OREX

{{for multi|the company traded under the stock symbol OREX|Orexigen Therapeutics|the NASA asteroid sample return mission|OSIRIS-REx}}

{{Infobox spaceflight

| name = Ryusei

| image = H-II_rocket_fairing_02.jpg

| image_caption = 1:1 scale model of OREX and the Vehicle Evaluation Payload within the H-II fairing, at the Kakamigahara Air and Space Museum

| mission_type = Technology

| operator = NASDA

| website = {{url|http://www.jaxa.jp/projects/rockets/orex/index_e.html}}

| COSPAR_ID = 1994-007A

| SATCAT = 22978

| mission_duration = 2 hours

| manufacturer = NASDA

| launch_mass = {{convert|865|kg}}

| landing_mass = {{convert|761|kg}}

| launch_date = {{start-date|3 February 1994, 22:20|timezone=yes}} UTC{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|work=Jonathan's Space Page|access-date=9 November 2013}}

| launch_rocket = H-II

| launch_site = Tanegashima Yoshinobu 1

| launch_contractor =

| landing_date = {{end-date|4 February 1994, 00:30|timezone=yes}} UTC{{cite web|url=http://planet4589.org/space/jsr/back/news.183|title=Issue 183|work=Jonathan's Space Report|first=Jonathan|last=McDowell|date=7 February 1994|access-date=9 November 2013}}

| landing_site = Pacific Ocean

| orbit_epoch = 3 February 1994{{cite web|url=http://planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|work=Jonathan's Space Page|access-date=9 November 2013}}

| orbit_reference = Geocentric

| orbit_regime = Low Earth

| orbit_periapsis = {{convert|448|km|mi}}

| orbit_apoapsis = {{convert|458|km|mi}}

| orbit_inclination = 30.5 degrees

| orbit_period = 93.64 minutes

| apsis = gee

}}

OREX (Orbital Re-entry Experiment) was a NASDA re-entry demonstrator prototype which was launched in 1994 on the H-II launcher; the satellite was renamed {{Nihongo|Ryūsei|りゅうせい|Shooting star}}. It was a precursor for the Japanese space shuttle HOPE.

OREX tested various communications systems, heating profiles and heat shielding components for HOPE.