The Ham Radio Series 44 - More Intro to Moonbounce

A week ago, I did a post on communicating by bouncing ham radio signals off the moon (and gave the post a title so that after a few months I'll never find it again). Looking back at that, I found a few things that I didn't include that are very important, and another few things that make a good addition to it, so more on the subject tonight. 

The thing I forgot to mention is vitally important to getting started and describes my situation perfectly.  That article talked about sending a signal to the moon and hearing your own echoes, but it's possible to complete contacts via moonbounce without being able to hear your own echoes.  The important thing is there are two stations involved and it all comes down to whether the other operator can hear you, and his station is powerful enough for you to hear his signal bouncing off the moon. 

Let me just lift a little from that prior piece so that you don't have to keep another tab open.

The next big concern is the same as every communications link everywhere else: the amount the signal attenuates - weakens - over that 500,000 miles. The term for this is path loss, and back in the Voyager article, I used a handy form that gets you within less than half a dB of the more theoretically-backed equation.  

Path loss in dB = 37 dB + 20log(f) + 20log(d)  where,f is the frequency in MHz and d is the distance in miles.

So PL = 37 + 20log(50) and 20log(500,000) or 185 dB.  

Let's say we put 1000 W out of our antenna (it could be less power in the transmitter and more antenna gain, or a simpler antenna and more out of the transmitter).  That's +60 dBm (power compared to 1 milliwatt in 50 ohms) or one million milliwatts. 

That means the signal coming back is  +60dBm output -185dB path loss or -125 dBm at our receiver input. In a 50 ohm receiver, that's 0.13 microvolt (130 nV). Is that usable?  I almost hate to say this, but it depends.  It's weak for a 0.13 microvolt SSB (phone or voice) signal, but experienced CW operators won't have much trouble if it's a Morse code (CW) signal.

The thing you're looking for here is the sensitivity of the system - the heart of how we used to buy receivers as hams - and in a room temperature receiver the noise floor can be given by 

 Noise Floor in dBm = -174 dBm + 10log (receiver BW in Hz) + Noise Figure (or NF)

Let's say our 6m receiver has 4 dB NF, the CW noise floor could work out to  -170 + 10Log(500) or -143 dBm.  That means the -125 dBm signal from the moon has an 18 dB SNR - piece o' cake.  In SSB mode, I'll make that -170 + 10Log(2000) or -137 dBm and the resultant SNR is 12 dB, or 6 dB worse.  A 12 dB SNR for phone is not as easy to understand as an 18 dB SNR for CW, but it's not bad. Some speech compression to raise the volume of the quieter parts of speech would help.

Here I have to add there's a lot more potential places for this to break down in reality.  I alluded to how much signal is lost on the reflection from the moon:

Wait.  There's a nasty assumption hidden in there, that the reflection from the moon is perfect. No signal loss, it just changes direction. That implies the signal reflected back has an angular diameter less than the moon - or some would be lost  around the edges.  The diameter of the moon is just over 0.5 degree, which is very tight for an antenna beam.

Let's say the transmitting antenna's beam is twice the diameter of the moon - 1.0 degree.  That figures to be saying half the signal doesn't reflect back - the return is 3 dB less than the calculated 185 dB.  It also implies that the reflection off the moon's surface is the radio equivalent of  a perfect mirror. There are no losses. While I don't know that the losses are I'd be pretty sure there are some.  The transmit and receive numbers aren't including the actual power at the antenna, and there are always losses in the cables connecting the power amp to the antenna.  There shouldn't be much, tenths of a dB rather than whole numbers, but don't forget it's something to keep track of. 

The place where the most improvement seems to have come is in the Weak Signal digital modes that are available now, especially the WSJT-X software that has taken the amateur radio world by storm.  JT is Joe Taylor, a Princeton University physicist and ham who has developed algorithms that make these digital signal processing tools easy to get into your station. There's more than one mode that is specifically intended for moonbounce.  

JT4, JT9, and JT65 use nearly identical message structure and source encoding (the efficient compression of standard messages used for minimal QSOs). They use timed 60-second T/R sequences synchronized with UTC.  JT4 and JT65 were designed for EME ("moonbounce") on the VHF/UHF/microwave bands.  JT9 is optimized for the MF and HF bands.  It  is about 2 dB more sensitive than JT65 while using less than 10% of the bandwidth.  Q65 offers submodes with a wide range of T/R sequence lengths and tone spacings; it is highly recommended for EME, ionospheric scatter, and other weak signal work on VHF, UHF, and microwave bands.

Unfortunately, I've never seen numbers for things like the SNR or input signal required for given small error rates in the received signal. 

While every example I've worked and included was aimed at 6m, it might be that the easiest band to get started with moonbounce is 2m.  The same gain antenna is much smaller because everything scales by wavelength, so while those names (6m and 2m) aren't really the electrical lengths, 1/2 wave (approx. a yagi element) is 9'4" on 6m, it's 3'3" on 2. On 6m, I have a 5 element yagi that's 12' long.  That scales to 4' 2.5" long on 2m. Or more antenna gain in the same length.  Gain and low noise figure are relatively cheap on 2m compared to microwaves and there are many all mode radios for 2m. 

A screen capture from this video.

There are several videos where guys build a station that they only put in place for EME, like this.

Crew 8 Astronaut Released from Hospital

Last night, the story started showing up that one of the four Crew-8 astronauts who returned to Earth Friday before dawn was hospitalized. The news didn't say which of the four crew members it was or why that person was hospitalized while the other three returned to Houston. Everything mentioned was rather generic.

In an Oct. 25 statement, NASA said the unidentified astronaut “experienced a medical issue” after the Crew Dragon splashdown in the early morning hours off the coast of Pensacola, Florida. The astronaut “is in stable condition under observation as a precautionary measure” at Ascension Sacred Heart Pensacola hospital.

All four Crew-8 crewmembers were transported to the hospital for additional medical checks after undergoing routine post-flight medical examinations on the SpaceX recovery ship. “During routine medical assessments on the recovery ship, the additional evaluation of the crew members was requested out of an abundance of caution,” NASA stated.

Crew-8 consisted of NASA astronauts Matthew Dominick, Michael Barratt and Jeanette Epps along with Roscosmos cosmonaut Alexander Grebenkin. SpaceNews reported all four seemed to be in good condition when exiting the Crew Dragon spacecraft on the SpaceX recovery ship. A little more than half an hour after splashing down, the four could be seen smiling and waving at the camera. 

Apparently soon after that, one crew member started showing signs of some sort of medical problem and the four were taken to that hospital near Pensacola in the westernmost Florida panhandle. The landing zone itself is offshore the Pensacola area.

This afternoon we got the news that the crew member has been released from the hospital. 

