7 ms·

I keep telling people: Space is hard. > The rocket lost thrust after the first stage separation due to an “abnormal startup of the engine” on the vehicle’s sec

by mabbo 3y ago

I keep telling people: Space is hard. > The rocket lost thrust after the first stage separation due to an “abnormal startup of the engine” on the vehicle’s second stage that may have been caused by an instability in the engine and fuel system, according to KCNA. This is the challenge for most newcomers to space deal with. Every space startup in the US over the last couple years seems to have all had some trouble between stage 1 engine cut off and stage 2 operating. It's so easy in Kerbal Space Program! You need to: Stop your main engine; disconnect the first and second stage cleanly, successfully; put at least a little distance between first and second stage; Start the stage 2 engine in a vacuum and in freefall (which you cannot test out on the ground) and do it remotely/autonomously; have stage 2 correctly identify its own position and speed well enough to aim to the stable orbit you hoped for. Oh, and don't forget to successfully ditch your faring at some point or the satellite is trapped in an egg shell with no solar panels, communications equipment, or (in the case of a spy satellite) telescopes.

teeray 3y ago
Never mind the whole magic trick of landing the first stage on a barge and catching the faring in a big net.
- notfish 3y ago
  They actually just scoop em out of the ocean instead of catching the fairings now
  - sidewndr46 3y ago
    The recovery of the shuttles SRBs was always really cool to me. They float and the process even included manipulating their buoyancy to get them upright for easier recovery!
    - gabereiser 3y ago
      M/V FreedomStar and M/V LibertyStar were the recovery vessels. I named my sailboat the S/V FreedomStar in namesake. Out of Cape Canaveral, FL.
sidewndr46 3y ago
I believe you can start the second engine without stopping the first engine, then initiate separation and cut fuel to the first stage engines. A number of rockets feature this design and have a way for the rocket exhaust gas to pass to the outside of the hull before separation occurs.
- kjs3 3y ago
  The old Soviet Vostok did something similar with the third stage, AFAIK.
- m4rtink 3y ago
  Yep, its called hot staging & was used on some of the Titans for example. Another even more conservative option is to ground start all your engines and then throw some of them away directly (original Atlas) or with a stage (R7/Soyuz). There are certainly some tradeoffs with this, such as making it impossible to use a proper altitude/vacuum optimized nozzle if all your engines are ground started.
systems_glitch 3y ago
It was hard enough with two Estes engines! Often that second stage went off into the wild blue, never to be seen again, at some weird angle, or even spinning!
- vidanay 3y ago
  LOL. Me and my friends designed a two stage rocket, and of course we insisted that our first attempt use "D" size engines. The first stage took the rocket up about 75-100 ft and when the second stage lit off, the rocket somehow kicked over and was flying perfectly horizontal. The problem was, we were launching from the bottom of a retention basin at the local park district so we started out at -40 ft altitude. This meant the rocket went zooming across the neighborhood only slightly above tree top level.
  - Arrath 3y ago
    Oh that is just brilliant. Model rocket shenanigans were a highlight of my childhood. Turns out, duct taping extra motors onto the rocket body as a cluster of second stage engines, initiated by cannon fuse itself ignited by the first stage didn't work so hot.
    - WWLink 3y ago
      I had a few model rockets, but I also made some completely custom ones out of index cards wrapped around a small motor. I added curved fins so one would spin. THAT was interesting! One of my (normal estes) rockets was hanging from a tree over a bike path by the park for like a week until I finally brought a ladder and some poles to get it down. Honestly I'm surprised nobody ever tried to grab it lol. Edit: The very first estes rocket was from a kit - our teacher had a "rocket week" and we all made and launched rockets. Mine went up, a fin fell off, then it u-turned, and then went straight for the math teacher.
    - Metacelsus 3y ago
      yeah, the problem is if they don't ignite at exactly the same time, you'll get unbalanced thrust and wild spinning! lots of excitement there!
LegitShady 3y ago
some people think the goal of kerbel space program is to launch rockets into space ... i think its to have them fail in hilarious fashion. we are not the same.
deleted 3y ago
[deleted]
ericbarrett 3y ago
In this vein, I highly recommend the RP-1 mod set for KSP1, which introduces (among other things) ullage and engine start failures, launching from a realistic Earth. Really gave me a huge appreciation for the difficulty of achieving orbit. https://github.com/KSP-RO/RP-0 https://github.com/KSP-RO/RP-0
- heywoodlh 3y ago
  > [RP-1] Really gave me a huge appreciation for the difficulty of achieving orbit. One of my favorite things about (even un-modded) KSP was appreciating -- even on a super simplified level -- all that went into making things go into space. Even just launching in the same direction as the orbit of the planet to get a gravity assist seems so "duh" now but was something I had never considered before KSP. What a great game, will have to check out RP-1.
Gravityloss 3y ago
Atlas 1 and Space Shuttle hacked this by having all engines started on the pad.
- mabbo 3y ago
  Space shuttle still needed to restart their engines in space so that they could slow down enough to return to earth.
  - Gravityloss 3y ago
    Those are other engines, much smaller and using different propellants.
aio2 3y ago
It really is rocket science.
todd8 3y ago
In grad school I took a class from Robert Boyer and J Strother Moore (famous for Boyer-Moore string searching and the 2005 ACM Software System Award for the Boyer-Moore Theorem Prover). It was a long time ago, but I remember an anecdote that Boyer explained happened while working at NASA on the Apollo project. It is a good example of the simple things that can go wrong in space. (I hope I can explain it clearly and correctly, I took that class decades ago.) At one point, to return to earth the command module must separate from the landing module (after it has been on the surface of the moon and back) and fire the thrusters that will return the astronauts and some moon rocks to earth. The astronauts flip some switches to start this sequence. Shortly before the whole Apollo moon mission, programmers discovered a bug. The thruster doesn't know where the center of gravity of the orbiter is located, but it must adjust its gimbals so that the thrust is in line with the craft's center of gravity to prevent tumbling the spaceship. This is automatically done, rapidly at the startup of the thrusters, by firing and then wiggling the nozzle a bit to figure out the correct direction vector in line with the center of gravity by readings from gyros. It seems like this should work. The bug is that there would be a delay between flipping the switch to fire the thrusters and the actual firing because, in zero-gravity, the fuel is just a big floating ball of liquid in the fuel tanks and consequently there is a delay of a few seconds while little maneuvering gas jets start accelerating the craft causing the fuel to move to the back of the tank (where the fuel lines are) and finally making its way into the nozzle of the trusters where it ignites automatically. Unfortunately, the software assumed that the thruster would ignite right away, and would wiggle the nozzle and get a completely wrong answer for the calculated center of gravity because the engine wasn't ignited yet. Then, with the nozzle pointed in the totally wrong direction, ignition would cause the craft to be pitched into a dangerous tumble while trying to leave lunar orbit. This bug wouldn't be obvious during testing on earth because the fuel would be at the bottom of the tank and ready to fire without the delay. It was too late to patch the software so some instructions were taped next to the switches instructing the astronauts to put in the necessary delay manually.

