Review: F-Sim: Space Shuttle for iPhone, an amazing shuttle landing sim

Discovery lifts off on April 5 on STS-131, on its assembly mission to the International Space Station. It was Discovery's second-to-last planned flight, the fourth-to-last planned shuttle flight overall, and the last planned night launch for the shuttle program.

Back when I was 8 years old, I picked a CD case out of the bargain bin at Software Etc. for a game called Precision Approach--a $10 CD rerelease of a floppy-disk, DOS-era sim ("System requirements: IBM 386 or higher; Recommended addition: Math coprocessor"). Despite its age, it was a highly detailed and realistic flight simulation of one specific scenario: the space shuttle approach and landing sequence. I remember printing out and devouring its entire 150-page manual, which provided exhaustive documentation on not only how to play it, but reference material on the shuttle's real-life approach profile and procedures, which were meticulously recreated in the sim. I have lots of fond memories of that sim, and spent many a rainy Saturday (or even a beautiful, sunny one) perfecting my approaches. Seventeen years later, F-Sim has been quietly released in the App Store to little fanfare, and the highest compliment I can pay it is that is like Precision Approach's spiritual successor--on iPhone.

In fact, the gameplay is almost identical.


You take over command of the shuttle at around 50,000 ft just as its airspeed falls below Mach 1 approaching the Heading Alignment Cylinder (HAC), the shuttle's procedure turn that takes you through 180+ degrees to line you up for your final approach. The final is taken at a plunging 20 degree glideslope--over 6 times steeper than the tame three degrees standard in civil aviation--necessitating a pre-flare maneuver while still at 2000 ft Above Ground Level (AGL), establishing the shuttle on a 1.5 degree inner glide slope that brings you gently into the runway. After main gear touchdown, you gently derotate (lower the nose) until the nose gear touches down. If it sounds like a challenge, it is. But never fear--the instrumentation that helps you do all this is modeled equally meticulously in F-Sim. The Heads Up Display (HUD) view and the Precision Approach Path Indicator (PAPI) and ball-bar light systems placed around the runway are all implemented perfectly. Between them, you'll never be lacking a fly-to or glideslope indicator. Oh, and the graphics and audio are flat out awesome, with detailed ground textures and recordings of Mission Control and cockpit communications. The altitude call-outs from your pilot in the right seat are particularly useful. (An external chase view is an omission one might reasonably expect to find in such a sim; this feature is currently planned for a future update.)

In short, it does everything that that other iPhone space shuttle sim, the Space Shuttle edition of Austin Meyer's much celebrated series of X-Plane flight sim apps (spun off from his legendary X-Plane desktop flight sim) doesn't do. This isn't necessarily a dig at X-Plane: Space Shuttle, which takes a broader approach to shuttle operations. Unlike F-Sim, XPSS simulates launch (completely on autopilot, as in real life) and ISS docking phases (a very unique, excruciatingly precise challenge). Meyer also uses his much-lauded blade-element physics model to let you fly the critical atmospheric reentry phase preceding the approach (although with how much realism in hypersonic/plasma regimes, I'm uncertain--certainly the thermal and stress tolerances are relaxed or else it would be almost impossibly difficult; in real life, reentry is always flown by the autopilot for that reason). In this scenario, XPSS starts you off at 200,000 ft at Mach 10, 600 miles downrange and 12 minutes from touchdown, bringing energy management in the approach profile into play. Dissipating all that energy by maintaining a high angle-of-attack and performing S-turns (while still conserving enough to make it all the way to the runway) is a very satisfying challenge, indeed. But what F-Sim does do--those final 5 mins on the HAC and final approach--it does extremely well, with much more panache and attention to detail.


Now, unfortunately, I've never flown the space shuttle...so I couldn't say for certain how realistic F-Sim's flight model is, but it feels right--the notorious "flying brick" handling characteristics of the orbiter come across in full force (in real life, shuttle pilots train in a Gulfstream business jet with the thrust reversers deployed). In fact, I find the dynamics more satisfying and challenging than XPSS--if you're not careful and overcorrect, you can get some wicked pilot-induced oscillations going, as seen here in this 1970s landing of the test vehicle Enterprise flown by none other than Fred Haise, the same astronaut who was the pilot on Apollo 13 (played by Bill Paxton in the movie).




