Project LR1 Skyhammer: A New Shuttle [p1]

[kocmolyf]

Hey all,

I had to step away for a few weeks, but I've been back into the code for the last couple of days. Most of it has been bootstrapping the flight computer to get it to a state where the pilot can control all the different settings we have so far. In the last few days:

• Added the first four flight computer modes (Standby, Countdown, Boost, Free Flight).
• The RCS thrusters are now only active in Free Flight, and the main engines are only active in Boost.
• Removed the Alt+K key combination that used to shut down the outer engines. Outer engine shutdown is now handled by the flight computer, and it shut down engines in pairs rather than all four at once. I also removed all the related HUD annunciations.
• Added an apogee cutoff target to the flight computer, so you don't have to worry about hitting the shutdown key at the exact right moment.
• Removed the '+' key which ignited the engines. Instead, we now have a countdown managed by the flight computer. You can set the T-0 time either as MJD and begin the countdown immediately, or start with e.g. -30 seconds on the clock in a hold (resuming the count on your command). The engines are automatically ignited a few seconds before T-0, when the vehicle is released.
• Added a low-level propellant emergency cutoff to avoid destroying the turbopumps.

The goal for the next prototype is to be able to launch, insert to orbit, circularize, maneuver, and rendezvous with an orbiting target. The main things left to do are:

• Finish the ascent and reaction control MFD pages.
• Add rate damping to the main engine steering controller.
• Add a rate control mode to the RCS.
• Add the OMS engines - including steering control, dV cutoff, the OMS Burn flight computer mode, and an MFD page to use it.
• Some misc. graphical and audio cleanup work.

 

[Astro SG Wise]

LR1 SKYHAMMER - PROTOTYPE p1
------------------------------------------------------------------------------------

Welcome to the first prototype release of the LR1 Skyhammer!

This an ascent prototype only. It has enough functionality to get you off the pad and into orbit, but no further. It has:

- No RCS thrusters.
- No restartable engines.
- No orbital maneuvering engines.
- No aerodynamic control surfaces.
- No landing gear.
- No payload bay doors.

Umm, kocmolyf? Sounds pretty silly... :lol:

---------- Post added at 10:15 PM ---------- Previous post was at 10:14 PM ----------

Of course not, that would be silly. The LR1 will be able to do just about everything the Shuttle can do - that's the reason for the thread title, after all.

... as you were saying... have you changed your mind?

 

[K_Jameson]

?
I don't think so.
This is a complex project, and the current vehicle is a work-in-progress... as declared, a prototype. And a prototype typically hasn't the full capabilities of an operative vehicle: the YF-22 isn't the F-22A and Enterprise isn't Columbia.

 

[Astro SG Wise]

So, the vehicle is going to do all of the things a shuttle can, but currently it can not?

 

[K_Jameson]

:yes:

 

[Astro SG Wise]

Gotcha.

---------- Post added at 03:23 PM ---------- Previous post was at 12:40 AM ----------

Looking good! Can't wait to fly it sometime, especially with that Gimbal.

 

[kocmolyf]

Progress is slow but sure behind the scenes. There's a lot of plumbing to get through, as well as control analysis.

• Added the current propellant state permanently to the HUD.
• Added a cutoff timer. It first shows the time to the 7 engine cutoff, then the 5 engine cutoff, and finally total burnout (at the target apogee).
• Created a new attitude frame: BOOST. This is a pseudo-inertial frame, which points along the desired launch plane (you can now specify a desired launch azimuth to the flight computer!). The "up" direction is wings-level, though the LR1 flies heads-down during ascent.
• I added automatic roll control to the main engine steering controller, which required making a mini simulator and iterating on the control algorithm and gains. It comes in several modes:
  
  • AUTO will wait until the LR1 clears the tower, then roll aggressively to the heads-down orientation.
  • HOLD will maintain the current roll angle (once any rate has been killed).
  • RATE will null rates, or maintain a constant rate if the keys are held.
  • PULSE is direct commanding of gimbal angles.

The next immediate steps are to extend some of the control modes to pitch and yaw (we won't get an AUTO pitch program until I develop ascent guidance - that's still a ways in the future). Then there's MFD work and, of course, the OMS engines.

Things are looking good! As usual, lots more work remains. But this vehicle is becoming more legitimate every week.

Flying in the BOOST frame during ascent with automatic roll control (also note the cutoff timer, TCO7).

 

[Scav]

Things are looking good! As usual, lots more work remains. But this vehicle is becoming more legitimate every week.

Cool, thanks for the update! I had some questions, but carefully reading your changelog answered them quite nicely.

As usual I have a roster of astronauts whom have been spending their time doing public appearances and educational outreaches. This news will be sure to boost morale in the corps.

(Edit: We both know I'm speaking in a virtual sense when it comes to the astronauts but it is still good to hear from you! )

 

[aevionknight]

Haha. Well, we stranded the first batch in orbit by sending them up without an orbital maneuvering system. It's probably for the best that the second batch is on the outreach circuit. We could use the positive PR...

 

[kocmolyf]

I hit a definite slowdown in the past couple months due to crunch time at work (I've been tackling a pretty tough design problem). I've managed to get a bit of time on the LR1, though.

• Ascent attitude control is basically complete! The flight computer can now operate as a manual assistant or take over all attitude control. In manual mode, the flight computer fights aerodynamic torques and damp the roll and yaw channels. In automatic mode, it holds zero yaw and roll and accepts a single input - pitch rate. This frees the pilot to focus only on performing a gravity turn.
• Internally, I've been shuffling code around in preparation for enabling the orbital maneuvering engines.

I'm not sure if I'm going to create a proper ascent MFD page first, or start working on the orbital maneuvering system. Both will require MFD work, so it depends on which seems more fun next time I open the code.

As usual I have a roster of astronauts whom have been spending their time doing public appearances and educational outreaches.

Haha. That's good - we need the PR boost. The media wasn't too happy after they learned we've been sending all these test crews to orbit with no way back...

 

[kocmolyf]

I spent some time in Inkscape working through the boost display. I'm pretty happy with this layout:

The boost MFD page.