by mabbo 3y ago

teeray 3y ago

Never mind the whole magic trick of landing the first stage on a barge and catching the faring in a big net.

notfish 3y ago
They actually just scoop em out of the ocean instead of catching the fairings now
- sidewndr46 3y ago
  The recovery of the shuttles SRBs was always really cool to me. They float and the process even included manipulating their buoyancy to get them upright for easier recovery!
  - gabereiser 3y ago
    M/V FreedomStar and M/V LibertyStar were the recovery vessels. I named my sailboat the S/V FreedomStar in namesake. Out of Cape Canaveral, FL.

sidewndr46 3y ago

I believe you can start the second engine without stopping the first engine, then initiate separation and cut fuel to the first stage engines. A number of rockets feature this design and have a way for the rocket exhaust gas to pass to the outside of the hull before separation occurs.

kjs3 3y ago
The old Soviet Vostok did something similar with the third stage, AFAIK.
m4rtink 3y ago
Yep, its called hot staging & was used on some of the Titans for example. Another even more conservative option is to ground start all your engines and then throw some of them away directly (original Atlas) or with a stage (R7/Soyuz). There are certainly some tradeoffs with this, such as making it impossible to use a proper altitude/vacuum optimized nozzle if all your engines are ground started.

systems_glitch 3y ago

It was hard enough with two Estes engines! Often that second stage went off into the wild blue, never to be seen again, at some weird angle, or even spinning!