I could go on about all the other loving touches it has that sets it apart from XPSS--the dramatic (and realistic) way that the runway lighting casts criss-crossing beams of lights across the threshold on a night approach into KSC; its implementation of "tilt-with-device" (seen mainly in racing games with tilt-steering to keep the perspective level as the iPhone tilts around it, but which here serves to keep the HUD fixed as a visual reference); the ability to keep your iPod music playing in the background. But enough talk of its realism and polish as a sim, which F-Sim has in spades. What's even better is that it succeeds as a game, and one perfectly suited to its platform, at that. Flight simulators aren't exactly known for the kind of bite-sized and addictive gameplay that rules the App Store, which makes an admittedly niche title like F-Sim all the more impressive for the fact that it manages to be both. Flying a full approach in F-Sim requires continuous concentration and someplace stationary to not trip the accelerometer, but it also takes less than five minutes; a post-HAC final approach takes about two.


Upon touchdown, you can access a detailed analysis of your landing that serves as your score--how far off the centerline were you? What was your rate of descent at touchdown? Rate of pitch at nosewheel slapdown? Maximum weights on each of the wheels? F-Sim will tell you, and trust me, you will want another go. This is as easy as one touch to either reset the simulator or take you back to the main menu, where you can choose another randomized approach, or customize your own. (Loading times are spectacular; on my 2G iPod Touch, the app loads in 3 seconds and a flight loads in 2.)


Landing facilities at both the Kennedy Space Center and Edwards Air Force Base (CA) are modeled, and you can adjust the heading from which you approach the landing facility with the swipe of a finger, with your flight profile and HAC procedures adjusted accordingly. (Another neat touch: choosing an approach from the east at Edwards will let you know that such a reentry trajectory is impossible given the shuttle always launches eastward to take advantage of the earth's eastward spin; choosing an approach from the east at KSC will let you know that such an approach is plausible in the case that the shuttle must abort its launch and face a Return To Launch Site (RTLS) scenario.) Factor in the ability to toggle both day and night approaches in both clear and overcast conditions, and ramp up the (very realistic) wind gusts and turbulence, and you've got surprisingly excellent replay value.

I've played flight and racing sims on and off for 15 years--not as long as lots of people, but long enough to see plenty of them come and go. Of course, they're pretty complex heaps of code. The ones I've seen tend to either be put out by big-to-relatively big dev teams (Microsoft Flight Simulator, Falcon, IL-2, LOMAC) or are intense labors of love from one talented programmer (X-Plane, Orbiter). F-Sim falls into the latter category--created solely by Sascha Ledinsky, an Austrian developer. Either way, the amount of effort that went into them always meant that the release of a new one was a big deal; a big studio like Microsoft would command attention from all the trade mags and review sites, and a little guy like Austin Meyer would be drumming up support on the community forums with screenshots and demos. I find it astonishing that a flight simulator as polished as F-Sim has appeared out of nowhere, much less on the iPhone. F-Sim has been available in the App Store since the end of January and has placed high on the charts in Europe and Japan, but I don't think it has yet found its audience in the US.

It's amazing that gems like this can exist and go as unnoticed as F-Sim has. This is one of the premiere titles available for iPhone. If you have even the slightest passing interest in the shuttle, in space, in aviation, or science at all, shell out your two (only two!) bucks and download F-Sim now. If you have another two bucks to spare, you can pick up X-Plane: Space Shuttle as well. For $4, you can have an excellent simulation of all major space shuttle flight operations on your phone or iPod. It's things like these that make me feel that we are totally living in the future.

F-Sim by Sascha Ledinsky

$1.99
Developer's site
Interview with Techhaze

X-Plane: Space Shuttle by Austin Meyer

$1.99
Developer's site