-04T15:20:20","slug":"ula-hasnt-given-up-on-developing-a-long-lived-cryogenic-space-tug","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/ula-hasnt-given-up-on-developing-a-long-lived-cryogenic-space-tug\/","title":{"rendered":"ULA hasn\u2019t given up on developing a long-lived cryogenic space tug"},"content":{"rendered":"

The second flight of United Launch Alliance\u2019s Vulcan rocket, planned for Friday morning, has a primary goal of validating the launcher\u2019s reliability for delivering critical US military satellites to orbit.<\/p>\n

Tory Bruno, ULA\u2019s chief executive, told reporters Wednesday that he is \u201csupremely confident\u201d the Vulcan rocket will succeed in accomplishing that objective. The Vulcan\u2019s second test flight, known as Cert-2, follows a near-flawless debut launch of ULA\u2019s new rocket on January 8.<\/p>\n

\u201cAs I come up on Cert-2, I\u2019m pretty darn confident I\u2019m going to have a good day on Friday, knock on wood,\u201d Bruno said. \u201cThese are very powerful, complicated machines.\u201d<\/p>\n

The Vulcan launcher, a replacement for ULA\u2019s Atlas V and Delta IV rockets, is on contract to haul the majority of the US military\u2019s most expensive national security satellites into orbit over the next several years. The Space Force is eager to certify Vulcan to launch these payloads, but military officials want to see two successful test flights before committing one of its satellites to flying on the new rocket.<\/p>\n

If Friday\u2019s test flight goes well, ULA is on track to launch at least one\u2014and perhaps two\u2014operational missions for the Space Force by the end of this year. The Space Force has already booked 25 launches on ULA\u2019s Vulcan rocket for military payloads and spy satellites for the National Reconnaissance Office. Including the launch Friday, ULA has 70 Vulcan rockets in its backlog, mostly for the Space Force, the NRO, and Amazon\u2019s Kuiper satellite broadband network.<\/p>\n

The Vulcan rocket is powered by two methane-fueled BE-4 engines produced by Jeff Bezos\u2019 space company Blue Origin, and ULA can mount zero, two, four, or six strap-on solid rocket boosters from Northrop Grumman around the Vulcan\u2019s first stage to propel heavier payloads to space. The rocket\u2019s Centaur V upper stage is fitted with a pair of hydrogen-burning RL10 engines from Aerojet Rocketdyne.<\/p>\n

,<\/p>\n

The second Vulcan rocket will fly in the same configuration as the first launch earlier this year, with two strap-on solid-fueled boosters. The only noticeable modification to the rocket is the addition of some spray-on foam insulation around the outside of the first stage methane tank, which will keep the cryogenic fuel at the proper temperature as Vulcan encounters aerodynamic heating on its ascent through the atmosphere.<\/p>\n

\u201cThis will give us just over one second more usable propellant,\u201d Bruno wrote on X.<\/p>\n

There is one more change from Vulcan\u2019s first launch, which boosted a commercial lunar lander for Astrobotic on a trajectory toward the Moon. This time, there are no real spacecraft on the Vulcan rocket. Instead, ULA mounted a dummy payload to the Centaur V upper stage to simulate the mass of a functioning satellite.<\/p>\n

ULA originally planned to launch Sierra Space\u2019s first Dream Chaser spaceplane on the second Vulcan rocket. But the Dream Chaser won\u2019t be ready to fly its first mission to resupply the International Space Station until next year. Under pressure from the Pentagon, ULA decided to move ahead with the second Vulcan launch without a payload at the company\u2019s own expense, which Bruno tallied in the \u201chigh tens of millions of dollars.\u201d<\/p>\n

Heliocentricity<\/h2>\n

The test flight will begin with liftoff from Cape Canaveral Space Force Station, Florida, during a three-hour launch window opening at 6 am EDT (10:00 UTC). The 202-foot-tall (61.6-meter) Vulcan rocket will head east over the Atlantic Ocean, shedding its boosters, first stage, and payload fairing in the first few minutes of flight.<\/p>\n

