SPS-Aquarius Upper Stage

NOTE: This post will be updated as the ISP project progresses. This includes pictures, information, etc. Italicized words should have links in the future.

(statistics coming soon!)

The SPS-Aquarius, also refered to simply as the SPS-Aqr or the SPS (Storable Propellant Stage), is a rocket stage planned for use on multiple IPSA launch vehicles, but is intended primarily for use on the Aquarius B1 MLV.

The SPS is 3.96 meters (13 ft.) long, has a diameter of 4.24 meters (14 ft.) and is powered by a single NO-M2H-I engine burning monomethylhydrazine (MMH) and dinitrogen tetroxide (N2O4). These propellants are hypergolic, igniting on contact, which allows the SPS to have the ability of indefinite ignitions in orbit, allowing for very precise payload injection and also for reduced engine complexity. Both propellants are very poisonous, but are storable; they are "stable" and liquid at room temperature, so no special facilities are needed for it (with the exception that it is poisonous and thus handled with extreme caution), compared to using cryogenic hydrogen (LH2) and liquid oxygen (LOX).

The SPS was developed to give the Aquarius a cheap capability in the light and medium launch market. The Aquarius B1, with a SPS instead of the H-IVA upper stage, has been quoted as lifting about 7,000 kg to LEO. The SPS also has the capability and design to operate as a third stage, but it is particularly weak in this point; the three stage Aquarius B1, with the H-IVA and the SPS as upper stages, actually CARRIES LESS than the two stage Aquarius, with just the H-IVA upper stage.

Despite this shortcoming, the SPS is still attractive to IPSA, because of its modular capacity, and particularly, its ability to be adapted as a spacecraft bus. The SPS' NO-M2H-I engine is actually derived from the MPS used on the Courier CSM. IPSA has also implied that a future Courier flight will launch with a SPS attached; likely to be a unmanned test flight.

The first launch of a SPS is expected to be the seventh flight of the Aquarius B1, Aqr-F4, which will be launched from International Launch Complex H-32 at the Cape Canaveral Air Force Station around 2027, according to IPSA' launch schedule. This information is only current as of July 2025.

That mission is expected to place four GOADI (Geostationary Activities Director Intial) testbed satellites into Low Earth Orbit (LEO).


First post to have an official commentary section. It seemed kind of monotonous to NOT include one, but that's been happening for a while. Anyhow...

This one has been in the works for a while. The only problem with this post is the fact that I posted it before the Aquarius B1 got posted itself. Basically, it just here with no context.

That "statistics coming soon" up on the page will inevitably be replaced, with realistic data on the stage. I actually have this data already, but the fact that the SPS isn't a good third stage like it was originally meant to be kind of irks me, and I'm twiddling with the data I have now to see if I can find some margin to aprove upon it.

Overall, I like the way it came out, looking very detailed. The SPS, by the way, is based off the Ariane 5 ES' EPS upper stage. 

Oh, and this is very likely my last post before I go into hiatus until August. No, actually, it is my last post, unless I find something ISP-related to just toss out. Meh.