In a statement, NASA said the astronaut, whose identify has not been disclosed, was released from Ascension Sacred Heart Pensacola hospital after an overnight stay. “The crew member is in good health and will resume normal post-flight reconditioning with other crew members,” the agency said. 

It's generally being reported that some transient medical conditions aren't unusual after spending a long time in space.  That's part of the reason for the "normal post-flight reconditioning" NASA talks about.  Crew-8 was the longest of the numbered Crew missions at 235 days due to the delays induced by Starliner which had them wait for the Crew-9 mission to arrive at the station.  Return to Earth was further delayed by weather systems in Gulf. 

The Crew-8 Dragon capsule early Friday morning after splashdown off Pensacola.  Credit: SpaceX

India Preparing Next Lunar Landers

You'll remember India's successful lunar lander Chandrayaan-3 from last summer through the fall. With that mission, India became the fourth nation in world history to soft land a probe on the moon and the first to land as close to the south pole as they did, essentially 70 degrees south latitude. At last week's International Astronautical Congress (IAC) convention in Milan, the ISRO (Indian Space Research Organization) announced India’s plans for the Chandrayaan-4 lunar sample return mission. This mission will target a landing between 85 and 90 degrees south latitude. They also talked about a follow-up joint lander and rover mission with Japan. 

The Chandrayaan-4 mission will consist of two stacks launched on two separate rockets and will target the vicinity of the lunar south pole, according to P. Veeramuthuvel of the Indian Space Research Organization (ISRO), speaking at the International Astronautical Congress (IAC) in Milan, Oct. 17. 

The mission will aim to collect around three kilograms of samples from near the south pole, around which water-ice is thought to be available. ISRO will require several new technologies, including the ability to scoop from the surface and drill to a depth of around two meters to sample the subsurface.

They haven't completely finalized the landing location, but it's an ambitious mission that will include lunar landing, sampling, docking in lunar orbit and returning to Earth safely with the samples. All of these are technologies and techniques that will be useful for India in their plans to put astronauts on the moon by 2040.  

The separate Chandrayaan-4 stacks will each have a mass of around 4.6 tons, making a total mass of 9.2 tons, each launching on an LVM-3 launch vehicle. The modules will dock in geosynchronous transfer orbit—using a circuitous route to the moon, as with Chandrayaan-3—and travel to the moon as one. An earlier mission design envisioned using one LVM-3 and PSLV launcher for the two launches.  

As the infomercials on TV used to say, "but wait! There's more!"

JAXA also released some information on  the Chandrayaan-5 mission, also called LUPEX, which is a joint mission between ISRO and The Japan Aerospace Exploration Agency (JAXA). 

The landing mission will also target the lunar south pole, with coordinates of 89.45°S, 222.85°E, on an elevated ridge near Shackleton crater. There are permanently shadowed regions within the vicinity, potentially for the mission rover to explore. The rover will drive between 500 and 1,000 meters, taking in-situ measurements, including determining potential water-ice deposits.

India will provide the lander, mission planning and payloads, while Japan will contribute the launch vehicle, various payloads and the rover. Payloads will include ground penetrating radar, a range of spectrometers and water analysis instruments contributed by both sides.

Spacecraft renders for the Chandrayaan-4 and Chandrayaan-5/LUPEX moon missions. Credit: P. Veeramuthuvel/ISRO

It's interesting to see the determined efforts from ISRO. In addition to the Chandrayaan-4 mission, a Venus orbiter, their first crewed space station module, and a reusable launch vehicle also received approval last month.

It's a Boeing Kind of Day

A couple of unrelated small stories about the giant corporation.

Boeing is Still Bleeding Cash on Starliner

Boeing's new CEO, Kelly Ortberg, led the company's first quarterly finance report since becoming CEO on Monday, Oct. 21. The world was expecting a report of loss of value with the labor troubles, the resulting strike, and troubles with various products including Starliner. The company reported a loss of $6.2 billion. Starliner was a small part of that, $250 million or 4%.  Both of those numbers ($6.2b and $250m) are just from the last quarter: July through September. 

Back around the less-than-glorious conclusion of the Starliner Crewed Flight Test, I had found (and posted) that as of July, Boeing has reported nearly $1.6 billion in losses to pay for delays and fix technical problems on Starliner.  I think that means the $250 million is on top of the $1.6 billion. The problem flowing out of this one is that Boeing has to resolve the thruster problems and helium leaks that led NASA to tell them to leave astronauts Butch and Suni on the space station to bring Starliner home empty. Industry watchers say that could take many months, a year or more, and will cost additional hundreds of millions of dollars, and this was shown in the SEC filing Boeing submitted Wednesday.

After that September end of the mission, NASA said it didn't know when it would buy more Starliner missions and Boeing said they didn't know when they'd be ready - with an implication they may not be willing to spend the money.

A week after Starliner landed, Boeing's chief financial officer, Brian West, echoed that line. "There is important work to determine any next steps for the Starliner program, and we'll evaluate that," he said at a conference sponsored by Morgan Stanley. 

 One aspect of Ortberg's presentation stood out like a sore thumb to me.  

In response to questions Wednesday from Wall Street investment firms, Ortberg, who took the CEO job in August, suggested it's time for Boeing to look at cutting some of its losses and recalibrate how it pursues new business opportunities. Boeing's previous CEO, Dave Calhoun, said last year the company would no longer enter into fixed-price development contracts.

"I think that that we're better off being doing less and doing it better than doing more and not doing it well," Ortberg said. "So we're in the process of taking an evaluation of the portfolio. It's something a new CEO always does when you come into a business."
...
Ortberg didn't specify any programs that Boeing might consider trimming or canceling, but said the company's "core" business of commercial airplanes and military systems will stay.

In even fewer words, "we're an airplane company." There were some words that might convince me that they're willing to stay with programs like the Artemis/SLS program, which has been financially much worse for the American people and our space programs than for Boeing. I can't say I'm convinced they'll stay with Starliner.

NASA still wants to certify Boeing's Starliner spacecraft to provide the agency with a second commercial option for getting astronauts into orbit. A fundamental goal set out for NASA's commercial crew program more than a decade ago was to develop two dissimilar human-rated transportation systems for access to low-Earth orbit. The idea here is competition will drive down costs, and NASA will have a backup option if one of the commercial crew providers runs into difficulties.

NASA hasn't said they're going to require a crewed mission to the ISS before they'd grant certification to Starliner and there's talk they're looking at flying Starliner as a cargo ship to the ISS, which could allow them to verify that fixes done to the helium leaks and thruster issues have been successful. 

NASA is making moves while assuming Boeing will stay in the game. Astronauts are still assigned to train for the first operational Starliner mission, although it's not likely to happen until the end of next year or in 2026. Earlier this month, NASA announced SpaceX will launch a four-person crew to the International Space Station no earlier than July of next year, taking a slot that the agency once hoped Boeing would use.