The Centaur upper stage will fire its RL10 engines two times, completing the primary mission within about 35 minutes of launch. The rocket will then continue on for a series of technical demonstrations before ending up on an Earth escape trajectory into a heliocentric orbit around the Sun.<\/p>\n

,<\/p>\n

\u201cWe have a number of experiments that we\u2019re conducting that are really technology demonstrations and measurements that are associated with our high-performance, longer-duration version of Centaur V that we\u2019ll be introducing in the future,\u201d Bruno said. \u201cAnd these will help us go a little bit faster on that development. And, of course, because we don\u2019t have an active spacecraft as a payload, we also have more instrumentation that we\u2019re able to use for just characterizing the vehicle.\u201d<\/p>\n

\n

\"\"<\/p>\n

The Centaur V upper stage for the Vulcan rocket.<\/p>\n

Credit:
\n United Launch Alliance<\/p>\n<\/figure>\n

ULA engineers have worked on the design of a long-lived upper stage for more than a decade. Their vision was to develop an upper stage fed by super-efficient cryogenic liquid hydrogen and liquid oxygen propellants that could generate its own power and operate in space for days, weeks, or longer rather than an upper stage\u2019s usual endurance limit of several hours. This would allow the rocket to not only deliver satellites into bespoke high-altitude orbits but also continue on to release more payloads at different altitudes or provide longer-term propulsion in support of other missions.<\/p>\n

The concept was called the Advanced Cryogenic Evolved Stage (ACES). ULA\u2019s corporate owners, Boeing and Lockheed Martin, never authorized the full development of ACES, and the company said in 2020 that it was no longer pursuing the ACES concept.<\/p>\n

The Centaur V upper stage currently used on the Vulcan rocket is a larger version of the thin-walled, pressure-stabilized Centaur upper stage that has been flying since the 1960s. Bruno said the Centaur V design, as it is today, offers as much as 12 hours of operating life in space. This is longer than any other existing rocket using cryogenic propellants, which can boil off over time.<\/p>\n

,<\/p>\n

ULA\u2019s chief executive still harbors an ambition for regaining some of the same capabilities promised by ACES.<\/p>\n

\u201cWhat we are looking to do is to extend that by orders of magnitude,\u201d Bruno said. \u201cAnd what that would allow us to do is have a in-space transportation capability for in-space mobility and servicing and things like that.\u201d<\/p>\n

Space Force leaders have voiced a desire for future spacecraft to freely maneuver between different orbits, a concept the military calls \u201cdynamic space operations.\u201d This would untether spacecraft operations from fuel limitations and eventually require the development of in-orbit refueling, propellant depots, or novel propulsion technologies.<\/p>\n

No one has tried to store large amounts of super-cold propellants in space for weeks or longer. Accomplishing this is a non-trivial thermal problem, requiring insulation to keep heat from the Sun from reaching the liquid cryogenic propellant, stored at temperatures of several hundred degrees below zero.<\/p>\n

Bruno hesitated to share details of the experiments ULA plans for the Centaur V upper stage on Friday\u2019s test flight, citing proprietary concerns. He said the experiments will confirm analytical models about how the upper stage performs in space.<\/p>\n

\u201cSome of these are devices, some of these are maneuvers because maneuvers make a difference, and some are related to performance in a way,\u201d he said. \u201cIn some cases, those maneuvers are helping us with the thermal load that tries to come in and boil off the propellants.\u201d<\/p>\n

Eventually, ULA would like to eliminate hydrazine attitude control fuel and battery power from the Centaur V upper stage, Bruno said Wednesday. This sounds a lot like what ULA wanted to do with ACES, which would have used an internal combustion engine called Integrated Vehicle Fluids (IVF) to recycle gasified waste propellants to pressurize its propellant tanks, generate electrical power, and feed thrusters for attitude control. This would mean the upper stage wouldn\u2019t need to rely on hydrazine, helium, or batteries.<\/p>\n

,<\/p>\n

ULA hasn\u2019t talked much about the IVF system in recent years, but Bruno said the company is still developing it. \u201cIt\u2019s part of all of this, but that\u2019s all I will say, or I\u2019ll start revealing what all the gadgets are.\u201d<\/p>\n

