Mission profiles of early Soviet lunar probes

Sven Grahn

Contents

List of launches

The table below lists the known launches in the E-1, E-2, and E-3 series of lunar probes. It is also known that the first E-1 probe was scheduled for August 18, 1958, but postponed to September 1958 when the first U.S. Pioneer probe failed on August 17(2). The next attempt took place on 23 September, i.e. at roughly the same lunar age as that of the planned attempt the month before. When the launch attempt failed on 23 September the pressure to beat the U.S. to the Moon caused Korolev to launch the next rocket to compete with the next Thor-Able Pioneer probe planned to be launched on 11 October 1958.
 

No lunar age constraint?

As can be seen from the figure below the table the 11 October 1958 E-1 attempt took place at a much different lunar age than the previous one. Everything to beat the U.S.! Even the next launch, on 4 December, seems to have been timed to precede the first attempt by the US Army team to reach the Moon. The Luna 1 launch occurred roughly a month later. The two remaining launches in the E-1 lunar impact program occurred at roughly the same lunar age as that in September 1958. It seems that there was no specific boundary conditions for the launch of the E-1 probes that directly related to the age of the Moon. As we shall see later, there was probably another criterion that determined the launch window. The data in the table comes from many sources (3).

The arrival times for the E-1 launch failures are based on a flight time of 38 hours and 41 minutes (the same as for Luna 2) and 61 hours 33 min for the E-3 failures (same flight time as Luna 3).
 

Name Type Date Time (UT) Notes Arrival time Declination
at arrival
- E-1 23 Sep 1958 0703:23 Exploded at T+93 sec due to resonance oscillations 24 Sep
2144 UT		 -18.7
- E-1 11 Oct 1958 2141:58 Exploded at T+104 sec due to resonance oscillations 13 Oct
1223 UT		 -10.5
- E-1 4 Dec 1958 1818 Core stage engines failed at T+245 sec 6 Dec
0859 UT		 -5.5
Luna 1 E-1 2 Jan 1959 1641:21  Missed the moon by 6400 km  4 Jan
0259 UT		 -11.8
- E-1A 18 Jun 1959 0808 Inertial guidance system failed at T+153 sec 20 Jun
2249 UT		 -18.3
Luna 2 E-1A 12 Sep 1959 0639:42 Hit Moon at 2102:22 UT on 13 Sep 1959 13 Sep 59
2102:22 UT		 -13.5
Luna 3 E-2A 4 Oct 1959 0043:40 Closest approach to Moon at 1416 UT, 6 Oct 1959 6 Oct
1416 UT		 -18
- E-3 15 Apr 1960 1506:44  Engine of Block-E cut off too early. Apogee 200,000 km. 18 Apr
0439 UT		 -16.9
- E-3 16 Apr 1960 1607:43 One strap-on did not reach full thrust. Broke away at T+0.4 sec. 19 Apr
0440 UT		 -14.5

It is interesting to note that Pioneer 1 was launched at 0842 UT on 11 October 1958, i.e. 13 hours before the Soviet E-1 probe. However, the flight time of the Pioneer 1 to the Moon was intended to have been 57.5 hours until retro-firing, 62 hours to lunar orbit. This would have meant retrofire at 1812 UT and arrival at around 2300 UT on 13 October. The E-1 probe, because of its faster trajectory, would have hit the Moon at about 1220 UT, i.e. at least 6 hours before the Pioneer 1 probe could have been said to have "arrived" at the Moon. The Moon race never got much hotter!

The figure below shows the relationship between launch time and lunar age for the E-1/2/3 series. The red line has been computed as outlined in "How to compute the launch time of a lunar probe"   using an inclination of 65o and a flight time of 1.5 days. The Luna-3 point lies on this line despite the fact that the transfer orbit of Luna-3 to the Moon had an inclination of 55o and a flight-time to the moon of 2.5 days.

A lunar declination constraint?

It is somewhat surprising that the lunar age of these launch attempts are spread over the whole range of lunar phases. So, was there any other launch constraint that these launch attempts had to obey. The table of launches shows that the declination of the Moon at arrival was always negative. We can use the declination phase plotting method developed by Richard S Flagg (See "Mission profiles of 7K-L1 flights") and plot the E-1/2/3 mission in the declination phase/Age diagram. From the figure below it is again evident that the declination of the Moon for all launch attempts were negative! (This diagram shows the age/declination phase at launch - not arrival).
The explanation to this fact has been given in (1), where the author states that a negative  lunar declination requires less injection energy. The figure below shows two computer simulations of the flights of Luna 2 and the launch attempt on 4 December 1958. It seems that there were rather strict limitations on the shape of the ascent trajectory. The flight path angle could probably only be varied within a 5 degree range. Of course one can see the advantages of a parking orbit approach where the injection point can be varied to fit the lunar declination.

The flight time must be either 0.5, 1.5 or 2.5 days to permit viewing of the lunar approach from the Soviet Union. A flight time to the Moon of only 0.5 days would require a very high energy trajectory with an injection velocity of 13.7 km/s, clearly an impossible figure! Therefore the shortest flight time to the Moon was 1.5 days.

The figure below shows a simulation of the outbound trajectory of Luna 3. The simulation is based on a total energy of -0.68 km2/sec2, as given in (1).

Viewing the Moon's far side

It is interesting to note that the lunar age of the Luna-3 launch and the two E-3 probes in 1960 differ by about 17 days! How does this agree with the fact that both types of missions aimed at taking pictures of the Moon's far side? Well, the figure below shows approximately which parts of the Moon's far side that were illuminated at the time of Luna-3 and the E-3 launches. As can be seen from this simple diagram, the age of the Moon at the time of launch of the E-3 probes permitted the imaging of the areas of the Moon's far side not covered by Luna-3!

References

  1. Sedov, Leonid I, "The Orbits of Cosmic Rockets Towards The Moon", presented at the American Rocket Society's 14 th Annual Meeting, Sheraton Park Hotel, Nov 16-20, 1959, ARS paper no 1051A-59.
  2. Asif Siddiqi, "First to the Moon", JBIS, Vol. 51, pp. 231-238, June 1998.
  3. "S Baykonura: s lune, marsu, venere: vospominaniya veteranov Baykonura (Moscow, 2001)", in which the attempted launch times for three flights that never made it off the pad are given:
    Sep 06 1959 0349 Moscow Time (0049 UT)
    Sep 08 1959 0540:41 Moscow Time (0240:41 UT)
    Sep 09 1959 0640:03 Moscow Time (0340:03 UT)

     Deep Space Chronicle