Luna 25 and Chandrayaan 3 landers

[Keith Lofstrom]

After ISRO (Indian Space Research Organization) crashed its
first Chandrayaan-2 lunar lander in 2019, India launched
Chandrayaan-3 on July 14, scheduled to land August 23 or 24.

( note that the US Surveyor robot landers succeeded 5 times
and failed twice between 1966 and 1968; not bad, given the
"stone knives and bear skins" electronics of the 1960s. )

The 2008 Chandraayan-1 mission was an orbiter and an
impactor, detecting ice at the lunar south pole.

Russia/Roscosmos surprised the world by launching their
Luna 25 robotic lander on August 10, three weeks after
Chandrayaan-3. Russia can reach the Moon faster because
their launch rockets are more powerful. Mass-constrained
Chandrayaan-3 left Earth and circularized around the Moon
with multiple small periapsis burns, presumably using a
low thrust, low mass rocket engine.

Before Luna 25, Russia's "most recent" Luna 24 mission
landed on the Moon on 19 August 1976, 47 years ago.
Perhaps Russia did not want to be upstaged by "backwards"
India ... however ...

As I write this, a not-yet-officially-confirmed report
from TASS says that Luna 25 crashed into the moon a few
hours ago. Chandrayaan-3 is still in a near-Moon low
orbit, undergoing repeat testing, as planned. India
wants to nail this landing, and join the Moon Landing
Club with the US, the Soviet Union, and China. Note
that Israel, Japan, and now the Russian Federation have
failed to land on the Moon. Not an easy task.

Backsliding Russia uses its limited abilities to attack
Ukraine, and is on the way to losing half a million young
minds. Lets hope their strategic missiles and warheads
are failing as rapidly as their robotic space program.

This is relevant the Power Satellite Economics list
because India may evolve into a low-cost provider for
experimental and prototype SSPS launches. In the end,
the only thing costing money is skilled human attention;
low-cost India is developing their skills rapidly.

Keith L.

--
Keith Lofstrom kei...@keithl.com

[Keith Lofstrom]

On Sun, Aug 20, 2023 at 06:22:26AM -0700, Keith Lofstrom wrote:
> Russia/Roscosmos surprised the world by launching their
> Luna 25 robotic lander on August 10, three weeks after
> Chandrayaan-3.

...

> Before Luna 25, Russia's "most recent" Luna 24 mission
> landed on the Moon on 19 August 1976, 47 years ago.
> Perhaps Russia did not want to be upstaged by "backwards"
> India ... however ...

Official confirmation.

----

I wrote an extremely speculative, long, and WRONG "theory"
of what might have happened, early this morning.

I am glad I did not send it, launching a raft of bullshit
into the blogosphere.

What happened to Luna 25?

Here are some details of the near-lunar landing plan:

https://t.me/dobriy_ovchinnikov/2223

In Russian, but the numbers are readable. With some
effort (and google translate) the text is also readable,
but the diagram and the numbers tell an understandable
story.

Calculating simple Kepler orbits, plus my extensive
background in measurement, management wishful thinking,
and the relentless accumulation of errors in "open loop"
control systems, helps me speculate some plausible
explanations for the Luna 25 failure.

The diagram shows Luna 25 in a 100 km altitude circular
lunar orbit. Then a delta V at apolune into an 18 km
perilune 100 km apolune elliptical orbit.

This is discussed by "tolis" in reply #95 in this
coversation:

https://forum.nasaspaceflight.com/index.php?topic=59370.80

Tolis calculates an apolune delta V of 16 m/s to reduce
perilune from 100 km to 18 km altitude. If the delta V
was accidentally extended by only 4 m/s, perilune is
subsurface - CRASH!

More importantly, a few small errors in the ACTUAL orbit
altitude and the ACTUAL delta V can lead to far more
than a 4 m/s apogee insertion error.

My speculations:

Presumably, this delta V was made with the same rocket
engine used for circular orbit insertion from an
elliptical trans-lunar trajectory from Earth. A
formidable machine, capable of km/s delta V. What's
a meter per second compared to that?

The mission might be done with three separate maneuvers:
(1) circularize to lunar radius with an apogee burn,
then (2) drop into lunar orbit with another, then (3)
circularize to 100km lunar orbit with a third delta V.

It might be cheaper and faster (but far more risky) to
PRECISELY launch towards a PRECISE point 100 km above the
Moon, then with a PRECISE 3-axis delta V (trans lunar
injection, TLI) to a 100 km radius circular lunar orbit.