---

It's hard to assess blame on this addendum

Kelly Ortberg's stances that they're an aircraft company and they should work at "doing less and doing it better," seem like they could be a pretty solid introduction to this story.  

An Intelsat satellite in geosynchronous orbit that Boeing was the prime contractor on exploded on orbit, according to Intelsat declaring it "a total loss" on Monday Oct. 21. 

The Intelsat-33e communications satellite is no longer operational after an outage Oct. 19; affected customers are being moved to other platforms, the company added in a statement. Meanwhile, U.S. Space Force was tracking around 20 pieces shortly after the incident, the military branch noted on X, formerly Twitter.

The satellite had been in service for seven years while other satellites like it are rated for between 15 to 20 years.  Even then, failure by explosion is rare, which opens the possibility that a piece of space junk or space rock struck it.  In addition the report that the USSF was tracking "around 20 pieces" might have been a bit premature.  Swiss tracking company s2a Systems noted 40 fragments as of Monday (Oct. 21). Another tracking company in the U.S., ExoAnalytic Solutions, saw 57 pieces that same day. 

The geosynchronous orbit is a relatively small area of the sky, 22,236 miles above Earth and there are satellites spaced 2 degrees apart. I imagine tracking the exact positions of all the fragments is a bit more difficult than tracking larger objects but I have to assume (and the article says) that there is concern that the fragments could damage another satellite. 

An artist's impression of the Intelsat 33e communications satellite. (Image credit: Boeing)

ULA Prepares Vulcan For 1st Mission

While the Vulcan has not yet been approved for US National Security launches, and the investigation into the solid rocket booster failure isn't complete, United Launch Alliance has continued preparations for the first such launch "before the end of the year."  A bit optimistic but, the first rocket assembly milestone, "Launch Vehicle On Stand," took place Monday at Cape Canaveral Space Force Station in Florida.  

The first stage of ULA's third Vulcan rocket sports a different paint scheme than the first two missions, with solid red replacing a red flame pattern. Image credit: United Launch Alliance

Space Force officials say they expect to issue the approval without requiring another test mission.  The Vulcan has flown two certification missions, with the first in January and second at the start of October. The Cert-1 (first) mission was essentially flawless, while the second had an anomaly on one of the two strap-on Solid Rocket Boosters, with what appeared to be large sections of the engine's bell breaking off.

The rocket's twin BE-4 main engines, made by Blue Origin, corrected for the asymmetric thrust from the two strap-on boosters. Vulcan's Centaur V upper stage also fired its engines longer than planned to make up for the shortfall in performance from the damaged strap-on solid motor. Ultimately, the rocket reached its planned trajectory and delivered a dummy payload into interplanetary space.

Col. James Horne, who oversees launch execution for Space Systems Command, called the test flight a "successful launch" in an interview with Ars. The nozzle failure caused a "significant loss of thrust" from the damaged booster, he said.

The Vulcan rocket's ability to overcome the dramatic nozzle failure, which was easily visible in video of the launch, "really demonstrated the robustness of the total Vulcan system," Horne said.

Horne went on to note that he thought it might have been, "...probably one of the most accurate orbital insertions that I've seen them fly yet." Since the certification depends on them placing the payload in the claimed orbit, "one of the most accurate orbital insertions" is optimum. Horne considers the mission successful. 

As a side note, any control system designer will tell you there is a range of errors that can be adjusted out and systems typically have a point at which they lose control ("lose lock"). I think that it could be argued that this mission might have had a lot of spare ability in the corrections it could apply that won't always be there.  On a bigger payload with a bigger error injected by the SRB, it might lead to mission failure. The fact that Vulcan's systems corrected the SRB issue shouldn't mean they let the whole thing be forgotten about.

Investigation into the SRB problem is paramount.  

“I think, when folks zoom in on the video, they see thrust, hot gas burn-through, potentially, in the bottom of the rocket section," Horne said.

Tory Bruno, ULA's chief executive, posted on X shortly after the October 4 launch that initial findings suggested the rocket casing itself did not suffer a burn-through, which would allow super-hot gas to escape the booster. However, there were visual indications of a plume of hot exhaust appearing just above the bell-shaped nozzle, possibly near where it was bolted onto the booster's main body.
...
Horne said the Space Force is "assessing schedule impacts" to the next couple of Vulcan launches as engineers probe the booster malfunction. Military officials hoped to launch the first two national security missions on the Vulcan rocket by the end of this year. That's still the hope, Horne said, but he expects there will be "some impact" on the schedule for the next two Space Force missions, named USSF-106 and USSF-87.

The Vulcans that will be used for those next two launches will have four of those strap-on SRBs instead of the two the Cert-2 flight had. Does that double the chance of the kind of SRB nozzle failure seen on Cert-2?

Don't forget that ULA has a backlog of these National Security Missions.  Under existing contract, they're to launch a little more than half of the military's national security space missions over the next few years, (SpaceX is booked for the rest of the missions).  In the contract talked about two days ago, SpaceX won all the missions.

Tory Bruno has said they're targeting 25 launches a year but it may take a couple of years to get there. Next year, they're speculating "up to 20 launches," including the Vulcan and using up the last of the Atlas V missions. 

Starship Test Flight 5 "Worries" The IAC

The IAC; the International Astronautical Congress, the organization that held their annual meeting in Milan last week, that big professional organization expressed worries after Test Flight 5?  The mission that has gotten tons of pundits talking about what an incredible accomplishment it was - including a big group of pundits that aren't space reporters and don't follow everything going on - has gotten the IAC worried?  That's the headline at SpaceNews: "Latest Starship flight prompts praise and worries at IAC" and it caught my eye. 

SpaceX themselves kept a low key at the IAC. They didn't have a booth at the show, and didn't put on any big presentations. They let the test flight speak for itself. Along with some other big names that also spoke for it.

“Just yesterday, SpaceX has a very successful fifth launch as they develop this very large rocket,” NASA Administrator Bill Nelson said during an Oct. 14 plenary session that features the heads of several space agencies. “This was another one of the steps in the iteration of developing that.”

He added at a press conference the next day that work on the HLS version of Starship was on schedule. “I think you saw as a result of Sunday’s test of SpaceX and its big rocket that they are moving along very well, and that will determine ultimately the timing for the landing of Artemis 3 on the moon,” he said. “As of Sunday’s test, it was right on the mark.”

“They are right on making the benchmarks as they are planning to land in late ’26,” he said of SpaceX later in the briefing.

The worries end up being nothing negative about the test flight itself. The worries are that SpaceX is so far ahead of the rest of the industry that they can't catch up. Things like last night's post about them getting 100% of new contracts might become more common. 

