# Is there a lower limit on time-to-orbit from launch?

Since 2013, several launches up to the ISS have taken a fast-launch. First initiated by Soyuz TMA-08M, the fast rendezvous takes the crew up in 6 hours where the previous time-to-dock was around 2 days.

Obviously the human body is capable of surviving the acceleration/deceleration involved, and contemporary technology capable of the precision required in docking - cutting down time from 2D to 6H. Yet (please correct me if my assumption is misfounded) How long does it take to get to ISS? indicates the quantum of time to get to orbit itself is only a small fraction of the total time to rendezvous - and the time to orbit has not changed significantly over the years. From reading various reports available on the internet (e.g. STS reports) my take is time-to-orbit has consumed 30 to 40 minutes - and continues to do about the same.

Technology allows us to cut-down on time-to-rendezvous from 2D to 6H around 80% quicker. Say a mission does not need to get to ISS - it is only up-around-down; how much can the time to orbit from launch be reduced?

Apart from the physiological constraints on acceleration, and hardware -how much quicker can we get to orbit from launch? Can the time to orbit at-least be halved from approximately 30m to 15m?

• Just "any" (Earth) orbit, or a specific orbit? If the latter, what type of orbit?
– user
Mar 30, 2015 at 14:37
• Low-altitude flight must take air drag into account: going too fast wastes fuel on drag; going too slow wastes fuel because rocket power output is thrust times speed. If I remember correctly, you want to be going at terminal velocity in atmosphere flight as not to waste fuel. Mar 30, 2015 at 15:39
• @MichaelKjörling I looked at the STS status reports; so this was particular to ISS. The question though is meant to be broader ... Mar 30, 2015 at 16:15
• This video from SmartEveryDay explains exactly what takes from launch to orbit, to sinchonize the orbits and then to docking. youtube.com/watch?v=qFjw6Lc6J2g Mar 31, 2015 at 12:58
• @LawfulHacker Thanks for the link to Destin's video, it's great! After watching, I've asked What does Soyuz's button-pushing “fancy stick” look like?
– uhoh
Feb 6, 2018 at 1:03

I'm not sure where you're getting your 30-40 minute figure; initial orbital entry generally takes about 10. Getting into the exact orbit you want takes longer, of course, but getting from ground to a reasonably safe and stable orbit is pretty quick.

Getting to orbit substantially faster is possible, but rough on the passengers. Acceleration increases dramatically over the duration of a single ascent stage as fuel mass is expended, plus air resistance decreases and engine thrust increases as you gain altitude. Check out the the graphs near the bottom of this page. Saturn V limited acceleration to about 4g, but early American orbital flights on Atlas launchers got up around 8g:

• Agreed. STS MECO was about 8:30 and that was for a direct insertion profile with no OMS-1 required. Mar 30, 2015 at 15:57
• The STS-88 report, for instance, mentioned in-orbit activities commenced after a half-an-hour which is what I took as a baseline. Mar 30, 2015 at 16:18
• Presumably that's 10 minutes of ascent and 20 minutes of running through checklists, making sure everything worked right, and that the machine and the crew are prepared for what they're doing next. Mar 30, 2015 at 16:33
• There was an enormous amount of configuration required to turn the booster-orbiter into a space-orbiter. The governing checklist for this was the Post Insertion checklist, which gives you a hint that it was done after orbital insertion. You can peruse it here: nasa.gov/centers/johnson/pdf/539932main_PI_134_F_2.pdf Mar 30, 2015 at 20:13
• @OrganicMarble STS MECO put the shuttle in an elliptical orbit with a perigee too low to be maintainable. A stable orbit was established after about a 45-minute coast to apogee, at which point the OMS 2 burn circularized the orbit. While a trajectory could be established that would create a circular orbit in one burn, it would be less efficient. The low perigee at MECO also set up the ET for a predictable reentry. That's probably where the 30-40 minute figure comes from. Without that extra burn at apogee, they're coming right back down. Apr 10, 2015 at 15:45

According to the timeline at the bottom of this page on Spaceflight101, The Japanese SS-520-5 modified sounding rocket has demonstrated a launch to orbit time of 4 minutes and 24 seconds. I'm not sure if that is a record, but I haven't found any examples of it being done quicker.

• Do you have a link to back this up?
– user10509
Feb 5, 2018 at 9:01
• I found a reference for this. Feb 5, 2018 at 23:43