I count at least 3 precise 3D vectors above (two delta Vs
and one precise point in space), which is 9 numbers that
must be close to perfect. A more leisurely approach would
relax and separate the constraints, but take longer, and
land on the Moon after Chandrayaan-3 did ... thus
missing the political/propaganda target.

("When do you want us to launch the shuttle, Boisjoly?
Summer?")

The mission timing suggests "beat India" and "hurry hurry"
thinking drove the decisions, acceleration of a program
that might have succeeded a year or two later, with more
time to think and plan and measure and calculate.

Chernobyl thinking, STS-51-L thinking, though thankfully
with no lives lost. Cheap-fast-good, pick any two.

Delta V starting with Earth launch to trans-lunar ellipse,
delivered by the launch stages of the Soyuz-2 Fregat
launcher? 10,920 m/s . A tiny error in that velocity
(ppm) results in HUGE displacements in lunar arrival
radius (many kilometers). And HOW would the Russians
measure velocity and distance? They do not have a
worldwide space radar and communication network like
the US does, just one radar ship in the Pacific for
launch trajectory measurements from the Vostochny
Cosmodrome. Although the Earth will rotate Russia's
space radars below the Luna-25 trajectory a few times
on the way to the Moon, those measurements (plus the
large angular azimuth variance of the radar dishes)
will add much uncertainty to the lunar arrival radius.
Accuracy demands MANY radars, and triangulation.

In peacetime, I'm sure the US would gladly provide
Roscosmos with more accurate tracking data, and Russia may
rely on that data to plan and execute their space missions,
but not while insane Putin threatens the world.

Thus, it is likely that Luna 25 arrived at the Moon
with excessive position and velocity error. The nice
diagram is a goal, not a bedrock reality.

Translunar injection is approximately 3000 meters per
second. While the Luna 25 MISSION GOAL is a 100 km
altitude circular lunar orbit ... how would Russia
verify this? They could use Kepler's laws and orbit
period and doppler shift on the received radio data,
but that process may not be well-calibrated for a
POLAR lunar orbit over the mass-lumpy Moon.
More errors will creep into the mission.

If Luna 25 uses radar altimetry, that will be problematic
over the very rough mountainous terrain near the lunar
south pole. The time-spread of the radar returns will
degrade altitude measurements and calculations.

I worry about this happening to Chandrayaan 3 as well.
Some list members are ISRO friends. I hope they will risk
those friendships to provide some "pessimistic" oversight.
I'd rather ISRO delay the landing by a month, rather than
fail on schedule.

Future lunar operations near the poles will REQUIRE some
kind of lunar GPS, both orbital and surface beacons.
Until we (meaning all of humanity and all lunar mission
planners) have that, lunar exploration will be an
UNNECESSARILY imprecise and risky business. It would be
a WIN-WIN if the US and India collaborated on designing
and deploying such a system, sharing the ENCRYPTED
results with the peace-loving nations of the Earth.

Speak softly, and carry a big DATA STICK.

More important to us, SSPS deployment will be far more
reliable if we have long-baseline beacons for determining
position and velocity. Huge SSPS constellations, with
very high mass and ENORMOUS collision cross sections, is
a Kessler cascade candidate that makes playing with matches
while standing in a pool of gasoline seem "relatively
prudent". While the fate of Luna 25 and Chandrayaan-3
may seem off-topic to SSPS discussions, all these systems
REQUIRE a firm bedrock of caution and near-perfect
real-time measurement and control to reliably succeed.

Perhaps that's just me, an electronic measurement system
designer who adds ppms, not percents. My colleagues who
design sixteen terabit flash memory chips think in parts
per quadrillion; I'm a sloppy amateur compared to them.

Sadly, I am an insanely obsessive control freak compared
to the politician-appointed bureaucrats who oversee space
mission planning. Perhaps far more "control freaky" than
many of the "visionaries" on this list.

Disciplinarians are party poopers. Sorry about that.
But ask yourself: "Do we want to party? Or PRODUCE?"

[Narayanan Komerath]

Big questions are WHY? And WHY NOW?

As someone remarked back in 2016, "(President) Obama Plays Checkers. (President) Putin Plays Chess".

My rough guess is that there were a lot of features on the launcher/ etc etc. that had nothing to do with Lunar Exploration, but everything to do with CEP or guidance or "telemetry". The Luna25 Lander might have been a $20Mockup. Now no one will ever know until/unless some future Rover happens to see a tattered Flag fragment.