“Congratulations to SpaceX, what an incredible feat of engineering! Mars, here we come,” Rocket Factory Augsburg stated in a social media post Oct 14. “At the same time, the coin has a second side: it shows and confirms that Europe has completely lost touch. Can it still catch up? No chance. At least not the way things are going at the moment.”

Rocket Factory Augsburg?  They're the company that had a static fire test of their rocket end in a RUD in August (first story in a Roundup post). They're a privately owned space company but the European Space Agency isn't that far ahead of them. They used to be one of the world's major space agencies, but seem to have lost their recipes. 

In an Oct. 15 interview, Josef Aschbacher, director general of the European Space Agency, said he was “fascinated” by the launch from an engineering perspective. “I then have to think, what does it mean for Europe, and to see what would be the change in the landscape and the ecosystem, and what do we need to do.”

Europe, he acknowledged, cannot compete head-to-head with Starship but could instead take advantage of broader changes in the space economy enabled by Starship. “How do we position ourselves in this ecosystem that is developing now?” he said. “You can imagine that if Starship brings 100 tons into space frequently, this will change everything out there in space, how things are constructed and how space is being utilized.”

Screen grab from a video seconds before the grab. Image credit: SpaceX 

While the American "old space" industry still hasn't really come to the realization that reusability changes everything, the Chinese are getting close to reusability and the Indian Space Research Organization (ISRO) has announced a development program for a Next Generation Launch Vehicle that will provide increased payload performance over existing rockets and be based on a reusable booster. S. Somanath, chairman of the Indian space agency, estimated NGLV will take six years to develop.

“I think all of you realize that reusability is mandatory for launchers,” he said. 

Meanwhile, we have an American old space company (whose name I will omit out of too much courtesy) is figuratively saying, "we'll spit the engines out of the booster and let them fall into the ocean. Then we'll just clean 'em up and reuse 'em. They're more expensive than the rest of the booster."  This is reusability as an afterthought.

SpaceX Dominates ULA in latest Space Force Bidding

The US Space Force's Space Systems Command announced Friday that in their latest contract competition, it has ordered all nine launches from SpaceX.  This was in the bidding competition for the first batch of dozens of missions the military will buy in the next phase of national security launch contracts.

The nine launches are divided into two fixed-price "task orders" that Space Systems Command opened up for bids earlier this year.  One task order is for seven launches of missile tracking and data relay satellites for the Space Development Agency's constellation. The other is for two launches for the National Reconnaissance Office, the US government's spy satellite organization. SpaceX won both task orders for a combined value of $733.5 million. 

The only two companies invited to bid on the contract were SpaceX and the United Launch Alliance. 

The contracts they're reporting on appear to be the ones mentioned this June in that they use the same terminology of Phase and Lane. 

This is the Space Force's first firm order for rocket launches in the so-called Phase 3 round of launch procurements. The Space Force has divided 79 missions for competition in the Phase 3 procurement into two classifications: Lane 1 and Lane 2.

The task orders announced Friday are the first awarded in Phase 3 Lane 1, which is for less demanding launch profiles into low-Earth orbit.

"We are excited to kick off our innovative NSSL Phase 3 Lane 1 effort with two task orders that support critical NRO and SDA missions," said Lt. Col. Douglas Downs, Space Systems Command's material leader for space launch procurement. "Industry stepped up to the plate and delivered on this competition."

While the USSF has mentioned several more possible competitors for these Lane 1 launches, including Blue Origin's New Glenn, military officials require a rocket to complete at least one successful orbital launch to become qualified for a Lane 1 task order and New Glenn hasn't flown. While Vulcan has carried out two successful orbital test flights - they don't have the full certification for all USSF launches yet. That certification will be a requirement for the coming Lane 2 missions, which are going to be more challenging military missions, typically larger, more expensive payloads destined for higher orbits. 

The Space Force is expected to soon select launch providers for Lane 2 missions. These launches will require the Space Force to certify the rockets, whereas the military is comfortable accepting a little more risk for the Lane 1 missions.

SpaceX's Falcon 9 and Falcon Heavy are currently certified for national security launches. 

File photo of a Falcon 9 launch from Vandenberg Space Force Base, SLC-4E. Image credit: SpaceX

The other 90% of my weekend

I did a deep dive into an area of ham radio that I've known about for as long as I can remember, but never tried to get into because the price of entry has been just too high (in time, money, and effort). The common name for this is moonbounce, but the more technical guys tend to call it EME - for Earth Moon Earth.  

There were two reasons for trying more this weekend.  First, this weekend was a major EME contest, put on the American Radio Relay League, and these contests tend to bring out a lot of activity.  More activity means more people to listen for. The second reason was some online chatting with a guy who does quite a lot of it. He doesn't know about this blog, and I didn't ask for permission to talk about him so I won't. But he asked me if I was going to try to listen in this weekend and after some chatting about my station by email he gave me some hints on setting things up to try to listen and contact some of the guys who have invested a lot in EME activity.

Let me just put the "Bottom Line Up Front" (BLUF): I didn't hear a single station in the couple of hours I thought my station might be able to turn the trick.  Neither Friday or Saturday around moonrise. 

So let's start at the beginning. For newbies, I did a post about trying to communicate with the two Voyager satellites. The concerns are identical but the numbers are vastly different.

This was all done at 50.2 MHz. The idea is simple: you point an antenna at the moon, 250,000 miles away (not exactly) and listen for signals coming from the moon. If you've got a really good station, you can hear your own signal after you wait for the echo from the moon.  The speed of light (which is radio) is 186,000 miles/second.  Remember, your signal has to go from your station to the moon and back or 500,000 miles. That means you'll hear the echo 2.69 seconds later.  

The next big concern is the same as every communications link everywhere else: the amount the signal attenuates - weakens - over that 500,000 miles. The term for this is path loss, and back in the Voyager article, I used a handy form that gets you within less than half a dB of the more theoretically-backed equation.  

Path loss in dB = 37 dB + 20log(f) + 20log(d)  where,f is the frequency in MHz and d is the distance in miles.

So PL = 37 + 20log(50) and 20log(500,000) or 185 dB. 

Wait.  There's a nasty assumption hidden in there, that the reflection from the moon is perfect. No signal loss, it just changes direction. That implies the signal reflected back has an angular diameter less than the moon - or some would be lost  around the edges.  The diameter of the moon is just over 0.5 degree, which is very tight for an antenna beam. OK, let's just keep a note on that. Maybe there's a useful approximation people have made. Maybe someone said just add (some number) of dBs to your path loss.

Where does this leave us?  Let's say we put 1000 W out of our antenna (it could be less power in the transmitter and more antenna gain, or a simpler antenna and more out of the transmitter).  That's +60 dBm (power compared to 1 milliwatt in 50 ohms) or one million milliwatts.

