Peregrine still operational but expected to burn up in Earth’s atmosphere
Click for original image.
According to an update yesterday from Astrobotic’s engineering team, the damaged lunar lander is likely to enter the atmosphere burn up when its orbit brings it back to Earth in about a week.
In an update the day before, the company released a graph of the spacecraft’s position in relation to the Earth and Moon, shown to the right. From that update:
Peregrine remains operational at about 238,000 miles from Earth, which means that we have reached lunar distance! As we posted in Update #10, the Moon is not where the spacecraft is now (see graphic). Our original trajectory had us arriving at the Moon on day 15 post launch. Our propellant estimates currently have us running out of fuel before this 15-day mark
The plan had apparently been to circle the Earth twice in this elongated orbit, with the second orbit (after some mid-course corrections) bringing Peregrine close enough to the Moon (after it had moved further in its orbit) to be captured by its sphere of influence. With the loss of fuel due to the leak, the spacecraft doesn’t have the fuel to do any of the required engine burns, including one that would avoid the Earth’s atmosphere upon return.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Click for original image.
According to an update yesterday from Astrobotic’s engineering team, the damaged lunar lander is likely to enter the atmosphere burn up when its orbit brings it back to Earth in about a week.
In an update the day before, the company released a graph of the spacecraft’s position in relation to the Earth and Moon, shown to the right. From that update:
Peregrine remains operational at about 238,000 miles from Earth, which means that we have reached lunar distance! As we posted in Update #10, the Moon is not where the spacecraft is now (see graphic). Our original trajectory had us arriving at the Moon on day 15 post launch. Our propellant estimates currently have us running out of fuel before this 15-day mark
The plan had apparently been to circle the Earth twice in this elongated orbit, with the second orbit (after some mid-course corrections) bringing Peregrine close enough to the Moon (after it had moved further in its orbit) to be captured by its sphere of influence. With the loss of fuel due to the leak, the spacecraft doesn’t have the fuel to do any of the required engine burns, including one that would avoid the Earth’s atmosphere upon return.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Dumb questions from me:
If the Peregrine is essentially at Moon’s orbit in location (as shown) wouldn’t it’s eventual orbit be much further than shown? I assume the prior plan of two orbits around the Earth was to time the path such that the Peregrine would be “captured” by the Moon’s gravity. But now it is missing it.
I don’t know if the Peregrine achieved Earth’s escape velocity (25K MPH I believe); but if so would it not “escape” now that it is “missing”{ the Moon?
Or, perhaps the Moon now moving toward the trajectory of the Peregrine will capture or influence it and hold it in the Earth-Moon system. With that, would it then be a Three-Body system and very hard to predict trajectory?
Chris: Peregrine did not achieve escape velocity, which is why it is still in Earth orbit and falling back to Earth.
You are correct in your assumption about the orbit, at least as how I see it. The plan appears to have been to go around the Earth twice (maybe three times?) in an orbit that reached the Moon’s orbit, with one of those later orbits passing through the Moon’s gravitational sphere of influence and getting captured by it.
This approach was used to save weight and cost. Peregrine’s engines weren’t powerful enough to achieve the necessary speed to reache escape velocity, but were enough (in conjunction with the Vulcan engines) to put it in this eccentric Earth orbit. Gravity was to do the rest.
Thank you Bob
Chris,
The orbit has some similarities to the Apollo lunar missions. They, too were placed in orbits that did not escape Earth, but they did intercept the Moon on the first pass.
Astrobotic may have intentionally made the orbit intercept the Earth’s atmosphere, in the case that something happened on the first orbit, so that Peregrine would not become space debris after its first encounter with the Moon, in an orbit that becomes increasingly random with each future encounter with the Moon. If this is the case, then it is unfortunate that this contingency plan has had to be used, but good thinking that it was in place, to be used.
Edward,
It would preserve more options for Astrobotics to have the orbit of Peregrine NOT intersect with Earths atmosphere on its return from encountering the moon. ‘If something happened on its first orbit’… could have been anything and not necessarily this particular malfunction. It might have been something that could have been fixed in time, more time than they would have if Peregrine was programed to hit Earth. It also would not rule out the possibility of a future salvage mission to recover, if nothing else, the DNA samples and the cremation remains.
Without knowing what’s in the heads of those at Astrobotics, I wouldn’t assume they have the high conscience to deliberately send a failed Peregrine to a fiery end just to avoid being space litterbugs. Are there fines or citations for creating space junk? Not yet, as far as I know.
As to the comparison with Apollo, NASA would do all it could to avoid those ships, with human crew, to have an uncontrolled reentry into Earths atmosphere while on the way back in the event something went wrong.
Allan: See this update from Astrobotic from January 14, 2024. To quote:
Allan,
The comparison with Apollo was that the Command-Service Module was not put in an escape velocity, hyperbolic orbit.
The designed orbit was always intended to intercept the Moon and to return to the Earth if the lunar orbit insertion did not take place. It was known as “free return trajectory,” and is a fascinating coordination between a hyperbolic lunar escape velocity orbit with the Moon and the velocity of the Moon as the spacecraft travelled around it. This is one of those cases where a sketch is worth a thousand words, but I cannot sketch on this type of comment mechanism.
The free return trajectory seems to always be drawn as a figure 8, but that is what is seen in a rotating frame of reference. It is misleading, because it gives the impression that orbital mechanics works this way. The figure 8 comes about because the reference frame is rotating with the Moon’s travel around the Earth, so that the Moon appears in the same place relative to the Earth (e.g. on the right side of the image with the orbital plot).
This four-minute video shows the hyperbolic trajectory from the Moon’s reference frame. This explanation begins at the 2:05 mark and the hyperbolic orbit starts at the 2:20 mark. (Note: in this image, the Moon is fixed on the left side.)
https://www.youtube.com/watch?v=UmDoHDVuZfo (“Introduction to Lunar Free-Return Trajectories”)
At the end of the Moon’s gravitational influence, the spacecraft is headed back to the Earth, because the Moon was traveling at a speed that “dragged” the spacecraft along with it fast enough to send the spacecraft almost, but not quite, straight back to the Earth. The narrator approximates the motion using two elliptical orbits, one for the outbound journey, and another for the return journey, where the influence of the Moon transfers the spacecraft from the first to the second approximated eliptical orbits.
If the Moon had not been there, however, the orbit of the Apollo spacecraft would have been a regular ellipse that would have its perigee near the Earth. This is what we see in the wildly out-of-scale Astrobotic image in Robert’s post.
With Apollo, NASA did all it could to assure that those ships, with human crew, would safely reenter into Earth’s atmosphere while on the way back, in the event something went wrong.
edward-
good stuff.
Why Spacecraft Are Using These Crazy Routes To The Moon – Weak Stability and Ballistic Capture
Scott Manley (December 2022)
https://youtu.be/WVrWcbyOmxY
13:59
Thanks, Robert and Edward.
In the not so distant future, the boys at the space station (One of many but this one devoted to reconstruction and maintenance of in orbit satellites) would grab a return vehicle with spare fuel for this purpose and chase down the craft before reentry, pull it into the cargo bay, and return to the space station where the lander will be repaired, refueled, and a second try attempted.