The decision to shoot with 1 or 2 Hohman transfers (I am guessing) may have had nothing to do any "race" and everything to do with rocket testing without triggering the usual screams.

nk

--
You received this message because you are subscribed to the Google Groups "Power Satellite Economics" group.
To unsubscribe from this group and stop receiving emails from it, send an email to power-satellite-ec...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/power-satellite-economics/20230821030629.GA4158%40gate.kl-ic.com.

[Narayanan Komerath]

Point is it DID hit the Moon. Or did it?

nk

[k.a.c...@sympatico.ca]

Keith;

You wrote:

> More importantly, a few small errors in the ACTUAL orbit altitude and the

> ACTUAL delta V can lead to far more than a 4 m/s apogee insertion error...

> Presumably, this delta V was made with the same rocket engine used for
> circular orbit insertion from an elliptical trans-lunar trajectory from Earth. A
> formidable machine, capable of km/s delta V. What's a meter per second

> compared to that?..

>
> Translunar injection is approximately 3000 meters per second. While the
> Luna 25 MISSION GOAL is a 100 km altitude circular lunar orbit ... how would
> Russia verify this?

The same way that was done for the Apollo spacecraft: point the rocket in the right direction (which assumes that you have an attitude control system that is working adequately well), and measure acceleration when the rocket is thrusting, using an accelerometer. Use dead-reckoning in real-time during thrusting to estimate speed change in that direction (and hence velocity vector change). Use the dead-reckoning signal to determine when you've reached the desired velocity change, and at that point terminate thrust. This will have *some* error due to noise and bias-drift in the accelerometer, but for a high-thrust propulsion system and using an ICBM-grade accelerometer (which the Russians certainly have), the residual error in delta-V will be quite small. (For what happens when you have a low-thrust propulsion system, see this presentation of mine: https://www.researchgate.net/publication/303519852_Inertial_Navigation_for_Low-Thrust_Spacecraft)

Certainly also use radio range/range-rate tracking to estimate that residual error. Time your propulsive manoeuvres so that you have radio-tracking coverage for them.

- Kieran

[a.p.kothari astrox.com]

 

“Instead of the planned 84 seconds, it worked for 127 seconds. This was the main reason for the emergency,” Borisov told Russian state news channel Russia 24."

 

https://abcnews.go.com/Technology/wireStory/russian-space-agency-chief-blames-decades-inactivity-luna-102429374

 

Does not look like a 4 KN engine for this ~1700 kg craft as some in NSF blog mentions.

 

Some numbers for Luna.

	a	ae	e	Mu=R0*R0*G0		Vp	Va	DelVp	DelVa	TotDelV
	semi-major (km)		eccentricity			m/s	m/s	m/s	m/s	m/s
for 0 to 10 circ	1739.2575	9.2575	0.005322674	4854.4838	1.010702	1679.582	1661.796944	4.45216822	4.440335096	8.892503
for 5 to 10 circ	1743.88625	4.62875	0.002654273	4854.4838	1.005323	1672.882	1664.024486	2.21573217	2.212793536	4.428526
for 5 to 20 circ	1753.14375	13.88625	0.007920771	4854.4838	1.015968	1677.269	1650.907518	6.6034303	6.577329144	13.18076
for 20 to 20 (check only)	1767.03	1.98952E-13	1.12591E-16	4854.4838	1	1657.485	1657.484847	0	0	0
for 10 to 20 circ	1757.7725	9.2575	0.005266609	4854.4838	1.010589	1670.619	1653.114423	4.38194798	4.37042401	8.752372
for 10 to LSO	48026.7575	46259.7275	0.963207385	4854.4838	53.35873	2322.377	43.52383282	656.13937	183.3603229	839.4997
for 10 nm to 100 km circ	1789.257535	40.74253522	0.022770638	4854.4838	1.046602	1685.101	1610.068037	18.8638617	18.65025811	37.51412

 

-------------------------------------------------------

Dr. Ajay P. Kothari

President

Astrox Corporation

 AIAA Associate Fellow

 

Ph: 301-935-5868

Web:  www.astrox.com

Email: a.p.k...@astrox.com

-------------------------------------------------------

--

[Keith Lofstrom]

First, thank you for all the useful information and
the occasional application of the cluestick.

On Mon, Aug 21, 2023 at 09:58:14PM +0000, a.p.kothari astrox.com wrote:
> “Instead of the planned 84 seconds, it worked for 127 seconds. This was the main reason for the emergency,” Borisov told Russian state news channel Russia 24."