Signal coming back is  +60dBm -185dB path loss or -125 dBm at our receiver input. 

So what? It's a good time to say, "what does that mean?  Is that a useful signal?  Do I need more power, or more gain, to get more signal at the receiver? 

At this point, we have to dive into the improvements that have made EME more accessible to more hams than when we operated voice or CW (Morse code).  That's a topic for another day.

A graphic from a guy who's among the biggest names in EME, especially 6m EME. Lance Collister, from Montana. From there, he links to his main web page on EME.

Just a Little Thing to Share - Ham Radio Event

We are in the midst of a Special Event that caught my eye.  For people who think hams are too serious or have no sense of humor, I give you National Sasquatch Awareness Day. 

As you can see this is a week-long special event, and working various combinations and numbers of special stations listed in that first paragraph gets you a BIGFOOT Certificate! (Suitable for framing, I'm sure).  This is a screen grab from station W7B's page on QRZ.com.

While that Special Event Station screen capture follows the "click-it to embig-it" rules of thumb, this version gets Even Bigger when you click it:

The desire to collect certificates for special events or other contacts that are out-of-the ordinary in some way is almost universal in ham radio.  Pretty much every day, and especially on weekends, two of the most popular things to do are go to a nearby park or the top of a nearby hill and operate Parks On The Air (POTA) or Summits On The Air (SOTA).  The person going to ("activating") the park or hilltop gets their own points, and the people contacting ("working") those stations get a different credit.  Each and every one of those pieces of what's generally referred to as wallpaper is valuable only to the people who collect them. 

No - Just No, Space.com

Space.com posts a story I saw references to last night, that Sierra Space has a contract to produce a trash compactor for the International Space Station.  

An International Space Station (ISS) resupply mission in 2026 will send up the Sierra Space trash compactor for testing, company officials stated in a press release on Wednesday (Oct. 16). Like many other space station testbeds, this trash compactor will assess how to deal with the problem of garbage on eventual crewed moon or Mars missions, where disposal will be even more of an issue.

All well and good - but then they added:

and some media outlets say the machine looks like Wall-E.

No. I never saw the movie but I know what Wall-E looked like and I see no resemblance whatsoever.  Here's the two, side by side:

Unsurprisingly, a bunch of artists in a movie company that specializes (or did back then) in animation could produce a much more anthropogenic robot with much a more expressive "face" than a hardware company that's, well, producing what used to be called a trash masher.

Not that there's anything wrong with a trash masher (compactor), or what Sierra Space is doing here. It just doesn't look like the movie star robot.

Don't Count on Next Year's Artemis II Flight

Eric Berger at Ars Technica has gone through some Fed.gov General Accountability Office reports on preparations for next September's Artemis II launch, the first mission back to the moon since the end of the Apollo programs, and says they have pretty much used every bit of schedule slack they had reserved. His conclusion was, "It’s increasingly unlikely that humans will fly around the Moon next year."  

A new report from the US Government Accountability Office found that NASA's Exploration Ground Systems program—this is, essentially, the office at Kennedy Space Center in Florida responsible for building ground infrastructure to support the Space Launch System rocket and Orion—is in danger of missing its schedule for Artemis II.
...
The new report, published Thursday, finds that the Exploration Ground Systems program had several months of schedule margin in its work toward a September 2025 launch date at the beginning of the year. But now, the program has allocated all of that margin to technical issues experienced during work on the rocket's mobile launcher and pad testing.

NASA has been reasonably cautious in following the step-by-step approach Apollo used in going with the unmanned Artemis I and then the lunar fly-by of this mission next September ('25) followed by the Artemis III lunar landing mission in September '26.  The Apollo program had more hardware and concepts to test, and did so after the Apollo I disaster before landing with Apollo XI. There were many more test missions than in the Artemis program. Still, Artemis I was almost two years ago (November of '22) and NASA still hasn't reached a decision on what seems to be the most critical thing: the Orion capsule's heat shield issues. 

The report continues:

"Earlier in 2024, the program was reserving that time for technical issues that may arise during testing of the integrated SLS and Orion vehicle or if weather interferes with planned activities, among other things," the report states. "Officials said it is likely that issues will arise because this is the first time testing many of these systems. Given the lack of margin, if further issues arise during testing or integration, there will likely be delays to the September 2025 Artemis II launch date."

Weather?  Like the Hurricane of the Month Club?    

This kind of boggles the mind. Yes, the ground systems program has had to complete some important work since the Artemis I mission in late 2022, including building an emergency egress system for astronauts in the event of a problem during the launch countdown. But by September of next year, the agency will have had the better part of three years to work on those and other accommodations. At this point, there is no longer any margin in the schedule.

Artemis I mission during one of its trips to the pad that didn't result in flying, August 2022.   NASA Photo.

Eric Berger's conclusion:

To prepare for the Artemis II launch next September, Artemis officials had previously said they planned to begin stacking operations of the rocket in September of this year. But so far, this activity remains on hold pending a decision on the heat shield issue. Asked when NASA now plans to start stacking operations, the space agency official said, "We are still tracking toward stacking beginning this fall."

The bottom line is that NASA is facing schedule challenges on multiple fronts for the Artemis II mission. Although a launch delay is unlikely to be announced soon, we can be fairly confident that it is eventually coming.

I saw a story today that Michael Bloomberg, the founder of Bloomberg News and a former US Presidential candidate, called for cancelling the SLS program. The only thing I'm sure cancelling the SLS would do is guarantee that the next boots on the moon will have launched from China, and that may happen regardless of what we do about the outrageously bad SLS program. China says they plan to land a crew on the moon in 2030, but I wouldn't be surprised if they did it sooner.

Axiom Reveals New Artemis Lunar EVA Suit

It's actually a little weirder than that.  It's a joint effort by Axiom Space, and Prada, the fashion company. Perhaps fittingly, the new space suit was revealed in one of the fashion capitals of the world, Milan, Italy. Not at a fashion show, but at the International Astronautical Congress (IAC) held on Oct. 16 in Milan, six hours ahead of Eastern US time, and two hours ahead of UTC.

First, you might recall how the first look at these suits came across back in March of '23. If not, I have a picture (and links to others) here.  These suits look nothing like those, nor do they look like the SpaceX EVA suits we saw a few weeks ago during Polaris Dawn. Thankfully, they don't look much like Prada fashion, either. 

Axiom Space and Prada revealed the Axiom Extravehicular Mobility Unit (AxEMU) spacesuit in a press conference held at the International Astronautical Congress (IAC) here today (Oct. 16).

AxEMU will be used for NASA's Artemis 3 mission, which is currently scheduled to launch in late 2026. It has been specially designed for the lunar south pole, which will be a colder environment than astronauts experienced on the Apollo missions, which landed around the moon's equator.

