Grumman Cygnus can carry resupply cargo bags but not ISPRs. The intent behind the HTV's modularized design was to use different module configurations to match different mission requirements. However, to reduce the development cost it was decided to fly the mixed PLC/ULC configuration only. To control the HTV's attitude and perform the orbital maneuvers such as rendezvous and reentry, the craft has four 500-N-class main thrusters and twenty-eight 110-N-class attitude control thrusters. Both use bipropellant, namely monomethylhydrazine (MMH) as fuel and mixed oxides of nitrogen (MON3) as oxidizer. HTV-1, HTV-2, and HTV-4 use Aerojet's 110 N R-1E, Space Shuttle's vernier engine, and the 500 N based on the Apollo spacecraft's R-4D. Later HTVs use 500 N class HBT-5 thrusters and 120 N class HBT-1 thrusters made by Japanese manufacturer IHI Aerospace Co., Ltd. The HTV carries about 2400 kg of propellant in four tanks. After the unloading process is completed, the HTV is loaded with waste and unberthed. The vehicle then deorbits and is destroyed during reentry, the debris falling into the Pacific Ocean. Flights Initially seven missions were planned in 2008–2015. With the extension of the ISS project through 2028, three more missions were added, with the tenth flight seeing an improved, cost-reduced version called the HTV-X. The first vehicle was launched on an H-IIB rocket, a more powerful version of the earlier H-IIA, at 17:01 UTC on 10 September 2009, from Launch Pad 2 of the Yoshinobu Launch Complex at the Tanegashima Space Center. , a total of nine missions successfully launched — one each year for 2015–2019 (though there was no launch in 2017, pushing back the latest to 2020) — one fewer total mission than had been planned in August 2013 at the time the fourth HTV mission was underway. The improved version of the craft HTV-X is planned to be first used for the tenth flight and will perform scheduled ISS resupply duties for 2021-2024 (with a first launch scheduled for February 2022). In addition, JAXA has agreed to provide HTV-X logistic resupply flights to the Gateway mini-space station (launched by either Falcon Heavy or Ariane 6) as part of its Gateway contribution in addition to co-developing a habitation module with the ESA. Successor HTV-X In May 2015, Japan's Ministry of Education, Culture, Sports, Science and Technology announced a proposal to replace the HTV with an improved, cost-reduced version preliminary called HTV-X. In December 2015,