> https://abcnews.go.com/Technology/wireStory/russian-space-agency-chief-blames-decades-inactivity-luna-102429374

My bad. I should have sent Roscosmos a windup kitchen timer.

Seriously, how can a rocket engine burn an extra 43
seconds? Valve that fails to close? Batteries too weak?
Perhaps "cruelty-free rocket design, no testing."
In any case, if Luna 25 was so ready-to-fail, if it
hadn't failed when it did, it would likely fail during
final descent, far more stressful than a 10 to 20 m/s
delta V lunar orbit tweak. That would mess up what is
presumably a better-than-average-interest landing site.

I should have spent more time looking for technical
design details for Luna-25, before I wrote my prior post.
I don't know much about the current state of the Russian
space program, or the technology still accessible to them,
after they burned their bridges to the world via Ukraine.

My main point was that Luna-25 was a rush job, an attempt
by Russia to appear space-capable in the 21st century, and
Putin attempting to be more than a некультурный варвар.

The people of Russia are capable of so very much more.

----

I know a few smart Russians, but I know WAY MORE smart
Indians (and Indian-Americans). I would bet on India
winning any technology competition against Russia ...
and many competitions with/against the US.

I much prefer collaborations; working together, India
and the US can kick major butt.

India struggled for decades to throw off the dead weights
of British imperialism and local ancient superstition.
Their progress so far has been awesome. I bet their
progress over the next two decades will draw much of the
rest of the world into line behind them. Hopefully the
US and Europe can march beside India, but we will need
to pick up the pace, and lose some arrogance, to do so.

BTW, I am biased, because so much of India's best technical
work is published in English. And their movies are fun.

----

So ... I am REALLY REALLY looking forward to the Weds
August 23 telecast of Chandrayaan-3's soft landing. Online
video coverage starts at 17:20 IST, which is Wednesday
4:50 am Pacific Daylight time, here on the Left Coast.

https://www.isro.gov.in/
https://www.isro.gov.in/Chandrayaan3.html
https://www.isro.gov.in/Chandrayaan3SoftLandingMessage.html
https://www.youtube.com/watch?v=DLA_64yz8Ss
https://www.facebook.com/ISRO

Launch coverage a few weeks ago was mostly in English,
candid, and informative.

Current status, second deboosting operation has reduced
Chandrayaan's lunar orbit to 25 km x 134 km lunar altitude,
similar to what Roscosmos tried to do ( 16 km x 100 km ).

जय हो - Jai ho - Be victorious!

[a.p.kothari astrox.com]

I know this does not relate to PSE, but please allow me to reply this time to express my thanks to Keith.

Now that CY 3 has just landed softly, it maybe more apropos. I also hear that the Lander and the Rover both will be doing some tests about water-ice there. I hope for positive results here as it would make a huge difference. I also hear that there is a small chance the Pragyan rover may be able to charge its batteries for another 14-day period. Not sure of this though.

KeithL,

You are not only very smart but also very kind for saying what you did! Very buoyant and ebullient! (:)

" I much prefer collaborations; working together, India and the US can kick major butt."

I agree. If the State Dinner for Indian PM, and his (Modi's) speech to US Congress, Biden's impending visit to India soon (Sept 7-10) are any indications, this may be happening. Both these two countries have much in common: diverse racial mix (for India over last 5-10 thousand years), democratic tendencies, multi religious bent, and now thanks to the Brits (in India and US both!), English as a major language.

Also another item:
"According to the Russian Academy of Sciences’ Keldysh Institute of Applied Mathematics, the spacecraft fell into the 42-kilometer Pontecoulant G crater in the southern hemisphere of the moon at 2:58 p.m. Moscow time on August 19."

Thanks.
-Ajay

-------------------------------------------------------
Dr. Ajay P. Kothari
President
Astrox Corporation
 AIAA Associate Fellow

Ph: 301-935-5868
Web:  www.astrox.com
Email: a.p.k...@astrox.com
-------------------------------------------------------

-----Original Message-----
From: power-satell...@googlegroups.com On Behalf Of Keith Lofstrom
Sent: Monday, August 21, 2023 11:15 PM
To: Power Satellite Economics <power-satell...@googlegroups.com>
Subject: Re: Luna 25 and Chandrayaan 3 landers (speculation)

--
You received this message because you are subscribed to the Google Groups "Power Satellite Economics" group.
To unsubscribe from this group and stop receiving emails from it, send an email to power-satellite-ec...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/power-satellite-economics/20230822031456.GA25558%40gate.kl-ic.com.