The new spacesuit incorporates multiple redundant systems and an onboard diagnostic system to ensure safety for crewmembers, according to Axiom. It features lights and an HD camera on the helmet, 4G/LTE communication, a suit control interface, biometric monitoring, regenerable carbon dioxide scrubbing and portable life support to keep astronauts safe for up to eight hours. It can also accommodate a wide range of crewmembers, male or female.

The suit. 

White and not black like the ones we saw in March '23?  Matt Ondler, Axiom Space President, has said that during development, Axiom Space used a dark cover layer for display to conceal the suit’s proprietary technology. However, the spacesuit worn on the lunar surface will be made from a white material that reflects heat and protects astronauts from extreme high temperatures and lunar dust. 

If you're like me, you're probably wondering what a company like Prada would have to do with something that's more "industrial" than fashionable. It turned out it was a partnership between engineers and artisans that each have specialized knowledge of their own. 

The partnership with Prada was highlighted as a cross-industry collaboration success. "I'm very proud of the result we're showing today, which is just the first step in a long-term collaboration with Axiom Space," said Lorenzo Bertelli, Prada chief marketing officer, in a statement. "We've shared our expertise on high-performance materials, features, and sewing techniques, and we learned a lot."

Russell Ralston, Axiom's executive vice president of extravehicular activity, speaking at the unveiling, said the partnership was groundbreaking.

"This collaboration exemplifies the power to create better technology solutions together by merging Axiom Space's elite engineering experience with Prada's all-round craftsmanship. We've blended engineering, science and art to produce the ultimate garments, ensuring that astronauts can perform their tasks and missions in safety and comfort."

The collaboration doesn't stop there. Because the Artemis missions and therefore the suits are aimed at the lunar South Pole, that's going to mean the sun is lower in the sky and that means the astronauts are going to need more protection from the sun than the Apollo astronauts did landing much closer to the equator. "We've partnered with others like Oakley for optimal system design to enhance astronaut visibility," Ondler said.

Axiom's summary of their suits' features. It brings to mind the one in this post, but they're not conducive to point-by-point comparison. 

It's worth pointing out that this is still early in the AxEMU suit development and much testing lies ahead at this point. It's a safe bet that there will be changes. Axiom also intends to use the suits in places besides the lunar surface: there are discussions about using it in their planned space station work and other work in the low Earth orbit arena. "We also think there are commercial opportunities to work with commercial and private astronauts," Ondler said.

SpaceX Goes Over 100 Launches for the Year

It's kind of a slow news day. ULA is still trying to figure out why the nozzle broke off that Solid Rocket Booster on their Cert-2 flight.  To summarize that article, "yeah that nozzle broke off and screwed up a lot of stuff, but, boy howdy, that Vulcan sure did correct it out!  What a rocket!"

Another good one is that nuclear rockets could get us to Mars in like half the time, but getting those reactors designed right for space sure is hard!  Just like how they say space is hard? Designing pretty much anything for use in space is hard, and to be perfectly honest, designing anything that has never been done in human history is hard. I wonder what they'd think of designing the recovery system for SuperHeavy we just watched? 

Ah, well...

Elon Musk once said a sign of success for him as well as SpaceX is when launches get boring. You expect them to go smoothly and every step to work the way it's supposed to. In keeping  with that, SpaceX launched their missions #100 and 101 of 2024 this morning (Oct. 15).  Both were loads of Starlink satellites.

The first was from Cape Canaveral SFS at 2:10 AM EDT. As usual, the booster successfully landed about 8 minutes later, landing on the drone ship "A Shortfall of Gravitas" off the Florida coast.  This was the 11th flight for this booster, putting it in that odd position of being unimaginably old to the rest of the world, but just getting into its prime to SpaceX.

Two hours later, a second Falcon 9 lifted off from Vandenberg SFB's SLC-4E, at 4:21AM EDT (1:21 AM PDT). This was the 19th flight for this booster, which also successfully landed - this time on the drone ship "Of Course I Still Love You" off the California coast. This booster is respectably old to SpaceX, incomprehensibly old to the rest of the world. 

Time exposure of this morning's second launch, from Vandenberg Space Force Base. Image credit: SpaceX.

So, let's see... Sunday we saw Starship Flight test 5, Monday we saw Falcon Heavy launch Europa Clipper, and Tuesday morning we saw two launches of a load of 23 Starlink Satellites - one from each coast.  NextSpaceflight says on Thursday at 3:55 PM EDT we'll see another Falcon 9 carrying a load of Starlink satellites from SLC-40 here at CCSFS, and Sunday morning at 1:09 (EDT again) a load of OneWeb satellites (a direct competitor to Starlink) from Vandenberg SLC-4E.  That will be six launches since Sunday 10/13. Kinda reinforces that idea that the world's space program is SpaceX and second place is too far back to bother naming

Europa Clipper Started its 5+ Year trip today

NASA's Europa Clipper satellite to explore the named moon of Jupiter lifted off today at 12:06 PM EDT from pad 39A at the Kennedy Space Center.  The launch, originally set for Thursday the 10th, was delayed by Hurricane Milton and days of cleanup. 

The Falcon Heavy lifts off this morning (Oct. 14) from the Kennedy Space Center carrying NASA's Europa Clipper spacecraft. Credit: Brandon Lindner

The skies were that clear and blue down here at "Castle Graybeard" as well, giving us good views through the two side boosters and the core booster being dropped sequentially.  All three Falcon 9 cores were expended due to the size of the satellite and the needed trajectory using up all available fuel. 

Europa Clipper is one of NASA’s most expensive science missions yet, with an estimated total lifecycle cost, including four years of operations after arriving at Jupiter in 2030, of $5.2 billion. It was one of the top priorities for flagship-class planetary science missions in decadal surveys by planetary scientists, building on proposals for Europa orbiters or flyby missions for at least two decades.
...
The spacecraft weighed 5,700 kilograms fully fueled at launch (6.28 tons) and its solar arrays, when fully deployed, will make the spacecraft 30.5 meters (100 feet) long.

The solar arrays are a bit longer than an NBA basketball court, but recent experience with solar arrays like that have been easier to live with than nuclear power sources like the Radioisotope Thermal Generators that have powered the Voyager satellites for 47 years.

While you'll see many places describing the mission as searching for life on the frigid moon, NASA/JPL won't use those that term. 

The spacecraft will not search for life itself but rather see if the moon does have the right conditions to support life. “We continue to underscore that Europa Clipper is not actually a life-detection mission but a habitability investigation,” said Gina DiBraccio, acting director of NASA’s planetary science division, at an Oct. 13 briefing about the mission’s science.