vidanay 3y ago
LOL. Me and my friends designed a two stage rocket, and of course we insisted that our first attempt use "D" size engines. The first stage took the rocket up about 75-100 ft and when the second stage lit off, the rocket somehow kicked over and was flying perfectly horizontal. The problem was, we were launching from the bottom of a retention basin at the local park district so we started out at -40 ft altitude. This meant the rocket went zooming across the neighborhood only slightly above tree top level.
- Arrath 3y ago
  Oh that is just brilliant. Model rocket shenanigans were a highlight of my childhood. Turns out, duct taping extra motors onto the rocket body as a cluster of second stage engines, initiated by cannon fuse itself ignited by the first stage didn't work so hot.
  - WWLink 3y ago
    I had a few model rockets, but I also made some completely custom ones out of index cards wrapped around a small motor. I added curved fins so one would spin. THAT was interesting! One of my (normal estes) rockets was hanging from a tree over a bike path by the park for like a week until I finally brought a ladder and some poles to get it down. Honestly I'm surprised nobody ever tried to grab it lol. Edit: The very first estes rocket was from a kit - our teacher had a "rocket week" and we all made and launched rockets. Mine went up, a fin fell off, then it u-turned, and then went straight for the math teacher.
  - Metacelsus 3y ago
    yeah, the problem is if they don't ignite at exactly the same time, you'll get unbalanced thrust and wild spinning! lots of excitement there!

LegitShady 3y ago

some people think the goal of kerbel space program is to launch rockets into space ... i think its to have them fail in hilarious fashion. we are not the same.

deleted 3y ago

[deleted]

ericbarrett 3y ago

In this vein, I highly recommend the RP-1 mod set for KSP1, which introduces (among other things) ullage and engine start failures, launching from a realistic Earth. Really gave me a huge appreciation for the difficulty of achieving orbit. https://github.com/KSP-RO/RP-0 https://github.com/KSP-RO/RP-0

heywoodlh 3y ago
> [RP-1] Really gave me a huge appreciation for the difficulty of achieving orbit. One of my favorite things about (even un-modded) KSP was appreciating -- even on a super simplified level -- all that went into making things go into space. Even just launching in the same direction as the orbit of the planet to get a gravity assist seems so "duh" now but was something I had never considered before KSP. What a great game, will have to check out RP-1.

Gravityloss 3y ago

Atlas 1 and Space Shuttle hacked this by having all engines started on the pad.

mabbo 3y ago
Space shuttle still needed to restart their engines in space so that they could slow down enough to return to earth.
- Gravityloss 3y ago
  Those are other engines, much smaller and using different propellants.

aio2 3y ago

It really is rocket science.

todd8 3y ago

In grad school I took a class from Robert Boyer and J Strother Moore (famous for Boyer-Moore string searching and the 2005 ACM Software System Award for the Boyer-Moore Theorem Prover). It was a long time ago, but I remember an anecdote that Boyer explained happened while working at NASA on the Apollo project. It is a good example of the simple things that can go wrong in space. (I hope I can explain it clearly and correctly, I took that class decades ago.) At one point, to return to earth the command module must separate from the landing module (after it has been on the surface of the moon and back) and fire the thrusters that will return the astronauts and some moon rocks to earth. The astronauts flip some switches to start this sequence. Shortly before the whole Apollo moon mission, programmers discovered a bug. The thruster doesn't know where the center of gravity of the orbiter is located, but it must adjust its gimbals so that the thrust is in line with the craft's center of gravity to prevent tumbling the spaceship. This is automatically done, rapidly at the startup of the thrusters, by firing and then wiggling the nozzle a bit to figure out the correct direction vector in line with the center of gravity by readings from gyros. It seems like this should work. The bug is that there would be a delay between flipping the switch to fire the thrusters and the actual firing because, in zero-gravity, the fuel is just a big floating ball of liquid in the fuel tanks and consequently there is a delay of a few seconds while little maneuvering gas jets start accelerating the craft causing the fuel to move to the back of the tank (where the fuel lines are) and finally making its way into the nozzle of the trusters where it ignites automatically. Unfortunately, the software assumed that the thruster would ignite right away, and would wiggle the nozzle and get a completely wrong answer for the calculated center of gravity because the engine wasn't ignited yet. Then, with the nozzle pointed in the totally wrong direction, ignition would cause the craft to be pitched into a dangerous tumble while trying to leave lunar orbit. This bug wouldn't be obvious during testing on earth because the fuel would be at the bottom of the tank and ready to fire without the delay. It was too late to patch the software so some instructions were taped next to the switches instructing the astronauts to put in the necessary delay manually.