\n

\"\"<\/p>\n

A comparison between ULA\u2019s legacy Centaur upper stage and the new Centaur V.<\/p>\n

Credit:
\n United Launch Alliance<\/p>\n<\/figure>\n

George Sowers, former vice president and chief scientist at ULA, was one of the company\u2019s main advocates for extending the lifetime of upper stages and developing technologies for refueling and propellant depot. He retired from ULA in 2017 and is now a professor at the Colorado School of Mines and an independent aerospace industry consultant.<\/p>\n

In an interview with Ars earlier this year, Sowers said ULA solved many of the problems with keeping cryogenic propellants at the right temperature in space.<\/p>\n

\u201cWe had a lot of data on boil-off, just from flying Centaurs all the way to geosynchronous orbit, which doesn\u2019t involve weeks, but it involves maybe half a day or so, which is plenty of time to get all the temperatures to stabilize at deep space levels,\u201d Sowers said. \u201cSo you have to understand the heat transfer very well. Good models are very important.\u201d<\/p>\n

ULA experimented with different types of insulation and vapor cooling, which involves taking cold gas that boiled off of cryogenic fuel and blowing it on heat penetration points into the tanks.<\/p>\n

\u201cThere are tricks to managing boil-off,\u201d he said. \u201cOne of the tricks is that you never want to boil oxygen. You always want to boil hydrogen. So you size your propellant tanks and your propellant loads, assuming you\u2019re going to have that extra hydrogen boil-off. Then what you can do is use the hydrogen to keep the oxygen cold to keep it from boiling.<\/p>\n

,<\/p>\n

\u201cThe amount of heat that you can reject by boiling off one kilogram of hydrogen is about five times what you would reject by boiling off one kilogram of oxygen. So those are some of the thermodynamic tricks,\u201d Sowers said. \u201cThe way ULA accomplished that is by having a common bulkhead, so the hydrogen tank and the oxygen tank are in thermal contact. So hydrogen keeps the oxygen cold.\u201d<\/p>\n

ULA\u2019s experiments showed it could get the hydrogen boil-off rate down to about 10 percent per year, based on thermodynamic models calibrated by data from flying older versions of the Centaur upper stage on Atlas V rockets, according to Sowers.<\/p>\n

\u201cIn my mind, that kind of cemented the idea that distribution depots and things like that are very well in hand without having to have exotic cryocoolers, which tend to use a lot of power,\u201d Sowers said. \u201cIt\u2019s about efficiency. If you can do it passively, you don\u2019t have to expend energy on cryocoolers.\u201d<\/p>\n

\u201cWe\u2019re going to go to days, and then we\u2019re going to go to weeks, and then we think it\u2019s possible to take us to months,\u201d Bruno said. \u201cThat\u2019s a game changer.\u201d<\/p>\n

However, ULA\u2019s corporate owners haven\u2019t yet fully bought into this vision. Bruno said the Vulcan rocket and its supporting manufacturing and launch infrastructure cost between $5 billion and $7 billion to develop. ULA also plans to eventually recover and reuse BE-4 main engines from the Vulcan rocket, but that is still at least several years away.<\/p>\n

But ULA is reportedly up for sale, and a well-capitalized buyer might find the company\u2019s long-duration cryogenic upper stage more attractive and worth the investment.<\/p>\n

\u201cThere\u2019s a whole lot of missions that enables,\u201d Bruno said. \u201cSo that\u2019s a big step in capability, both for the United States and also commercially.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

The second flight of United Launch Alliance\u2019s Vulcan rocket, planned for Friday morning, has a primary goal of validating the launcher\u2019s reliability for delivering critical US military satellites to orbit. Tory Bruno, ULA\u2019s chief executive, told reporters Wednesday that he is \u201csupremely confident\u201d the Vulcan rocket will succeed in accomplishing that objective. The Vulcan\u2019s second […]<\/p>\n","protected":false},"author":1,"featured_media":44708,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1392,291,25,257,750,364],"class_list":["post-44705","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-centaur","tag-commercial-space","tag-launch","tag-military-space","tag-united-launch-alliance","tag-vulcan"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/44705"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=44705"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/44705\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/44708"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=44705"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=44705"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=44705"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}