“We want to understand whether Europa has the key ingredients to support life in its oceans,” said Robert Pappalardo, Europa Clipper project scientist at the Jet Propulsion Laboratory, at the briefing.

Europa Clipper is equipped with nine dedicated instruments ranging from cameras and spectrometers to magnetometers, as well as a gravity and radio science experiment. Much like the predecessor Juno satellite which has been orbiting Jupiter for well over eight years, Europa Clipper will enter an orbit that loops around Europa, currently said to orbit 49 times.  The flight to Europa is described as taking five years, but it's more like 5-1/2, with arrival expected in April 2030.  

You probably recall that the controversy a few years ago was that Europa Clipper had been set to fly on the SLS with its Exploration Upper Stage - which has never flown. I don't know an expected date, but would guess it won't fly until the probe is orbiting Europa  and well into its mission.  Then there's the issue that SLS missions are estimated to cost $4.4 billion (WITHOUT the EUS); today's Falcon Heavy launch cost $178 million.

They're not exactly the same missions.  SLS with the EUS could have gotten Europa Clipper to Europa faster - three years instead of 5-1/2 - if only it existed. And they could afford another $5 billion for the launch vehicle. The spacecraft will instead make a gravity assist flyby of Mars early next year and of Earth in late 2026 to arrive at Jupiter in April 2030.

Wow... Just Wow... Again!

Starship Flight Test 5. This went beyond Wow, all the way to "Holy Crap!"  It's beyond testing a couple of things, and as far as I can tell, it met every objective. I was here to watch this and watched the whole coverage that SpaceX linked to on X. Full screen, 1080p video for just about all of it.

The quote SpaceX uses all the time is, "the payload for this flight is data;" the whole purpose is to examine changes made since the last test with a handful of milestones in mind. They're fond of saying that no matter what they try, only excitement is guaranteed. That was easily exceeded in IFT-5.

After a flawless liftoff and the couple of minutes until stage separation, followed by the return to the pad at Starbase Boca Chica, we saw this:

We've known about the plans to return to the Orbital Launch Mount and desire to catch the Super Heavy booster for years.  We've seen videos created by various folks depicting what it would look like. It didn't prepare me. I caught myself watching the seconds before that screen capture shown above quietly saying, "Holy Crap!" Many of us watch them land the boosters after a Falcon 9 or Falcon Heavy launch and say it never gets old.  I think this is going to be the same way.

Bear in mind SpaceX made a video of all the failures on the way to their first successful Falcon 9 landing called "How Not to Land an Orbital Rocket Booster" - a tribute both to their work and their sense of humor.  That video was made seven years ago. There are no scenes out of today's mission for a similar video on how to catch the world's most powerful rocket booster.  Around 500 tons worth of booster. 

As impressive as catching SuperHeavy in the air was, it was only half the mission. Starship was still flying a suborbital flight to the Indian Ocean, off the NW coast of Australia. Catching SuperHeavy was 6:55 into the mission, the splashdown into the ocean was almost exactly an hour later. The plasma and heating we'd seen on earlier missions was just as mind-boggling as before but the video didn't show the flap melting away as it did on IFT-4.  Don't forget that this is SpaceX.  They went to the spot in the ocean that they were aiming for and put some buoys with cameras on them to capture the splashdown.  This is just after the still extremely hot engine nozzles dumped into the ocean.

(Screen grab from Space.com VideoFromSpace)  Yes, it exploded. As one of the SpaceX announcers said, they didn't plan to recover any part of that Starship.  The video leading up to that moment is from a camera pointed down at the bottom of the Starship from the top.  The ocean surface becomes visible, then it apparently plunges into the ocean because the entire scene changes color. 

If you haven't seen the video of the whole mission, it's worth the time. A minute or three after Mechazilla catches the booster, they go about a half hour with no chatting or narration, starting up again at about T+40 minutes. Go pick a video presenter you like or go to SpaceX's video on their own servers. It's a historic mission.

A comment I read somewhere said that with this, mankind has become a space-faring civilization. That seems a bit of an overreach to me, but it certainly made the talk about flying unmanned Starships to Mars in 2026 and sending people by 2028 sound more likely.

Just About Done with Milton Repairs

As I mentioned in my first update Thursday afternoon, we had very little damage from Milton.  Power was out very little, if at all, and there were only a couple of things that needed repair. The big one seemed to be that an element broke off of my HF Log Periodic antenna (a Tennadyne T6) on one side of the boom, very much like what happened back during Ian two years ago.  The second was that our east side fence gate broke, throwing the metal piece that latches the gate closed about six to eight feet from the fence. 

The antenna fix ended up being different from the last one and while I thought I could just go find a piece of the 1/2" aluminum bar that I used to fix it last time, the unnoticed curve ball was that the tubing for this element is larger diameter than the one that snapped two years ago.  That one had an Inside Diameter of 1/2" while this one was 5/8".  I went looking for a piece of 3/4 or 1" bar I could reduce in diameter until it fit in the antenna tube, but didn't have one.  I absolutely didn't want to leave this one on the ground and order a piece of bar stock - that would take days to a week. That's when I found a piece I had originally bought to fix the antenna after Ian, a piece of metric-sized aluminum tube that was a bit oversized in Outside Diameter: 17mm OD, or about 0.670".  

My lathe has been obsoleted by Little Machine Shop, but it's SIEG SC4 type, 8-1/2 by 20", they sold as their model 3540. Yes, SIEG is the Chinese machine producer that makes the vast majority of the smaller home/"hobby" lathes in the 7x10, 8x12 and similar small sizes. This one is capable of doing automated cuts by using some controls on the carriage originally intended for threading, so to reduce this bar from that 0.670" OD down to 0.620 (or so) is a matter of setting up for repetitive cuts, put the cutter in position, throw a lever and just keep an eye on things. Pretty much. At the end of the cut, flip the lever, return the carriage to the starting point, move the cutting bit to the next cut's depth and repeat.

I turned it down to the point where the ends measured close to 0.625 and then pulled the tube out to check in the antenna element. It's not uncommon for a part to not come out to the same diameter over its entire length (at least not on my lathe ... or not on these "hobbyist" lathes), and while the ends fit well, I took off another .003" and it made a nice easy fit.  As with the last time I did this, I used a gun cleaning wire brush in my battery powered drill to scrub the insides of both parts of the element.  As with the last time, it was full of dirt that I believe was stuck in the tubes by mud dauber wasps.

Here's what it looked like put back together.  Before cranking the tower back up, I did a NanoVNA sweep of the antenna and it looked fine. Then I swept my other antenna on the tower, the VHF beam, and it looked unaffected, too.

The aluminum tube has a blue line drawn on it to mark the halfway point and you can see that in the gap where the two pieces meet. I smeared the (right) half of the tube with nail polish to glue the tube in place, then drilled a clearance hole for the 6-32 hardware: a screw, flat washer on the far side, lock washer on this side. Yes, that's a brass nut on a stainless screw. 

