International Space Transportation System
Ascent Roadmap
Brief History
The Root
ISTS Concepts
Ascent Roadmap

The Ascent Roadmap replaces the International Space Transportation System concept map.  This was posted in September 2007.

This is all very tentative, and likely to change when the concepts are subjected to feasibility and design analyses.
Prochron is intended to be the smallest possible orbital booster, and when not equipped with its upper stage for orbital flights, will be operable as an amateur rocket in Canada, or under FAA proposed rules for Class 4 Advanced High Power Rocket (same term in both sets of rules.)  Its payload goal is a triple pod of CubeSats, or 3kg.  The strap-on system will provide enough thrust so that it attains enough speed to use passive fin stabilization by the time it clears its launch rails.  Much like ordinary amateur rocket stages, these strap-ons are recovered, reloaded and reused.  They accellerate the core to some 200m/s, where its main motor is set at relatively low thrust to overcome drag and continue to climb.  This approach reduces gravity losses.  The second stage is used only if the booster is intended to make orbit.  It is likely that the core first stage will be recoverable only in the sounding rocket mode.  The most likely propellant combination for the core stages is oxypropane.


Symtex has already had its configuration map set using oxykerosene lower stages. It is quite likely that this will change to oxypropane as this propellant combination has simpler thermal management and pressurization challenges, likely to lower the cost of the stage.

The Prochron core stage becomes the Symtex strap-on, and the core will use up to four motors of the same type. If Prochron is still on hybrids, a development program may be undertaken for Symtex' new core, or Symtex may use a hybrid callandria arrangment (i.e. single wide oxidizer tank, many hybrid modules underneath it.) Symtex' core would like to grow independently of the strap-ons, building for reusability and performance. The definitive version of the Symtex core will be a reusable composite constructed stage with a reliable method of recovery, fast refurbishment and post-flight checkout for reuse. Increasing Isp and thrust will make up for increasing dry mass incurred by the recovery system.

The Symtex upper stage will use oxymethane propellants and rotorpump engines to achieve high performance for a stage of this size (slightly larger than the AVUM for Vega.)


Kilder is intended for the 2000-8000kg class, and therefore is a big booster for pressure-fed technology. The core stage will rely on a single shaft-coupled dual Barske impeller turbopump engine with a single, large regenerative thrust chamber operating on oxykerosene propellants. The Symtex core stage will be used as the strap-on (a recurring theme.) Kilder is expected to have three- and five-body versions without crossfeed, using throttle profiling for "serialization" (i.e.: getting the core to last significantly longer than the outboard modules.)  The five-body version may be knocked out by the small variant capability of Lilmax.

Most improvements to Kilder are expected in the upper stages, which will move from the Symtex upper stage up to larger, possibly oxyhydrogen, upper stages.


Lilmax comes in one-, three-, and five-body configurations, with the three body configuration being of particular interest to commercial space tourism. The single body version is of the greatest interest to the GEO market, but is unlikely to beat existing brands, such as Ariane, Atlas, and Proton. The first stage module uses four of the engines developed for Kilder. The ability to shut down and restart these engines gives Lilmax lower stage an unprecedented depth of throttle capability. The three body lower composite is expected to develop into three configurations:

- High energy: with Kilder's upper stage, this version would be best suited for launching GEO satellites and robotic planetary missions.
- Low energy: A new upper stage with a boost turbopumps and a high expansion nozzle in the single oxykerosene engine (otherwise of the same type as Kilder) and lower pressure tanks. This stage is far larger than the high energy version, and is best suited for launching space hotels and manned planetary mission elements. This configuration is the main contender for MDMD departure.
- Passenger: A passenger orbiter replaces the upper stage, and completes ascent to LEO with integral propulsion. This integral propulsion also provides for the craft's intact abort capabilities.


Bluestar, as orginally envisioned, launches like one airliner and lands like two. Since this is a huge technical challenge, and may not be economically feasible, the upper stage may be compromized to employ ballistic recovery methods. The booster is also likely to tank its oxidizer in the air. This system is designed to make the launching of 8000kg payloads (including passengers) to LEO routine and cheap. The booster system masses roughly 500 tonnes when fully loaded, likely requiring a modification of the A380 to serve as the LOX tanker.
The current concept tanks the LOX for both the booster and orbiter in the air to eliminate the need to add flaps and slats to the booster's wings as well as to lighten the landing gear.  A small reduction in wing area is also likely to result.  While the booster will have a small landing gear for the size of the aircraft, the orbiter will not have one at all.  Instead of landing on a runway, the orbiter will deploy a ram-air parasol and land in a pond.


The Saturn/NOVA class booster has not been defined as of yet (there is an INSEA Freezerburn, but not much more of it has been defined either.) It is intended to launch 10m diameter class payloads of 100-500 tonnes mass on LEO. These will likely be large space hotels, space colonies, and interplanetary cruisers.

2007 After Columbia Project