The other issue, the fence gate had much less progress. It looks to me like that gate needs to be rebuilt or replaced.  We have a "poly-something-or-other" fence and the gate latch was ripped apart.  I forgot to grab a photo of it, but it's this basic idea, except the highlighted part looks to be about twice the size of the highlighted one in this picture and holds twice as many screws on the side of the right angle closest to the camera. That's the part that ripped off the gate post and got thrown.

Where the screw holes are in this pic, ours has slots, 1/4" wide and 1/2" long.  Every screw was ripped out of the plastic post, ripping the screw holes in the door (4x4) wider.  I found the ripped off piece about 8 or 10 feet away from the gate.  The screws are self-drilling steel screws that are just under 1/4" major diameter (across the screw threads).  While a "standard fix" might be to go to larger diameter screws, the metal won't handle that and the slots would have to be widened, perhaps going to 5/16 or 3/8".  Not an outrageous job for the CNC mill, but not a one hour job either.  The issue is how much damage that the post this mounts to sustained.

The antenna is fixed and operating; the gate not so much. Our neighbors on two sides, backdoor and next-door, have trees in corners of their lots that overgrow our lot all the time. Where the three of our lots touch, I'm constantly pruning their trees and repairing next-door neighbor's fence. Milty brought more attention to that because excessive wind from the wrong direction could have put backdoor neighbor's tree through the roof of my shop. It turns out the tree came down in their yard. This time. Turns out I had trimmed those back between Helene and Milton.

FAA Lifts Falcon 9 Flight Restrictions

In a statement late in the day on Friday, Oct. 11, the FAA said it cleared launches of the Falcon 9 that, with one exception, had been on hold since a Falcon 9 upper stage suffered a problem with a final deorbit burn on the Sept. 28 launch of the Crew-9 mission for NASA.  The engine burn occurred and the upper stage re-entered as it should but not ended up not being disposed of in the Pacific where it was supposed to end up.

The launch of the European Hera mission on Monday was given a separate permission to launch. The agency said it was because the upper stage wasn't going to reenter but was to accelerate the Hera spacecraft to escape velocity.

Gee... the Falcon 9 was grounded from just after midnight, the morning of September 29 until October 11. Twelve days! The first time was 14 days. Like the first time, this one must have been a gut-wrenching few minutes of troubleshooting - maybe a whole half hour!  (I really need to figure out where I left that sarcasm font.) Neither the FAA nor SpaceX elaborated on the findings of that investigation or the corrective actions that resulted from it.

Lift off of this past Monday morning's Hera mission from SLC-40 on Cape Canaveral SFS. T +4 seconds.

Somewhat off-subject is that Starship Flight Test 5 is still penciled in for Sunday morning at 8:00 AM EDT, although I can't find evidence the FAA has approved this test. Since it wasn't related to this FAA hold, it's not covered by this lifting of it. The last thing heard from SpaceX is that they expected approval in time for the Sunday Flight Test. 

SpaceX Upgrades the Dragon Capsules for Propulsive Landing

It's not exactly a new feature, more like an ability that was put aside in the past and got renewed interest recently.  Back on September 27th, SpaceX announced a new capability for the Dragon spacecraft. Dragon now has built-in redundancy to propulsively land using its SuperDraco thrusters. In the unlikely event of a parachute failure, the propulsive landing could save the vehicle and potential crew from a rough landing or imminent danger. 

The concept of landing on the SuperDraco thrusters dates back to 2014, when the Commercial Crew Program was getting started.

SpaceX introduced the concept of a propulsive landing Dragon over ten years ago. When SpaceX revealed Dragon 2, it was marketed as capable of propulsively landing anywhere on Earth and was initially designed to land exclusively with the SuperDracos. However, SpaceX ultimately pursued the use of parachutes as the main form of recovery for Dragon 2 missions.

A Tweet from 2014 shows this:

The reasons come back to SpaceX's overarching goal of Rapid Reusability. 

Landing on a concrete landing pad on land rather than in the ocean has many advantages, particularly when it comes to the long-term reusability and refurbishment of Dragon capsules. When landing in the ocean, saltwater can corrode the aluminum body and carbon fiber bonds that Dragon is constructed of. Propulsively landing on Earth would have prevented invasive corrosion from occurring in the first place, making rapid reusability a much more achievable goal.

What’s more, landing Dragon propulsively would’ve also been safer for the crew when exiting the spacecraft. Getting astronauts out of a capsule is an extended process, especially when they have been exposed to microgravity for extended periods of time. The motion of ocean waves and the process of retrieving Dragon from the water has proven to be quite lengthy, and landing on a solid pad on land would have allowed recovery teams to approach and egress the crew inside Dragon substantially quicker.

The role of getting NASA approval for every aspect of the certification of the Dragon played a part in the decision to downplay the propulsive landing and emphasize using parachutes to splashdown in the ocean. 

With parachutes now serving as Dragon’s main landing system, propulsively landing Dragon was no longer a main focus of Dragon 2’s development. It was later revealed that NASA desired a higher “loss of crew” reliability rating for Dragon and felt more comfortable with a parachute landing system than a propulsive landing system. NASA also believed that the small openings in Dragon’s heat shield for the four extendable landing legs could lead to the quick formation of hotspots during reentry, potentially leading to the break up of the vehicle. 

Followers of SpaceX and the Crew Dragon may recall that in 2019, after a test mission of one capsule to the ISS, it was subjected to a test of its SuperDraco thrusters and exploded on the test stand less than one second before it was to have ignited its thrusters. It suffered an anomaly, NASA speak for "cratering explosion on the test stand".

Today, Crew Dragon is known to be an extremely reliable and well-tested vehicle — flying 15 successful crewed missions to the ISS and other low-Earth orbits and suffering little to no issues with its parachute landing system. During the Crew-9 pre-launch briefing, NASA announced that Dragon now had the capability to activate its SuperDraco engines and perform a propulsive landing if a failure of the parachutes were to occur. Should an anomaly with the parachutes occur, the four main parachutes would be cut and Dragon would ignite its eight SuperDraco engines to slowly perform a propulsive splashdown. NASA stated that such a landing would be “tolerable” for any crew inside Dragon.

SpaceX testing Dragon’s eight SuperDraco’s during a hover test in 2015. Image credit: SpaceX

Perhaps surprisingly, the propulsive landing system was available for the first time on Crew-7 in August 2023 and has been functional on all private SpaceX missions since then.  It's expected to be used for future NASA ISS crew missions.  Now I'm stoked to watch a returning Dragon spacecraft do a vertical propulsive landing at one of the poured concrete Landing Zones that returning Falcon 9 boosters have landed on.